| 1. |
- Assadi, Ghazaleh, et al.
(författare)
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Functional Analyses of the Crohn's Disease Risk Gene LACC1
- 2016
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Ingår i: PLOS ONE. - San Francisco, USA : Public Library of Science. - 1932-6203. ; 11:12
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Tidskriftsartikel (refereegranskat)abstract
- Background: Genetic variation in the Laccase (multicopper oxidoreductase) domain-containing 1 (LACC1) gene has been shown to affect the risk of Crohn's disease, leprosy and, more recently, ulcerative colitis and juvenile idiopathic arthritis. LACC1 function appears to promote fatty-acid oxidation, with concomitant inflammasome activation, reactive oxygen species production, and anti-bacterial responses in macrophages. We sought to contribute to elucidating LACC1 biological function by extensive characterization of its expression in human tissues and cells, and through preliminary analyses of the regulatory mechanisms driving such expression.Methods: We implemented Western blot, quantitative real-time PCR, immunofluorescence microscopy, and flow cytometry analyses to investigate fatty acid metabolism-immune nexus (FAMIN; the LACC1 encoded protein) expression in subcellular compartments, cell lines and relevant human tissues. Gene-set enrichment analyses were performed to initially investigate modulatory mechanisms of LACC1 expression. A small-interference RNA knockdown in vitro model system was used to study the effect of FAMIN depletion on peroxisome function.Results: FAMIN expression was detected in macrophage-differentiated THP-1 cells and several human tissues, being highest in neutrophils, monocytes/macrophages, myeloid and plasmacytoid dendritic cells among peripheral blood cells. Subcellular co-localization was exclusively confined to peroxisomes, with some additional positivity for organelle endomembrane structures. LACC1 co-expression signatures were enriched for genes involved in peroxisome proliferator-activated receptors (PPAR) signaling pathways, and PPAR ligands downregulated FAMIN expression in in vitro model systems.Conclusion: FAMIN is a peroxisome-associated protein with primary role(s) in macrophages and other immune cells, where its metabolic functions may be modulated by PPAR signaling events. However, the precise molecular mechanisms through which FAMIN exerts its biological effects in immune cells remain to be elucidated.
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| 2. |
- Belkic, Karen, et al.
(författare)
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Imaging surveillance programs for women at high breast cancer risk in Europe : Are women from ethnic minority groups adequately included?
- 2015
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Ingår i: International Journal of Oncology. - : Spandidos Publications. - 1019-6439 .- 1791-2423. ; 47:3, s. 817-839
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Tidskriftsartikel (refereegranskat)abstract
- Women from ethnic minority groups, including immigrants and refugees are reported to have low breast cancer (BC) screening rates. Active, culturally-sensitive outreach is vital for increasing participation of these women in BC screening programs. Women at high BC risk and who belong to an ethnic minority group are of special concern. Such women could benefit from ongoing trials aimed at optimizing screening strategies for early BC detection among those at increased BC risk. Considering the marked disparities in BC survival in Europe and its enormous and dynamic ethnic diversity, these issues are extremely timely for Europe. We systematically reviewed the literature concerning European surveillance studies that had imaging in the protocol and that targeted women at high BC risk. The aim of the present review was thereby to assess the likelihood that women at high BC risk from minority ethnic groups were adequately included in these surveillance programs. Twenty-seven research groups in Europe reported on their imaging surveillance programs for women at increased BC risk. The benefit of strategies such as inclusion of magnetic resonance imaging and/or more intensive screening was clearly documented for the participating women at increased BC risk. However, none of the reports indicated that sufficient outreach was performed to ensure that women at increased BC risk from minority ethnic groups were adequately included in these surveillance programs. On the basis of this systematic review, we conclude that the specific screening needs of ethnic minority women at increased BC risk have not yet been met in Europe. Active, culturally-sensitive outreach is needed to identify minority women at increased BC risk and to facilitate their inclusion in on-going surveillance programs. It is anticipated that these efforts would be most effective if coordinated with the development of European-wide, population-based approaches to BC screening.
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| 3. |
- Berglund, Erik, et al.
(författare)
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Functional role of the Ca2+-activated Cl- channel DOG1/TMEM16A in gastrointestinal stromal tumor cells
- 2014
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Ingår i: Experimental Cell Research. - : Elsevier BV. - 0014-4827 .- 1090-2422. ; 326:2, s. 315-325
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Tidskriftsartikel (refereegranskat)abstract
- DOG1, a Ca2+-activated Cl- channel (CaCC), was identified in 2004 to be robustly expressed in gastrointestinal stromal tumors (GIST). It was rapidly included as a tumor marker in routine diagnostics, but the functional role remained unknown. CaCCs are important regulators of normal physiological functions, but also implicated in tumorigenesis, cancer progression, metastasis, cell migration, apoptosis, proliferation and viability in several malignancies. We therefore investigated whether DOG1 plays a role in the three latter in GIST by utilizing in vitro cell model systems. Confocal microscopy identified different subcellular localizations of DOG1 in imatinib-sensitive and imatinib-resistant cells. Electrophysiological studies confirmed that DOG1-specific pharmacological agents possess potent activating and inhibiting properties. Proliferation assays showed small effects up to 72 h, and flow cytometric analysis of adherent cells with 7-AAD/Annexin V detected no pharmacological effects on viable GIST cells. However, inhibition of DOG1 conveyed pro-apoptotic effects among early apoptotic imatinib-resistant cells. In conclusion, DOG1 generates Cl- currents in GIST that can be regulated pharmacologically, with small effects on cell viability and proliferation in vitro. Inhibition of DOG1 might act pro-apoptotic on some early apoptotic GIST cell populations. Further studies are warranted to fully illuminate the function of DOG1 and its potential as therapeutic target.
