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Biochem Biophys Res Commun. 2008 Jul 18;372(1):168-72. doi: 10.1016/j.bbrc.2008.05.027. Epub 2008 May 16.

Tyr-phosphorylation signals translocate RIN3, the small GTPase Rab5-GEF, to early endocytic vesicles.

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Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.


The small GTPase Rab5 plays a key role in early endocytic pathway, and its activation requires guanine-nucleotide exchange factors (GEFs). Rab5-GEFs share a conserved VPS9 domain for the GEF action, and RIN3 containing additional domains, such as Src-homology 2, RIN-family homology (RH), and Ras-association (RA), was identified as a new Rab5-GEF. However, precise functions of the additional domains and the activation mechanism of RIN3 remain unknown. Here, we found tyrosine-phosphorylation signals are involved in the Rab5-GEF activation. Treatment of HeLa cells with pervanadate translocates RIN3 from cytoplasm to the Rab5-positive vesicles. This RIN3 translocation was applied to various mutants lacking each domain of RIN3. Our present results suggest that a Ras GTPase(s) activated by tyrosine-phosphorylation signals interacts with the inhibitory RA domain, resulting in an active conformation of RIN3 as a Rab5-GEF and that RIN-unique RH domain constitutes a Rab5-binding region for the progress of GEF action.

[Indexed for MEDLINE]

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