| 1. |
- Singh, Abeer Prakash, 1988, et al.
(author)
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Molecular Connectivity of Mitochondrial Gene Expression and OXPHOS Biogenesis
- 2020
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In: Molecular Cell. - : Elsevier BV. - 1097-2765 .- 1097-4164. ; 79:6
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Journal article (peer-reviewed)abstract
- Mitochondria contain their own gene expression systems, including membrane-bound ribosomes dedicated to synthesizing a few hydrophobic subunits of the oxidative phosphorylation (OXPHOS) complexes. We used a proximity-dependent biotinylation technique, BiolD, coupled with mass spectrometry to delineate in baker's yeast a comprehensive network of factors involved in biogenesis of mitochondrial encoded proteins. This mitochondrial gene expression network (MiGENet) encompasses proteins involved in transcription, RNA processing, translation, or protein biogenesis. Our analyses indicate the spatial organization of these processes, thereby revealing basic mechanistic principles and the proteins populating strategically important sites. For example, newly synthesized proteins are directly handed over to ribosomal tunnel exit-bound factors that mediate membrane insertion, co-factor acquisition, or their mounting into OXPHOS complexes in a special early assembly hub. Collectively, the data reveal the connectivity of mitochondrial gene expression, reflecting a unique tailoring of the mitochondrial gene expression system.
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| 2. |
- Aufschnaiter, Andreas, Dr. rer. nat. 1988-, et al.
(author)
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Yeast Mitoribosome Purification and Analyses by Sucrose Density Centrifugation and Immunoprecipitation
- 2023
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In: The Mitoribosome. - : Humana Press. - 9781071631706 - 9781071631713 ; , s. 119-132
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Book chapter (other academic/artistic)abstract
- Mitochondrial protein biosynthesis is maintained by an interplay between the mitochondrial ribosome (mitoribosome) and a large set of protein interaction partners. This interactome regulates a diverse set of functions, including mitochondrial gene expression, translation, protein quality control, and respiratory chain assembly. Hence, robust methods to biochemically and structurally analyze this molecular machinery are required to understand the sophisticated regulation of mitochondrial protein biosynthesis. In this chapter, we present detailed protocols for immunoprecipitation, sucrose cushions, and linear sucrose gradients to purify and analyze mitoribosomes and their interaction partners.
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| 3. |
- Aufschnaiter, Andreas, Dr. rer. nat. 1988-, et al.
(author)
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Yeast Mitoribosome Purification and Analyses by Sucrose Density Centrifugation and Immunoprecipitation
- 2023
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In: Methods in Molecular Biology. - : Humana Press. - 1064-3745 .- 1940-6029. ; , s. 119-132, s. 119-132
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Book chapter (other academic/artistic)abstract
- Mitochondrial protein biosynthesis is maintained by an interplay between the mitochondrial ribosome (mitoribosome) and a large set of protein interaction partners. This interactome regulates a diverse set of functions, including mitochondrial gene expression, translation, protein quality control, and respiratory chain assembly. Hence, robust methods to biochemically and structurally analyze this molecular machinery are required to understand the sophisticated regulation of mitochondrial protein biosynthesis. In this chapter, we present detailed protocols for immunoprecipitation, sucrose cushions, and linear sucrose gradients to purify and analyze mitoribosomes and their interaction partners.
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| 4. |
- Carlström, Andreas, et al.
(author)
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Mrx4 orchestrates cytochrome b biogenesis at the yeast mitoribosomal tunnel exit
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Other publication (other academic/artistic)abstract
- Mitochondrial gene expression is highly regulated to ensure proper stoichiometry with imported proteins expressed from the nucleus. In yeast, one way to regulate mitochondrial translation is through feedback loops involving lowly expressed proteins called translational activators. The expression of cytochrome b (Cytb or COB), a core subunit of complex III in the respiratory chain, is regulated by five proteins called Cbp1, Cbs1, Cbs2 and Cbp3-Cbp6. All of these translational activators are needed for activation of COB translation. Here, we have identified the previously uncharacterized inner membrane protein Mrx4 as an additional regulator of Cytb biogenesis. Mrx4 interacts with the large subunit of the mitoribosome, but also with Cbp3-Cbp6 and Cbs2 as shown with crosslinking purifications. Intriguingly, deletion of MRX4 completely restores COB translation in cells devoid of Cbp3-Cbp6, indicating a repressor function of Mrx4. Further experiments using cob::ARG8 reporter strains showed that deletion of MRX4 disrupts the COB translational feedback loop, making Cbp3-Cbp6 dispensible for translation activation. We postulate that this effect is mediated by increased freedom of Cbs2 and Cbs1 to shuttle the COB mRNA to the mRNA exit site, on the mitoribosomal small subunit, and aid in translation initiation. However, disruption of the feedback loop has negative impact on the cell, as both increased levels of oxidate stress and cell death could be observed. This point to an evolutionary advantage of the feedback loop system for the yeast cell, to better adapt to changes in its environment.