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| 4. |
- Carlred, Louise, et al.
(författare)
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Imaging of amyloid-β in alzheimer’s disease transgenic mouse brains with ToF-SIMS using immunoliposomes
- 2016
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Ingår i: Biointerphases. - : American Institute of Physics (AIP). - 1934-8630 .- 1559-4106. ; 11:2, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- Time-of-flight secondary ion mass spectrometry (ToF-SIMS) has been proven to successfully image different kinds of molecules, especially a variety of lipids, in biological samples. Proteins, however, are difficult to detect as specific entities with this method due to extensive fragmentation. To circumvent this issue, the authors present in this work a method developed for detection of proteins using antibody-conjugated liposomes, so called immunoliposomes, which are able to bind to the specific protein of interest. In combination with the capability of ToF-SIMS to detect native lipids in tissue samples, this method opens up the opportunity to analyze many different biomolecules, both lipids and proteins, at the same time, with high spatial resolution. The method has been applied to detect and image the distribution of amyloid-β (Aβ), a biologically relevant peptide in Alzheimer’s disease (AD), in transgenic mouse brain tissue. To ensure specific binding, the immunoliposome binding was verified on a model surface using quartz crystal microbalance with dissipation monitoring. The immunoliposome binding was also investigated on tissue sections with fluorescence microscopy, and compared with conventional immunohistochemistry using primary and secondary antibodies, demonstrating specific binding to Aβ. Using ToF-SIMS imaging, several endogenous lipids, such as cholesterol and sulfatides, were also detected in parallel with the immunoliposome-labeled Aβ deposits, which is an advantage compared to fluorescence microscopy. This method can thus potentially provide further information about lipid–protein interactions, which is important to understand the mechanisms of neurodegeneration in AD.
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| 5. |
- Carlred, Louise M, 1985, et al.
(författare)
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Imaging of Amyloid-β in Alzheimer’s disease transgenic mouse brains with Time-of-Flight Secondary Ion Mass Spectrometry using Immunoliposomes
- 2016
-
Ingår i: Biointerphases. - : American Vacuum Society. - 1559-4106 .- 1934-8630. ; 11:2, s. 1-11
-
Tidskriftsartikel (refereegranskat)abstract
- Time-of-flight secondary ion mass spectrometry (ToF-SIMS) has been proven to successfully image different kinds of molecules, especially a variety of lipids, in biological samples. Proteins, however, are difficult to detect as specific entities with this method due to extensive fragmentation. To circumvent this issue, the authors present in this work a method developed for detection of proteins using antibody-conjugated liposomes, so called immunoliposomes, which are able to bind to the specific protein of interest. In combination with the capability of ToF-SIMS to detect native lipids in tissue samples, this method opens up the opportunity to analyze many different biomolecules, both lipids and proteins, at the same time, with high spatial resolution. The method has been applied to detect and image the distribution of amyloid-β (Aβ), a biologically relevant peptide in Alzheimer's disease (AD), in transgenic mouse braintissue. To ensure specific binding, the immunoliposome binding was verified on a model surface using quartz crystal microbalance with dissipation monitoring. The immunoliposome binding was also investigated on tissue sections with fluorescence microscopy, and compared with conventional immunohistochemistry using primary and secondary antibodies, demonstrating specific binding to Aβ. Using ToF-SIMS imaging, several endogenous lipids, such as cholesterol and sulfatides, were also detected in parallel with the immunoliposome-labeled Aβ deposits, which is an advantage compared to fluorescence microscopy. This method can thus potentially provide further information about lipid–protein interactions, which is important to understand the mechanisms of neurodegeneration in AD.
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| 6. |
- Carlred, Louise M, 1985, et al.
(författare)
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Simultaneous imaging of amyloid-β and lipids in brain tissue using antibody-coupled liposomes and time-of-flight secondary ion mass spectrometry
- 2014
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 136:28, s. 9973-9981
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Tidskriftsartikel (refereegranskat)abstract
- The spatial localization of amyloid-β peptide deposits, the major component of senile plaques in Alzheimer's disease (AD), was mapped in transgenic AD mouse brains using time-of-flight secondary ion mass spectrometry (ToF-SIMS), simultaneously with several endogenous molecules that cannot be mapped using conventional immunohistochemistry imaging, including phospholipids, cholesterol and sulfatides. Whereas the endogenous lipids were detected directly, the amyloid-β deposits, which cannot be detected as intact entities with ToF-SIMS because of extensive ion-induced fragmentation, were identified by specific binding of deuterated liposomes to antibodies directed against amyloid-β. Comparative investigation of the amyloid-β deposits using conventional immunohistochemistry and fluorescence microscopy suggests similar sensitivity but a more surface-confined identification due to the shallow penetration depth of the ToF-SIMS signal. The recorded ToF-SIMS images thus display the localization of lipids and amyloid-β in a narrow (∼10 nm) two-dimensional plane at the tissue surface. As compared to a frozen nontreated tissue sample, the liposome preparation protocol generally increased the signal intensity of endogenous lipids, likely caused by matrix effects associated with the removal of salts, but no severe effects on the tissue integrity and the spatial distribution of lipids were observed with ToF-SIMS or scanning electron microscopy (SEM). This method may provide an important extension to conventional tissue imaging techniques to investigate the complex interplay of different kinds of molecules in neurodegenerative diseases, in the same specimen. However, limitations in target accessibility of the liposomes as well as unspecific binding need further consideration. © 2014 American Chemical Society.
