Transforming growth factor-beta2 regulates C3 secretion in monocytes through a protein kinase C-dependent pathway.
Previously, we reported that TGF-beta2 regulates the C3 gene expression in a dose- and time-dependent manner in monocytes. To extend these studies, we examined the role of PKC in the TGF-beta2-mediated induction of C3 expression by the human monocyte cell line, U937. Treatment of U937 cells with the PKC inhibitors, H7 and calphostin C, suppressed TGF-beta2-mediated induction of C3 protein levels, but not mRNA levels, in a dose-dependent manner. At the highest concentrations of H7 and calphostin C, C3 protein levels were inhibited 50% and 93%, respectively, compared to control levels. Treatment of U937 cells with HA1004, a weak PKC inhibitor used as a control for H7, did not inhibit induction of C3 protein levels. Down-modulating PKC with a prolonged exposure of U937 cells to PMA also suppressed TGF-beta2-mediated C3 protein induction by as much as 82%. Incubating cell extracts isolated from TGF-beta2-treated U937 cells with the PKC substrate, MIBP(4-14), resulted in increased substrate phosphorylation compared to cell extracts isolated from untreated cells. Addition of calphostin C suppressed the increased substrate phosphorylation by TGF-beta2. Furthermore, biosynthetic labeling of U937 cells treated with TGF-beta2 and calphostin C demonstrated an accumulation of C3 protein within cell lysates compared to controls. Collectively, these studies suggest a role for PKC in the secretion of C3 protein during TGF-beta2-mediated regulation of C3 expression in U937 cells.
Department of Microbiology, University of Alabama at Birmingham, 35294, USA.
S M
SM
Drouin
S C
SC
Kiley
J A
JA
Carlino
S R
SR
Barnum
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000494:pharmacology; D003176:Complement C3 / Q000378:metabolism*; D004347:Drug Interactions; D006801:Humans; D007249:Inflammation / Q000276:immunology; D007527:Isoenzymes / Q000378:metabolism; D007546:Isoquinolines / Q000494:pharmacology; D009000:Monocytes / Q000276:immunology*; D009281:Naphthalenes / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015398:Signal Transduction; D013449:Sulfonamides; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D003176:Complement C3; D007527:Isoenzymes; D007546:Isoquinolines; D009281:Naphthalenes; D013449:Sulfonamides; D016212:Transforming Growth Factor beta; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; C043204:N-(2-guanidinoethyl)-5-isoquinolinesulfonamide; D011493:Protein Kinase C; C058819:calphostin C; D013755:Tetradecanoylphorbol Acetate