Munc18-1 domain-1 controls vesicle docking and secretion by interacting with syntaxin-1 and chaperoning it to the plasma membrane

Han, Gayoung A.; Malintan, Nancy T.; Saw, Ner Mu Nar; Li, Lijun; Han, Liping; Meunier, Frédéric A.; Collins, Brett M.; Sugita, Shuzo

doi:10.1091/mbc.e11-02-0135

Cited by 56 publications

(73 citation statements)

References 59 publications

(122 reference statements)

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“…4). This same cavity has been implicated in the binding of SNARE complexes (24,26,27). The Munc18 binding site of the Sx H3 helix is not definitive in our model; indeed, it is likely to be very flexible.…”

Section: Discussionmentioning

confidence: 66%

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Low-resolution solution structures of Munc18:Syntaxin protein complexes indicate an open binding mode driven by the Syntaxin N-peptide

Christie¹,

Whitten²,

King³

et al. 2012

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

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When nerve cells communicate, vesicles from one neuron fuse with the presynaptic membrane releasing chemicals that signal to the next. Similarly, when insulin binds its receptor on adipocytes or muscle, glucose transporter-4 vesicles fuse with the cell membrane, allowing glucose to be imported. These essential processes require the interaction of SNARE proteins on vesicle and cell membranes, as well as the enigmatic protein Munc18 that binds the SNARE protein Syntaxin. Here, we show that in solution the neuronal protein Syntaxin1a interacts with Munc18-1 whether or not the Syntaxin1a N-peptide is present. Conversely, the adipocyte protein Syntaxin4 does not bind its partner Munc18c unless the N-peptide is present. Solution-scattering data for the Munc18-1:Syntaxin1a complex in the absence of the N-peptide indicates that this complex adopts the inhibitory closed binding mode, exemplified by a crystal structure of the complex. However, when the N-peptide is present, the solution-scattering data indicate both Syntaxin1a and Syntaxin4 adopt extended conformations in complexes with their respective Munc18 partners. The low-resolution solution structure of the open Munc18:Syntaxin binding mode was modeled using data from cross-linking/mass spectrometry, small-angle X-ray scattering, and small-angle neutron scattering with contrast variation, indicating significant differences in Munc18:Syntaxin interactions compared with the closed binding mode. Overall, our results indicate that the neuronal Munc18-1:Syntaxin1a proteins can adopt two alternate and functionally distinct binding modes, closed and open, depending on the presence of the N-peptide, whereas Munc18c:Syntaxin4 adopts only the open binding mode. membrane fusion | protein interactions | small-angle neutron scattering | small-angle X-ray scattering M embrane trafficking is an essential and highly regulated process whereby cargo-carrying vesicles are directed to dock and fuse with specific cell membranes. The process requires soluble N-ethylmaleimide-sensitive factor attachment receptor (SNARE) proteins on vesicle and target membranes. These interact to form high-affinity SNARE complexes required for docking and membrane fusion (1, 2). Structurally, the SNARE complex is a parallel four-helix bundle comprising helices contributed from several partner SNAREs (3). This helical bundle promotes vesicle fusion by bringing the vesicle and plasma membranes into close proximity and by providing the energy required for membrane fusion (4, 5).In the neuronal synapse, neurotransmitters are released from nerve cells by SNARE-mediated fusion of vesicles with the plasma membrane in response to action potentials. In this process, one of four SNARE helices is contributed by Syntaxin (Sx) 1a, a protein localized at the plasma membrane by a transmembrane helix. In addition to its membrane-anchored SNARE helix (H3), Sx1a has an Habc domain that can bind to the H3 helix (6) forming a closed Sx1a conformation (Fig. 1A). This closed conformation inactivates Sx1a by preventing H3 inter...

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Section: Discussionmentioning

confidence: 66%

“…Rathore et al showed that the Sx Npeptide recruits Munc18-1 for assembly of the SNARE:SM complex and does not need to be attached to Sx to exert this effect (25). Finally, the central cavity of the SM protein has been linked to binding of closed Sx1a and to binding of the core helical bundle of SNARE complexes (24,26,27).…”

mentioning

confidence: 99%

Low-resolution solution structures of Munc18:Syntaxin protein complexes indicate an open binding mode driven by the Syntaxin N-peptide