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| 7. |
- Hugonin, Loïc, et al.
(författare)
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Calcium influx into phospholipid vesicles caused by dynorphin neuropeptides
- 2008
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Ingår i: Biochimica et Biophysica Acta - Biomembranes. - : Elsevier BV. - 0005-2736 .- 1879-2642 .- 0006-3002. ; 1778:5, s. 1267-1273
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Tidskriftsartikel (refereegranskat)abstract
- Dynorphins, endogeneous opioid peptides, function as ligands to the opioid kappa receptors but also induce non-opioid excitotoxic effects. Dynorphin A can increase the intra-neuronal calcium concentration through a non-opioid and non-NMDA mechanism. In this investigation, we show that big dynorphin, dynorphin A and to some extent dynorphin A (1-13), but not dynorphin B, allow calcium to enter into large unilamellar phospholipid vesicles with partly negative headgroups. The effects parallel the previously studied potency of dynorphins to translocate through biological membranes and to cause calcein leakage from large unilamellar phospholipid vesicles. There is no calcium ion influx into vesicles with zwitterionic headgroups. We have also investigated if the dynorphins can translocate through the vesicle membranes and estimated the relative strength of interaction of the peptides with the vesicles by fluorescence resonance energy transfer. The results show that dynorphins do not translocate in this membrane model system. There is a strong electrostatic contribution to the interaction of the peptides with the membrane model system.
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| 8. |
- Korberg, Izabella Baranowska, et al.
(författare)
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WNT3 involvement in human bladder exstrophy and cloaca development in zebrafish
- 2015
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Ingår i: Human Molecular Genetics. - : Oxford University Press (OUP). - 0964-6906 .- 1460-2083. ; 24:18, s. 5069-5078
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Tidskriftsartikel (refereegranskat)abstract
- Bladder exstrophy, a severe congenital urological malformation when a child is born with an open urinary bladder, is the most common form of bladder exstrophy-epispadias complex (BEEC) with an incidence of 1: 30,000 children of Caucasian descent. Recent studies suggest that WNT genes may contribute to the etiology of bladder exstrophy. Here, we evaluated WNT-pathway genes in 20 bladder exstrophy patients using massively parallel sequencing. In total 13 variants were identified in WNT3, WNT6, WNT7A, WNT8B, WNT10A, WNT11, WNT16, FZD5, LRP1 and LRP10 genes and predicted as potentially disease causing, of which seven variants were novel. One variant, identified in a patient with a de novo nonsynonymous substitution in WNT3 (p.Cys91Arg), was further evaluated in zebrafish. Knock down of wnt3 in zebrafish showed cloaca malformations, including disorganization of the cloaca epithelium and expansion of the cloaca lumen. Our study suggests that the function of the WNT3 p.Cys91Arg variant was altered, since RNA overexpression of mutant Wnt3 RNA does not result in embryonic lethality as seen with wild-type WNT3 mRNA. Finally, we also mutation screened the WNT3 gene further in 410 DNA samples from BEEC cases and identified one additional mutation c.638G> A (p.Gly213Asp), which was paternally inherited. In aggregate our data support the involvement of WNT-pathway genes in BEEC and suggest that WNT3 in itself is a rare cause of BEEC.
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| 9. |
- Krmpot, Aleksandar J., et al.
(författare)
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Functional Fluorescence Microscopy Imaging : Quantitative Scanning-Free Confocal Fluorescence Microscopy for the Characterization of Fast Dynamic Processes in Live Cells
- 2019
-
Ingår i: Analytical Chemistry. - : AMER CHEMICAL SOC. - 0003-2700 .- 1520-6882. ; 91:17, s. 11129-11137
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Tidskriftsartikel (refereegranskat)abstract
- Functional fluorescence microscopy imaging (fFMI), a time-resolved (21 mu s/frame) confocal fluorescence microscopy imaging technique without scanning, is developed for quantitative characterization of fast reaction-transport processes in solution and in live cells. The method is based on massively parallel fluorescence correlation spectroscopy (FCS). Simultaneous excitation of fluorescent molecules in multiple spots in the focal plane is achieved using a diffractive optical element (DOE). Fluorescence from the DOE-generated 1024 illuminated spots is detected in a confocal arrangement by a matching matrix detector comprising 32 x 32 single-photon avalanche photodiodes (SPADs). Software for data acquisition and fast auto- and cross-correlation analysis by parallel signal processing using a graphic processing unit (GPU) allows temporal autocorrelation across all pixels in the image frame in 4 s and cross-correlation between first- and second-order neighbor pixels in 45 s. We present here this quantitative, time-resolved imaging method with single-molecule sensitivity and demonstrate its usefulness for mapping in live cell location-specific differences in the concentration and translational diffusion of molecules in different subcellular compartments. In particular, we show that molecules without a specific biological function, e.g., the enhanced green fluorescent protein (eGFP), exhibit uniform diffusion. In contrast, molecules that perform specialized biological functions and bind specifically to their molecular targets show location-specific differences in their concentration and diffusion, exemplified here for two transcription factor molecules, the glucocorticoid receptor (GR) before and after nuclear translocation and the Sex combs reduced (Scr) transcription factor in the salivary gland of Drosophila ex vivo.
