COORDINATE REGULATION OF PP90RSK AND A DISTINCT PROTEIN-SERINE THREONINE KINASE-ACTIVITY THAT PHOSPHORYLATES RECOMBINANT PP90RSK INVITRO

被引:69
作者
CHUNG, JK [1 ]
CHEN, RH [1 ]
BLENIS, J [1 ]
机构
[1] HARVARD UNIV,SCH MED,DEPT CELLULAR & MOLEC PHYSIOL,25 SHATTUCK ST,BOSTON,MA 02115
关键词
D O I
10.1128/MCB.11.4.1868
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Protein kinase assays that use recombinant pp90rsk as a substrate were developed in an attempt to identify growth-regulated enzymes responsible for the phosphorylation and activation of pp90rsk S6 phosphotransferase activity. With this assay we have identified a pp60v-src-, growth factor-, phorbol ester-, and vanadate-regulated serine/threonine protein kinase activity that is not related to two other cofactor-independent, growth-regulated protein kinases, pp70-S6 protein kinase and pp90rsk. The pp90rsk-protein kinase activity (referred to as rsk-kinase) is also not related to cofactor-dependent signal transducing protein kinases such as the cyclic AMP-dependent protein kinases, members of the protein kinase C family, or other Ca2+ -dependent protein kinases. In vitro, partially purified rsk-kinase phosphorylates several of the sites (serine and threonine) that are phosphorylated in growth-stimulated cultured cells. A detailed examination of the mitogen-regulated activation kinetics of rsk-kinase and pp90rsk activities demonstrated that they are coordinately regulated. In addition, protein kinase C is not absolutely required for epidermal and fibroblast growth factor-stimulated activation of rsk-kinase, whereas, like pp90rsk, platelet-derived growth factor- and vanadate-stimulated rsk-kinase activity exhibits a greater dependence on protein kinase C-mediated signal transduction. The characterization and future purification of the rsk-kinase(s) will improve our understanding of the early signaling events regulating cell growth.
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页码:1868 / 1874
页数:7
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