Calcium-dependent involucrin expression is inversely regulated by protein kinase C (PKC)alpha and PKCdelta.
Calcium is an important physiologic regulator of keratinocyte function that may regulate keratinocyte differentiation via modulation of protein kinase C (PKC) activity. PKCalpha and PKCdelta are two PKC isoforms that are expressed at high levels in keratinocytes. In the present study, we examine the effect of PKCdelta and PKCalpha on calcium-dependent keratinocyte differentiation as measured by effects on involucrin (hINV) gene expression. Our studies indicate that calcium increases hINV promoter activity and endogenous hINV gene expression. This response requires PKCdelta, as evidenced by the observation that treatment with dominant-negative PKCdelta inhibits calcium-dependent hINV promoter activity, whereas wild type PKCdelta increases activity. PKCalpha, in contrast, inhibits calcium-dependent hINV promoter activation, a finding that is consistent with the ability of dominant-negative PKCalpha and the PKCalpha inhibitor, Go6976, to increase hINV gene expression. The calcium-dependent regulatory response is mediated by an AP1 transcription factor-binding site located within the hINV promoter distal regulatory region that is also required for PKCdelta-dependent regulation; moreover, both calcium and PKCdelta produce similar, but not identical, changes in AP1 factor expression. A key question is whether calcium directly influences PKC isoform function. Our studies show that calcium does not regulate PKCalpha or delta levels or cause a marked redistribution to membranes. However, tyrosine phosphorylation of PKCdelta is markedly increased following calcium treatment. These findings suggest that PKCalpha and PKCdelta are required for, and modulate, calcium-dependent keratinocyte differentiation in opposing directions.
Deucher
Anne
A
Department of Physiology, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106-4970, USA.
Efimova
Tatiana
T
Eckert
Richard L
RL
D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D002227:Carbazoles / Q000494:pharmacology; D002454:Cell Differentiation; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation; D005799:Genes, Dominant; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D007477:Ions; D007527:Isoenzymes / Q000378:metabolism*; D015603:Keratinocytes / Q000378:metabolism; D008856:Microscopy, Fluorescence; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms; D011493:Protein Kinase C / Q000737:chemistry / Q000378:metabolism*; D051571:Protein Kinase C-alpha; D051745:Protein Kinase C-delta; D011498:Protein Precursors / Q000096:biosynthesis*; D016329:Sp1 Transcription Factor / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D013997:Time Factors; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014162:Transfection; D014443:Tyrosine / Q000378:metabolism
D002227:Carbazoles; D004791:Enzyme Inhibitors; D007211:Indoles; D007477:Ions; D007527:Isoenzymes; D020033:Protein Isoforms; D011498:Protein Precursors; D016329:Sp1 Transcription Factor; D018808:Transcription Factor AP-1; C081021:Go 6976; D014443:Tyrosine; C032253:involucrin; C496628:PRKCA protein, human; C497258:PRKCD protein, human; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha; D051745:Protein Kinase C-delta; D002118:Calcium