| Interaction with factor associated with neutral sphingomyelinase activation , a WD motif containing protein , identifies receptor for activated C kinase 1 as a novel component of the signaling pathways of the p 55 TNF receptor . ^^^ Mapping studies in yeast revealed that RACK 1 is recruited to the C terminal WD repeat region of FAN and binds to FAN through a domain located within WD repeats 5 to 7 of RACK 1 . ^^^ The interaction of FAN and RACK 1 was verified in vitro by glutathione S transferase based coprecipitation assays as well as in eukaryotic cells by coimmunoprecipitation experiments . ^^^ Colocalization studies in transfected cells suggest that TNF R 55 forms a complex with FAN and that this complex recruits RACK 1 to the plasma membrane . ^^^ Furthermore , activation of N SMase by TNF was strongly enhanced when RACK 1 , FAN , and a noncytotoxic TNF R 55 mutant were expressed concurrently , suggesting RACK 1 as a modulator of N SMase activation . ^^^ |