Collybistin splice variants differentially interact with gephyrin and Cdc42 to regulate gephyrin clustering at GABAergic synapses.

摘要: Collybistin (CB) is a guanine-nucleotide-exchange factor (GEF) selectively activating Cdc42. CB mutations cause X-linked mental retardation due to defective clustering of gephyrin, postsynaptic protein associated with both glycine and GABA(A) receptors. Using combination biochemistry cell biology we provide novel insights into the roles CB2 splice variants, CB2(SH3+) CB2(SH3-), their substrate, Cdc42, in regulating gephyrin at GABAergic synapses. Transfection Myc-tagged CB2(SH3-) cultured neurons revealed strong, but distinct, effects promoting clustering, denoting mechanistic differences function. In addition, overexpression constitutively active or dominant-negative Cdc42 mutants identified new function shape size clusters. biochemical assays native brain tissue, identify direct interaction between independent its activation state. Finally, our data show that not CB2(SH3+), can form ternary complex providing substrate for distinct contribution these isoforms sites. Taken together, results as major regulators densities.