Comprehensive Screening for Novel Rab-Binding Proteins by GST Pull-Down Assay Using 60 Different Mammalian Rabs [double dagger]

• Published in: Traffic (Copenhagen, Denmark) Vol. 11; no. 4; pp. 491 - 507
• Main Authors: Kanno, Eiko, Ishibashi, Koutaro, Kobayashi, Hotaka, Matsui, Takahide, Ohbayashi, Norihiko, Fukuda, Mitsunori
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.04.2010; Blackwell Publishing Ltd
• Subjects: ADP-Ribosylation Factors - genetics; ADP-Ribosylation Factors - isolation & purification; ADP-Ribosylation Factors - metabolism; Animals; Ankyrin Repeat; Cdc16 domain; comprehensive screening; effector; Glutathione Transferase - genetics; Glutathione Transferase - isolation & purification; Glutathione Transferase - metabolism; GTPase-activating proteins; GTPase-Activating Proteins - genetics; GTPase-Activating Proteins - isolation & purification; GTPase-Activating Proteins - metabolism; GTPase‐activating protein; Humans; Membrane Proteins - genetics; Membrane Proteins - isolation & purification; Membrane Proteins - metabolism; membrane traffic; Molecular Sequence Data; Monomeric GTP-Binding Proteins - genetics; Monomeric GTP-Binding Proteins - isolation & purification; Monomeric GTP-Binding Proteins - metabolism; Neurites - chemistry; Neurites - metabolism; PC12 Cells; Protein Binding; Protein Interaction Mapping; Rab; rab GTP-Binding Proteins - analysis; rab GTP-Binding Proteins - genetics; rab GTP-Binding Proteins - metabolism; Rats; Tre-2 /Bub2; Tre‐2 /Bub2/ Cdc16 domain
• ISSN: 1398-9219; 1600-0854
• DOI: 10.1111/j.1600-0854.2010.01038.x

The Rab family belongs to the Ras-like small GTPase superfamily and is implicated in membrane trafficking through interaction with specific effector molecules. Because of the large number of Rab isoforms in mammals, however, the effectors of most of the mammalian Rabs are yet to be identified. In this study, we systematically screened five different cell or tissue lysates for novel Rab effectors by a combination of glutathione S-transferase (GST) pull-down assay with 60 different mammalian Rabs and mass spectroscopic analysis. Three of the 21 Rab-binding proteins we identified, mKIAA1055/TBC1D2B (Rab22-binding protein), GAPCenA/TBC1D11 (Rab36-binding protein) and centaurin β2/ACAP2 (Rab35-binding protein), are GTPase-activating proteins (GAPs) for Rab or Arf. Although it has recently been proposed that the Rab-GAP (Tre-2 /Bub2/Cdc16) domain physically interacts with its substrate Rab, these three GAPs interacted with specific Rabs via a domain other than a GAP domain, e.g. centaurin β2 binds GTP-Rab35 via the ankyrin repeat (ANKR) domain. Although centaurin β2 did not exhibit any Rab35-GAP activity in vitro, the Rab35-binding ANKR domain of centaurin β2 was found to be required for its plasma membrane localization and regulation of Rab35-dependent neurite outgrowth of PC12 cells through inactivation of Arf6. These findings suggest a novel mode of interaction between Rab and GAP.