Fig. 5.
P70S6 kinase activation may be independent of Akt activation in B cells.
Parental A20 cells or those transfected with the Myr Akt-ER were serum starved for 16 hours and then left unstimulated, stimulated for 5 minutes by cross-linking the BCR alone (B), or co–cross-linking the BCR+FcγRIIB1 (B+F) in the absence or presence of 4-HT. Cell lysates were immunoprecipitated with anti-p70S6k antibody, and in vitro kinase activity was assessed using a Rsk substrate peptide. The protein levels in the precipitates were analyzed by anti-p70S6k immunoblotting. The data are representative of at least 3 independent experiments.