The T cell antigen receptor activates phosphatidylinositol 3-kinase-regulated serine kinases protein kinase B and ribosomal S6 kinase 1

The present study has explored T cell antigen receptor-regulated serine kin ases in human T cells. The results identify two phosphatidylinositol 3-kina se (PI3K)-controlled serine kinases operating downstream of the T cell rece ptor (TCR) in primary T cells: (i) protein kinase B whose activation regula tes the phosphorylation of glycogen synthase kinase 3 and (ii) ribosomal S6 kinase 1, a kinase with a critical role in the regulation of protein synth esis and cell growth, T cells express two isoforms of S6k1: a 70 kDa cytopl asmic kinase and an 85 kDa isoform that has a classic nuclear localisation. TCR ligation triggers a parallel engagement of both the 70 and 85 kDa isof orms of S6k1 in a response that requires PI3K function. (C) 2000 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.