| 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 . ^^^ |