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| 10. |
- Krmpot, Aleksandar J., et al.
(författare)
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Quantitative confocal fluorescence microscopy of dynamic processes by multifocal fluorescence correlation spectroscopy
- 2015
-
Ingår i: ADVANCED MICROSCOPY TECHNIQUES IV; AND NEUROPHOTONICS II. - : SPIE. - 9781628417012
-
Konferensbidrag (refereegranskat)abstract
- Quantitative confocal fluorescence microscopy imaging without scanning is developed for the study of fast dynamical processes. The method relies on the use of massively parallel Fluorescence Correlation Spectroscopy (mpFCS). Simultaneous excitation of fluorescent molecules across the specimen is achieved by passing a single laser beam through a Diffractive Optical Element (DOE) to generate a quadratic illumination matrix of 32x32 light sources. Fluorescence from 1024 illuminated spots is detected in a confocal arrangement by a matching matrix detector consisting of the same number of single-photon avalanche photodiodes (SPADs). Software was developed for data acquisition and fast auto- and cross-correlation analysis by parallel signal processing using a Graphic Processing Unit (GPU). Instrumental performance was assessed using a conventional single-beam FCS instrument as a reference. Versatility of the approach for application in biomedical research was evaluated using ex vivo salivary glands from Drosophila third instar larvae expressing a fluorescently-tagged transcription factor Sex Combs Reduced (Scr) and live PC12 cells stably expressing the fluorescently tagged mu-opioid receptor (MOPeGFP). We show that quantitative mapping of local concentration and mobility of transcription factor molecules across the specimen can be achieved using this approach, which paves the way for future quantitative characterization of dynamical reaction-diffusion landscapes across live cells/tissue with a sub-millisecond temporal resolution (presently 21 mu s/frame) and single-molecule sensitivity.
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| 11. |
- Lundin, Johanna, et al.
(författare)
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Further support linking the 22q11.2 microduplication to an increased risk of bladder exstrophy and highlighting LZTR1 as a candidate gene
- 2019
-
Ingår i: Molecular Genetics and Genomic Medicine. - : Wiley. - 2324-9269. ; 7:6
-
Tidskriftsartikel (refereegranskat)abstract
- Background: The bladder exstrophy-epispadias complex (BEEC) is a congenital malformation of the bladder and urethra. The underlying causes of this malformation are still largely unknown; however, aside from environment, genetics is thought to play an essential role. The recurrent 22q11.2 microduplication is the most persistently detected genetic aberration found in BEEC cases. Methods: We performed array comparative genomic hybridization (array-CGH) analysis of 76 Swedish BEEC patients. Statistical analysis was performed on current dataset pooled with previously published data on the 22q11.2 microduplication in BEEC patients. We performed massive parallel sequencing (MPS) of the 22q11.2 region in 20 BEEC patients without the 22q11.2 microduplication followed by functional studies. Results: We identified three additional cases with the 22q11.2 microduplication. Pooling data from this study with previously published reports showed a statistically significant enrichment of the 22q11.2 microduplication in BEEC patients (2.61% in cases vs. 0.08% in controls; OR = 32.6; p = 8.7 × 10−4). MPS of the 22q11.2 region in 20 BEEC patients without the 22q11.2 microduplication identified a novel variant in LZTR1 (p.Ser698Phe) in one patient. Functional evaluation of the LZTR1 p.Ser698Phe variant in live NIH 3T3 cells showed that the concentration and cytoplasmic mobility differ between the Lztr1wt and Lztr1mut, indicating a potential functional effect of the LZTR1mut. Conclusion: Our study further emphasizes the involvement of the 22q11.2 region in BEEC development and highlights LZTR1 as a candidate gene underlying the urogenital malformation.
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| 12. |
- Marinova, Zoya, et al.
(författare)
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Translocation of dynorphin neuropeptides across the plasma membrane. A putative mechanism of signal transmission.
- 2005
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 280:28
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Tidskriftsartikel (refereegranskat)abstract
- Several peptides, including penetratin and Tat, are known to translocate across the plasma membrane. Dynorphin opioid peptides are similar to cell-penetrating peptides in a high content of basic and hydrophobic amino acid residues. We demonstrate that dynorphin A and big dynorphin, consisting of dynorphins A and B, can penetrate into neurons and non-neuronal cells using confocal fluorescence microscopy/immunolabeling. The peptide distribution was characterized by cytoplasmic labeling with minimal signal in the cell nucleus and on the plasma membrane. Translocated peptides were associated with the endoplasmic reticulum but not with the Golgi apparatus or clathrin-coated endocytotic vesicles. Rapid entry of dynorphin A into the cytoplasm of live cells was revealed by fluorescence correlation spectroscopy. The translocation potential of dynorphin A was comparable with that of transportan-10, a prototypical cell-penetrating peptide. A central big dynorphin fragment, which retains all basic amino acids, and dynorphin B did not enter the cells. The latter two peptides interacted with negatively charged phospholipid vesicles similarly to big dynorphin and dynorphin A, suggesting that interactions of these peptides with phospholipids in the plasma membrane are not impaired. Translocation was not mediated via opioid receptors. The potential of dynorphins to penetrate into cells correlates with their ability to induce non-opioid effects in animals. Translocation across the plasma membrane may represent a previously unknown mechanism by which dynorphins can signal information to the cell interior.