Christie¹,

Whitten²,

King³

et al. 2012

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

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“…We previously found that Munc18-1/2 DKD causes not only a strong reduction in syntaxin-1 level but also perturbation of its plasmalemmal localization in PC12 cells (15,16). We therefore examined whether the subcellular localization of syntaxin-11 can be significantly altered by Munc18-1/2 DKD in RBL-2H3 cells ( Fig.…”

Section: Resultsmentioning

confidence: 97%

“…The Munc18 family of proteins has been revealed to play multiple functions, which include both chaperoning cognate syntaxins (14)(15)(16)(17)(18)(19) and priming/stimulating membrane fusion through interaction with the SNARE complex (20-23) (reviewed in ref. 24).…”

mentioning

confidence: 99%

Crucial role of the hydrophobic pocket region of Munc18 protein in mast cell degranulation

Bin

Jung

Piggott

et al. 2013

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

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The function of the Munc18-1 protein hydrophobic pocket, which interacts with the syntaxin-1 N-terminal peptide, has been highly controversial in neurosecretion. Recent analysis of patients with familial hemophagocytic lymphohistiocytosis type 5 has identified the E132A mutation in the hydrophobic pocket of Munc18-2, prompting us to examine the role of this region in the context of immune cell secretion. Double knockdown of Munc18-1 and Munc18-2 in RBL-2H3 mast cells eliminates both IgE-dependent and ionomycin-induced degranulation and causes a significant reduction in syntaxin-11 without altering expressions of the other syntaxin isoforms examined. These phenotypes were effectively rescued on reexpression of wild-type Munc18-1 or Munc18-2 but not the mutants (F115E, E132A, and F115E/E132A) in the hydrophobic pocket of Munc18. In addition, these mutants show that they are unable to directly interact with syntaxin-11, as tested through protein interaction experiments. Our results demonstrate the crucial roles of the hydrophobic pocket of Munc18 in mast cell degranulation, which include the regulation of syntaxin-11. We also suggest that the functional importance of this region is significantly different between neuronal and immune cell exocytosis.membrane fusion | FHL5

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“…To examine whether the reduction in fusion events resulted from reduced SV docking in response to stimulation, we used PC12 cells engineered to knock down Munc18-1 and Munc18-2 (DKD-PC12 cells) 31 , which have been shown to exhibit defective vesicle docking 31,33 . Electron microscopy analysis revealed that the number of predocked granules in these cells was significantly reduced in comparison with that in DKD-PC12 cells in which wild-type Munc18-1 (Munc18-1) expression was rescued (Fig.…”

Section: Svs and Cortical Actin Approach The Plasmalemma On Stimulationmentioning

confidence: 99%

Activity-driven relaxation of the cortical actomyosin II network synchronizes Munc18-1-dependent neurosecretory vesicle docking

et al. 2015

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In neurosecretory cells, secretory vesicles (SVs) undergo Ca 2 þ -dependent fusion with the plasma membrane to release neurotransmitters. How SVs cross the dense mesh of the cortical actin network to reach the plasma membrane remains unclear. Here we reveal that, in bovine chromaffin cells, SVs embedded in the cortical actin network undergo a highly synchronized transition towards the plasma membrane and Munc18-1-dependent docking in response to secretagogues. This movement coincides with a translocation of the cortical actin network in the same direction. Both effects are abolished by the knockdown or the pharmacological inhibition of myosin II, suggesting changes in actomyosin-generated forces across the cell cortex. Indeed, we report a reduction in cortical actin network tension elicited on secretagogue stimulation that is sensitive to myosin II inhibition. We reveal that the cortical actin network acts as a 'casting net' that undergoes activity-dependent relaxation, thereby driving tethered SVs towards the plasma membrane where they undergo Munc18-1-dependent docking.

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Munc18-1 domain-1 controls vesicle docking and secretion by interacting with syntaxin-1 and chaperoning it to the plasma membrane

Abstract: Striking correlations exist between the abilities of domain-1 cleft mutants of Munc18-1 to bind and chaperone syntaxin-1 and their ability to restore vesicle docking and secretion.

Cited by 56 publications

References 59 publications

Low-resolution solution structures of Munc18:Syntaxin protein complexes indicate an open binding mode driven by the Syntaxin N-peptide

Low-resolution solution structures of Munc18:Syntaxin protein complexes indicate an open binding mode driven by the Syntaxin N-peptide

Crucial role of the hydrophobic pocket region of Munc18 protein in mast cell degranulation

Activity-driven relaxation of the cortical actomyosin II network synchronizes Munc18-1-dependent neurosecretory vesicle docking

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