Role of RACK1 protein in the regulation of apoptosis

RACK1 (Receptor for Activated C Kinase 1) is a multifunctional scaffold protein involved in numerous signaling pathways, including stress responses and apoptosis. Its subcellular localization, particularly recruitment into stress granules (SGs) under cellular stress, may influence its ability to regulate apoptotic signaling. This study aimed to investigate how RACK1 expression levels affect apoptosis and to assess RACK1 localization, including mutant forms with reduced SG recruitment, under stress conditions. We generated RACK1 mutants designed to reduce localization into SGs and assessed their subcellular distribution using immunofluorescence. The mutants exhibited less SG localization compared to wild-type RACK1. To investigate the underlying mechanism, we performed co-immunoprecipitation to examine interactions with G3BP1, a core SG protein that may account for the differential localization. To evaluate the apoptotic response, the effects of RACK1 depletion and overexpression on stress kinase activity (JNK, ERK), Bcl-2 family protein expression, and caspase-3/7 activation were analyzed. RACK1 depletion reduced phosphorylation of JNK and ERK, suggesting diminished early pro-apoptotic signaling, yet simultaneously decreased anti- apoptotic Bcl-2 proteins and slightly increased pro-apoptotic Bcl-2...