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| 13. |
- Papadopoulos, Dimitrios K., et al.
(författare)
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Control of Hox transcription factor concentration and cell-to-cell variability by an auto-regulatory switch
- 2019
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Ingår i: Development. - : The Company of Biologists. - 0950-1991 .- 1477-9129. ; 146:12
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Tidskriftsartikel (refereegranskat)abstract
- The variability in transcription factor concentration among cells is an important developmental determinant, yet how variability is controlled remains poorly understood. Studies of variability have focused predominantly on monitoring mRNA production noise. Little information exists about transcription factor protein variability, as this requires the use of quantitative methods with single-molecule sensitivity. Using Fluorescence Correlation Spectroscopy (FCS), we have characterized the concentration and variability of 14 endogenously tagged TFs in live Drosophila imaginal discs. For the Hox TF Antennapedia, we investigated whether protein variability results from random stochastic events or is developmentally regulated. We found that Antennapedia transitioned from low concentration/high variability early, to high concentration/low variability later, in development. FCS and temporally resolved genetic studies uncovered that Antennapedia itself is necessary and sufficient to drive a developmental regulatory switch from auto-activation to auto-repression, thereby reducing variability. This switch is controlled by progressive changes in relative concentrations of preferentially activating and repressing Antennapedia isoforms, which bind chromatin with different affinities. Mathematical modeling demonstrated that the experimentally supported auto-regulatory circuit can explain the increase of Antennapedia concentration and suppression of variability over time.
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| 14. |
- Papadopoulos, Dimitrios K., et al.
(författare)
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Probing the kinetic landscape of Hox transcription factor-DNA binding in live cells by massively parallel Fluorescence Correlation Spectroscopy
- 2015
-
Ingår i: Mechanisms of Development. - : Elsevier BV. - 0925-4773 .- 1872-6356. ; 138, s. 218-225
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Tidskriftsartikel (refereegranskat)abstract
- Hox genes encode transcription factors that control the formation of body structures, segment-specifically along the anterior-posterior axis of metazoans. Hox transcription factors bind nuclear DNA pervasively and regulate a plethora of target genes, deploying various molecular mechanisms that depend on the developmental and cellular context. To analyze quantitatively the dynamics of their DNA-binding behavior we have used confocal laser scanning microscopy (CLSM), single-point fluorescence correlation spectroscopy (FCS), fluorescence cross-correlation spectroscopy (FCCS) and bimolecular fluorescence complementation (BiFC). We show that the Hox transcription factor Sex combs reduced (Scr) forms dimers that strongly associate with its specific fork head binding site (fkh250) in live salivary gland cell nuclei. In contrast, dimers of a constitutively inactive, phosphomimicking variant of Scr show weak, non-specific DNA-binding. Our studies reveal that nuclear dynamics of Scr is complex, exhibiting a changing landscape of interactions that is difficult to characterize by probing one point at a time. Therefore, we also provide mechanistic evidence using massively parallel FCS (mpFCS). We found that Scr dimers are predominantly formed on the DNA and are equally abundant at the chromosomes and an introduced multimeric fkh250 binding-site, indicating different mobilities, presumably reflecting transient binding with different affinities on the DNA. Our proof-of-principle results emphasize the advantages of mpFCS for quantitative characterization of fast dynamic processes in live cells.
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| 15. |
- Papadopoulos, Evangelos, et al.
(författare)
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Solution structure and biophysical properties of MqsA, a Zn-containing antitoxin from Escherichia coli
- 2012
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Ingår i: Biochimica et Biophysica Acta - Proteins and Proteomics. - : Elsevier BV. - 1570-9639 .- 1878-1454. ; 1824:12, s. 1401-1408
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Tidskriftsartikel (refereegranskat)abstract
- The gene ygiT (mqsA) of Escherichia coli encodes MqsA, the antitoxin of the motility quorum sensing regulator (MqsR). Both proteins are considered to form a DNA binding complex and to be involved in the formation of biofilms and persisters. We have determined the three-dimensional solution structure of MqsA by high-resolution NMR. The protein comprises a well-defined N-terminal domain with a Zn finger motif usually found in eukaryotes, and a defined C-terminal domain with a typical prokaryotic DNA binding helix-turn-helix motif. The two well-defined domains of MqsA have almost identical structure in solution and in the two published crystal structures of dimeric MqsA bound to either MqsR or DNA. However, the connection of the two domains with a flexible linker yields a large variety of possible conformations in solution, which is not reflected in the crystal structures. MqsA binds Zn with all four cysteines, a stoichiometry of 1:1 and a femtomolar affinity (K-a >= 10(17) M-1 at 23 degrees C, pH 7.0).
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| 16. |
- Radoi, Vlad, et al.
