Protein kinase C delta blocks immediate-early gene expression in senescent cells by inactivating serum response factor.
Fibroblasts lose the ability to replicate in response to growth factors and become unable to express growth-associated immediate-early genes, including c-fos and egr-1, as they become senescent. The serum response factor (SRF), a major transcriptional activator of immediate-early gene promoters, loses the ability to bind to the serum response element (SRE) and becomes hyperphosphorylated in senescent cells. We identify protein kinase C delta (PKC delta) as the kinase responsible for inactivation of SRF both in vitro and endogenously in senescent cells. This is due to a higher level of PKC delta activity as cells age, production of the PKC delta catalytic fragment, and its nuclear localization in senescent but not in low-passage-number cells. The phosphorylation of T160 of SRF by PKC delta in vitro and in vivo led to loss of SRF DNA binding activity. Both the PKC delta inhibitor rottlerin and ectopic expression of a dominant negative form of PKC delta independently restored SRE-dependent transcription and immediate-early gene expression in senescent cells. Modulation of PKC delta activity in vivo with rottlerin or bistratene A altered senescent- and young-cell morphology, respectively. These observations support the idea that the coordinate transcriptional inhibition of several growth-associated genes by PKC delta contributes to the senescent phenotype.
Wheaton
Keith
K
Department of Biochemistry and Molecular Biology, Southern Alberta Cancer Centre, University of Calgary, Calgary, Alberta, Canada.
Riabowol
Karl
K
D000081:Acetamides / Q000378:metabolism; D000098:Acetophenones / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001578:Benzopyrans / Q000378:metabolism; D048429:Cell Size; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology*; D005786:Gene Expression Regulation; D017781:Genes, Immediate-Early; D006131:Growth Inhibitors / Q000378:metabolism; D006801:Humans; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051745:Protein Kinase C-delta; D011714:Pyrans / Q000378:metabolism; D011817:Rabbits; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D026362:Serum Response Factor / Q000235:genetics / Q000378:metabolism*; D013141:Spiro Compounds / Q000378:metabolism; D014158:Transcription, Genetic
D000081:Acetamides; D000098:Acetophenones; D001578:Benzopyrans; D004791:Enzyme Inhibitors; D006131:Growth Inhibitors; D007527:Isoenzymes; D010446:Peptide Fragments; D011714:Pyrans; D011994:Recombinant Proteins; D026362:Serum Response Factor; D013141:Spiro Compounds; C059975:bistratene A; C085746:rottlerin; C497258:PRKCD protein, human; D011493:Protein Kinase C; D051745:Protein Kinase C-delta