Proteomic analysis of endocytic vesicles: Rab1a regulates motility of early endocytic vesicles

Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Journal of Cell Science (Impact Factor: 5.43). 03/2011; 124(Pt 5):765-75. DOI: 10.1242/jcs.079020
Source: PubMed


Texas-Red-asialoorosomucoid (ASOR) fluorescence-sorted early and late endocytic vesicles from rat liver were subjected to proteomic analysis with the aim of identifying functionally important proteins. Several Rab GTPases, including Rab1a, were found. The present study immunolocalized Rab1a to early and late endocytic vesicles and examined its potential role in endocytosis. Huh7 cells with stable knockdown of Rab1a exhibited reduced endocytic processing of ASOR. This correlated with the finding that Rab1a antibody reduced microtubule-based motility of rat-liver-derived early but not late endocytic vesicles in vitro. The inhibitory effect of Rab1a antibody was observed to be specifically towards minus-end-directed motility. Total and minus-end-directed motility was also reduced in early endocytic vesicles prepared from Rab1a-knockdown cells. These results corresponded with virtual absence of the minus-end-directed kinesin Kifc1 from early endocytic vesicles in Rab1a knockdown cells and imply that Rab1a regulates minus-end-directed motility largely by recruiting Kifc1 to early endocytic vesicles.

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    • "RAB1A localises predominantly to the ERGIC membrane and recruits the tethering factor p115 to the COPII coated vesicles, facilitating the formation of a fusion complex and thus directing COPII vesicles to the Golgi for delivery of their cargo (Allan et al., 2000). However, in addition to its function in ER to Golgi transport, RAB1A is also involved in early Golgi trafficking (Yamasaki et al., 2009), the motility of early endocytotic vesicles, early endosome to Golgi trafficking (Mukhopadhyay et al., 2011), regulation of the actin cytoskeleton (Kicka et al., 2011), recycling of the integrin protein ITGB1 to the cell surface (Wang et al., 2010) and autophagy (Winslow et al., 2010). RAB1A is therefore a multifunctional protein with roles in varied cellular processes. "
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    • "Rab1 exists as two isoforms (Rab1a and Rab1b) that are thought to be largely functionally redundant in the early secretory pathway (Tisdale et al., 1992), while Rab1a is also reported to play a role in early-endosome-to-Golgi trafficking (Mukhopadhyay et al., 2011; Sclafani et al., 2010) and autophagy (Winslow et al., 2010). In the early secretory pathway, Rab1 is required for membrane recruitment of GBF1 (Dumaresq-Doiron et al., 2010; Monetta et al., 2007; Nuoffer et al., 1994; Schwartz et al., 2007) and vesicular transport between the ER and Golgi compartments (Allan et al., 2000; Bannykh et al., 2005; Monetta et al., 2007; Pind et al., 1994; Plutner et al., 1990). "
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