| Transfection studies showed that TRAF 4 functions in p70S6K activation : TNF induced phosphorylation of S 6 , the main intracellular substrate of the kinase , in cells stably expressing TRAF 4 , but not in TRAF 4 negative cells . ^^^ In addition to its role in p70S6K activation , we postulate an anti apoptotic role for TRAF 4 , because the agonistic anti Fas antibody CH 11 induced apoptosis in untransfected HEK 293 cells , but not in TRAF 4 expressing HEK 293 cells . ^^^ In conclusion : ( 1 ) TNF receptor activation leads to activation of the p70S6K ; ( 2 ) TRAF 4 is a mediator in this TNF induced signaling pathway ; and ( 3 ) TRAF 4 inhibits Fas induced apoptosis . . ^^^ |