C2 domain membrane penetration by group IVA cytosolic phospholipase A2 induces membrane curvature changes

Ward, Katherine E.; Ropa, James; Adu-Gyamfi, Emmanuel; Stahelin, Robert V.

doi:10.1194/jlr.m030718

Cited by 24 publications

(39 citation statements)

References 62 publications

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“…1E and Movie S1). The reversibility of the process suggests that successive treatment of cells with hypotonic and isotonic media can be used to investigate the mechanisms of various ER membrane remodeling phenomena such as tubulation and fusion (33)(34)(35). The membrane of the ER is thinner than the PM due to its reduced cholesterol content and it has yet to be shown that this membrane has the physical-chemical capacity for temperature-dependent phase separation (8,15,36).…”

Section: Resultsmentioning

confidence: 99%

ER membranes exhibit phase behavior at sites of organelle contact

King

Sengupta

Seo

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

138

114

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The endoplasmic reticulum (ER) is the site of synthesis of secretory and membrane proteins and contacts every organelle of the cell, exchanging lipids and metabolites in a highly regulated manner. How the ER spatially segregates its numerous and diverse functions, including positioning nanoscopic contact sites with other organelles, is unclear. We demonstrate that hypotonic swelling of cells converts the ER and other membrane-bound organelles into micrometerscale large intracellular vesicles (LICVs) that retain luminal protein content and maintain contact sites with each other through localized organelle tethers. Upon cooling, ER-derived LICVs phase-partition into microscopic domains having different lipid-ordering characteristics, which is reversible upon warming. Ordered ER lipid domains mark contact sites with ER and mitochondria, lipid droplets, endosomes, or plasma membrane, whereas disordered ER lipid domains mark contact sites with lysosomes or peroxisomes. Tethering proteins concentrate at ER-organelle contact sites, allowing time-dependent behavior of lipids and proteins to be studied at these sites. These findings demonstrate that LICVs provide a useful model system for studying the phase behavior and interactive properties of organelles in intact cells. endoplasmic reticulum | contact sites | phase partitioning | organelle tethers I t has long been hypothesized that small, diffraction-limited, liquid-ordered (L o ) microdomains can form on the plasma membrane (PM) of cells (1-3). Lipids such as cholesterol and sphingolipids are concentrated in these domains, and membrane and membrane-associated proteins can preferentially segregate into these domains to allow sorting of proteins and localized signal transduction (2, 4). Giant PM vesicles (GPMVs) isolated from mammalian PM have been an important tool for studying these properties in physiological membranes (5-8). GPMVs contain the complex mixture of lipids and proteins found in intact PM, are not contaminated with membranes from other organelles, and phase-separate into microscopically visible L o -like and liquiddisordered-like lipid domains (8). These features make GPMVs a suitable model system for studying the lipid domain preference of membrane proteins (7,9,10). Phase-like membrane heterogeneities with physical properties similar to the lipid phases in GPMVs are also thought to occur in the intact PM, albeit on a smaller scale due to constant lipid turnover and membrane trafficking (11). As an example, a recent study demonstrated a functional role of lipidbased phase separation in mammalian PM by showing ordered L olike domain formation during HIV assembly at the PM, a process driving sorting of specific proteins into HIV membranes (4).

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Section: Resultsmentioning

confidence: 99%

ER membranes exhibit phase behavior at sites of organelle contact

King

Sengupta

Seo

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

138

114

View full text Add to dashboard Cite

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“…This could be simply due to the lack of tethered granules or because Munc13-4 performs a second, Ca 2+ -dependent process that is important for SNARE-mediated fusion. C2 domains in other proteins have been shown to insert into bilayers presumably to promote membrane fusion (69, 70). At this stage, our experiments do not differentiate these two possibilities.…”

Section: Discussionmentioning

confidence: 99%

Role of Munc13-4 as a Ca2+-dependent tether during platelet secretion

Chicka

Ren

Richards

et al. 2016

Biochemical Journal

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The Munc13 family of exocytosis regulators has multiple Ca2+-binding, C2 domains. Here, we probed the mechanism by which Munc13-4 regulates in vitro membrane fusion and platelet exocytosis. We show that Munc13-4 enhances in vitro SNARE-dependent, proteoliposome fusion in a Ca2+- and phosphatidylserine (PS)-dependent manner that was independent of SNARE concentrations. Munc13-4-SNARE interactions, under the conditions used, were minimal in the absence or presence of Ca2+. However, Munc13-4 was able to bind and cluster liposomes harboring PS in response to Ca2+. Interestingly, Ca2+-dependent liposome binding/clustering and enhancement of proteoliposome fusion required both Munc13-4 C2 domains, but only the Ca2+-liganding aspartate residues of the C2B domain. Analytical ultracentrifugation measurements indicated that, in solution, Munc13-4 was a monomeric prolate ellipsoid with dimensions consistent with a molecule that could bridge two fusing membranes. To address the potential role of Munc13-4 as a tethering protein in platelets, we examined mepacrine-stained, dense granule mobility and secretion in platelets from wild-type and Munc13-4 null (Unc13dJinx) mice. In the absence of Munc13-4, dense granules were highly mobile in both resting and stimulated platelets, and stimulation-dependent granule release was absent. These observations suggest that dense granules are stably docked in resting platelets awaiting stimulation and that Munc13-4 plays a vesicle-stabilizing or tethering role in resting platelets and also in activated platelets in response to Ca2+. In summary, we show that Munc13-4 conveys Ca2+ sensitivity to platelet SNARE-mediated membrane fusion and reveal a potential mechanism by which Munc13-4 bridges and stabilizes apposing membranes destined for fusion. (246 words)

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“…The C2A domain of Dysferlin has been shown to have a canonical C2A and a variant (C2Av1) these two molecules have different Ca 2+ -binding properties and different ligand preferences (Fuson et al 2013). In addition to diverse roles in Ca 2+ selectivity and lipid-binding some C2 domains have been shown to induce membrane curvature changes upon membrane association (Martens et al 2007; Hui et al 2009; Ward et al 2012; Yu et al 2013; Sot et al 2013). This biophysical property of some C2 domains may be important to vesicle trafficking and exocytosis as well as cellular localization and activity.…”

Section: Phosphoinositide Binding Modulesmentioning

confidence: 99%

Cellular and molecular interactions of phosphoinositides and peripheral proteins

Stahelin

Scott

Frick

2014

Chemistry and Physics of Lipids

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Anionic lipids act as signals for the recruitment of proteins containing cationic clusters to biological membranes. A family of anionic lipids known as the phosphoinositides (PIPs) are low in abundance, yet play a critical role in recruitment of peripheral proteins to the membrane interface. PIPs are mono-, bis-, or trisphosphorylated derivatives of phosphatidylinositol (PI) yielding seven species with different structure and anionic charge. The differential spatial distribution and temporal appearance of PIPs is key to their role in communicating information to target proteins. Selective recognition of PIPs came into play with the discovery that the substrate of protein kinase C termed pleckstrin possessed the first PIP binding region termed the pleckstrin homology (PH) domain. Since the discovery of the PH domain, more than ten PIP binding domains have been identified including PH, ENTH, FYVE, PX, and C2 domains. Representative examples of each of these domains have been thoroughly characterized to understand how they coordinate PIP headgroups in membranes, translocate to specific membrane docking sites in the cell, and function to regulate the activity of their full-length proteins. In addition, a number of novel mechanisms of PIP-mediated membrane association have emerged, such as coincidence detection – specificity for two distinct lipid headgroups. Other PIP-binding domains may also harbor selectivity for a membrane physical property such as charge or membrane curvature. This review summarizes the current understanding of the cellular distribution of PIPs and their molecular interaction with peripheral proteins.

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C2 domain membrane penetration by group IVA cytosolic phospholipase A2 induces membrane curvature changes

Cited by 24 publications

References 62 publications

ER membranes exhibit phase behavior at sites of organelle contact

ER membranes exhibit phase behavior at sites of organelle contact

Role of Munc13-4 as a Ca2+-dependent tether during platelet secretion

Cellular and molecular interactions of phosphoinositides and peripheral proteins

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