PKCeta associates with cyclin E/Cdk2 complex in serum-starved MCF-7 and NIH-3T3 cells.
Protein kinase C (PKC) encodes a family of enzymes implicated in cellular differentiation, growth control, and tumor promotion. However, very little is known with respect to the molecular mechanisms that link protein kinase C to cell cycle control. Here we report that PKCeta associates with the cyclin E/Cdk2 complex. This is shown for the ectopically overexpressed PKCeta in NIH-3T3 cells, the inducibly expressed PKCeta in MCF-7 cells (under control of the tetracycline-responsive promoter), and the endogenously expressed PKCeta in mouse mammary epithelial HC11 cells. Subcellular cell fractionation experiments revealed that the complex with cyclin E is formed mostly in the nuclear fractions, although in these cells PKCeta is predominantly expressed in the cytosolic fractions. The complex of PKCeta and cyclin E was studied at various phases of the cell cycle, in serum-starved quiescent cells and in cells stimulated with serum to reenter the cell cycle. Interestingly, the interaction between PKCeta and cyclin E was most prominent in serum-starved cells and was disintegrated when cells entered the cells cycle. Immunofluorescence staining demonstrated that in serum-starved cells PKCeta is concentrated at the perinuclear zone, which is also the site of its colocalization with cyclin E. Colocalization of PKCeta and cyclin E in the perinuclear region was observed in serum-starved cells, and less in proliferating cells. These experiments suggest that the interaction between PKCeta and cyclin E is carefully regulated, and is correlated with the inactivated form of the cyclin E/Cdk2 complex. Thus, our studies support an important link between PKC and cell cycle control.
Shtutman
Marat
M
Department of Microbiology and Immunology, Faculty of Health Sciences and the Cancer Research Center, Ben Gurion University, Beer Sheva 84105, Israel.
Hershko
Tzippi
T
Maissel
Adva
A
Fima
Eyal
E
Livneh
Etta
E
D016475:3T3 Cells; D000230:Adenocarcinoma; D000818:Animals; D001943:Breast Neoplasms; D042846:CDC2-CDC28 Kinases; D002453:Cell Cycle / Q000502:physiology; D002458:Cell Fractionation; D002467:Cell Nucleus / Q000378:metabolism; D016895:Culture Media, Serum-Free; D019927:Cyclin E / Q000378:metabolism*; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D046911:Macromolecular Substances; D051379:Mice; D011493:Protein Kinase C / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D016895:Culture Media, Serum-Free; D019927:Cyclin E; D046911:Macromolecular Substances; C081975:protein kinase C eta; D017346:Protein Serine-Threonine Kinases; D011493:Protein Kinase C; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; C495893:Cdk2 protein, mouse; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases