RhoN, a novel small GTP-binding protein expressed predominantly in neuronsand hepatic stellate cells

A cDNA encoding a novel member of the small molecular weight GTP-binding pr otein (small G-protein) superfamily was cloned from rat spinal cord. The de duced amino acid sequence was highly homologous with those of so-far-known Rho proteins, Rho proteins were reported to alter many important cellular f unctions including formation of both actin stress fibers and focal adhesion s. RNA blot hybridization and in situ hybridization analyses indicated that the novel small G-protein is expressed specifically in neurons in the brai n and spinal cord and also in hepatic stellate cells. Based on the sequence similarity and neuron-specific expression in the brain, this protein was n amed RhoN. Unlike classical Rho proteins, RhoN was not susceptible to the A DP-ribosylation reaction by C3 botulinum toxin. Accordingly, RhoN seemed to be specifically involved in neuronal and hepatic functions as a C3 toxin-i nsensitive member of the Rho subfamily. Then, a mouse genomic DNA segment c ontaining the RhoN gene was cloned. The locus was mapped on the mouse chrom osome 11C-D. The sequence data showed that the protein-coding sequence for RhoN is divided by 4 introns, and that the defined 5 exons may encode intra molecular domains serving for different functions. (C) 1999 Elsevier Scienc e B.V. All rights reserved.