Activation of Galphai3 and interacting protein, TNFAIP8, inhibits TNFalpha-induced death and promotes transformation in mouse fibroblast

Abstract

Stimulation of dopamine D2S receptor introduced in Balb/c-3T3 cells induces Galphai3-dependent transformation. Galphai3 interacts with DED2-containing protein, TNFAIP8, in yeast mating and in FLAG-TNFAIP8 transfected Balb/c-3T3 cells. TNFAIP8 inhibits caspase-8 activity and is elevated in certain cancers as well as in metastatic, radiation resistant, chemo-resistant and angiogenic tumours. This study looks at Galphai3 activation of TNFAIP8 leading to the inhibition of TNFalpha-induced cell death in Balb/c-3T3 cells coexpressing D2S and either TNFAIP8 over-expression or TNFAIP8 antisense-knockdown with assays for foci formation, cell death and executioner caspase activation. The data showed D2S increases basal foci formation; this is blocked in TNFAIP8 antisense cells. D2S activation further increases foci formation; also completely blocked in TNFAIP8 antisense cells. D2S activation reduces cell death except in TNFAIP8 antisense cells. D2S activation reduces caspase-active cells. These results show that D2S mediated inhibition of caspase activity and death resulting in transformation is dependent on TNFAIP8.