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| 5. |
- Carlström, Mattias, et al.
(author)
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Nitric oxide deficiency and increased adenosine response of afferent arterioles in hydronephrotic mice with hypertension
- 2008
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In: Hypertension. - : American Heart Association. - 0194-911X .- 1524-4563. ; 51:5, s. 1386-1392
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Research review (peer-reviewed)abstract
- Afferent arterioles were used to investigate the role of adenosine, angiotensin II, NO, and reactive oxygen species in the pathogenesis of increased tubuloglomerular feedback response in hydronephrosis. Hydronephrosis was induced in wild-type mice, superoxide dismutase-1 overexpressed mice (superoxide-dismutase-1 transgenic), and deficient mice (superoxide dismutase-1 knockout). Isotonic contractions in isolated perfused arterioles and mRNA expression of NO synthase isoforms, adenosine, and angiotensin II receptors were measured. In wild-type mice, N(G)-nitro-L-arginine methyl ester (L-NAME) did not change the basal arteriolar diameter of hydronephrotic kidneys (-6%) but reduced it in control (-12%) and contralateral arterioles (-43%). Angiotensin II mediated a weaker maximum contraction of hydronephrotic arterioles (-18%) than in control (-42%) and contralateral arterioles (-49%). The maximum adenosine-induced constriction was stronger in hydronephrotic (-19%) compared with control (-8%) and contralateral kidneys (+/-0%). The response to angiotensin II became stronger in the presence of adenosine in hydronephrotic kidneys and attenuated in contralateral arterioles. L-NAME increased angiotensin II responses of all of the groups but less in hydronephrotic kidneys. The mRNA expression of endothelial NO synthase and inducible NO synthase was upregulated in the hydronephrotic arterioles. No differences were found for adenosine or angiotensin II receptors. In superoxide dismutase-1 transgenic mice, strong but similar L-NAME response (-40%) was observed for all of the groups. This response was totally abolished in arterioles of hydronephrotic superoxide dismutase-1 knockout mice. In conclusion, hydronephrosis is associated with changes in the arteriolar reactivity of both hydronephrotic and contralateral kidneys. Increased oxidative stress, reduced NO availability, and stronger reactivity to adenosine of the hydronephrotic kidney may contribute to the enhanced tubuloglomerular feedback responsiveness in hydronephrosis and be involved in the development of hypertension.
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| 6. |
- Carlström, Mattias, et al.
(author)
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Superoxide Dismutase 1 Limits Renal Microvascular Remodeling and Attenuates Arteriole and Blood Pressure Responses to Angiotensin II via Modulation of Nitric Oxide Bioavailability
- 2010
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In: Hypertension. - 0194-911X .- 1524-4563. ; 56:5, s. 907-913
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Journal article (peer-reviewed)abstract
- Oxidative stress is associated with vascular remodeling and increased preglomerular resistance that are both implicated in the pathogenesis of renal and cardiovascular disease. Angiotensin II induces superoxide production, which is metabolized by superoxide dismutase (SOD) or scavenged by NO. We investigated the hypothesis that SOD1 regulates renal microvascular remodeling, blood pressure, and arteriolar responsiveness and sensitivity to angiotensin II using SOD1-transgenic (SOD1-tg) and SOD1-knockout (SOD1-ko) mice. Blood pressure, measured telemetrically, rose more abruptly during prolonged angiotensin II infusion in SOD1-ko mice. The afferent arteriole media: lumen ratios were reduced in SOD1-tg and increased in SOD1-ko mice. Afferent arterioles from nontreated wild types had graded contraction to angiotensin II (sensitivity: 10(-9) mol/L; responsiveness: 40%). Angiotensin II contractions were less sensitive (10(-8) mol/L) and responsive (14%) in SOD1-tg but more sensitive (10(-13) mol/L) and responsive (89%) in SOD1-ko mice. Arterioles from SOD1-ko had 4-fold increased superoxide formation with angiotensin II at 10(-9) mol/L. N-G-nitro-L-arginine methyl ester reduced arteriole diameter of SOD1-tg and enhanced angiotensin II sensitivity and responsiveness of wild-type and SOD1-tg mice to the level of SOD1-ko mice. SOD mimetic treatment with Tempol increased arteriole diameter and normalized the enhanced sensitivity and responsiveness to angiotensin II of SOD1-ko mice but did not affect wild-type or SOD1-tg mice. Neither SOD1 deficiency nor overexpression was associated with changes in nitrate/nitrite excretion or renal mRNA expression of NO synthase, NADPH oxidase, or SOD2/SOD3 isoforms and angiotensin II receptors. In conclusion, SOD1 limits afferent arteriole remodeling and reduces sensitivity and responsiveness to angiotensin II by reducing superoxide and maintaining NO bioavailability. This may prevent an early and exaggerated blood pressure response to angiotensin II.
