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Munc18a does not alter fusion rates mediated by neuronal SNAREs, synaptotagmin, and complexin.

Zhang Y, Diao J, Colbert KN, Lai Y, Pfuetzner RA, Padolina MS, Vivona S, Ressl S, Cipriano DJ, Choi UB, Shah N, Weis WI, Brunger AT - J. Biol. Chem. (2015)

Bottom Line: Moreover, a phosphorylation mimic mutant of Munc18a with reduced affinity to syntaxin-1A results in less reduction of vesicle association.In summary, Munc18a does not directly affect fusion, although it has an effect on the t-SNARE complex, depending on the presence of other factors and experimental conditions.Our results suggest that Munc18a primarily acts at the prefusion stage.

View Article: PubMed Central - PubMed

Affiliation: From the Departments of Molecular and Cellular Physiology, Neurology and Neurological Sciences, Structural Biology, and Photon Science and.

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Related in: MedlinePlus

Munc18a binds soluble t-SNAREs and SNARE complex with similar thermodynamics. t-SNAREs (A) or SNARE complex (100–180 μm) (B) was titrated into Munc18a (9–11 μm). The top panel shows the heat signals corresponding to each injection. The bottom panel shows the integrated areas versus molar ratio of interacting species. Data were fit to a single binding site model using a nonlinear least squares fit (solid line). Thermodynamic parameters are presented in Table 1.
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Figure 3: Munc18a binds soluble t-SNAREs and SNARE complex with similar thermodynamics. t-SNAREs (A) or SNARE complex (100–180 μm) (B) was titrated into Munc18a (9–11 μm). The top panel shows the heat signals corresponding to each injection. The bottom panel shows the integrated areas versus molar ratio of interacting species. Data were fit to a single binding site model using a nonlinear least squares fit (solid line). Thermodynamic parameters are presented in Table 1.

Mentions: So far, there is little evidence from reconstitution experiments that Munc18a plays a major role in fusion itself, although stimulatory effects by SM proteins on SNARE-dependent lipid mixing were observed using ensemble fluorescence assays (16–18). A stimulatory effect of Munc18a was also observed in conjunction with neuronal SNAREs using a single vesicle-vesicle lipid-mixing assay (19). However, all of these experiments only used neuronal SNAREs in addition to Munc18a. Subsequent ensemble experiments that reconstituted neuronal SNAREs in liposomes along with neuron-specific proteins synaptotagmin-1 and complexin-1 showed only a relatively small increase of spontaneous (i.e. at zero Ca2+ concentration) lipid mixing and content mixing upon Munc18a inclusion when complexin-1 was present (see Fig. 3 (D and F) in Ref. 20).


Munc18a does not alter fusion rates mediated by neuronal SNAREs, synaptotagmin, and complexin.

Zhang Y, Diao J, Colbert KN, Lai Y, Pfuetzner RA, Padolina MS, Vivona S, Ressl S, Cipriano DJ, Choi UB, Shah N, Weis WI, Brunger AT - J. Biol. Chem. (2015)

Munc18a binds soluble t-SNAREs and SNARE complex with similar thermodynamics. t-SNAREs (A) or SNARE complex (100–180 μm) (B) was titrated into Munc18a (9–11 μm). The top panel shows the heat signals corresponding to each injection. The bottom panel shows the integrated areas versus molar ratio of interacting species. Data were fit to a single binding site model using a nonlinear least squares fit (solid line). Thermodynamic parameters are presented in Table 1.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4400359&req=5

Figure 3: Munc18a binds soluble t-SNAREs and SNARE complex with similar thermodynamics. t-SNAREs (A) or SNARE complex (100–180 μm) (B) was titrated into Munc18a (9–11 μm). The top panel shows the heat signals corresponding to each injection. The bottom panel shows the integrated areas versus molar ratio of interacting species. Data were fit to a single binding site model using a nonlinear least squares fit (solid line). Thermodynamic parameters are presented in Table 1.
Mentions: So far, there is little evidence from reconstitution experiments that Munc18a plays a major role in fusion itself, although stimulatory effects by SM proteins on SNARE-dependent lipid mixing were observed using ensemble fluorescence assays (16–18). A stimulatory effect of Munc18a was also observed in conjunction with neuronal SNAREs using a single vesicle-vesicle lipid-mixing assay (19). However, all of these experiments only used neuronal SNAREs in addition to Munc18a. Subsequent ensemble experiments that reconstituted neuronal SNAREs in liposomes along with neuron-specific proteins synaptotagmin-1 and complexin-1 showed only a relatively small increase of spontaneous (i.e. at zero Ca2+ concentration) lipid mixing and content mixing upon Munc18a inclusion when complexin-1 was present (see Fig. 3 (D and F) in Ref. 20).

Bottom Line: Moreover, a phosphorylation mimic mutant of Munc18a with reduced affinity to syntaxin-1A results in less reduction of vesicle association.In summary, Munc18a does not directly affect fusion, although it has an effect on the t-SNARE complex, depending on the presence of other factors and experimental conditions.Our results suggest that Munc18a primarily acts at the prefusion stage.

View Article: PubMed Central - PubMed

Affiliation: From the Departments of Molecular and Cellular Physiology, Neurology and Neurological Sciences, Structural Biology, and Photon Science and.

Show MeSH
Related in: MedlinePlus