Identification of an integral plasma membrane pool of protein kinase C in mammalian tissues and cells.
Protein kinase C (PKC) is a family of serine/threonine protein kinases that are pivotal in cellular regulation. Since its discovery in 1977, PKCs have been known as cytosolic and peripheral membrane proteins. However, there are reports that PKC can insert into phospholipids vesicles in vitro. Given the intimate relationship between the plasma membrane and the activation of PKC, it is important to determine whether such "membrane-inserted" form of PKC exists in mammalian cells or tissues. Here, we report the identification of an integral plasma membrane pool for all the 10 PKC isozymes in vivo by their ability to partition into the detergent-rich phase in Triton X-114 phase partitioning, and by their resistance to extractions with 0.2 M sodium carbonate (pH 11.5), 2 M urea and 2 M sodium chloride. The endogenous integral membrane pool of PKC in mouse fibroblasts is found to be acutely regulated by phorbol ester or diacylglycerol, suggesting that this pool of PKC may participate in cellular processes known to be regulated by PKC. At least for PKC(alpha), the C2-V3 region at the regulatory domain of the kinase is responsible for membrane integration. Further exploration of the function of this novel integral plasma membrane pool of PKC will not only shed new light on molecular mechanisms underlying its cellular functions but also provide new strategies for pharmaceutical modulation of this important group of kinases.
Department of Biochemistry, Faculty of Medicine, The National University of Singapore, 8 Medical Drive, Singapore 117597, Singapore.
Yimin
Y
Zhu
Wee Guan
WG
Lim
Bee Jen
BJ
Tan
Tian Seng
TS
Teo
Wei
W
Duan
D000818:Animals; D019556:COS Cells; D002462:Cell Membrane / Q000201:enzymology*; D002522:Chlorocebus aethiops; D004075:Diglycerides / Q000494:pharmacology; D007527:Isoenzymes / Q000032:analysis / Q000378:metabolism; D050356:Lipid Metabolism; D051379:Mice; D011493:Protein Kinase C / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D051571:Protein Kinase C-alpha; D017434:Protein Structure, Tertiary; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D004075:Diglycerides; D007527:Isoenzymes; C496630:Prkca protein, mouse; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha; D013755:Tetradecanoylphorbol Acetate