Functional expression cloning reveals a central role for the receptor for activated protein kinase C 1 (RACK1) in T cell apoptosis

Mammalian cDNA expression cloning was used to identify novel genes that regulate apoptosis. Using a functional screen, we identified a partial cDNA for the receptor for activated protein kinase C 1 (RACK1) through selection for resistance to phytohemagglutinin and gamma-irradiation. Expression of this partial cDNA in T cell lines using a mammalian expression vector produced an increase in RACK1 expression and resulted in resistance to dexamethasone- and ultraviolet-induced apoptosis. Down-regulation of RACK1 using RNA interference abolished the resistance of the transfected cells to apoptosis. Overexpression of full-length RACK1 also resulted in the suppression of apoptosis mediated by several apoptotic stimuli, and this effect was quantitatively consistent with the effects of the original cDNA isolated on endogenous RACK1 levels. Together, these findings suggest that RACK1 plays an important role in the intracellular signaling pathways that lead to apoptosis in T cells.