The Experts below are selected from a list of 17133 Experts worldwide ranked by ideXlab platform
Dimitrios Stamou - One of the best experts on this subject based on the ideXlab platform.
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Quantitative investigation of negative Membrane Curvature sensing and generation by I-BARs in filopodia of living cells
Soft matter, 2019Co-Authors: Artù Breuer, Line Lauritsen, Elena Bertseva, Ivana Vonkova, Dimitrios StamouAbstract:Membrane Curvature has recently been recognized as an active regulator of cellular function, with several protein families identified as sensors and generators of Membrane Curvature. Amongst them, the inverse Bin/Amphiphysin/Rvs (I-BAR) domain family has been implicated in the sensing and generation of Membrane structures with negative Membrane Curvature e.g. filopodia or dendritic spines. However, to date, quantitative biophysical investigations of I-BAR domains have mostly taken place in reconstitution. Here, we use fluorescence microscopy to quantitatively investigate Membrane Curvature sensing and generation by I-BARs in filopodia of living cells. As a model system, we selected two prototypic members of the I-BAR family, the insulin receptor substrate p53 and missing-in-metastasis. Our data demonstrated how I-BARs sense negative Membrane Curvature in the complex environment of live cells by revealing a dependence on Membrane Curvature for both their binding affinity to Membranes and their saturation density. The non-monotonic dependence of protein sorting with negative Membrane Curvature allowed us to apply previously developed thermodynamic models to provide estimates of the effective intrinsic Curvature and bending rigidity of the two I-BARs bound at the plasma Membrane. Our results agree with studies performed on the insulin receptor substrate p53 in reconstitution. To quantitate Membrane Curvature generation by I-BARs we measured how their overexpression reduces the peak and the width of the size distribution of filopodia, resulting in filopodia populations with smaller and more uniform diameters. Our findings provide a quantitative biophysical insight in the ability of I-BARs to sense and generate negative Membrane Curvature in the crowded environment of living cells.
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Membrane Curvature and Lipid Composition Synergize To Regulate N-Ras Anchor Recruitment.
Biophysical journal, 2017Co-Authors: Jannik B. Larsen, Celeste Kennard, Søren L. Pedersen, Knud J. Jensen, Mark J. Uline, Nikos S. Hatzakis, Dimitrios StamouAbstract:Abstract Proteins anchored to Membranes through covalently linked fatty acids and/or isoprenoid groups play crucial roles in all forms of life. Sorting and trafficking of lipidated proteins has traditionally been discussed in the context of partitioning to Membrane domains of different lipid composition. We recently showed that Membrane shape/Curvature can in itself mediate the recruitment of lipidated proteins. However, exactly how Membrane Curvature and composition synergize remains largely unexplored. Here we investigated how three critical structural parameters of lipids, namely acyl chain saturation, headgroup size, and acyl chain length, modulate the capacity of Membrane Curvature to recruit lipidated proteins. As a model system we used the lipidated minimal Membrane anchor of the GTPase, N-Ras (tN-Ras). Our data revealed complex synergistic effects, whereby tN-Ras binding was higher on planar DOPC than POPC Membranes, but inversely higher on curved POPC than DOPC Membranes. This variation in the binding to both planar and curved Membranes leads to a net increase in the recruitment by Membrane Curvature of tN-Ras when reducing the acyl chain saturation state. Additionally, we found increased recruitment by Membrane Curvature of tN-Ras when substituting PC for PE, and when decreasing acyl chain length from 14 to 12 carbons (DMPC versus DLPC). However, these variations in recruitment ability had different origins, with the headgroup size primarily influencing tN-Ras binding to planar Membranes whereas the change in acyl chain length primarily affected binding to curved Membranes. Molecular field theory calculations recapitulated these findings and revealed lateral pressure as an underlying biophysical mechanism dictating how Curvature and composition synergize to modulate recruitment of lipidated proteins. Our findings suggest that the different compositions of cellular compartments could modulate the potency of Membrane Curvature to recruit lipidated proteins and thereby synergistically regulate the trafficking and sorting of lipidated proteins.
