Overexpression of Raidd cDNA inhibits differentiation of mouse preadipocytes

RAIDD (RIP-associated ICH-1 homologous protein with a death domain) is an adaptor molecule that mediates the action of cysteine proteases involved in apoptosis. To study the possibility of a novel system of cell ablation mediated by RAIDD, a preadipocyte cell line (3T3L1) was stably transfected with a plasmid containing the murine Raidd cDNA under the control of the adipocyte specific promoter aP2. Instead of the expected apoptosis, a blockage to differentiation upon hormonal induction was observed as judged by an absence of lipid accumulation, a lack of expression of adipocyte-specific genes and a fibroblastic appearance. Proliferation rate of Raidd-transfected clones remained unaffected. Overexpression of Raidd cDNA in 3T3L1 cell therefore inhibited differentiation, suggesting that Raidd plays a role in controlling differentiation of mouse preadipocytes and, perhaps, in other cell types, in addition to its established role in apoptosis.