The scaffolding protein CASK mediates the interaction between rabphilin3a and β-neurexins

CASK, a member of the membrane-associated guanylate kinase (MAGUK) superfamily, binds to the carboxyl-terminus of beta -neurexins on the intracellular side of the presynaptic membrane. The guanylate kinase-like (GUK) domains of MAGUKs lack kinase activities, but might he important for mediating specific protein-protein interaction. By a yeast two-hybrid approach, we identified an interaction between the GUK domain of CASK and the C2B domain of rabphilin3a, a presynaptic protein involved in synaptic vesicle exocytosis. The interaction was confirmed by in vitro CST pull-down and co-immunoprecipitation assays. It,vas proposed that presynaptic vesicles might be guided to the vicinity of points of exocytosis defined by beta -neurexins via the interaction between rabphilin3a-CASK-beta -neurexins. (C) 2001 Federation of European Biochemical Societies. Published by Elsevier Science B,V. All rights reserved.