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InterMembrane Docking Reactions Are Regulated by Membrane Curvature
Biophysical journal, 2011Co-Authors: Andreas Hjarne Kunding, Vikram K. Bhatia, Michael W. Mortensen, Sune M. Christensen, Ivan Makarov, Ralf Metzler, Dimitrios StamouAbstract:The polymorphism of eukaryotic cellular Membranes is a tightly regulated and well-conserved phenotype. Recent data have revealed important regulatory roles of Membrane Curvature on the spatio-temporal localization of proteins and in Membrane fusion. Here we quantified the influence of Membrane Curvature on the efficiency of interMembrane docking reactions. Using fluorescence microscopy, we monitored the docking of single vesicle–vesicle pairs of different diameter (30–200 nm) and therefore Curvature, as mediated by neuronal soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) and streptavidin-biotin. Surprisingly, the interMembrane docking efficiency exhibited an ∼30–60 fold enhancement as a function of Curvature. In comparison, synaptotagmin and calcium accelerate SNARE-mediated fusion in vitro by a factor of 2–10. To explain this finding, we formulated a biophysical model. On the basis of our findings, we propose that Membrane Curvature can regulate interMembrane tethering reactions and consequently any downstream process, including the fusion of vesicles and possibly viruses with their target Membranes.
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Membrane Curvature Induction and Tubulation Are Common Features of Synucleins and Apolipoproteins
The Journal of biological chemistry, 2010Co-Authors: Jobin Varkey, Christine C. Jao, Vikram K. Bhatia, Dimitrios Stamou, Jose Mario Isas, Martin Borch Jensen, Naoko Mizuno, Jitka Petrlova, John C. Voss, Alasdair C. StevenAbstract:Synucleins and apolipoproteins have been implicated in a number of Membrane and lipid trafficking events. Lipid interaction for both types of proteins is mediated by 11 amino acid repeats that form amphipathic helices. This similarity suggests that synucleins and apolipoproteins might have comparable effects on lipid Membranes, but this has not been shown directly. Here, we find that α-synuclein, β-synuclein, and apolipoprotein A-1 have the conserved functional ability to induce Membrane Curvature and to convert large vesicles into highly curved Membrane tubules and vesicles. The resulting structures are morphologically similar to those generated by amphiphysin, a Curvature-inducing protein involved in endocytosis. Unlike amphiphysin, however, synucleins and apolipoproteins do not require any scaffolding domains and Curvature induction is mediated by the Membrane insertion and wedging of amphipathic helices alone. Moreover, we frequently observed that α-synuclein caused Membrane structures that had the appearance of nascent budding vesicles. The ability to function as a minimal machinery for vesicle budding agrees well with recent findings that α-synuclein plays a role in vesicle trafficking and enhances endocytosis. Induction of Membrane Curvature must be under strict regulation in vivo; however, as we find it can also cause disruption of Membrane integrity. Because the degree of Membrane Curvature induction depends on the concerted action of multiple proteins, controlling the local protein density of tubulating proteins may be important. How cellular safeguarding mechanisms prevent such potentially toxic events and whether they go awry in disease remains to be determined.
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A unifying mechanism accounts for sensing of Membrane Curvature by BAR domains, amphipathic helices and Membrane-anchored proteins
Seminars in cell & developmental biology, 2009Co-Authors: Vikram K. Bhatia, Nikos S. Hatzakis, Dimitrios StamouAbstract:The discovery of proteins that recognize Membrane Curvature created a paradigm shift by suggesting that Membrane shape may act as a cue for protein localization that is independent of lipid or protein composition. Here we review recent data on Membrane Curvature sensing by three structurally unrelated motifs: BAR domains, amphipathic helices and Membrane-anchored proteins. We discuss the conclusion that the Curvature of the BAR dimer is not responsible for sensing and that the sensing properties of all three motifs can be rationalized by the physicochemical properties of the curved Membrane itself. We thus anticipate that Membrane Curvature will promote the redistribution of proteins that are anchored in Membranes through any type of hydrophobic moiety, a thesis that broadens tremendously the implications of Membrane Curvature for protein sorting, trafficking and signaling in cell biology.
Vikram K. Bhatia - One of the best experts on this subject based on the ideXlab platform.
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Membrane Curvature enables n ras lipid anchor sorting to liquid ordered Membrane phases
Nature Chemical Biology, 2015Co-Authors: Jannik B. Larsen, Vikram K. Bhatia, Søren L. Pedersen, Mark J. Uline, Martin Borch Jensen, Thomas Bjørnholm, Lars Iversen, Igal Szleifer, Knud J. JensenAbstract:Membrane sorting of Ras and its isolated lipid anchor is based on Membrane Curvature, sensed by Ras itself. This helps to explain the previous inability to match in vivo results in vitro in promoting the raftophilic Ras to partition with Membrane lipid rafts.
