|Budget Amount *help
¥3,600,000 (Direct Cost : ¥3,600,000)
Fiscal Year 1998 : ¥1,300,000 (Direct Cost : ¥1,300,000)
Fiscal Year 1997 : ¥2,300,000 (Direct Cost : ¥2,300,000)
There is a small G protein superfamily occurring in species from yeast to mammals and consisting of more than sixty members.Rab3A, a member of the small G protein superfamily, and its regulatory proteins, Rab3 GAP and Rab3 GEP, were discovered in our laboratory.Rab3A is involved in regulated secretion such as neurotransmitter release.During this support from 1997 to 1998, we have accumulated the evidence that these regulatory proteins play important roles in neurotransmitter release, and have furthermore found novel components of the neurotransmitter release machinery.The results obtained are as follows :
(1) We have characterized GAP specific for the Rab3 subfamily including Rab3A, -B, -C, and -D.Rab3 GAP is a heterodimer consisting of p130, a catalytic subunit, and p150, a non catalytic subunit.Both the proteins are highly concentrated in the presynaptic nerve terminals.The study using the growth hormone (GH) co-expression assay system of PC12 cells indicates that both the proteins ar
e indeed involved in Ca_<2+>-dependent exocytosis.
(2) It has been shown that Munc18 interacts with syntaxin-1 and inhibits the formation of the SNARE complex.We have isolated a novel syntaxin-1-binding protein and named it Tomosyn.Tomosyn has at least three splicing isoforms (b-, m-, and s-Tomosyns).m- and s-Tomosyns are present in brain but b-Tomosyn is ubiquitously expressed.All the Tomosyn isoforms have a VAMP-like region on their C-terminal portion and bind to syntaxin-1 through their VAMP-like region on m-Tomosyn is capable of dissociating Munc18 from syntaxin-1 and forms a novel 10S complex with syntaxin-1, SNAP-25, and synaptotagmin, but not with VAMP.The study using the GH co-expression assay system of PC12 cells indicates that m-Tomosyn is indeed involved in Ca^<2+>-dependent exocytosis.Since accumulating evidence suggests that the Rab family regulates the formation of the SNARE complex, it is possible that Tomosyn is involved in the Rab3A-dependent process of neurotransmitter release. Less