| 1. |
- Abrahamsson, S., et al.
(författare)
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Multifocus structured illumination microscopy for fast volumetric super-resolution imaging
- 2017
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Ingår i: Biomedical Optics Express. - : OSA - The Optical Society. - 2156-7085. ; 8:9, s. 4135-4140
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Tidskriftsartikel (refereegranskat)abstract
- We here report for the first time the synergistic implementation of structured illumination microscopy (SIM) and multifocus microscopy (MFM). This imaging modality is designed to alleviate the problem of insufficient volumetric acquisition speed in superresolution biological imaging. SIM is a wide-field super-resolution technique that allows imaging with visible light beyond the classical diffraction limit. Employing multifocus diffractive optics we obtain simultaneous wide-field 3D imaging capability in the SIM acquisition sequence, improving volumetric acquisition speed by an order of magnitude. Imaging performance is demonstrated on biological specimens.
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| 2. |
- Agostinho, Ana, et al.
(författare)
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High density of REC8 constrains sister chromatid axes and prevents illegitimate synaptonemal complex formation
- 2016
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Ingår i: EMBO Reports. - Stockholm : Wiley-VCH Verlagsgesellschaft. - 1469-221X .- 1469-3178. ; 17:6, s. 901-913
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Tidskriftsartikel (refereegranskat)abstract
- During meiosis, cohesin complexes mediate sister chromatid cohesion (SCC), synaptonemal complex (SC) assembly and synapsis. Here, using super-resolution microscopy, we imaged sister chromatid axes in mouse meiocytes that have normal or reduced levels of cohesin complexes, assessing the relationship between localization of cohesin complexes, SCC and SC formation. We show that REC8 foci are separated from each other by a distance smaller than 15% of the total chromosome axis length in wild-type meiocytes. Reduced levels of cohesin complexes result in a local separation of sister chromatid axial elements (LSAEs), as well as illegitimate SC formation at these sites. REC8 but not RAD21 or RAD21L cohesin complexes flank sites of LSAEs, whereas RAD21 and RAD21L appear predominantly along the separated sister-chromatid axes. Based on these observations and a quantitative distribution analysis of REC8 along sister chromatid axes, we propose that the high density of randomly distributed REC8 cohesin complexes promotes SCC and prevents illegitimate SC formation.
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| 3. |
- Agostinho, A., et al.
(författare)
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Sexual dimorphism in the width of the mouse synaptonemal complex
- 2018
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Ingår i: Journal of Cell Science. - : Company of Biologists Ltd. - 0021-9533 .- 1477-9137. ; 131:5
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Tidskriftsartikel (refereegranskat)abstract
- Sexual dimorphism has been used to describe morphological differences between the sexes, but can be extended to any biologically related process that varies between males and females. The synaptonemal complex (SC) is a tripartite structure that connects homologous chromosomes in meiosis. Here, aided by superresolution microscopy techniques, we show that the SC is subject to sexual dimorphism, in mouse germ cells. We have identified a significantly narrower SC in oocytes and have established that this difference does not arise from a different organization of the lateral elements nor from a different isoform of transverse filament protein SYCP1. Instead, we provide evidence for the existence of a narrower central element and a different integration site for the C-termini of SYCP1, in females. In addition to these female-specific features, we speculate that post-translation modifications affecting the SYCP1 coiled-coil region could render a more compact conformation, thus contributing to the narrower SC observed in females.
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| 4. |
- Akkuratov, Evgeny E., et al.
(författare)
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Ouabain Modulates the Functional Interaction Between Na,K-ATPase and NMDA Receptor.
- 2020
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Ingår i: Molecular Neurobiology. - : Springer Science and Business Media LLC. - 0893-7648 .- 1559-1182. ; 57:10, s. 4018-4030
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Tidskriftsartikel (refereegranskat)abstract
- The N-methyl-D-aspartate (NMDA) receptor plays an essential role in glutamatergic transmission and synaptic plasticity and researchers are seeking for different modulators of NMDA receptor function. One possible mechanism for its regulation could be through adjacent membrane proteins. NMDA receptors coprecipitate with Na,K-ATPase, indicating a potential interaction of these two proteins. Ouabain, a mammalian cardiotonic steroid that specifically binds to Na,K-ATPase and affects its conformation, can protect from some toxic effects of NMDA receptor activation. Here we have examined whether NMDA receptor activity and downstream effects can be modulated by physiological ouabain concentrations. The spatial colocalization between NMDA receptors and the Na,K-ATPase catalytic subunits on dendrites of cultured rat hippocampal neurons was analyzed with super-resolution dSTORM microscopy. The functional interaction was analyzed with calcium imaging of single hippocampal neurons exposed to 10 μM NMDA in presence and absence of ouabain and by determination of the ouabain effect on NMDA receptor-dependent long-term potentiation. We show that NMDA receptors and the Na,K-ATPase catalytic subunits alpha1 and alpha3 exist in same protein complex and that ouabain in nanomolar concentration consistently reduces the calcium response to NMDA. Downregulation of the NMDA response is not associated with internalization of the receptor or with alterations in its state of Src phosphorylation. Ouabain in nanomolar concentration elicits a long-term potentiation response. Our findings suggest that ouabain binding to a fraction of Na,K-ATPase molecules that cluster with the NMDA receptors will, via a conformational effect on the NMDA receptors, cause moderate but consistent reduction of NMDA receptor response at synaptic activation.
