title: Interaction of activated Rab5 with actin-bundling proteins, L- and T-plastin and its relevance to endocytic functions in mammalian cells.
abstract: Rab5 is a GTP-binding protein that is crucial for endocytic machinery functions. We previously identified L-plastin as a binding protein for Rab5, using an affinity column with constitutively active Rab5. L- and T-plastin are isoforms of a plastin protein family belonging to actin-bundling proteins that are implicated in the regulation of cell morphology, lamellipodium protrusion, bacterial invasion and tumor progression. However, the physiological relevance of Rab5 binding to plastin has remained unclear. Here, we show that L- and T-plastin interacted only with activated Rab5 and that they co-localized with Rab5 on the plasma membrane and endosome. Rab5 activity was also higher in both L- and T-plastin over-expressing Cos-1 cells. Furthermore, expression of L- and T-plastin increased the rate of fluid-phase endocytosis. These findings imply that the Rab5 is either activated or the activity is sustained by interaction with plastin, and that this interaction influences endocytic activity.
authors.affiliation: Department of Agricultural Chemistry, Graduate School of Agriculture, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya-ku, Tokyo 156-8502, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Hagiwara
authors.forename: Hiroto
authors.initials: H
authors.lastname: Shinomiya
authors.forename: Masakuni
authors.initials: M
authors.lastname: Kashihara
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Kobayashi
authors.forename: Tadahiro
authors.initials: T
authors.lastname: Tadokoro
authors.forename: Yuji
authors.initials: Y
authors.lastname: Yamamoto
mesh_terms: D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D004705:Endocytosis; D004789:Enzyme Activation; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008840:Microfilament Proteins / Q000378:metabolism*; D020696:rab5 GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D008562:Membrane Glycoproteins; D008840:Microfilament Proteins; C026742:plastin; D020696:rab5 GTP-Binding Proteins