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Lipid-Anchored Ras is Sorted by Membrane Curvature Both In Vitro and in Living Cells
Biophysical Journal, 2013Co-Authors: Jannik B. Larsen, Vikram K. Bhatia, Søren L. Pedersen, Knud J. Jensen, Martin Borch Jensen, Thomas Bjørnholm, Monika Köhnke, Daniel Abankwa, Kirill Alexandrov, Nikos S. HatzakisAbstract:In vivo studies have reported preferential partitioning of Ras GTPases into ordered lipid-protein Membrane domains, a process believed to regulate both cellular signaling and protein trafficking.1 However studies in vitro have failed to quantify a preferential partitioning of full length Ras proteins into the liquid ordered phase2,3 and thus a biophysically validated mechanism for in vivo sorting of Ras is still missing. We recently showed that lipidated proteins localize to highly curved Membranes in vitro.4 Here we study both in vitro and in vivo whether recruitment by Membrane Curvature can sort full length lipid-anchored Ras.We employ a single vesicle fluorescence based assay to quantify in vitro the sorting by Membrane Curvature of full-length Ras proteins. We demonstrate a more than 50 fold increase in protein density on Membranes of high Curvature as compared to the density on flat Membranes. To test for recruitment by Membrane Curvature in vivo we utilize hypo-osmotic swelling of cells, which flattens curved Membrane regions. By measuring the local protein density using FRET,5 we detect a significant reduction in the clustering of Ras and other lipidated proteins upon Membrane flattening. This demonstrates that recruitment by Membrane Curvature can sort Ras and potentially other lipidated proteins in cellular Membranes. Furthermore sorting by Membrane Curvature constitutes the first biophysical sorting mechanism for Ras validated by both in vitro and in vivo measurements.1 Hancock, J. F. Nat. Rev. Mol. Cell Biol.4 (2003).2 Johnson, S. A. et al.Biochim. Biophys. Acta - BioMembranes1798 (2010).3 Nicolini, C. et al.J. Am. Chem. Soc.128 (2006).4 Hatzakis, N. S. et al.Nat. Chem. Biol.5 (2009).5 Kohnke, M. et al.Chem. Biol.19 (2012).
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InterMembrane Docking Reactions Are Regulated by Membrane Curvature
Biophysical journal, 2011Co-Authors: Andreas Hjarne Kunding, Vikram K. Bhatia, Michael W. Mortensen, Sune M. Christensen, Ivan Makarov, Ralf Metzler, Dimitrios StamouAbstract:The polymorphism of eukaryotic cellular Membranes is a tightly regulated and well-conserved phenotype. Recent data have revealed important regulatory roles of Membrane Curvature on the spatio-temporal localization of proteins and in Membrane fusion. Here we quantified the influence of Membrane Curvature on the efficiency of interMembrane docking reactions. Using fluorescence microscopy, we monitored the docking of single vesicle–vesicle pairs of different diameter (30–200 nm) and therefore Curvature, as mediated by neuronal soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) and streptavidin-biotin. Surprisingly, the interMembrane docking efficiency exhibited an ∼30–60 fold enhancement as a function of Curvature. In comparison, synaptotagmin and calcium accelerate SNARE-mediated fusion in vitro by a factor of 2–10. To explain this finding, we formulated a biophysical model. On the basis of our findings, we propose that Membrane Curvature can regulate interMembrane tethering reactions and consequently any downstream process, including the fusion of vesicles and possibly viruses with their target Membranes.