(författare)
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Non-Peptide Opioids Differ in Effects on Mu-Opioid (MOP) and Serotonin 1A (5-HT1A) Receptors Heterodimerization and Cellular Effectors (Ca2+, ERK 1/2 and p38) Activation
- 2022
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Ingår i: Molecules. - : MDPI AG. - 1431-5157 .- 1420-3049. ; 27:7
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Tidskriftsartikel (refereegranskat)abstract
- The importance of the dynamic interplay between the opioid and the serotonin neuromodulatory systems in chronic pain is well recognized. In this study, we investigated whether these two signalling pathways can be integrated at the single-cell level via direct interactions between the mu-opioid (MOP) and the serotonin 1A (5-HT1A) receptors. Using fluorescence cross-correlation spectroscopy (FCCS), a quantitative method with single-molecule sensitivity, we characterized in live cells MOP and 5-HT1A interactions and the effects of prolonged (18 h) exposure to selected non-peptide opioids: morphine, codeine, oxycodone and fentanyl, on the extent of these interactions. The results indicate that in the plasma membrane, MOP and 5-HT1A receptors form heterodimers that are characterized with an apparent dissociation constant K-d(app) = (440 +/- 70) nM). Prolonged exposure to all non-peptide opioids tested facilitated MOP and 5-HT1A heterodimerization and stabilized the heterodimer complexes, albeit to a different extent: K-d,Fentanyl(app) = (80 +/- 70) nM), K-d,FMorphine(app) = (200 +/- 70) nM, K-d,Codeine(app) = (100 +/- 70) nM and K-d,(app)(Oxycodone) = (200 +/- 70) nM. The non-peptide opioids differed also in the extent to which they affected the mitogen-activated protein kinases (MAPKs) p38 and the extracellular signal-regulated kinase (Erk1/2), with morphine, codeine and fentanyl activating both pathways, whereas oxycodone activated p38 but not ERK1/2. Acute stimulation with different non-peptide opioids differently affected the intracellular Ca2+ levels and signalling dynamics. Hypothetically, targeting MOP-5-HT1A heterodimer formation could become a new strategy to counteract opioid induced hyperalgesia and help to preserve the analgesic effects of opioids in chronic pain.
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| 17. |
- Solé-Domènech, Santiago, et al.
(författare)
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Localization of cholesterol, amyloid and glia in Alzheimer's disease transgenic mouse brain tissue using time-of-flight secondary ion mass spectrometry (ToF-SIMS) and immunofluorescence imaging
- 2013
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Ingår i: Acta Neuropathologica. - : Springer Science and Business Media LLC. - 0001-6322 .- 1432-0533. ; 125:1, s. 145-157
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Tidskriftsartikel (refereegranskat)abstract
- The spatial distributions of lipids, amyloid-beta deposits, markers of neurons and glial cells were imaged, at submicrometer lateral resolution, in brain structures of a mouse model of Alzheimer's disease using a new methodology that combines time-of-flight secondary ion mass spectrometry (ToF-SIMS) and confocal fluorescence microscopy. The technology, which enabled us to simultaneously image the lipid and glial cell distributions in Tg2576 mouse brain structures, revealed micrometer-sized cholesterol accumulations in hippocampal regions undergoing amyloid-beta deposition. Such cholesterol granules were either associated with individual amyloid deposits or spread over entire regions undergoing amyloidogenesis. Subsequent immunohistochemical analysis of the same brain regions showed increased microglial and astrocytic immunoreactivity associated with the amyloid deposits, as expected from previous studies, but did not reveal any particular astrocytic or microglial feature correlated with cholesterol granulation. However, dystrophic neurites as well as presynaptic vesicles presented a distribution similar to that of cholesterol granules in regions undergoing amyloid-beta accumulation, thus indicating that these neuronal endpoints may retain cholesterol in areas with lesions. In conclusion, the present study provides evidence for an altered cholesterol distribution near amyloid deposits that would have been missed by several other lipid analysis methods, and opens for the possibility to study in detail the putative liaison between lipid environment and protein structure and function in Alzheimer's disease.
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| 18. |
- Tiiman, Ann, et al.
(författare)
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Amyloidogenic Nanoplaques in Blood Serum of Patients with Alzheimer's Disease Revealed by Time-Resolved Thioflavin T Fluorescence Intensity Fluctuation Analysis
- 2019
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Ingår i: Journal of Alzheimer's Disease. - : IOS PRESS. - 1387-2877 .- 1875-8908. ; 68:2, s. 571-582
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Tidskriftsartikel (refereegranskat)abstract
- Background: Biomarkers are central to current research on molecular mechanisms underlying Alzheimer's disease (AD). Their further development is of paramount importance for understanding pathophysiological processes that eventually lead to disease onset. Biomarkers are also crucial for early disease detection, before clinical manifestation, and for development of new disease modifying therapies. Objective: The overall aim of this work is to develop a minimally invasive method for fast, ultra-sensitive and cost-effective detection of structurally modified peptide/protein self-assemblies in the peripheral blood and in other biological fluids. Specifically, we focus here on using this method to detect structured amyloidogenic oligomeric aggregates in the blood serum of apparently healthy individuals and patients in early AD stage, and measure their concentration and size. Methods: Time-resolved detection of Thioflavin T (ThT) fluorescence intensity fluctuations in a sub-femtoliter observation volume element was used to identify in blood serum ThT-active structured amyloidogenic oligomeric aggregates, hereafter called nanoplaques, and measure with single-particle sensitivity their concentration and size. Results: The concentration and size of structured amyloidogenic nanoplaques are significantly higher in the blood serum of individuals diagnosed with AD than in control subjects. Conclusion: A new method with the ultimate, single-particle sensitivity was successfully developed. The proposed approach neither relies on the use of immune-based probes, nor on the use of radiotracers, signal-amplification or protein separation techniques, and provides a minimally invasive test for fast and cost-effective early determination of structurally modified peptides/proteins in the peripheral blood, as shown here, but also in other biological fluids.
