DIFFERENTIAL EXPRESSION AND CHARACTERIZATION OF PROTOONCOGENE PRODUCTHA-RAS GTPASE IN CAMEL TISSUES

Pas proto-oncogene product is known to be involved in transducing sign als for growth, differentiation and oncogenesis in mammalian cells. Us ing a monoclonal antibody to human Ha-Ras, a camel homolog of Ha-Ras p rotein having an apparent molecular mass of 21 kDa was identified. The expression level of Ha-Ras protein in various tissues of camel was co mpared with that of mouse tissues. In camel it was found that expressi on of Ha-Ras protein was highest in the kidney and moderate in the liv er. Expression of Ha-Ras in camel lung, testis, spleen, heart, brain, intestine and muscle was found to be very low. While Ha-Ras expression in mouse was found to be highest in the intestine. A moderate express ion of Ha-Ras was found in mouse testis, kidney and heart. The kidney tissue extract of camel was immunoprecipitated using the same human Ha -Ras antibody. Biochemical characterization of the immunoprecipitate r evealed that like most other G proteins, the camel homolog of Ras is a GTPase. The GTPase activity was found to be stimulated specifically b y recombinant human Ras GAP p120 and neurofibromin. It suggests that b oth camel and human share the same Ras mediated growth signaling proce ss and that human Ras GAP might be able to complement camel Ras GAP fu nction. Camel homolog of Raf-1 and MAP kinase (member of Ras signaling pathway) were also identified by immunoblot. This is the first demons tration showing the existence of a Ras mediated growth signal transduc tion pathway in camel.