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Membrane Curvature Induction and Tubulation Are Common Features of Synucleins and Apolipoproteins
The Journal of biological chemistry, 2010Co-Authors: Jobin Varkey, Christine C. Jao, Vikram K. Bhatia, Dimitrios Stamou, Jose Mario Isas, Martin Borch Jensen, Naoko Mizuno, Jitka Petrlova, John C. Voss, Alasdair C. StevenAbstract:Synucleins and apolipoproteins have been implicated in a number of Membrane and lipid trafficking events. Lipid interaction for both types of proteins is mediated by 11 amino acid repeats that form amphipathic helices. This similarity suggests that synucleins and apolipoproteins might have comparable effects on lipid Membranes, but this has not been shown directly. Here, we find that α-synuclein, β-synuclein, and apolipoprotein A-1 have the conserved functional ability to induce Membrane Curvature and to convert large vesicles into highly curved Membrane tubules and vesicles. The resulting structures are morphologically similar to those generated by amphiphysin, a Curvature-inducing protein involved in endocytosis. Unlike amphiphysin, however, synucleins and apolipoproteins do not require any scaffolding domains and Curvature induction is mediated by the Membrane insertion and wedging of amphipathic helices alone. Moreover, we frequently observed that α-synuclein caused Membrane structures that had the appearance of nascent budding vesicles. The ability to function as a minimal machinery for vesicle budding agrees well with recent findings that α-synuclein plays a role in vesicle trafficking and enhances endocytosis. Induction of Membrane Curvature must be under strict regulation in vivo; however, as we find it can also cause disruption of Membrane integrity. Because the degree of Membrane Curvature induction depends on the concerted action of multiple proteins, controlling the local protein density of tubulating proteins may be important. How cellular safeguarding mechanisms prevent such potentially toxic events and whether they go awry in disease remains to be determined.
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A unifying mechanism accounts for sensing of Membrane Curvature by BAR domains, amphipathic helices and Membrane-anchored proteins
Seminars in cell & developmental biology, 2009Co-Authors: Vikram K. Bhatia, Nikos S. Hatzakis, Dimitrios StamouAbstract:The discovery of proteins that recognize Membrane Curvature created a paradigm shift by suggesting that Membrane shape may act as a cue for protein localization that is independent of lipid or protein composition. Here we review recent data on Membrane Curvature sensing by three structurally unrelated motifs: BAR domains, amphipathic helices and Membrane-anchored proteins. We discuss the conclusion that the Curvature of the BAR dimer is not responsible for sensing and that the sensing properties of all three motifs can be rationalized by the physicochemical properties of the curved Membrane itself. We thus anticipate that Membrane Curvature will promote the redistribution of proteins that are anchored in Membranes through any type of hydrophobic moiety, a thesis that broadens tremendously the implications of Membrane Curvature for protein sorting, trafficking and signaling in cell biology.
Nikos S. Hatzakis - One of the best experts on this subject based on the ideXlab platform.
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Membrane Curvature and Lipid Composition Synergize To Regulate N-Ras Anchor Recruitment.
Biophysical journal, 2017Co-Authors: Jannik B. Larsen, Celeste Kennard, Søren L. Pedersen, Knud J. Jensen, Mark J. Uline, Nikos S. Hatzakis, Dimitrios StamouAbstract:Abstract Proteins anchored to Membranes through covalently linked fatty acids and/or isoprenoid groups play crucial roles in all forms of life. Sorting and trafficking of lipidated proteins has traditionally been discussed in the context of partitioning to Membrane domains of different lipid composition. We recently showed that Membrane shape/Curvature can in itself mediate the recruitment of lipidated proteins. However, exactly how Membrane Curvature and composition synergize remains largely unexplored. Here we investigated how three critical structural parameters of lipids, namely acyl chain saturation, headgroup size, and acyl chain length, modulate the capacity of Membrane Curvature to recruit lipidated proteins. As a model system we used the lipidated minimal Membrane anchor of the GTPase, N-Ras (tN-Ras). Our data revealed complex synergistic effects, whereby tN-Ras binding was higher on planar DOPC than POPC Membranes, but inversely higher on curved POPC than DOPC Membranes. This variation in the binding to both planar and curved Membranes leads to a net increase in the recruitment by Membrane Curvature of tN-Ras when reducing the acyl chain saturation state. Additionally, we found increased recruitment by Membrane Curvature of tN-Ras when substituting PC for PE, and when decreasing acyl chain length from 14 to 12 carbons (DMPC versus DLPC). However, these variations in recruitment ability had different origins, with the headgroup size primarily influencing tN-Ras binding to planar Membranes whereas the change in acyl chain length primarily affected binding to curved Membranes. Molecular field theory calculations recapitulated these findings and revealed lateral pressure as an underlying biophysical mechanism dictating how Curvature and composition synergize to modulate recruitment of lipidated proteins. Our findings suggest that the different compositions of cellular compartments could modulate the potency of Membrane Curvature to recruit lipidated proteins and thereby synergistically regulate the trafficking and sorting of lipidated proteins.