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| 19. |
- Tiiman, Ann, et al.
(författare)
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Heterogeneity and Turnover of Intermediates during Amyloid-beta (A beta) Peptide Aggregation Studied by Fluorescence Correlation Spectroscopy
- 2015
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 54:49, s. 7203-7211
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Tidskriftsartikel (refereegranskat)abstract
- Self-assembly of amyloid beta (A beta) peptide molecules into large aggregates is a naturally occurring process driven in aqueous solution by a dynamic interplay between hydrophobic interactions among A beta molecules, which promote aggregation, and steric and overall electrostatic hindrance, which stifles it. A beta self-association is entropically unfavorable, as it implies order increase in the system, but under favorable kinetic conditions, the process proceeds at appreciable rates, yielding A beta aggregates of different sizes and structures. Despite the great relevance and extensive research efforts, detailed kinetic mechanisms underlying A beta aggregation remain only partially understood. In this study, fluorescence correlation spectroscopy (FCS) and Thioflavin T (ThT) were used to monitor the time dependent growth of structured aggregates and characterize multiple components during the aggregation of A beta peptides in a heterogeneous aqueous solution. To this aim, we collected data during a relatively large number of observation periods, 30 consecutive measurements lasting 10 s each, at what we consider to be a constant time point in the slow aggregation process. This approach enabled monitoring the formation of nanomolar concentrations of structured amyloid aggregates and demonstrated the changing distribution of amyloid aggregate sizes throughout the aggregation process. We identified aggregates of different sizes with molecular weight from 260 to more than 1 x 10(6) kDa and revealed the hitherto unobserved kinetic turnover of intermediates during A beta aggregation. The effect of different A beta concentrations, A beta:ThT ratios, differences between the 40 (A beta 40) and 42 (A beta 42) residue long variants of A beta, and the effect of stirring were also examined.
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| 20. |
- Vasconcelos, Luis, et al.
(författare)
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Simultaneous membrane interaction of amphipathic peptide monomers, self-aggregates and cargo complexes detected by fluorescence correlation spectroscopy
- 2018
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Ingår i: Biochimica et Biophysica Acta - Biomembranes. - : Elsevier BV. - 0005-2736 .- 1879-2642. ; 1860:2, s. 491-504
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Tidskriftsartikel (refereegranskat)abstract
- Peptides able to translocate cell membranes while carrying macromolecular cargo, as cell-penetrating peptides (CPPs), can contribute to the field of drug delivery by enabling the transport of otherwise membrane impermeable molecules. Formation of non-covalent complexes between amphipathic peptides and oligonucleotides is driven by electrostatic and hydrophobic interactions. Here we investigate and quantify the coexistence of distinct molecular species in multiple equilibria, namely peptide monomer, peptide self-aggregates and peptide/oligonucleotide complexes. As a model for the complexes, we used a stearylated peptide from the PepFect family, PF14 and siRNA. PF14 has a cationic part and a lipid part, resembling some characteristics of cationic lipids. Fluorescence correlation spectroscopy (FCS) and fluorescence cross-correlation spectroscopy (FCCS) were used to detect distinct molecular entities in solution and at the plasma membrane of live cells. For that, we labeled the peptide with carboxyrhodamine 6G and the siRNA with Cyanine 5. We were able to detect fluorescent entities with diffusional properties characteristic of the peptide monomer as well as of peptide aggregates and peptide/oligonucleotide complexes. Strategies to avoid peptide adsorption to solid surfaces and self-aggregation were developed and allowed successful FCS measurements in solution and at the plasma membrane. The ratio between the detected molecular species was found to vary with pH, peptide concentration and the proximity to the plasma membrane. The present results suggest that the diverse cellular uptake mechanisms, often reported for amphipathic CPPs, might result from the synergistic effect of peptide monomers, self-aggregates and cargo complexes, distributed unevenly at the plasma membrane.
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| 21. |
- Vukojević, Vladana, et al.
(författare)
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ELOA - equine lysozyme complexes with oleic acid. structure and cytotoxicity studied by bio-imaging techniques
- 2014
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Ingår i: Bio-nanoimaging. - : Academic Press. - 9780123944313 ; , s. 453-462
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Bokkapitel (refereegranskat)abstract
- Complexes of equine lysozyme with oleic acid (ELOA) belong to the group of proteinaceous complexes with oleic acid, among which 'human α-lactalbumin made lethal to tumor cells' (HAMLET) was the first to be discovered and is the most well known. The major functional feature of these complexes is their newly acquired cytotoxicity, which is absent in the original protein molecules; this indicates that the interaction of these proteins with oleic acid can create a new functionality. Modern single molecule-single cell techniques, such as atomic force microscopy, fluorescent correlation spectroscopy and confocal microscopy, together with other biophysical and biochemical methods, can provide a powerful insight into the molecular mechanisms of the ELOA interactions with cells and, in particular, how the cell membrane is targeted. HAMLET-type complexes have significant therapeutic potential in combating cancers, hence, understanding their molecular interactions with cells will help us to use them under a variety of in vivo conditions for the elimination of specific, unwanted cells.
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| 22. |
- Vukojevic, Vladana, et al.
