title: Rab3 reversibly recruits rabphilin to synaptic vesicles by a mechanism analogous to raf recruitment by ras.
abstract: GTP activates the interaction between the synaptic vesicle proteins rabphilin and rab3. This raises the question of whether rabphilin is a resident vesicle protein that recruits rab3 in a stage-dependent fashion, or if it is instead an effector protein recruited by rab3. We now show that rabphilin, like rab3, dissociates from synaptic vesicles after exocytosis in a manner requiring both Ca2+ and membrane fusion. Rabphilin interacts with GTP-rab3 via a N-terminal domain comprising a novel Zn2+(-)finger motif, and this interaction is essential for rabphilin binding to synaptic vesicles. Thus, in the same way that ras recruits raf to the plasma membrane, rab3 reversibly recruits rabphilin to synaptic vesicles in a stage-dependent manner. These results reveal an unexpected similarity between the molecular mechanisms by which small G protein function in recruiting effector proteins to membranes during membrane traffic and signal transduction.
authors.affiliation: Department of Pharmacology, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, CT 06510, USA.
authors.forename: B
authors.initials: B
authors.lastname: Stahl
authors.forename: J H
authors.initials: JH
authors.lastname: Chou
authors.forename: C
authors.initials: C
authors.lastname: Li
authors.forename: T C
authors.initials: TC
authors.lastname: Südhof
authors.forename: R
authors.initials: R
authors.lastname: Jahn
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D017931:DNA Primers / Q000235:genetics; D019143:Evolution, Molecular; D005089:Exocytosis; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D066298:In Vitro Techniques; D008561:Membrane Fusion; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019908:Proto-Oncogene Proteins c-raf; D051381:Rats; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013572:Synaptic Vesicles / Q000378:metabolism*; D033921:Vesicular Transport Proteins; D016335:Zinc Fingers / Q000235:genetics; D020691:rab GTP-Binding Proteins; D020692:rab3 GTP-Binding Proteins; D018631:ras Proteins / Q000378:metabolism*; D000097624:Rabphilin-3A
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D017931:DNA Primers; D019204:GTP-Binding Proteins; D006160:Guanosine Triphosphate; D009419:Nerve Tissue Proteins; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D019908:Proto-Oncogene Proteins c-raf; D033921:Vesicular Transport Proteins; D020691:rab GTP-Binding Proteins; D020692:rab3 GTP-Binding Proteins; D018631:ras Proteins; D000097624:Rabphilin-3A