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Membrane Curvature regulates ligand-specific Membrane sorting of GPCRs in living cells.
Nature chemical biology, 2017Co-Authors: Kadla R. Rosholm, Søren L. Pedersen, Knud J. Jensen, Natascha Leijnse, Anna Mantsiou, Vadym Tkach, Volker F. Wirth, Lene B. Oddershede, Karen L. Martinez, Nikos S. HatzakisAbstract:The targeted spatial organization (sorting) of Gprotein-coupled receptors (GPCRs) is essential for their biological function and often takes place in highly curved Membrane compartments such as filopodia, endocytic pits, trafficking vesicles or endosome tubules. However, the influence of geometrical Membrane Curvature on GPCR sorting remains unknown. Here we used fluorescence imaging to establish a quantitative correlation between Membrane Curvature and sorting of three prototypic class A GPCRs (the neuropeptide Y receptor Y2, the β1 adrenergic receptor and the β2 adrenergic receptor) in living cells. Fitting of a thermodynamic model to the data enabled us to quantify how sorting is mediated by an energetic drive to match receptor shape and Membrane Curvature. Curvature-dependent sorting was regulated by ligands in a specific manner. We anticipate that this Curvature-dependent biomechanical coupling mechanism contributes to the sorting, trafficking and function of transMembrane proteins in general.
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Lipid-Anchored Ras is Sorted by Membrane Curvature Both In Vitro and in Living Cells
Biophysical Journal, 2013Co-Authors: Jannik B. Larsen, Vikram K. Bhatia, Søren L. Pedersen, Knud J. Jensen, Martin Borch Jensen, Thomas Bjørnholm, Monika Köhnke, Daniel Abankwa, Kirill Alexandrov, Nikos S. HatzakisAbstract:In vivo studies have reported preferential partitioning of Ras GTPases into ordered lipid-protein Membrane domains, a process believed to regulate both cellular signaling and protein trafficking.1 However studies in vitro have failed to quantify a preferential partitioning of full length Ras proteins into the liquid ordered phase2,3 and thus a biophysically validated mechanism for in vivo sorting of Ras is still missing. We recently showed that lipidated proteins localize to highly curved Membranes in vitro.4 Here we study both in vitro and in vivo whether recruitment by Membrane Curvature can sort full length lipid-anchored Ras.We employ a single vesicle fluorescence based assay to quantify in vitro the sorting by Membrane Curvature of full-length Ras proteins. We demonstrate a more than 50 fold increase in protein density on Membranes of high Curvature as compared to the density on flat Membranes. To test for recruitment by Membrane Curvature in vivo we utilize hypo-osmotic swelling of cells, which flattens curved Membrane regions. By measuring the local protein density using FRET,5 we detect a significant reduction in the clustering of Ras and other lipidated proteins upon Membrane flattening. This demonstrates that recruitment by Membrane Curvature can sort Ras and potentially other lipidated proteins in cellular Membranes. Furthermore sorting by Membrane Curvature constitutes the first biophysical sorting mechanism for Ras validated by both in vitro and in vivo measurements.1 Hancock, J. F. Nat. Rev. Mol. Cell Biol.4 (2003).2 Johnson, S. A. et al.Biochim. Biophys. Acta - BioMembranes1798 (2010).3 Nicolini, C. et al.J. Am. Chem. Soc.128 (2006).4 Hatzakis, N. S. et al.Nat. Chem. Biol.5 (2009).5 Kohnke, M. et al.Chem. Biol.19 (2012).
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A unifying mechanism accounts for sensing of Membrane Curvature by BAR domains, amphipathic helices and Membrane-anchored proteins
Seminars in cell & developmental biology, 2009Co-Authors: Vikram K. Bhatia, Nikos S. Hatzakis, Dimitrios StamouAbstract:The discovery of proteins that recognize Membrane Curvature created a paradigm shift by suggesting that Membrane shape may act as a cue for protein localization that is independent of lipid or protein composition. Here we review recent data on Membrane Curvature sensing by three structurally unrelated motifs: BAR domains, amphipathic helices and Membrane-anchored proteins. We discuss the conclusion that the Curvature of the BAR dimer is not responsible for sensing and that the sensing properties of all three motifs can be rationalized by the physicochemical properties of the curved Membrane itself. We thus anticipate that Membrane Curvature will promote the redistribution of proteins that are anchored in Membranes through any type of hydrophobic moiety, a thesis that broadens tremendously the implications of Membrane Curvature for protein sorting, trafficking and signaling in cell biology.
