Protein kinase C isoform expression during the differentiation of 3T3-L1 preadipocytes: loss of protein kinase C-alpha isoform correlates with loss of phorbol 12-myristate 13-acetate activation of nuclear factor kappaB and acquisition of the adipocyte phenotype.
The regulated expression of protein kinase C (PKC) isoforms was examined during the differentiation program of 3T3-L1 preadipocytes. In a parallel analysis, differentiation was blocked by treatment of the cells with tumor necrosis factor-alpha (TNF) to determine differentiation-specific changes in isoform expression from growth or treatment-induced effects. This analysis revealed that the expression of the conventional PKC-alpha isoform was reduced by 85% as cells attained the adipocyte phenotype. PKC-beta expression was measurable only during the early stages of the differentiation process and was not detectable in fully differentiated cells. An upregulation of PKC-theta, a novel PKC isoform, occurred during the latter stage of differentiation. Expression of PKC-zeta an atypical PKC isoform suggested to participate in TNF signal transduction, occurred throughout the time course with similar levels of expression in both preadipocytes and adipocytes. Nuclear run-on analysis demonstrated an approximately 85% reduction in the transcription of the PKC-alpha gene during differentiation. The reduced expression of this isoform corresponded with the decreased ability to activate nuclear factor kapppaB (NF-kappaB) in response to phorbol 12-myristate 13-acetate (PMA) treatment in the adipocytes. These data suggest that PMA responsiveness in 3T3-L1 adipocytes is markedly diminished.
McGowan
K
K
Department of Biochemistry, School of Medicine, East Carolina University, Greenville, North Carolina 27858, USA.
DeVente
J
J
Carey
J O
JO
Ways
D K
DK
Pekala
P H
PH
D017667:Adipocytes / Q000166:cytology / Q000378:metabolism*; D000818:Animals; D001483:Base Sequence; D002273:Carcinogens / Q000494:pharmacology*; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D007527:Isoenzymes / Q000096:biosynthesis*; D051379:Mice; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000378:metabolism*; D011493:Protein Kinase C / Q000096:biosynthesis*; D051571:Protein Kinase C-alpha; D011994:Recombinant Proteins / Q000494:pharmacology; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D002273:Carcinogens; D007527:Isoenzymes; D016328:NF-kappa B; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; C496630:Prkca protein, mouse; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha; D013755:Tetradecanoylphorbol Acetate