Molecular Mechanisms of Platelet Exocytosis: Requirements for α-Granule Release

Lemons, Paula P.; Chen, Dong; Whiteheart, Sidney W.

doi:10.1006/bbrc.1999.2039

Cited by 99 publications

(132 citation statements)

References 34 publications

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“…SNAP-23 is also expressed in platelets [34] and antibodies against SNAP-23 inhibit α-granule secretion from permeabilized platelets [44]. In platelets, VAMP3 forms ternary complexes with syntaxin4 and SNAP-23 [34].…”

Section: Discussionmentioning

confidence: 99%

Membrane fusion by VAMP3 and plasma membrane t-SNAREs

Hardee

Minnear

2007

Experimental Cell Research

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Pairing of SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins on vesicles (v-SNAREs) and SNARE proteins on target membranes (t-SNAREs) mediates intracellular membrane fusion. VAMP3/cellubrevin is a v-SNARE that resides in recycling endosomes and endosome-derived transport vesicles. VAMP3 has been implicated in recycling of transferrin receptors, secretion of α-granules in platelets, and membrane trafficking during cell migration. Using a cell fusion assay, we examined membrane fusion capacity of the ternary complexes formed by VAMP3 and plasma membrane t-SNAREs syntaxin1, syntaxin4, SNAP-23 and SNAP-25. VAMP3 forms fusogenic pairing with t-SNARE complexes syntaxin1/SNAP-25, syntaxin1/SNAP-23 and syntaxin4/SNAP-25, but not with syntaxin4/SNAP-23. Deletion of the Nterminal domain of syntaxin4 enhanced membrane fusion more than two fold, indicating that the Nterminal domain negatively regulates membrane fusion. Differential membrane fusion capacities of the ternary v-/t-SNARE complexes suggest that transport vesicles containing VAMP3 have distinct membrane fusion kinetics with domains of the plasma membrane that present different t-SNARE proteins.

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Section: Discussionmentioning

confidence: 99%

Membrane fusion by VAMP3 and plasma membrane t-SNAREs

Hardee

Minnear

2007

Experimental Cell Research

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“…Others have shown that NSF regulates the disassembly of the SNARE complex, a step necessary for exocytosis in a wide variety of biological systems (36,42,52). Reed and coworkers (39,41) and Whiteheart and coworkers (53) have shown that NSF and SNARE molecules regulate platelet exocytosis. Our data show that NO covalently modifies NSF in platelets, thereby blocking exocytosis.…”

Section: Discussionmentioning

confidence: 99%

Regulation of platelet granule exocytosis by S-nitrosylation

Morrell

Matsushita

Chiles

et al. 2005

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

127

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Nitric oxide (NO) regulates platelet activation by cGMP-dependent mechanisms and by mechanisms that are not completely defined. Platelet activation includes exocytosis of platelet granules, releasing mediators that regulate interactions between platelets, leukocytes, and endothelial cells. Exocytosis is mediated in part by N-ethylmaleimide-sensitive factor (NSF), an ATPase that disassembles complexes of soluble NSF attachment protein receptors. We now demonstrate that NO inhibits exocytosis of dense granules, lysosomal granules, and ␣-granules from human platelets by Snitrosylation of NSF. Platelets lacking endothelial NO synthase show increased rolling on venules, increased thrombosis in arterioles, and increased exocytosis in vivo. Regulation of exocytosis is thus a mechanism by which NO regulates thrombosis.␣-granules ͉ nitric oxide N itric oxide (NO) plays a major role in vascular homeostasis, regulating vascular tone, leukocyte trafficking, and platelet adhesion and aggregation (1-4). NO regulates thrombosis in part by inhibition of platelet adhesion and aggregation (2, 5, 6). One well described pathway by which NO regulates platelet activation is mediated by guanylate cyclase (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24). NO activates guanylate cyclase in platelets, leading to an increase in cGMP (25)(26)(27). Targets of cGMP in platelets include cGMP-regulated phosphodiesterases (PDEs) PDE2 and PDE5, cGMP-dependent protein kinase type I␤, and perhaps cAMP-dependent protein kinases as well (28). The cGMP pathway mediates many of the effects of NO on platelet activation, such as inhibition of platelet aggregation. Thus, cGMP is a major mediator of NO signal transduction in platelets.NO also regulates platelets by cGMP-independent pathways. For example, certain NO donors inhibit platelet aggregation in a cGMP-independent manner (12,(29)(30)(31). Furthermore, NO activates platelet ADP-ribosyltransferase in a cGMP-independent manner (32). Finally, NO inhibits Ca 2ϩ mobilization in platelets independent of cGMP (33). Thus, NO inhibits platelet activation by both cGMP-dependent and less well characterized cGMPindependent pathways.Exocytosis of platelet granules is an important process by which platelets mediate thrombosis and vascular inflammation. The three types of platelet granules: dense granules, ␣-granules, and lysosomal granules, contain molecules that are released into the blood or are translocated to the platelet surface after exocytosis. Dense granules, the first to be released upon activation, contain small molecules such as serotonin, ATP and ADP, which are involved in platelet recruitment and activation. Contents of the ␣-granule include von Willebrand factor, P-selectin, and ␤-thromboglobulin, which promote platelet adherence, aggregation, and rolling on vessel walls. Lysosomal granules are the last to be released and contain degradative enzymes (34,35).Platelet granule exocytosis is mediated by a set of proteins that regulate vesicle trafficking (35)(36)(37)(38). Soluble N-...

