scholarly journals Eisosome proteins assemble into a membrane scaffold

2011 ◽  
Vol 195 (5) ◽  
pp. 889-902 ◽  
Author(s):  
Lena Karotki ◽  
Juha T. Huiskonen ◽  
Christopher J. Stefan ◽  
Natasza E. Ziółkowska ◽  
Robyn Roth ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Self Assembly ◽  
Spatial Organization ◽  
Protein Complexes ◽  
Lipid Binding ◽  
Yeast Cells ◽  
Core Components ◽  
The Many ◽  
Plasma Membrane Domain ◽  
Membrane Scaffold

Spatial organization of membranes into domains of distinct protein and lipid composition is a fundamental feature of biological systems. The plasma membrane is organized in such domains to efficiently orchestrate the many reactions occurring there simultaneously. Despite the almost universal presence of membrane domains, mechanisms of their formation are often unclear. Yeast cells feature prominent plasma membrane domain organization, which is at least partially mediated by eisosomes. Eisosomes are large protein complexes that are primarily composed of many subunits of two Bin–Amphiphysin–Rvs domain–containing proteins, Pil1 and Lsp1. In this paper, we show that these proteins self-assemble into higher-order structures and bind preferentially to phosphoinositide-containing membranes. Using a combination of electron microscopy approaches, we generate structural models of Pil1 and Lsp1 assemblies, which resemble eisosomes in cells. Our data suggest that the mechanism of membrane organization by eisosomes is mediated by self-assembly of its core components into a membrane-bound protein scaffold with lipid-binding specificity.

scholarly journals Probing the biogenesis pathway and dynamics of thylakoid membranes

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Tuomas Huokko ◽  
Tao Ni ◽  
Gregory F. Dykes ◽  
Deborah M. Simpson ◽  
Philip Brownridge ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Photosystem I ◽  
Spatial Organization ◽  
Electron Flux ◽  
Protein Complexes ◽  
Thylakoid Membranes ◽  
Thylakoid Biogenesis ◽  
Photosynthetic Complexes ◽  
Photosynthetic Machinery ◽  
Pcc 7942

AbstractHow thylakoid membranes are generated to form a metabolically active membrane network and how thylakoid membranes orchestrate the insertion and localization of protein complexes for efficient electron flux remain elusive. Here, we develop a method to modulate thylakoid biogenesis in the rod-shaped cyanobacterium Synechococcus elongatus PCC 7942 by modulating light intensity during cell growth, and probe the spatial-temporal stepwise biogenesis process of thylakoid membranes in cells. Our results reveal that the plasma membrane and regularly arranged concentric thylakoid layers have no physical connections. The newly synthesized thylakoid membrane fragments emerge between the plasma membrane and pre-existing thylakoids. Photosystem I monomers appear in the thylakoid membranes earlier than other mature photosystem assemblies, followed by generation of Photosystem I trimers and Photosystem II complexes. Redistribution of photosynthetic complexes during thylakoid biogenesis ensures establishment of the spatial organization of the functional thylakoid network. This study provides insights into the dynamic biogenesis process and maturation of the functional photosynthetic machinery.

scholarly journals TORC2 Plasma Membrane Localization Is Essential for Cell Viability and Restricted to a Distinct Domain

2009 ◽  
Vol 20 (5) ◽  
pp. 1565-1575 ◽  
Author(s):  
Doris Berchtold ◽  
Tobias C. Walther
Keyword(s):  
Plasma Membrane ◽  
Actin Polymerization ◽  
Lipid Binding ◽  
Membrane Localization ◽  
Cellular Functions ◽  
Signaling Specificity ◽  
Downstream Signaling ◽  
Plasma Membrane Localization ◽  
Membrane Compartment ◽  
Plasma Membrane Domain

The conserved target of rapamycin (TOR) kinases regulate many aspects of cellular physiology. They exist in two distinct complexes, termed TOR complex 1 (TORC1) and TOR complex 2 (TORC2), that posses both overlapping and distinct components. TORC1 and TORC2 respond differently to the drug rapamycin and have different cellular functions: whereas the rapamycin-sensitive TORC1 controls many aspects of cell growth and has been characterized in great detail, the TOR complex 2 is less understood and regulates actin polymerization, cell polarity, and ceramide metabolism. How signaling specificity and discrimination between different input signals for the two kinase complexes is achieved is not understood. Here, we show that TORC1 and TORC2 have different localizations in Saccharomyces cerevisiae. TORC1 is localized exclusively to the vacuolar membrane, whereas TORC2 is localized dynamically in a previously unrecognized plasma membrane domain, which we term membrane compartment containing TORC2 (MCT). We find that plasma membrane localization of TORC2 is essential for viability and mediated by lipid binding of the C-terminal domain of the Avo1 subunit. From these data, we suggest that the TOR complexes are spatially separated to determine downstream signaling specificity and their responsiveness to different inputs.

