Physical and Functional Interactions of Doc2 and Munc13 in Ca2+-dependent Exocytotic Machinery

• Published in: The Journal of biological chemistry Vol. 272; no. 26; pp. 16081 - 16084
• Main Authors: Orita, Satoshi, Naito, Akira, Sakaguchi, Gaku, Maeda, Miki, Igarashi, Hisanaga, Sasaki, Takuya, Takai, Yoshimi
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 27.06.1997; American Society for Biochemistry and Molecular Biology
• Subjects: Animals; Caenorhabditis elegans Proteins; Calcium - physiology; Calcium-Binding Proteins - chemistry; Calcium-Binding Proteins - physiology; Carrier Proteins; Diglycerides - physiology; Exocytosis; Growth Hormone - metabolism; Helminth Proteins - metabolism; Humans; Nerve Tissue Proteins - chemistry; Nerve Tissue Proteins - physiology; PC12 Cells; Rats; Tetradecanoylphorbol Acetate - pharmacology
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.272.26.16081

Doc2 has two C2 domains that interact with Ca2+ and phospholipid. Munc13 has two C2 domains and one C1 domain that interacts with phorbol ester or diacylglycerol (DAG) and phospholipid. Both Doc2 and Munc13 are implicated in Ca2+-dependent neurotransmitter release, but their modes of action still remain unclear. We show here that Doc2 interacts with Munc13 both in a cell-free system and in intact PC12 cells during the high K+-induced Ca2+-dependent exocytosis. The Doc2-Munc13 interactions are stimulated by phorbol ester through the C1 domain of Munc13. Overexpression of the Doc2-interacting domain of Munc13 reduces the Ca2+-dependent exocytosis from PC12 cells, and co-expression with Doc2 suppresses this reduction. These results, together with the earlier findings that secretagogues produce DAG and elevate cytoplasmic Ca2+, suggest that the DAG-induced Doc2-Munc13 interactions play an important role in Ca2+-dependent exocytotic machinery.