Bruno Antonny - One of the best experts on this subject based on the ideXlab platform.
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Membrane Curvature Sensing by Amphipathic Helices Is Modulated by the Surrounding Protein Backbone
PloS one, 2015Co-Authors: Christine Doucet, Nina Esmery, Maud De Saint-jean, Bruno AntonnyAbstract:Membrane Curvature is involved in numerous biological pathways like vesicle trafficking, endocytosis or nuclear pore complex assembly. In addition to its topological role, Membrane Curvature is sensed by specific proteins, enabling the coordination of biological processes in space and time. Amongst Membrane Curvature sensors are the ALPS (Amphipathic Lipid Packing Sensors). ALPS motifs are short peptides with peculiar amphipathic properties. They are found in proteins targeted to distinct curved Membranes, mostly in the early secretory pathway. For instance, the ALPS motif of the golgin GMAP210 binds trafficking vesicles, while the ALPS motif of Nup133 targets nuclear pores. It is not clear if, besides Curvature sensitivity, ALPS motifs also provide target specificity, or if other domains in the surrounding protein backbone are involved. To elucidate this aspect, we studied the subcellular localization of ALPS motifs outside their natural protein context. The ALPS motifs of GMAP210 or Nup133 were grafted on artificial fluorescent probes. Importantly, ALPS motifs are held in different positions and these contrasting architectures were mimicked by the fluorescent probes. The resulting chimeras recapitulated the original proteins localization, indicating that ALPS motifs are sufficient to specifically localize proteins. Modulating the electrostatic or hydrophobic content of Nup133 ALPS motif modified its avidity for cellular Membranes but did not change its organelle targeting properties. In contrast, the structure of the backbone surrounding the helix strongly influenced targeting. In particular, introducing an artificial coiled-coil between ALPS and the fluorescent protein increased Membrane Curvature sensitivity. This coiled-coil domain also provided Membrane Curvature sensitivity to the amphipathic helix of Sar1. The degree of Curvature sensitivity within the coiled-coil context remains correlated to the natural Curvature sensitivity of the helices. This suggests that the chemistry of ALPS motifs is a key parameter for Membrane Curvature sensitivity, which can be further modulated by the surrounding protein backbone.
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Arf1 and Membrane Curvature cooperate to recruit Arfaptin2 to liposomes.
PloS one, 2013Co-Authors: Ernesto Esteban Ambroggio, Bruno Antonny, Jean-baptiste Manneville, James E. Sillibourne, Bruno GoudAbstract:Arfaptin2 contains a Bin/Amphiphysin/Rvs (BAR) domain and directly interacts with proteins of the Arf/Arl family in their active GTP-bound state. It has been proposed that BAR domains are able to sense Membrane Curvature and to induce Membrane tubulation. We report here that active Arf1 is required for the recruitment of Arfaptin2 to artificial liposomes mimicking the Golgi apparatus lipid composition. The Arf1-dependent recruitment of Arfaptin2 increases with Membrane Curvature, while the recruitment of Arf1 itself is not sensitive to Curvature. At high protein concentrations, the binding of Arfaptin2 induces Membrane tubulation. Finally, Membrane-bound Arfaptin2 is released from the liposome when ArfGAP1 catalyzes the hydrolysis of GTP to GDP in Arf1. These results show that both Arf1 activation and high Membrane Curvature are required for efficient recruitment of Arfaptin2 to Membranes.
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α-Synuclein and ALPS motifs are Membrane Curvature sensors whose contrasting chemistry mediates selective vesicle binding.