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| 5. |
- Bernhem, Kristoffer, et al.
(författare)
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Quantification of endogenous and exogenous protein expressions of Na,K-ATPase with super-resolution PALM/STORM imaging
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Annan publikation (populärvet., debatt m.m.)abstract
- Transient transfection of fluorescent fusion proteins is a key enabling technology in fluorescent microscopy to spatio-temporally map cellular protein distributions. Transient transfection of proteins may however bypass normal regulation of expression, leading to overexpression artefacts like misallocations and excess amounts. In this study we investigate the ability to quantitatively monitor endogenous and exogenous protein expression competition on the single molecule level. Through incorporation of an N-terminal hemagglutinin (HA) epitope to amMaple3 fused Na,K-ATPase (α1 isoform), using PALM and STORM imaging we investigatethe increase in plasma membrane density at the cost of competitive expression. Quantification of plasma membrane protein density revealed a time dependent increase over time of totalprotein content. Results show that plasma membrane densities increased by more than 60%,comparing 17h and 41h transfection times, whilst endogenous levels were simultaneously reduced by 20 %.
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| 6. |
- Bernhem, Kristoffer, et al.
(författare)
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Quantification of endogenous and exogenous protein expressions of Na,K-ATPase with super-resolution PALM/STORM imaging
- 2018
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203.
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Tidskriftsartikel (refereegranskat)abstract
- Transient transfection of fluorescent fusion proteins is a key enabling technology in fluorescent microscopy to spatio-temporally map cellular protein distributions. Transient transfection of proteins may however bypass normal regulation of expression, leading to overexpression artefacts like misallocations and excess amounts. In this study we investigate the use of STORM and PALM microscopy to quantitatively monitor endogenous and exogenous protein expression. Through incorporation of an N-terminal hemagglutinin epitope to a mMaple3 fused Na,K-ATPase (α1 isoform), we analyze the spatial and quantitative changes of plasma membrane Na,K-ATPase localization during competitive transient expression. Quantification of plasma membrane protein density revealed a time dependent increase of Na,K-ATPase, but no increase in size of protein clusters. Results show that after 41h transfection, the total plasma membrane density of Na,K-ATPase increased by 63% while the endogenous contribution was reduced by 16%.
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| 7. |
- Bernhem, Kristoffer, et al.
(författare)
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Super-resolution microscopy reveals that Na+/K+-ATPase signaling protects against glucose-induced apoptosis by deactivating Bad
- 2021
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Ingår i: Cell Death and Disease. - : Springer Nature. - 2041-4889 .- 2041-4889. ; 12:8
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Tidskriftsartikel (refereegranskat)abstract
- Activation of the apoptotic pathway is a major cause of progressive loss of function in chronic diseases such as neurodegenerative and diabetic kidney diseases. There is an unmet need for an anti-apoptotic drug that acts in the early stage of the apoptotic process. The multifunctional protein Na+,K+-ATPase has, in addition to its role as a transporter, a signaling function that is activated by its ligand, the cardiotonic steroid ouabain. Several lines of evidence suggest that sub-saturating concentrations of ouabain protect against apoptosis of renal epithelial cells, a common complication and major cause of death in diabetic patients. Here, we induced apoptosis in primary rat renal epithelial cells by exposing them to an elevated glucose concentration (20mM) and visualized the early steps in the apoptotic process using super-resolution microscopy. Treatment with 10nM ouabain interfered with the onset of the apoptotic process by inhibiting the activation of the BH3-only protein Bad and its translocation to mitochondria. This occurred before the pro-apoptotic protein Bax had been recruited to mitochondria. Two ouabain regulated and Akt activating Ca2+/calmodulin-dependent kinases were found to play an essential role in the ouabain anti-apoptotic effect. Our results set the stage for further exploration of ouabain as an anti-apoptotic drug in diabetic kidney disease as well as in other chronic diseases associated with excessive apoptosis.