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| 7. |
- Kohler, Andreas, Dr. rer. nat. 1988-, et al.
(author)
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Early fate decision for mitochondrially encoded proteins by a molecular triage
- 2023
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In: Molecular Cell. - : Cell Press. - 1097-2765 .- 1097-4164. ; 83:19
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Journal article (peer-reviewed)abstract
- Folding of newly synthesized proteins poses challenges for a functional proteome. Dedicated protein quality control (PQC) systems either promote the folding of nascent polypeptides at ribosomes or, if this fails, ensure their degradation. Although well studied for cytosolic protein biogenesis, it is not understood how these processes work for mitochondrially encoded proteins, key subunits of the oxidative phosphorylation (OXPHOS) system. Here, we identify dedicated hubs in proximity to mitoribosomal tunnel exits coordinating mitochondrial protein biogenesis and quality control. Conserved prohibitin (PHB)/m-AAA protease supercomplexes and the availability of assembly chaperones determine the fate of newly synthesized proteins by molecular triaging. The localization of these competing activities in the vicinity of the mitoribosomal tunnel exit allows for a prompt decision on whether newly synthesized proteins are fed into OXPHOS assembly or are degraded.
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| 8. |
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| 9. |
- Berner, Andreas, et al.
(author)
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STREET: Swedish Tool for Risk/Resource Estimation at EvenTs. Part one, risk assessment – face validity and inter–rater reliability
- 2015
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In: Journal of Acute Disease. - 2221-6189. ; 4:1, s. 37-43
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Journal article (peer-reviewed)abstract
- Objective To develop a validated and generalized high reliability organizations collaborative tool in order to conduct common assessments and information sharing of potential risks during mass-gatherings. Methods The Swedish resource and risk estimation guide was used as foundation for the development of the generalized collaborative tool, by three different expert groups, and then analyzed. Analysis of inter-rater reliability was conducted through simulated cases that showed weighted and unweight κ-statistics. Results The results revealed a mean of unweight κ-value from the three cases of 0.37 and a mean accuracy of 62% of the tool. Conclusions The collaboration tool, “STREET”, showed acceptable reliability and validity to be used as a foundation for high reliability organization collaboration in a simulated environment. However, the lack of reliability in one of the cases highlights the challenges of creating measurable values from simulated cases. A study on real events can provide higher reliability but need, on the other hand, an already developed tool.
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| 10. |
- Carlström, Andreas, 1988, et al.
(author)
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Insights into conformational changes in cytochrome b during the early steps of its maturation
- 2024
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In: FEBS LETTERS. - 0014-5793 .- 1873-3468. ; 598:11, s. 1438-1448
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Journal article (peer-reviewed)abstract
- Membrane proteins carrying redox cofactors are key subunits of respiratory chain complexes, yet the exact path of their folding and maturation remains poorly understood. Here, using cryo-EM and structure prediction via Alphafold2, we generated models of early assembly intermediates of cytochrome b (Cytb), a central subunit of complex III. The predicted structure of the first assembly intermediate suggests how the binding of Cytb to the assembly factor Cbp3-Cbp6 imposes an open configuration to facilitate the acquisition of its heme cofactors. Moreover, structure predictions of the second intermediate indicate how hemes get stabilized by binding of the assembly factor Cbp4, with a concomitant weakening of the contact between Cbp3-Cbp6 and Cytb, preparing for the release of the fully hemylated protein from the assembly factors.
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| 11. |
- Carlström, Andreas, 1988-, et al.
(author)
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Insights into conformational changes occurring during the early steps of cytochrome b maturation
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Journal article (other academic/artistic)abstract
- Membrane proteins carrying redox cofactors are key subunits of respiratory chain complexes, yet the exact path of their folding and maturation remains poorly understood. Here, using cryo-EM and structure prediction via Alphafold2, we generated models of the early assembly intermediates of cytochrome b (Cytb), a central catalytic subunit of complex III, indicating which conformational changes could occur during its assembly. Previous work has shown that newly synthesized Cytb progresses through a series of assembly intermediates that support heme co-factor acquisition, steps that need to occur before the protein is joined with further subunits of the fully mature complex III. The predicted structure of the first assembly intermediate suggests how binding of Cytb to the assembly factor Cbp3-Cbp6 imposes an open configuration, which should facilitate acquisition of its heme cofactors. Moreover, structure predictions of the second intermediate indicate how these hemes get stabilized by binding of the subsequent assembly factor Cbp4, with a concomitant weakening of the contact between Cbp3-Cbp6 and Cytb, preparing a release of the fully hemylated protein from the assembly factors. These results therefore allow to formulate a hypothesis about the structural rearrangements as they occur during biogenesis of Cytb.
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| 12. |
- Carlström, Andreas, et al.
