A mechanism of Munc18b-syntaxin 3-SNAP25 complex assembly in regulated epithelial secretion.
Syntaxin and Munc18 are essential for regulated exocytosis in all eukaryotes. It was shown that Munc18 inhibition of neuronal syntaxin 1 can be overcome by CDK5 phosphorylation, indicating that structural change disrupts the syntaxin-Munc18 interaction. Here, we show that this phosphorylation promotes the assembly of Munc18b-syntaxin 3-SNAP25 tripartite complex and membrane fusion machinery SNARE. Using siRNAs to screen for genes required for regulated epithelial secretion, we identified the requirements of CDK5 and Munc18b in cAMP-dependent gastric acid secretion. Biochemical characterization revealed that Munc18b bears a syntaxin 3-selective binding site located at its most C-terminal 53 amino acids. Significantly, the phosphorylation of Thr572 by CDK5 attenuates Munc18b-syntaxin 3 interaction and promotes formation of Munc18b-syntaxin 3-SNAP25 tripartite complex, leading to an assembly of functional Munc18b-syntaxin 3-SNAP25-VAMP2 membrane fusion machinery. Thus, our studies suggest a novel regulatory mechanism in which phosphorylation of Munc18b operates vesicle docking and fusion in regulated exocytosis.
Liu
Ya
Y
Cellular Dynamics, Hefei National Laboratory & University of Science & Technology of China, Hefei 230027, China.
Ding
Xia
X
Wang
Dongmei
D
Deng
Hui
H
Feng
Mingye
M
Wang
Min
M
Yu
Xue
X
Jiang
Kai
K
Ward
Tarsha
T
Aikhionbare
Felix
F
Guo
Zhen
Z
Forte
John G
JG
Yao
Xuebiao
X
D000818:Animals; D002478:Cells, Cultured; D051360:Cyclin-Dependent Kinase 5 / Q000235:genetics / Q000378:metabolism; D004848:Epithelium / Q000201:enzymology / Q000378:metabolism*; D051938:Munc18 Proteins / Q000378:metabolism*; D010295:Parietal Cells, Gastric / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D050765:Qa-SNARE Proteins / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D011817:Rabbits; D050825:Synaptosomal-Associated Protein 25 / Q000378:metabolism*
D051938:Munc18 Proteins; D050765:Qa-SNARE Proteins; D034741:RNA, Small Interfering; D050825:Synaptosomal-Associated Protein 25; D051360:Cyclin-Dependent Kinase 5
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