scholarly journals Annexin A2–dependent actin bundling promotes secretory granule docking to the plasma membrane and exocytosis

2015 ◽  
Vol 210 (5) ◽  
pp. 785-800 ◽  
Author(s):  
Marion Gabel ◽  
Franck Delavoie ◽  
Valérie Demais ◽  
Cathy Royer ◽  
Yannick Bailly ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Spatial Organization ◽  
Electron Tomography ◽  
Secretory Granules ◽  
Membrane Lipid ◽  
Lipid Binding ◽  
Annexin A2 ◽  
Cortical Actin ◽  
Lipid Microdomains ◽  
Lipid Domain

Annexin A2, a calcium-, actin-, and lipid-binding protein involved in exocytosis, mediates the formation of lipid microdomains required for the structural and spatial organization of fusion sites at the plasma membrane. To understand how annexin A2 promotes this membrane remodeling, the involvement of cortical actin filaments in lipid domain organization was investigated. 3D electron tomography showed that cortical actin bundled by annexin A2 connected docked secretory granules to the plasma membrane and contributed to the formation of GM1-enriched lipid microdomains at the exocytotic sites in chromaffin cells. When an annexin A2 mutant with impaired actin filament–bundling activity was expressed, the formation of plasma membrane lipid microdomains and the number of exocytotic events were decreased and the fusion kinetics were slower, whereas the pharmacological activation of the intrinsic actin-bundling activity of endogenous annexin A2 had the opposite effects. Thus, annexin A2–induced actin bundling is apparently essential for generating active exocytotic sites.

scholarly journals Annexin A2 Egress during Calcium-Regulated Exocytosis in Neuroendocrine Cells

Cells ◽  
2020 ◽  
Vol 9 (9) ◽  
pp. 2059 ◽  
Author(s):  
Marion Gabel ◽  
Cathy Royer ◽  
Tamou Thahouly ◽  
Valérie Calco ◽  
Stéphane Gasman ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Plasminogen Activator ◽  
Tissue Plasminogen Activator ◽  
Chromaffin Cells ◽  
Spatial Organization ◽  
Lipid Binding ◽  
Annexin A2 ◽  
Neuroendocrine Cells ◽  
Outer Face ◽  
Tissue Plasminogen

Annexin A2 (AnxA2) is a calcium- and lipid-binding protein involved in neuroendocrine secretion where it participates in the formation and/or stabilization of lipid micro-domains required for structural and spatial organization of the exocytotic machinery. We have recently described that phosphorylation of AnxA2 on Tyr23 is critical for exocytosis. Considering that Tyr23 phosphorylation is known to promote AnxA2 externalization to the outer face of the plasma membrane in different cell types, we examined whether this phenomenon occurred in neurosecretory chromaffin cells. Using immunolabeling and biochemical approaches, we observed that nicotine stimulation triggered the egress of AnxA2 to the external leaflets of the plasma membrane in the vicinity of exocytotic sites. AnxA2 was found co-localized with tissue plasminogen activator, previously described on the surface of chromaffin cells following secretory granule release. We propose that AnxA2 might be a cell surface tissue plasminogen activator receptor for chromaffin cells, thus playing a role in autocrine or paracrine regulation of exocytosis.

scholarly journals The Hob proteins are novel and conserved lipid binding proteins at ER-PM contact sites

2021 ◽  
Author(s):  
Sarah D. Neuman ◽  
Jeff R. Jorgensen ◽  
Amy T. Cavanagh ◽  
Jeremy T. Smyth ◽  
Jane E. Selegue ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Protein Composition ◽  
Lipid Binding ◽  
Model Systems ◽  
Yeast Cells ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Critical Junctures ◽  
C Terminus ◽  
Membrane Contact

ABSTRACTMembrane contact sites are critical junctures for organelle signaling and communication. Endoplasmic reticulum-plasma membrane (ER-PM) contact sites were the first membrane contact sites to be described; however, the protein composition and molecular function of these sites is still emerging. Here, we leverage yeast and Drosophila model systems to uncover a novel role for the Hobbit/Hob proteins at ER-PM contact sites. We find that Hobbit localizes to ER-PM contact sites in both yeast cells and the Drosophila larval salivary glands, and this localization is mediated by an N-terminal ER membrane anchor and conserved C-terminal sequences. The C-terminus of Hobbit binds to plasma membrane phosphatidylinositols, and the distribution of these lipids is altered in hobbit mutant cells. Notably, the Hobbit protein is essential for viability in higher animals, providing one of the first examples of a membrane contact site-localized lipid binding protein that is required for development.

scholarly journals The Hob proteins are novel and conserved lipid-binding proteins at ER–PM contact sites

2021 ◽  
Vol 135 (5) ◽  
Author(s):  
Sarah D. Neuman ◽  
Jeff R. Jorgensen ◽  
Amy T. Cavanagh ◽  
Jeremy T. Smyth ◽  
Jane E. Selegue ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Protein Composition ◽  
Lipid Binding ◽  
Model Systems ◽  
Yeast Cells ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Critical Junctures ◽  
C Terminus ◽  
Membrane Contact