Journal of Cell Biology, 2011Co-Authors: Iwona M Pranke, Bruno Antonny, Joëlle Bigay, Vincent Morello, Kimberley Gibson, Jean-marc Verbavatz, Catherine L JacksonAbstract:Membrane Curvature sensors have diverse structures and chemistries, suggesting that they might have the intrinsic capacity to discriminate between different types of vesicles in cells. In this paper, we compare the in vitro and in vivo Membrane-binding properties of two Curvature sensors that form very different amphipathic helices: the amphipathic lipid-packing sensor (ALPS) motif of a Golgi vesicle tether and the synaptic vesicle protein α-synuclein, a causative agent of Parkinson's disease. We demonstrate the mechanism by which α-synuclein senses Membrane Curvature. Unlike ALPS motifs, α-synuclein has a poorly developed hydrophobic face, and this feature explains its dual sensitivity to negatively charged lipids and to Membrane Curvature. When expressed in yeast cells, these two Curvature sensors were targeted to different classes of vesicles, those of the early secretory pathway for ALPS motifs and to negatively charged endocytic/post-Golgi vesicles in the case of α-synuclein. Through structures with complementary chemistries, α-synuclein and ALPS motifs target distinct vesicles in cells by direct interaction with different lipid environments.
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Mechanisms of Membrane Curvature Sensing
Annual review of biochemistry, 2011Co-Authors: Bruno AntonnyAbstract:Bacteria and eukaryotic cells contain geometry-sensing tools in their cytosol: protein motifs or domains that recognize the Curvature, concave or convex, deep or shallow, of lipid Membranes. These sensors contrast with classical lipid-binding domains by their extended structure and, sometimes, counterintuitive chemistry. Among the sensors are long amphipathic helices, such as the ALPS motif and the N-terminal region of α-synuclein, whose apparent "design defects" translate into a remarkable ability to specifically adsorb to the surface of small vesicles. Fundamental differences in the lipid composition of Membranes of the early and late secretory pathways probably explain why some sensors use mostly electrostatics whereas others take advantage of the hydrophobic effect. Membrane Curvature sensors help to organize very diverse reactions, such as lipid transfer between Membranes, the tethering of vesicles at the Golgi apparatus, and the assembly-disassembly cycle of protein coats.
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Amphipathic helices and Membrane Curvature
FEBS letters, 2009Co-Authors: Guillaume Drin, Bruno AntonnyAbstract:Numerous data have been collected on lipid-binding amphipathic helices involved in Membrane-remodeling machineries and vesicular transport. Here we describe how, with regard to lipid composition, the physicochemical features of some amphipathic helices explain their ability to recognize Membrane Curvature or to participate in Membrane remodeling. We propose that sensing highly-curved Membranes requires that the polar and hydrophobic faces of the helix do not cooperate in lipid binding. A more detailed description of the interaction between amphipathic helices and lipids is however needed; notably to explain how new helices contribute to detection of modest changes in Curvature or even negative Curvature.
Knud J. Jensen - One of the best experts on this subject based on the ideXlab platform.
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Membrane Curvature and Lipid Composition Synergize To Regulate N-Ras Anchor Recruitment.
Biophysical journal, 2017Co-Authors: Jannik B. Larsen, Celeste Kennard, Søren L. Pedersen, Knud J. Jensen, Mark J. Uline, Nikos S. Hatzakis, Dimitrios StamouAbstract:Abstract Proteins anchored to Membranes through covalently linked fatty acids and/or isoprenoid groups play crucial roles in all forms of life. Sorting and trafficking of lipidated proteins has traditionally been discussed in the context of partitioning to Membrane domains of different lipid composition. We recently showed that Membrane shape/Curvature can in itself mediate the recruitment of lipidated proteins. However, exactly how Membrane Curvature and composition synergize remains largely unexplored. Here we investigated how three critical structural parameters of lipids, namely acyl chain saturation, headgroup size, and acyl chain length, modulate the capacity of Membrane Curvature to recruit lipidated proteins. As a model system we used the lipidated minimal Membrane anchor of the GTPase, N-Ras (tN-Ras). Our data revealed complex synergistic effects, whereby tN-Ras binding was higher on planar DOPC than POPC Membranes, but inversely higher on curved POPC than DOPC Membranes. This variation in the binding to both planar and curved Membranes leads to a net increase in the recruitment by Membrane Curvature of tN-Ras when reducing the acyl chain saturation state. Additionally, we found increased recruitment by Membrane Curvature of tN-Ras when substituting PC for PE, and when decreasing acyl chain length from 14 to 12 carbons (DMPC versus DLPC). However, these variations in recruitment ability had different origins, with the headgroup size primarily influencing tN-Ras binding to planar Membranes whereas the change in acyl chain length primarily affected binding to curved Membranes. Molecular field theory calculations recapitulated these findings and revealed lateral pressure as an underlying biophysical mechanism dictating how Curvature and composition synergize to modulate recruitment of lipidated proteins. Our findings suggest that the different compositions of cellular compartments could modulate the potency of Membrane Curvature to recruit lipidated proteins and thereby synergistically regulate the trafficking and sorting of lipidated proteins.
