RUTBC2 protein, a Rab9A effector and GTPase-activating protein for Rab36.
Rab GTPases regulate vesicle budding, motility, docking, and fusion. In cells, their cycling between active, GTP-bound states and inactive, GDP-bound states is regulated by the action of opposing enzymes called guanine nucleotide exchange factors and GTPase-activating proteins (GAPs). The substrates for most RabGAPs are unknown, and the potential for cross-talk between different membrane trafficking pathways remains uncharted territory. Rab9A and its effectors regulate recycling of mannose 6-phosphate receptors from late endosomes to the trans Golgi network. We show here that RUTBC2 is a TBC domain-containing protein that binds to Rab9A specifically both in vitro and in cultured cells but is not a GAP for Rab9A. Biochemical screening of Rab protein substrates for RUTBC2 revealed highest GAP activity toward Rab34 and Rab36. In cells, membrane-associated RUTBC2 co-localizes with Rab36, and expression of wild type RUTBC2, but not the catalytically inactive, RUTBC2 R829A mutant, decreases the amount of membrane-associated Rab36 protein. These data show that RUTBC2 can act as a Rab36 GAP in cells and suggest that RUTBC2 links Rab9A function to Rab36 function in the endosomal system.
Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305, USA.
Ryan M
RM
Nottingham
Ganesh V
GV
Pusapati
Ian G
IG
Ganley
Francis A
FA
Barr
David G
DG
Lambright
Suzanne R
SR
Pfeffer
D000595:Amino Acid Sequence; D000818:Animals; D002522:Chlorocebus aethiops; D011992:Endosomes / Q000378:metabolism*; D020558:GTP Phosphohydrolases / Q000378:metabolism; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D006868:Hydrolysis; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009447:Neuroblastoma; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D021381:Protein Transport / Q000502:physiology*; D020798:Two-Hybrid System Techniques; D014709:Vero Cells; D020691:rab GTP-Binding Proteins / Q000378:metabolism*
D020558:GTP Phosphohydrolases; D047908:Intracellular Signaling Peptides and Proteins; D020691:rab GTP-Binding Proteins; C523294:SGSM1 protein, human; C079856:RAB9A protein, human; C117391:RAB36 protein, human