title: A mechanism of Munc18b-syntaxin 3-SNAP25 complex assembly in regulated epithelial secretion.
abstract: 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.
authors: Cellular Dynamics, Hefei National Laboratory & University of Science & Technology of China, Hefei 230027, China.
authors: Ya
authors: Y
authors: Liu
authors: Xia
authors: X
authors: Ding
authors: Dongmei
authors: D
authors: Wang
authors: Hui
authors: H
authors: Deng
authors: Mingye
authors: M
authors: Feng
authors: Min
authors: M
authors: Wang
authors: Xue
authors: X
authors: Yu
authors: Kai
authors: K
authors: Jiang
authors: Tarsha
authors: T
authors: Ward
authors: Felix
authors: F
authors: Aikhionbare
authors: Zhen
authors: Z
authors: Guo
authors: John G
authors: JG
authors: Forte
authors: Xuebiao
authors: X
authors: Yao
mesh_terms: 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*
chemical_list: 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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