Published 5 July 2004. doi:10.1083/jcb.200405002
The Rockefeller University Press, 0021-9525 $8.00
JCB, Volume 166, Number 1, 17-25
Regulation of SNAREs by tomosyn and ROCK
:
implication in extension and retraction of neurites
Toshiaki Sakisaka,
Takeshi Baba,
Shintaro Tanaka,
Genkichi Izumi,
Masato Yasumi, and
Yoshimi Takai
Department of Molecular Biology and Biochemistry, Osaka University Graduate School of Medicine/Faculty of Medicine, Suita, Osaka 565-0871, Japan
Address correspondence to Yoshimi Takai, Dept. of Molecular Biology and Biochemistry, Osaka University Graduate School of Medicine/Faculty of Medicine, Suita, Osaka 565-0871, Japan. Tel.: (81) 6-6879-3410. Fax: (81) 6-6879-3419. email: ytakai{at}molbio.med.osaka-u.ac.jp
Abstract
Extension of neurites requires the SNARE-dependent fusion of plasmalemmal precursor vesicles with the plasma membrane of growth cones. Here, we show that tomosyn localizes at the palm of growth cones and inhibits the fusion of the vesicles there, thus promoting transport of the vesicles to the plasma membrane of the leading edges of growth cones. Tomosyn localizes because ROCK activated by Rho small G protein phosphorylates syntaxin-1, which increases the affinity of syntaxin-1 for tomosyn and forms a stable complex with tomosyn, resulting in inhibition of the formation of the SNARE complex. In retraction of neurites, tomosyn localizes all over the edges of the neurites and inhibits fusion of the vesicles with the plasma membrane. Thus, tomosyn demarcates the plasma membrane by binding to syntaxin-1 phosphorylated by ROCK, and thereby regulates extension and retraction of neurites.
Key Words: tomosyn; ROCK; syntaxin; SNAREs; neurite outgrowth
Abbreviations used in this paper: db-cAMP, dibutyryl cyclic AMP; LPA, lysophosphatidic acid; MTs, microtubules; ROCK, Rho-associated serine/threonine kinase; siRNA, small interfering RNA.

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