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Membrane Curvature regulates ligand-specific Membrane sorting of GPCRs in living cells.
Nature chemical biology, 2017Co-Authors: Kadla R. Rosholm, Søren L. Pedersen, Knud J. Jensen, Natascha Leijnse, Anna Mantsiou, Vadym Tkach, Volker F. Wirth, Lene B. Oddershede, Karen L. Martinez, Nikos S. HatzakisAbstract:The targeted spatial organization (sorting) of Gprotein-coupled receptors (GPCRs) is essential for their biological function and often takes place in highly curved Membrane compartments such as filopodia, endocytic pits, trafficking vesicles or endosome tubules. However, the influence of geometrical Membrane Curvature on GPCR sorting remains unknown. Here we used fluorescence imaging to establish a quantitative correlation between Membrane Curvature and sorting of three prototypic class A GPCRs (the neuropeptide Y receptor Y2, the β1 adrenergic receptor and the β2 adrenergic receptor) in living cells. Fitting of a thermodynamic model to the data enabled us to quantify how sorting is mediated by an energetic drive to match receptor shape and Membrane Curvature. Curvature-dependent sorting was regulated by ligands in a specific manner. We anticipate that this Curvature-dependent biomechanical coupling mechanism contributes to the sorting, trafficking and function of transMembrane proteins in general.
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Membrane Curvature enables n ras lipid anchor sorting to liquid ordered Membrane phases
Nature Chemical Biology, 2015Co-Authors: Jannik B. Larsen, Vikram K. Bhatia, Søren L. Pedersen, Mark J. Uline, Martin Borch Jensen, Thomas Bjørnholm, Lars Iversen, Igal Szleifer, Knud J. JensenAbstract:Membrane sorting of Ras and its isolated lipid anchor is based on Membrane Curvature, sensed by Ras itself. This helps to explain the previous inability to match in vivo results in vitro in promoting the raftophilic Ras to partition with Membrane lipid rafts.
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Lipid-Anchored Ras is Sorted by Membrane Curvature Both In Vitro and in Living Cells
Biophysical Journal, 2013Co-Authors: Jannik B. Larsen, Vikram K. Bhatia, Søren L. Pedersen, Knud J. Jensen, Martin Borch Jensen, Thomas Bjørnholm, Monika Köhnke, Daniel Abankwa, Kirill Alexandrov, Nikos S. HatzakisAbstract:In vivo studies have reported preferential partitioning of Ras GTPases into ordered lipid-protein Membrane domains, a process believed to regulate both cellular signaling and protein trafficking.1 However studies in vitro have failed to quantify a preferential partitioning of full length Ras proteins into the liquid ordered phase2,3 and thus a biophysically validated mechanism for in vivo sorting of Ras is still missing. We recently showed that lipidated proteins localize to highly curved Membranes in vitro.4 Here we study both in vitro and in vivo whether recruitment by Membrane Curvature can sort full length lipid-anchored Ras.We employ a single vesicle fluorescence based assay to quantify in vitro the sorting by Membrane Curvature of full-length Ras proteins. We demonstrate a more than 50 fold increase in protein density on Membranes of high Curvature as compared to the density on flat Membranes. To test for recruitment by Membrane Curvature in vivo we utilize hypo-osmotic swelling of cells, which flattens curved Membrane regions. By measuring the local protein density using FRET,5 we detect a significant reduction in the clustering of Ras and other lipidated proteins upon Membrane flattening. This demonstrates that recruitment by Membrane Curvature can sort Ras and potentially other lipidated proteins in cellular Membranes. Furthermore sorting by Membrane Curvature constitutes the first biophysical sorting mechanism for Ras validated by both in vitro and in vivo measurements.1 Hancock, J. F. Nat. Rev. Mol. Cell Biol.4 (2003).2 Johnson, S. A. et al.Biochim. Biophys. Acta - BioMembranes1798 (2010).3 Nicolini, C. et al.J. Am. Chem. Soc.128 (2006).4 Hatzakis, N. S. et al.Nat. Chem. Biol.5 (2009).5 Kohnke, M. et al.Chem. Biol.19 (2012).