(författare)
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Fluorescence Imaging with Single-Molecule Sensitivity and Fluorescence Correlation Spectroscopy of Cell-Penetrating Neuropeptides
- 2011
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Ingår i: Neuropeptides. - Totowa, NJ : Humana Press. - 9781617793097 ; 789, s. 147-70
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Bokkapitel (refereegranskat)abstract
- Neuropeptide plasma membrane interactions in the absence of a corresponding specific receptor may result in neuropeptide translocation into the cell. Trans location across the plasma membrane may represent a previously unknown mechanism by which neuropeptides can signal information to the cell interior. We introduce here two complementary optical methods with single-molecule sensitivity, fluorescence imaging with avalanche photodiode detectors (APD imaging) and fluorescence correlation spectroscopy (FCS), and demonstrate how they may be applied for the analysis of neuropeptide ability to penetrate into live cells in real time. APD imaging enables us to visualize fluorescently labeled neuropeptide molecules at very low, physiologically relevant concentrations, whereas FCS enables us to characterize quantitatively their concentration and diffusion properties in different cellular compartments. Application of these methodologies for the analysis of the endogenous opioid peptide dynorphin A (Dyn A), a ligand for the kappa-opioid receptor (KOP), demonstrated that this neuropeptide may translocate across the plasma membrane of living cells and enter the cellular interior without binding to its cognate receptor.
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| 23. |
- Vukojevic, Vladana, et al.
(författare)
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Lipoprotein complex of equine lysozyme with oleic acid (ELOA) interactions with the plasma membrane of live cells
- 2010
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Ingår i: Langmuir. - : American Chemical Society. - 0743-7463 .- 1520-5827. ; 26:18, s. 14782-14787
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Tidskriftsartikel (refereegranskat)abstract
- Recent evidence supports the idea that early aggregates, protein, and lipoprotein oligomers but not large aggregates like fibrils that are formed at late stages of the aggregation process are responsible for cytotoxicity. Oligomers can interact with the cellular plasma membrane affecting its structure and/or dynamics or may be taken up by the cells. In either case, disparate cascades of molecular interactions are activated in the attempt to counteract the disturbance induced by the oligomers. If unsuccessful, cell death follows. Here, we study the molecular and cellular mechanisms underlying PC12 cell death caused by ELOA oligomers. ELOA, a lipoprotein complex formed by equine lysozyme (EL) and oleic acid (OA), induces cell death in all tested cell lines, but the actual mechanism of its action is not known. We have used methods with single-molecule sensitivity, fluorescence correlation spectroscopy (FCS), fluorescence cross-correlation spectroscopy (FCCS), and confocal laser scanning microscopy (CLSM) imaging by avalanche photodiodes (APD), so-called APD imaging, to study ELOA interactions with the plasma membrane in live PC12 cells. We detected ELOA accumulation in the cell surroundings, observed ELOA interactions with the plasma membrane, and local changes in plasma membrane lipid dynamics in the vicinity of ELOA complexes. These interactions resulted in plasma membrane rupture, followed by rapid influx and distribution of ELOA inside the already dead cell. In order to probe the ELOA−plasma membrane interaction sites at the molecular and atomic levels, the ELOA complexes were further studied by photochemically induced dynamic nuclear polarization (photo-CIDNP) spectroscopy, nuclear magnetic resonance (NMR) and atomic force microscopy (AFM). We observed a novel mechanism of oligomer toxicity−cell death induced by continuous disturbance of the plasma membrane, eventually causing permanent plasma membrane damage and identified the sites in ELOA that are potentially involved in the interactions with the plasma membrane.
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| 24. |
- Vukojević, Vladana, et al.
(författare)
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Mu-opioid receptor activation in live cells
- 2008
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Ingår i: The FASEB Journal. - : Wiley. - 0892-6638 .- 1530-6860. ; 22:10, s. 3537-3548
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Tidskriftsartikel (refereegranskat)abstract
- Interaction of the mu-opioid receptor (MOP) with selected ligands was investigated in live cells using advanced imaging by confocal laser scanning microscopy integrated with fluorescence correlation spectroscopy and fluorescence cross-correlation spectroscopy. In PC12 cells stably transformed to express the fluorescently labeled MOP-enhanced green fluorescent protein construct, two pools of MOP were identified that could be discriminated by differences in their lateral mobility in the cell membrane. The majority of MOP receptors (80 +/- 10%) were characterized by a diffusion coefficient D-MOP,D-1 = (4 +/- 2) X 10(-11) m(2) s(-1), compared with the slowly moving fraction, D-MOP,D- 2 = (4 +/- 2) x 10(-12) m(2) s(-1). On stimulation with selected agonists ([D-Ala(2),N-MePhe(4),Gly-ol(5)]enkephalin, enkephalin-heptapeptide Tyr-Gly-Gly-Phe-Met-Arg-Phe, morphine, and methadone), surface density of the MOP decreased, whereas the lateral mobility increased. In contrast, antagonists (naloxone and naltrexone) "froze" the receptor in the membrane, i.e., increased MOP surface density and decreased lateral mobility. Agonist activation was also accompanied by pronounced changes in the dynamics of plasma membrane lipids, as revealed by the general lipid marker 1,1'-dioctadecyl-3,3,3',3'-tetramethylindo-carbocyanine perchlorate dye. The results provide new information about MOP activation in live cells at the molecular level, with a special focus on the dynamics of the intricate interplay between this receptor and the surrounding lipids.
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| 25. |
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