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| 8. |
- Blom, Hans, et al.
(författare)
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Nearest neighbor analysis of dopamine D1 receptors and Na plus -K plus -ATPases in dendritic spines dissected by STED microscopy
- 2012
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Ingår i: Microscopy research and technique (Print). - : Wiley. - 1059-910X .- 1097-0029. ; 75:2, s. 220-228
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Tidskriftsartikel (refereegranskat)abstract
- Protein localization in dendritic spines is the focus of intense investigations within neuroscience. Applications of super-resolution microscopy to dissect nanoscale protein distributions, as shown in this work with dual-color STED, generate spatial correlation coefficients having quite small values. This means that colocalization analysis to some extent looses part of its correlative impact. In this study we thus introduced nearest neighbor analysis to quantify the spatial relations between two important proteins in neurons, the dopamine D1 receptor and Na+,K+-ATPase. The analysis gave new information on how dense the D1 receptor and Na+,K+-ATPase constituting nanoclusters are located both with respect to the homogenous (self to same) and the heterogeneous (same to other) topology. The STED dissected nanoscale topologies provide evidence for both a joint as well as a separated confinement of the D1 receptor and the Na+,K+-ATPase in the postsynaptic areas of dendritic spines. This confined topology may have implications for generation of local sodium gradients and for structural and functional interactions modulating slow synaptic transmission processes. Microsc. Res. Tech., 2011.
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| 9. |
- Blom, Hans, et al.
(författare)
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Sodium pump organization in dendritic spines
- 2016
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Ingår i: NEUROPHOTONICS. - : SPIE - International Society for Optical Engineering. - 2329-423X. ; 3:4
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Tidskriftsartikel (refereegranskat)abstract
- Advancement in fluorescence imaging with the invention of several super-resolution microscopy modalities (e.g., PALM/STORM and STED) has opened up the possibility of deciphering molecular distributions on the nanoscale. In our quest to better elucidate postsynaptic protein distribution in dendritic spines, we have applied these nanoscopy methods, where generated results could help improve our understanding of neuronal functions. In particular, we have investigated the principal energy transformer in the brain, i.e., the Na+; K+-ATPase (or sodium pump), an essential protein responsible for maintaining resting membrane potential and a major controller of intracellular ion homeostasis. In these investigations, we have focused on estimates of protein amount, giving assessments of how variations may depend on labeling strategies, sample analysis, and choice of nanoscopic imaging method, concluding that all can be critical factors for quantification. We present a comparison of these results and discuss the influences this may have for homeostatic sodium regulation in neurons and energy consumption.
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| 10. |
- Blom, Hans, et al.
(författare)
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Spatial Distribution of DARPP-32 in Dendritic Spines
- 2013
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:9, s. e75155-
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Tidskriftsartikel (refereegranskat)abstract
- The phosphoprotein DARPP-32 (dopamine and cyclic adenosine 3́, 5́-monophosphate-regulated phosphoprotein, 32 kDa) is an important component in the molecular regulation of postsynaptic signaling in neostriatum. Despite the importance of this phosphoprotein, there is as yet little known about the nanoscale distribution of DARPP-32. In this study we applied superresolution stimulated emission depletion microscopy (STED) to assess the expression and distribution of DARPP-32 in striatal neurons. Primary culture of striatal neurons were immunofluorescently labeled for DARPP-32 with Alexa-594 and for the dopamine D1 receptor (D1R) with atto-647N. Dual-color STED microscopy revealed discrete localizations of DARPP-32 and D1R in the spine structure, with clustered distributions in both head and neck. Dissected spine structures reveal that the DARPP-32 signal rarely overlapped with the D1R signal. The D1R receptor is positioned in an "aggregated" manner primarily in the spine head and to some extent in the neck, while DARPP-32 forms several neighboring small nanoclusters spanning the whole spine structure. The DARPP-32 clusters have a mean size of 52 +/- 6 nm, which is close to the resolution limit of the microscope and corresponds to the physical size of a few individual phosphoprotein immunocomplexes. Dissection of synaptic proteins using superresolution microscopy gives possibilities to reveal in better detail biologically relevant information, as compared to diffraction-limited microscopy. In this work, the dissected postsynaptic topology of the DARPP-32 phosphoprotein provides strong evidence for a compartmentalized and confined distribution in dendritic spines. The protein topology and the relatively low copy number of phosphoprotein provides a conception of DARPP-32's possibilities to fine-tune the regulation of synaptic signaling, which should have an impact on the performance of the neuronal circuits in which it is expressed.
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