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OBJECTIVE:To investigate whether the expression of a dominant negative (DN) farnesyl-and geranygeranyl-transferase I (FTase=GGTase I) a-subunit in 3T3-L1 pre-adipocytes can inhibit insulin's ability to induce differentiation. DESIGN: 3T3-L1 pre-adipocytes were stably transfected with vector alone or vector expressing a mutated DN FTase=GGTase I a-subunit (S60A)(S62A) and incubated in serum-free medium in the absence and presence of insulin. MEASUREMENTS: Various assays were performed to determine the effect of DN FTase=GGTase I a-subunit expression in 3T3-L1 pre-adipocyte on insulin-induced DNA synthesis, cell count, phosphorylation of the FTase=GGTase I a-subunit, FTase and GGTase I activity, amounts of prenylated p21Ras and RhoA, phosphorylation of MAP kinase and Akt, and differentiation to mature fat cells. RESULTS: Expression of DN FTase=GGTase I a-subunit inhibited insulin's ability to increase DNA synthesis, cell count, FTase and GGTase I activity, amounts of prenylated p21Ras and RhoA, and magnitude of phosphorylation of MAP kinase. Expression of DN FTase=GGTase I a-subunit in 3T3-L1 pre-adipocytes was without effect on insulin-induced Akt phosphorylation. CONCLUSION: Expression of DN FTase=GGTase I a-subunit inhibits insulin-induced differentiation of 3T3-L1 pre-adipocytes to mature adipocytes, and thus could indicate potential therapeutic avenues to assuage the deleterious effects of obesity and type 2 diabetes.

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