RRC ID 49527
Author Matsui T, Ohbayashi N, Fukuda M.
Title The Rab interacting lysosomal protein (RILP) homology domain functions as a novel effector domain for small GTPase Rab36: Rab36 regulates retrograde melanosome transport in melanocytes.
Journal J Biol Chem
Abstract Small GTPase Rab functions as a molecular switch that drives membrane trafficking through specific interaction with its effector molecule. Thus, identification of its specific effector domain is crucial to revealing the molecular mechanism that underlies Rab-mediated membrane trafficking. Because of the large numbers of Rab isoforms in higher eukaryotes, however, the effector domains of most of the vertebrate- or mammalian-specific Rabs have yet to be determined. In this study we screened for effector molecules of Rab36, a previously uncharacterized Rab isoform that is largely conserved in vertebrates, and we succeeded in identifying nine Rab36-binding proteins, including RILP (Rab interacting lysosomal protein) family members. Sequence comparison revealed that five of nine Rab36-binding proteins, i.e. RILP, RILP-L1, RILP-L2, and JIP3/4, contain a conserved coiled-coil domain. We identified the coiled-coil domain as a RILP homology domain (RHD) and characterized it as a common Rab36-binding site. Site-directed mutagenesis of the RHD of RILP revealed the different contributions by amino acids in the RHD to binding activity toward Rab7 and Rab36. Expression of RILP in melanocytes, but not expression of its Rab36 binding-deficient mutants, induced perinuclear aggregation of melanosomes, and this effect was clearly attenuated by knockdown of endogenous Rab36 protein. Moreover, knockdown of Rab36 in Rab27A-deficient melanocytes, which normally exhibit perinuclear melanosome aggregation because of increased retrograde melanosome transport activity, caused dispersion of melanosomes from the perinucleus to the cell periphery, but knockdown of Rab7 did not. Our findings indicated that Rab36 mediates retrograde melanosome transport in melanocytes through interaction with RILP.
Volume 287(34)
Pages 28619-31
Published 2012-8-17
DOI 10.1074/jbc.M112.370544
PII M112.370544
PMID 22740695
PMC PMC3436592
MeSH Adaptor Proteins, Signal Transducing / genetics Adaptor Proteins, Signal Transducing / metabolism Animals Biological Transport / physiology COS Cells Carrier Proteins / genetics Carrier Proteins / metabolism* Chlorocebus aethiops Gene Knockdown Techniques Male Melanocytes / metabolism* Melanosomes / genetics Melanosomes / metabolism* Mice Mutagenesis, Site-Directed Nerve Tissue Proteins / genetics Nerve Tissue Proteins / metabolism Protein Structure, Tertiary rab GTP-Binding Proteins / genetics rab GTP-Binding Proteins / metabolism*
IF 4.238
Times Cited 36
DNA material pEF-HA-mouse RILP (RDB15389) pEF-HA-mouse RILP-L1 (RDB15390) pEF-HA-mouse RILP-L2 (RDB15391).