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A novel function of theC‐terminal lipid moieties of Rab3A small G protein implicated in Ca 2+ ‐dependent exocytosis — inhibition of interaction with GTP and reduction of this inhibition by phospholipid
Author(s) -
Jinno Yasunari,
Shirataki Hiromichi,
Senbonmatsu Takaaki,
Yamamoto Tomomi,
Fujita Yasuyuki,
Nakanishi Hiroyuki,
Takai Yoshimi
Publication year - 1997
Publication title -
genes to cells
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.912
H-Index - 115
eISSN - 1365-2443
pISSN - 1356-9597
DOI - 10.1111/j.1365-2443.1997.120gc0318.x
Subject(s) - biology , exocytosis , gtp' , function (biology) , biochemistry , microbiology and biotechnology , enzyme , membrane
Background : Rab3A small G protein is implicated in Ca 2+ ‐dependent exocytosis. It undergoes post‐translational lipid‐modifications at its C‐terminal region. These lipid moieties are important for the actions of the regulators of Rab3A, but not for the interaction with its downstream target. Results :We have found another function of the C‐terminal lipid moieties of Rab3A. GTP rapidly associates with the guaninenucleotide‐free form of unmodified Rab3A, but not with the same form of modified Rab3A. Moreover, GTP rapidly dissociates from the GTP‐bound form of modified Rab3A, but not from the same form of unmodified Rab3A. The association of GTP with the guaninenucleotide‐free form of modified Rab3A is stimulated by the Rab3GDP/GTP exchange protein (Rab3 GEP), and the dissociation of GTP from the GTP‐bound form is markedly reduced by synaptic vesiclephospholipid. Conclusions : These results suggest that the interaction of the lipid moieties of Rab3A with Rab3GEP or synaptic vesicles is required for the interaction of modified Rab3A with GTP. Moreover, these results — together with the fact that Rabphilin‐3A associated withsynaptic vesicles inhibits the activity of Rab3GTPase‐activating protein — suggest that the GTP‐bound form of modified Rab3A is associated with synaptic vesicles through both Rabphilin‐3A and the vesicle phospholipid.