(author)
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The Analysis of Yeast Mitochondrial Translation
- 2021
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In: Mitochondrial Gene Expression. - New York : Humana Press. - 9781071608333 - 9781071608340 ; , s. 227-242
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Book chapter (peer-reviewed)abstract
- The mitochondrial genome encodes only a handful of proteins, but methods to track their synthesis are highly limited. Saccharomyces cerevisiae is a model organism that offers possibilities to expand the classical systems to analyze mitochondrial translation. In this chapter, we present two approaches of monitoring mitochondrial protein synthesis. Labeling of mitochondrially translated products with radioactive amino acids can be performed either in intact cells or in isolated mitochondria. However, these classical methods have disadvantages that can affect cell physiology and hence are not suitable for all types of research questions. Some of these limitations can be overcome by the use of reporter genes that are inserted into yeast genetic screens mitochondrial DNA via biolistic transformation. These reporter genes can be used for yeast genetic screen and to monitor regulation and efficiency of mitochondrial translation with a variety of methods.
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| 13. |
- Carlström, Andreas, 1988-
(author)
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The mitoribosome as a hub for integrating mitochondrial gene expression : Regulation of translation and early assembly of cytochrome b
- 2024
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Doctoral thesis (other academic/artistic)abstract
- The mitochondrial proteome is a mosaic of proteins from two different genetic systems. The majority of mitochondrial proteins are encoded in the nuclear genome and are synthesized in the cytosol before imported to mitochondria. Interestingly, a handful of mitochondrial proteins are still encoded in the small mitochondrial genome, which is a remnant of its bacterial origin. These proteins are almost exclusively highly hydrophobic core subunits of the respiratory chain and ATP synthase. To synthesize these proteins, mitochondria contain its own complete gene expression system including factors for replication, transcription and translation. During the course of evolution, these machineries have diverged from its origin and have acquired organelle-specific characteristics. Mitochondrially encoded proteins are synthesized on the specialized and membrane-tethered mitoribosome. To avoid stoichiometric problems during assembly, translation in mitochondria needs to be coordinated with import of nuclear encoded subunits. However, the mechanisms behind regulation of mitochondrial protein biogenesis are still largely unclear.My research has focused on mitochondria in the yeast Saccharomyces cerevisiae. This provides a possibility to manipulate genes in both the nuclear and mitochondrial genomes to study effects on mitochondrial translation and respiration. In this thesis, I present results that contributes to our understanding of how translation regulation is connected to early assembly of mitochondrially encoded proteins. Using a proximity labelling technique called Bio-ID, we constructed a proximity network of proteins covering the whole mitochondrial gene expression system. This revealed a close association of factors involved in transcription, translation, membrane insertion and assembly, with the mitoribosome as a central hub. In particular, the mitoribosomal polypeptide tunnel exit was found to host factors involved in both regulation of translation and early assembly of nascent polypeptides. Further analysis of the tunnel exit proximity interactome resulted in identification of the membrane protein Mrx4 as a novel repressor of cytochrome b (Cytb) synthesis. Cytb is a catalytic subunit of the respiratory complex III and is encoded by the gene COB on the mtDNA. Translation of COB is under control of the regulatory proteins Cbp1, Cbs1, Cbs2, and Cbp3-Cbp6. Mrx4 is shown to interact with Cbs2, likely to sequester COB mRNA at the tunnel exit in a repressed state, until binding of Cbp3-Cbp6 releases Cbs2 and triggers activation of COB translation. Cbp3-Cbp6 then interacts with the newly synthesized Cytb, as it emerges from the tunnel exit, to stabilize the nascent polypeptide in an early assembly intermediate. The thesis further describes this chaperone function of Cbp3-Cbp6 on Cytb using structural models and site-specific photo-crosslinking. The results indicated that conformational changes in Cytb, upon incorporation of heme bH, releases Cbp3-Cbp6 to activate a new round of COB translation.In summary, the work presented in this thesis demonstrates a high level of organization and novel connectivity of mitochondrial gene expression. In addition, it expands on our knowledge regarding the intricate feedback loop regulation of Cytb biogenesis and the importance to coordinate mitochondrial translation with import of nuclear encoded subunits.
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| 14. |
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| 15. |
- Carlström, Eric, 1957, et al.
