Physical and functional interactions of Doc2 and Munc13 in Ca2+-dependent exocytotic machinery.
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.
Orita
S
S
Shionogi Institute for Medical Science, Settsu 566, Japan.
Naito
A
A
Sakaguchi
G
G
Maeda
M
M
Igarashi
H
H
Sasaki
T
T
Takai
Y
Y
D000818:Animals; D029742:Caenorhabditis elegans Proteins; D002118:Calcium / Q000502:physiology*; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000502:physiology*; D002352:Carrier Proteins; D004075:Diglycerides / Q000502:physiology; D005089:Exocytosis; D013006:Growth Hormone / Q000378:metabolism; D015801:Helminth Proteins / Q000378:metabolism*; D006801:Humans; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000502:physiology*; D016716:PC12 Cells; D051381:Rats; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D029742:Caenorhabditis elegans Proteins; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; C091524:DOC2A protein, human; C490420:DOC2B protein, human; D004075:Diglycerides; C490419:Doc2a protein, rat; D015801:Helminth Proteins; D009419:Nerve Tissue Proteins; C083141:phorbol ester binding protein; D013006:Growth Hormone; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium