The synaptic vesicle exocytosis occurs by a highly regulated mechanism: syntaxin and 25 kDa synaptosome-associated protein (SNAP-25) are assembled with vesicle-associated membrane protein (VAMP) to form a synaptic core complex and then synaptotagmin participates as a Ca2+ sensor in the final step of membrane fusion. The 43 kDa growth-associated protein GAP-43 is a nerve-specific protein that is predominantly localized in the axonal growth cones and presynaptic terminal membrane. In the present study we have examined a possible interaction of GAP-43 with components involved in the exocytosis. GAP-43 was found to interact with syntaxin, SNAP-25 and VAMP in rat brain tissues and nerve growth factor-dependently differentiated PC12 cells, but not in undifferentiated PC12 cells. GAP-43 also interacted with synaptotagmin and calmodulin. These interactions of GAP-43 could be detected only when chemical cross-linking of proteins was performed before they were solubilized from the membranes with detergents, in contrast with the interaction of the synaptic core complex, which was detected without cross-linking. Experiments invitro showed that the interaction of GAP-43 with these proteins occurred Ca2+-dependently; its maximum binding with the core complex was observed at 100 μM Ca2+, whereas that of syntaxin with synaptotagmin was at 200 μM Ca2+. These values of Ca2+ concentration are close to that required for the Ca2+-dependent release of neurotransmitters. Furthermore we observed that the interaction invitro of GAP-43 with the synaptic core complex was coupled with protein kinase C-mediated phosphorylation of GAP-43. Taken together, our results suggest a novel function of GAP-43 that is involved in the Ca2+-dependent fusion of synaptic vesicles.
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Research Article|
July 15 1997
Ca2+-dependent interaction of the growth-associated protein GAP-43 with the synaptic core complex
Tatsumi HARUTA;
Tatsumi HARUTA
*Department of Biochemistry, Fukuoka University School of Medicine, Nanakuma, Jonan-ku, Fukuoka 814-80, Japan
†Department of Neurosurgery, Oita Medical University, Hazama-cho, Oita 879-55, Japan
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Noboru TAKAMI;
Noboru TAKAMI
‡Radioisotope Laboratory, Fukuoka University School of Medicine, Nanakuma, Jonan-ku, Fukuoka 814-80, Japan
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Manami OHMURA;
Manami OHMURA
‡Radioisotope Laboratory, Fukuoka University School of Medicine, Nanakuma, Jonan-ku, Fukuoka 814-80, Japan
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Yoshio MISUMI;
Yoshio MISUMI
*Department of Biochemistry, Fukuoka University School of Medicine, Nanakuma, Jonan-ku, Fukuoka 814-80, Japan
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Yukio IKEHARA
Yukio IKEHARA
§
*Department of Biochemistry, Fukuoka University School of Medicine, Nanakuma, Jonan-ku, Fukuoka 814-80, Japan
§To whom correspondence should be addressed.
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Publisher: Portland Press Ltd
Received:
November 21 1996
Revision Received:
February 24 1997
Accepted:
March 18 1997
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London © 1997
1997
Biochem J (1997) 325 (2): 455–463.
Article history
Received:
November 21 1996
Revision Received:
February 24 1997
Accepted:
March 18 1997
Citation
Tatsumi HARUTA, Noboru TAKAMI, Manami OHMURA, Yoshio MISUMI, Yukio IKEHARA; Ca2+-dependent interaction of the growth-associated protein GAP-43 with the synaptic core complex. Biochem J 15 July 1997; 325 (2): 455–463. doi: https://doi.org/10.1042/bj3250455
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