(author)
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Medical Emergencies During a Half Marathon Race - The Influence of Weather
- 2019
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In: International Journal of Sports Medicine. - Stuttgart : Georg Thieme Verlag KG. - 0172-4622 .- 1439-3964. ; 40:5, s. 312-316
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Journal article (peer-reviewed)abstract
- The aim was to analyze the influence of weather conditions on medical emergencies in a half-marathon, specifically by evaluating its relation to the number of non-finishers, ambulance-required assistances, and collapses in need of ambulance as well as looking at the location of such emergencies on the race course. Seven years of data from the world's largest half marathon were used. Meteorological data were obtained from a nearby weather station, and the Physiological Equivalent Temperature (PET) index was used as a measure of general weather conditions. Of the 315,919 race starters, 104 runners out of the 140 ambulance-required assistances needed ambulance services due to collapses. Maximum air temperature and PET significantly co-variated with ambulance-required assistances, collapses, and non-finishers (R (2) =0.65-0.92; p=0.001-0.03). When air temperatures vary between 15-29 degrees C, an increase of 1 degrees C results in an increase of 2.5 (0.008/1000) ambulance-required assistances, 2.5 (0.008/1000) collapses (needing ambulance services), and 107 (0.34/1000) non-finishers. The results also indicate that when the daily maximum PET varies between 18-35 degrees C, an increase of 1 degrees C PET results in an increase of 1.8 collapses (0.006/1000) needing ambulance services and 66 non-finishers (0.21/1000).
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| 16. |
- Carlström, Göran, et al.
(author)
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Rapid NMR Relaxation Rate Measurements Using Optimal Non-Uniform Sampling of Multi-Dimensional Accordion Data Analyzed by a Sparse Reconstruction Method
- 2019
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In: The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory. - : American Chemical Society (ACS). - 1089-5639. ; 123:27, s. 5718-5723
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Journal article (peer-reviewed)abstract
- Nonuniform sampling (NUS) of multidimensional NMR data offers significant time savings while improving spectral resolution or increasing sensitivity per unit time. However, NUS has not been widely used for quantitative analysis because of the nonlinearity of most methods used to model NUS data, which leads to problems in estimating signal intensities, relaxation rate constants, and their error bounds. Here, we present an approach that avoids these limitations by combining accordion spectroscopy and NUS in the indirect dimensions of multidimensional spectra and then applying sparse exponential mode analysis, which is well suited for analyzing accordion-type relaxation data in a NUS context. By evaluating the Cramér-Rao lower bound of the variances of the estimated relaxation rate constants, we achieve a robust benchmark for the underlying reconstruction model. Furthermore, we design NUS schemes optimized with respect to the information theoretical lower bound of the error in the parameters of interest, given a specified number of sampling points. The accordion-NUS method compares favorably with conventional relaxation experiments in that it produces identical results, within error, while shortening the length of the experiment by an order of magnitude. Thus, our approach enables rapid acquisition of NMR relaxation data for optimized use of spectrometer time or accurate measurements on samples of limited lifetime.
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| 17. |
- Carlström, Mattias, et al.
(author)
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Role of NOX2 in the regulation of afferent arteriole responsiveness
- 2009
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In: American Journal of Physiology. Regulatory Integrative and Comparative Physiology. - : American Physiological Society. - 0363-6119 .- 1522-1490. ; 296:1, s. R72-R79
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Journal article (peer-reviewed)abstract
- NADPH oxidases (NOX) are the major source of reactive oxygen species (ROS) in the vasculature and contribute to the control of renal perfusion. The role of NOX2 in the regulation of blood pressure and afferent arteriole responsiveness was investigated in NOX2(-/-) and wild-type mice. Arteriole constrictions to ANG II (10(-14)-10(-6) mol/l) were weaker in NOX2(-/-) compared with wild types. N(omega)-nitro-l-arginine methyl ester (l-NAME; 10(-4) mol/l) treatment reduced basal diameters significantly more in NOX2(-/-) (-18%) than in wild types (-6%) and augmented ANG II responses. Adenosine (10(-11)-10(-4) mol/l) constricted arterioles of wild types but not of NOX2(-/-). However, simultaneous inhibition of adenosine type-2 receptors induced vasoconstriction, which was stronger in NOX2(-/-). Adenosine (10(-8) mol/l) enhanced the ANG II response in wild type, but not in NOX2(-/-). This sensitizing effect by adenosine was abolished by apocynin. Chronic ANG II pretreatment (14 days) did not change the ANG II responses in NOX2(-/-), but strengthened the response in wild types. ANG II pretreatment augmented the l-NAME response in NOX2(-/-) (-33%), but not in wild types. Simultaneous application of l-NAME and ANG II caused a stronger constriction in the NOX2(-/-) (-64%) than in wild types (-46%). Basal blood pressures were similar in both genotypes, however, chronic ANG II infusion elevated blood pressure to a greater extent in wild-type (15 +/- 1%) than in NOX2(-/-) (8 +/- 1%) mice. In conclusion, NOX2 plays an important role in the control of afferent arteriole tone and is involved in the contractile responses to ANG II and/or adenosine. NOX2 can be activated by elevated ANG II and may play an important role in ANG II-induced hypertension. NOX2-derived ROS scavenges nitric oxide, causing subsequent nitric oxide-deficiency.
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| 18. |
- Gao, Xiang, et al.
(author)
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Adenosine A(1)-receptor deficiency diminishes afferent arteriolar and blood pressure responses during nitric oxide inhibition and angiotensin II treatment
- 2011
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In: American Journal of Physiology. Regulatory Integrative and Comparative Physiology. - : American Physiological Society. - 0363-6119 .- 1522-1490. ; 301:6, s. R1669-R1681
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Journal article (peer-reviewed)abstract
- Adenosine mediates tubuloglomerular feedback responses via activation of A(1)-receptors on the renal afferent arteriole. Increased preglomerular reactivity, due to reduced nitric oxide (NO) production or increased levels of ANG II and reactive oxygen species (ROS), has been linked to hypertension. Using A(1)-receptor knockout (A(1)(-/-)) and wild-type (A(1)(+/+)) mice we investigated the hypothesis that A(1)-receptors modulate arteriolar and blood pressure responses during NO synthase (NOS) inhibition or ANG II treatment. Blood pressure and renal afferent arteriolar responses were measured in nontreated mice and in mice with prolonged N(omega)-nitro-L-arginine methyl ester hydrochloride (L-NAME) or ANG II treatment. The hypertensive responses to L-NAME and ANG II were clearly attenuated in A(1)(-/-) mice. Arteriolar contractions to L-NAME (10(-4) mol/l; 15 min) and cumulative ANG II application (10(-12) to 10(-6) mol/l) were lower in A(1)(-/-) mice. Simultaneous treatment with tempol (10(-4) mol/l; 15 min) attenuated arteriolar responses in A(1)(+/+) but not in A(1)(-/-) mice, suggesting differences in ROS formation. Chronic treatment with L-NAME or ANG II did not alter arteriolar responses in A(1)(-/-) mice, but enhanced maximal contractions in A(1)(+/+) mice. In addition, chronic treatments were associated with higher plasma levels of dimethylarginines (asymmetrical and symmetrical) and oxidative stress marker malondialdehyde in A(1)(+/+) mice, and gene expression analysis showed reduced upregulation of NOS-isoforms and greater upregulation of NADPH oxidases. In conclusion, adenosine A(1)-receptors enhance preglomerular responses during NO inhibition and ANG II treatment. Interruption of A(1)-receptor signaling blunts L-NAME and ANG II-induced hypertension and oxidative stress and is linked to reduced responsiveness of afferent arterioles.
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| 19. |
- Gao, Xiang, et al.
(author)
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Adenosine A1 receptor-dependent and independent pathways in modulating renal vascular responses to angiotensin II
- 2015
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In: Acta Physiologica. - : Wiley. - 1748-1708 .- 1748-1716. ; 213:1, s. 268-276
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Journal article (peer-reviewed)abstract
- AIM: Renal afferent arterioles are the effector site for autoregulation of glomerular perfusion and filtration. There is synergistic interaction between angiotensin II (ANG II) and adenosine (Ado) in regulating arteriolar contraction, however, the mechanisms are not clear. In this context, this study investigated the contribution of A1 receptor dependent and independent signaling mechanisms.METHODS: Isolated perfused afferent arterioles from transgenic mice (A1+/+ and A1-/-) were used for vascular reactivity studies. Cultured vascular smooth muscle cells (VSMC) were used for phosphorylation studies of signaling proteins that induce arteriolar contraction.RESULTS: Maximal arteriolar contraction to ANG II was attenuated in A1-/- (22%) compared with A1+/+ (40%). Simultaneous incubation with low dose Ado (10-8 mol/L) enhanced ANG II-induced contraction in A1+/+ (58%), but also in A1-/- (42%). An Ado transporter inhibitor (NBTI) abolished this synergistic effect in A1-/-, but not in wild-type mice. Incubation with Ado+ANG II increased p38 phosphorylation in aortic VSMC from both genotypes, but treatment with NBTI only blocked phosphorylation in A1-/-. Combination of ANG II+Ado also increased MLC phosphorylation in A1+/+ but not significantly in A1-/-, and NBTI had no effects. In agreement, Ado+ANG II-induced phosphorylation of p38 and MLC in rat preglomerular VSMC was not affected by NBTI. However, during pharmacological inhibition of the A1 receptor simultaneous treatment with NBTI reduced phosphorylation of both p38 and MLC to control levels.CONCLUSION: Interaction between ANG II and Ado in VSMC normally involves A1 receptor signaling, but this can be compensated by receptor independent actions that phosphorylate p38 MAPK and MLC.
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| 20. |
- Khorram-Manesh, Amir, 1958, et al.
(author)
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Facilitating Multiagency Collaboration Before Mass Gatherings - The Development of MAGRAT (Mass Gathering Risk Assessment Tool
- 2020
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In: Biomedical Journal of Scientific and Technical Research. - 2574-1241. ; 24:5, s. 18607-18616
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Journal article (peer-reviewed)abstract
- the community hosting the event and create security and public health challenges. We aimed to explore whether a mutual planning and risk assessment tool used by emergency public agencies (EPA=emergency medical services, police officers, and firefighters), and organizers may improve planning and resource utilization before any mass gathering. Study Design and Methods: Action research based on interdisciplinary group exercises using a validated method “Three Level Collaboration” and real scenarios. Results: The use of the assessment tool increased the grade of collaboration between public agencies, and organizers and improved the preplanning phase of a mass gathering, particularly for healthcare providers. It was easy to use, feasible for different scenarios and highlighted the significant role and responsibility of organizers in pre-event risk assessment. Conclusion: The new assessment tool (MAGRAT= Mass Gathering Risk Assessment Tool) is an innovative tool for pre-event
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| 21. |
- Lai, En Yin, et al.
(author)
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Angiotensin II enhances the afferent arteriolar response to adenosine through increases in cytosolic calcium
- 2009
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In: Acta Physiologica. - : Wiley. - 1748-1708 .- 1748-1716. ; 196:4, s. 435-445
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Journal article (peer-reviewed)abstract
- Aims: Angiotensin II (Ang II) is a strong renal vasoconstrictor and modulates the tubuloglomerular feedback (TGF). We hypothesized that Ang II at low concentrations enhances the vasoconstrictor effect of adenosine (Ado), the mediator of TGF. Methods: Afferent arterioles of mice were isolated and perfused, and both isotonic contractions and cytosolic calcium transients were measured. Results: Bolus application of Ang II (10(-12) and 10(-10)M) induced negligible vasoconstrictions, while Ang II at 10(-8) M reduced diameters by 35%. Ang II at 10(-12), 10(-10), and 10(-8) M clearly enhanced the arteriolar response to cumulative applications of Ado (10(-11) to 10(-4)M). Ado application increased the cytosolic calcium concentrations in the vascular smooth muscle, which were higher at 10(-5)M than at 10(-8)M. Ang II (10(-11) to 10(-6)M) also induced concentration-dependent calcium transients, which were attenuated by AT(1) receptor inhibition. Simultaneously applied Ang II (10(-10)M) additively enhanced the calcium transients induced by 10(-8) and 10(-5) M Ado. The transients were partly inhibited by AT(1) or A(1) receptor antagonists, but not significantly by A(2) receptor antagonists. Conclusion: A low dose of Ang II enhances Ado-induced constrictions, partly via AT(1) receptor-mediated calcium increase. Ado increases intracellular calcium by acting on A(1) but not A(2) receptors. The potentiating effect of Ang II on Ado-induced arteriolar vasoconstrictions may involve calcium sensitization of the contractile machinery, as Ang II only additively increased cytosolic calcium concentrations, while its effect on the arteriolar constriction was more than additive. The potentiating effect of Ang II might contribute to the resetting of TGF.
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| 22. |
- Ndi, Mama, et al.
(author)
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Structural basis for Cbp3 interaction with newly synthesized cytochrome b during mitochondrial respiratory chain assembly
- 2019
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In: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 294:45, s. 16663-16671
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Journal article (peer-reviewed)abstract
- Assembly of the mitochondrial respiratory chain requires the coordinated synthesis of mitochondrial and nuclear encoded subunits, redox co-factor acquisition, and correct joining of the subunits to form functional complexes. The conserved Cbp3–Cbp6 chaperone complex binds newly synthesized cytochrome b and supports the ordered acquisition of the heme co-factors. Moreover, it functions as a translational activator by interacting with the mitoribosome. Cbp3 consists of two distinct domains, an N-terminal domain present in mitochondrial Cbp3 homologs, and a highly conserved C-terminal domain comprising a ubiquinol–cytochrome c chaperone region. Here, we solved the crystal structure of this C-terminal domain from a bacterial homolog at 1.4 Å resolution, revealing a unique all-helical fold. This structure allowed mapping of the interaction sites of yeast Cbp3 with Cbp6 and cytochrome b via site-specific photo-crosslinking. We propose that mitochondrial Cbp3 homologs carry an N-terminal extension that positions the conserved C-terminal domain at the ribosomal tunnel exit for an efficient interaction with its substrate, the newly synthesized cytochrome b protein.
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| 23. |
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| 24. |
- Perez-Alcazar, Marta, et al.
(author)
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Altered cognitive performance and synaptic function in the hippocampus of mice lacking C3.
- 2014
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In: Experimental neurology. - : Elsevier BV. - 1090-2430 .- 0014-4886. ; 253C, s. 154-164
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Journal article (peer-reviewed)abstract
- Previous work implicated the complement system in adult neurogenesis as well as elimination of synapses in the developing and injured CNS. In the present study, we used mice lacking the third complement component (C3) to elucidate the role the complement system plays in hippocampus-dependent learning and synaptic function. We found that the constitutive absence of C3 is associated with enhanced place and reversal learning in adult mice. Our findings of lower release probability at CA3-CA1 glutamatergic synapses in combination with unaltered overall efficacy of these synapses in C3 deficient mice implicate C3 as a negative regulator of the number of functional glutamatergic synapses in the hippocampus. The C3 deficient mice showed no signs of spontaneous epileptiform activity in the hippocampus. We conclude that C3 plays a role in the regulation of the number and function of glutamatergic synapses in the hippocampus and exerts negative effects on hippocampus-dependent cognitive performance.
