Localization of the Rab3 Small G Protein Regulators in Nerve Terminals and Their Involvement in Ca2+-dependent Exocytosis
Open Access
- 1 December 1998
- journal article
- Published by Elsevier BV
- Vol. 273 (51), 34580-34585
- https://doi.org/10.1074/jbc.273.51.34580
Abstract
The Rab3 small G protein subfamily (Rab3) consists of four members, Rab3A, -B, -C, and -D. We have recently isolated and characterized the Rab3 regulators, GDP/GTP exchange protein (GEP) and GTPase activating protein (GAP), both of which are specific for the Rab3 subfamily. Rab3 GEP stimulates the conversion of the GDP-bound inactive form to the GTP-bound active form, whereas Rab3 GAP stimulates the reverse reaction. Of the four members of the Rab3 subfamily, evidence is accumulating that Rab3A is involved in Ca2+-dependent exocytosis, particularly in neurotransmitter release. We first analyzed the subcellular localization of Rab3 GEP and GAP in rat brain. Subcellular fractionation analysis showed that both Rab3 GEP and GAP were enriched in the synaptic soluble fraction. Immunocytochemical analysis in primary cultured rat hippocampal neurons showed that both Rab3 GEP and GAP were concentrated at the presynaptic nerve terminals. We then examined whether Rab3 GEP and GAP were involved in Ca2+-dependent exocytosis by use of human growth hormone (GH) co-expression assay system of cultured PC12 cells. Overexpression of the deletion mutant of Rab3 GEP possessing the catalytic activity reduced the high K+-induced GH release without affecting the basal GH release, whereas that of the deletion mutant lacking the catalytic activity showed no effect on the high K+-induced GH release. In contrast, overexpression of Rab3 GAP or its deletion mutant possessing the catalytic activity did not affect the high K+-induced GH release or the basal GH release. These results indicate that Rab3 GEP and GAP are colocalized with Rab3A at the synaptic release sites and suggest that they regulate the activity of Rab3A and are involved in Ca2+-dependent exocytosis.Keywords
This publication has 26 references indexed in Scilit:
- Function of Rab3 GDP–GTP ExchangeNeuron, 1997
- Isolation and Characterization of a GDP/GTP Exchange Protein Specific for the Rab3 Subfamily Small G ProteinsPublished by Elsevier BV ,1997
- Involvement of Rabphilin-3A in Ca2+-Dependent Exocytosis from PC12 CellsBiochemical and Biophysical Research Communications, 1996
- Synaptic targeting of rabphilin-3A, a synaptic vesicle Ca2+/phospholipid-binding protein, depends on rab3A/3CNeuron, 1994
- Tissue-specific expression of a novel GTP-binding protein (smg p25A) mRNA and its increase by nerve growth factor and cyclic AMP in rat pheochromocytoma PC-12 cellsBiochemical and Biophysical Research Communications, 1989
- Selective packaging of human growth hormone into synaptic vesicles in a rat neuronal (PC12) cell line.The Journal of cell biology, 1985
- Identification and localization of synaptophysin, an integral membrane glycoprotein of Mr 38,000 characteristic of presynaptic vesiclesCell, 1985
- Electrophoretic transfer of proteins from polyacrylamide gels to nitrocellulose sheets: procedure and some applications.Proceedings of the National Academy of Sciences of the United States of America, 1979
- A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye bindingAnalytical Biochemistry, 1976
- Cleavage of Structural Proteins during the Assembly of the Head of Bacteriophage T4Nature, 1970