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“…Platelet exocytosis is critical for hemostasis; however, it is increasingly obvious that platelets secrete components with (8)(9)(10)(11)(12)(13)(14). Further studies defined specific SNARE regulators, which control when and where the v-and t-SNAREs interact.…”

Section: Introductionmentioning

confidence: 99%

“…Interestingly, pretreatment with palmostatin B blocked the inhibitory effects of cerulenin suggesting that maintaining the acylation state is important for platelet function. Thus, our work shows that t-SNARE acylation is actively cycling in platelets and suggests that the enzymes regulating protein acylation could be potential targets to control platelet exocytosis in vivo.Platelet exocytosis is critical for hemostasis; however, it is increasingly obvious that platelets secrete components with (8)(9)(10)(11)(12)(13)(14). Further studies defined specific SNARE regulators, which control when and where the v-and t-SNAREs interact.…”

mentioning

confidence: 99%

“…SNAREs assemble into a trans-bilayer, four-helix bundle that mediates fusion between target membranes and cargo-containing vesicles (6,7). Genetic and biochemical studies have demonstrated roles for the vesicle/granule (v-or R-) SNAREs, Vesicle Associated Membrane Protein (VAMP) -7 and -8, and the target membrane (t-or Q) SNAREs, SNAP-23 (Q bc ), syntaxin-8, and -11 (Q a ) in mediating cargo release from all three classes of platelet granules (8)(9)(10)(11)(12)(13)(14). Further studies defined specific SNARE regulators, which control when and where the v-and t-SNAREs interact.…”

mentioning

confidence: 99%

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Dynamic cycling of t-SNARE acylation regulates platelet exocytosis

Zhang

Huang²,

Chen

et al. 2018

Journal of Biological Chemistry

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ABSTRACT:Platelets regulate vascular integrity by secreting a host of molecules that promote hemostasis and its sequelae. Given the importance of platelet exocytosis, it is critical to understand how it is controlled. The t-SNAREs, SNAP-23 and syntaxin-11, lack classical transmembrane domains (TMDs), yet both are associated with platelet membranes and redistributed into cholesterol-dependent, lipid rafts when platelets were activated. Using metabolic labeling and hydroxylamine/HCl (HA) treatment, we showed that both contain thioester-linked acyl groups. Mass spectrometry mapping further showed that syntaxin-11 was modified on Cysteine 275, 279, 280, 282, 283 and 285, was modified on Cysteine 79, 80, 83, 85, and 87. Interestingly, metabolic labeling studies showed incorporation of [ 3 H]-palmitate into the t-SNAREs increased though the protein levels were unchanged, suggesting that acylation turns over on the two t-SNAREs in resting platelets. Exogenously added fatty acids did compete with [ 3 H]-palmitate for t-SNARE labeling. To determine the effects of acylation, we measured aggregation, ADP/ATP release as well as P-selectin exposure in platelets treated with the acyl-transferase inhibitor, cerulenin, or the thioesterase inhibitor, palmostatin B. We found that cerulenin pretreatment inhibited t-SNARE acylation and platelet function in a dose-and time-dependent manner while palmostatin B had no detectable effect. Interestingly, pretreatment with palmostatin B blocked the inhibitory effects of cerulenin suggesting that maintaining the acylation state is important for platelet function. Thus, our work shows that t-SNARE acylation is actively cycling in platelets and suggests that the enzymes regulating protein acylation could be potential targets to control platelet exocytosis in vivo.Platelet exocytosis is critical for hemostasis; however, it is increasingly obvious that platelets secrete components with (8)(9)(10)(11)(12)(13)(14). Further studies defined specific SNARE regulators, which control when and where the v-and t-SNAREs interact. Aside from the role that I κ B Kinase-mediated phosphorylation plays in controlling SNAP-23/syntaxin-11 association (15), little is known about other post-translational modifications and their effects on the platelet exocytosis.Despite their importance to secretion, neither SNAP-23 nor syntaxin-11 contains a classical transmembrane domain (TMD), nor any identifiable CAAX motifs. Instead, both proteins contain cysteine-rich regions: human syntaxin-11 has 8 cysteines with 6 at its C-terminus, and SNAP-23 contains 6 cysteines with 5 in a central domain. These cysteine-rich regions have been shown, in some cells, to be important for membrane association and are potential sites for S-acylation (16)(17)(18)(19)(20) (27,28).Past studies have shown that acylation occurs in platelets (29). Dowal et al. characterized over 200 proteins in the platelet "palmitoylome", many of which appear to be involved in platelet signaling pathways (30). Consistently, Sim et al. showed that PAT-inhibit...

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Molecular Mechanisms of Platelet Exocytosis: Requirements for α-Granule Release

Cited by 99 publications

References 34 publications

Membrane fusion by VAMP3 and plasma membrane t-SNAREs

Membrane fusion by VAMP3 and plasma membrane t-SNAREs

Regulation of platelet granule exocytosis by S-nitrosylation

Dynamic cycling of t-SNARE acylation regulates platelet exocytosis

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