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| 25. |
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| 26. |
- Vargas Möller-Hergt, Braulio, et al.
(author)
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Insertion Defects of Mitochondrially Encoded Proteins Burden the Mitochondrial Quality Control System
- 2018
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In: Cells. - : MDPI AG. - 2073-4409. ; 7:10
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Journal article (peer-reviewed)abstract
- The mitochondrial proteome contains proteins from two different genetic systems. Proteins are either synthesized in the cytosol and imported into the different compartments of the organelle or directly produced in the mitochondrial matrix. To ensure proteostasis, proteins are monitored by the mitochondrial quality control system, which will degrade non-native polypeptides. Defective mitochondrial membrane proteins are degraded by membrane-bound AAA-proteases. These proteases are regulated by factors promoting protein turnover or preventing their degradation. Here we determined genetic interactions between the mitoribosome receptors Mrx15 and Mba1 with the quality control system. We show that simultaneous absence of Mrx15 and the regulators of the i-AAA protease Mgr1 and Mgr3 provokes respiratory deficiency. Surprisingly, mutants lacking Mrx15 were more tolerant against proteotoxic stress. Furthermore, yeast cells became hypersensitive against proteotoxic stress upon deletion of MBA1. Contrary to Mrx15, Mba1 cooperates with the regulators of the m-AAA and i-AAA proteases. Taken together, these results suggest that membrane protein insertion and mitochondrial AAA-proteases are functionally coupled, possibly reflecting an early quality control step during mitochondrial protein synthesis.
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| 27. |
- Vargas Möller-Hergt, Braulio, et al.
(author)
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The ribosome receptors Mrx15 and Mba1 jointly organize cotranslational insertion and protein biogenesis in mitochondria
- 2018
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In: Molecular Biology of the Cell. - 1059-1524 .- 1939-4586. ; 29:20, s. 2359-2507
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Journal article (peer-reviewed)abstract
- Mitochondrial gene expression in Saccharomyces cerevisiae is responsible for the production of highly hydrophobic subunits of the oxidative phosphorylation system. Membrane insertion occurs cotranslationally on membrane-bound mitochondrial ribosomes. Here, by employing a systematic mass spectrometry-based approach, we discovered the previously uncharacterized membrane protein Mrx15 that interacts via a soluble C-terminal domain with the large ribosomal subunit. Mrx15 contacts mitochondrial translation products during their synthesis and plays, together with the ribosome receptor Mba1, an overlapping role in cotranslational protein insertion. Taken together, our data reveal how these ribosome receptors organize membrane protein biogenesis in mitochondria.
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| 28. |
- Wernersson, Sven, et al.
(author)
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Rapid measurement of heteronuclear transverse relaxation rates using non-uniformly sampled R1ρ accordion experiments
- 2021
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In: Magnetic Resonance. - : Copernicus GmbH. - 2699-0016. ; 2:2, s. 571-587
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Journal article (peer-reviewed)abstract
- Multidimensional, heteronuclear NMR relaxation methods are used extensively to characterize the dynamics of biological macromolecules. Acquisition of relaxation datasets on proteins typically requires significant measurement time, often several days. Accordion spectroscopy offers a powerful means to shorten relaxation rate measurements by encoding the “relaxation dimension” into the indirect evolution period in multidimensional experiments. Time savings can also be achieved by non-uniform sampling (NUS) of multidimensional NMR data, which is used increasingly to improve spectral resolution or increase sensitivity per unit time. However, NUS is not commonly implemented in relaxation experiments, because most reconstruction algorithms are inherently nonlinear, leading to problems when estimating signal intensities, relaxation rate constants and their error bounds. We have previously shown how to avoid these shortcomings by combining accordion spectroscopy with NUS, followed by data reconstruction using sparse exponential mode analysis, thereby achieving a dramatic decrease in the total length of longitudinal relaxation experiments. Here, we present the corresponding transverse relaxation experiment, taking into account the special considerations required for its successful implementation in the framework of the accordion-NUS approach. We attain the highest possible precision in the relaxation rate constants by optimizing the NUS scheme with respect to the Cramér-Rao lower bound of the variance of the estimated parameter, given the total number of sampling points and the spectrum-specific signal characteristics. The resulting accordion-NUS R1ρ relaxation experiment achieves comparable precision in the parameter estimates compared to conventional CPMG (Carr-Purcell-Meiboom-Gill) R2 or spin-lock R1ρ experiments while saving an order of magnitude in experiment time.
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