ABSTRACT Membrane contact sites are critical junctures for organelle signaling and communication. Endoplasmic reticulum–plasma membrane (ER–PM) contact sites were the first membrane contact sites to be described; however, the protein composition and molecular function of these sites is still emerging. Here, we leverage yeast and Drosophila model systems to uncover a novel role for the Hobbit (Hob) proteins at ER–PM contact sites. We find that Hobbit localizes to ER–PM contact sites in both yeast cells and the Drosophila larval salivary glands, and this localization is mediated by an N-terminal ER membrane anchor and conserved C-terminal sequences. The C-terminus of Hobbit binds to plasma membrane phosphatidylinositols, and the distribution of these lipids is altered in hobbit mutant cells. Notably, the Hobbit protein is essential for viability in Drosophila, providing one of the first examples of a membrane contact site-localized lipid binding protein that is required for development.

Heterogeneity of Size and Distribution of Intramembrane Particles in the Plasma Membrane of Yeast

1977 ◽  
Vol 35 ◽  
pp. 596-597
Author(s):  
E. Keyhani
Keyword(s):  
Plasma Membrane ◽  
Candida Utilis ◽  
Synthetic Medium ◽  
Freeze Fracture ◽  
Translational Diffusion ◽  
Yeast Cells ◽  
Distilled Water ◽  
Intramembrane Particles ◽  
The Matrix ◽  
Water Cell

The matrix of biological membranes consists of a lipid bilayer into which proteins or protein aggregates are intercalated. Freeze-fracture techni- ques permit these proteins, perhaps in association with lipids, to be visualized in the hydrophobic regions of the membrane. Thus, numerous intramembrane particles (IMP) have been found on the fracture faces of membranes from a wide variety of cells (1-3). A recognized property of IMP is their tendency to form aggregates in response to changes in experi- mental conditions (4,5), perhaps as a result of translational diffusion through the viscous plane of the membrane. The purpose of this communica- tion is to describe the distribution and size of IMP in the plasma membrane of yeast (Candida utilis).Yeast cells (ATCC 8205) were grown in synthetic medium (6), and then harvested after 16 hours of culture, and washed twice in distilled water. Cell pellets were suspended in growth medium supplemented with 30% glycerol and incubated for 30 minutes at 0°C, centrifuged, and prepared for freeze-fracture, as described earlier (2,3).

Deformation of Yeast Plasma Membrane by Ethidium Bromide

1988 ◽  
Vol 46 ◽  
pp. 254-255
Author(s):  
E. Keyhani
Keyword(s):  
Plasma Membrane ◽  
Thin Section ◽  
Ethidium Bromide ◽  
Freeze Fracture ◽  
Mutagenic Effect ◽  
Yeast Cells ◽  
Hydrophobic Region ◽  
Thin Section Electron Microscopy ◽  
Section Electron ◽  
Deep Pits

The mutagenic effect of ethidium bromide on the mitochondrial DNA is well established. Using thin section electron microscopy, it was shown that when yeast cells were grown in the presence of ethidium bromide, besides alterations in the mitochondria, the plasma membrane also showed alterations consisting of 75 to 110 nm-deep pits. Furthermore, ethidium bromide induced an increase in the length and number of endoplasmic reticulum and in the number of intracytoplasmic vesicles.Freeze-fracture, by splitting the hydrophobic region of the membrane, allows the visualization of the surface view of the membrane, and consequently, any alteration induced by ethidium bromide on the membrane can be better examined by this method than by the thin section method.Yeast cells, Candida utilis. were grown in the presence of 35 μM ethidium bromide. Cells were harvested and freeze-fractured according to the procedure previously described.

Caveolin-1, galectin-3 and lipid raft domains in cancer cell signalling

2015 ◽  
Vol 57 ◽  
pp. 189-201 ◽  
Author(s):  
Jay Shankar ◽  
Cecile Boscher ◽  
Ivan R. Nabi
Keyword(s):  
Plasma Membrane ◽  
Lipid Rafts ◽  
Cancer Cell ◽  
Cellular Response ◽  
Spatial Organization ◽  
Essential Feature ◽  
Cell Signalling ◽  
Coated Pits ◽  
Signalling Molecules ◽  
Raft Domains

Spatial organization of the plasma membrane is an essential feature of the cellular response to external stimuli. Receptor organization at the cell surface mediates transmission of extracellular stimuli to intracellular signalling molecules and effectors that impact various cellular processes including cell differentiation, metabolism, growth, migration and apoptosis. Membrane domains include morphologically distinct plasma membrane invaginations such as clathrin-coated pits and caveolae, but also less well-defined domains such as lipid rafts and the galectin lattice. In the present chapter, we will discuss interaction between caveolae, lipid rafts and the galectin lattice in the control of cancer cell signalling.

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