title: Protein kinase C signals thromboxane induced increases in fibronectin synthesis and TGF-beta bioactivity in mesangial cells.
abstract: Previous studies have demonstrated that thromboxane (TX) stimulates matrix protein synthesis in mesangial cells (MC), and that this action is signalled by receptor mediated activation of protein kinase C (PKC). In the present study, we examined the hypothesis that activation of PKC by TX signals increases in transforming growth factor beta (TGF-beta) bioactivity, which in turn induces enhanced matrix protein synthesis. In cultured rat MC, the TXA2/prostaglandin endoperoxide analogue U-46619, but not exogenous human platelet TGF-beta 1, activated PKC as reflected by enhanced in situ phosphorylation of MARCKS protein, an endogenous substrate of PKC. U-46619 and TGF-beta 1 stimulated fibronectin (Fn) synthesis in MC, as shown by [35S]methionine incorporation into immunoprecipitable Fn. Pan-specific rabbit anti-TGF-beta antibody blocked the increases in Fn synthesis induced by exogenous TGF-beta and those induced by U-46619 at 24 to 72 hours after addition. Anti-TGF-beta antibody did not block the small increases in FN synthesis observed six hours after addition of U-46619, suggesting that this acute response was not dependent on TGF-beta. Anti-TGF-beta antibody also failed to block activation of PKC by U-46619. U-46619 and 50 nM of the PKC agonist phorbol dibutyrate (PDBu) significantly increased both the active fraction and total (latent plus active) TGF-beta in MC culture media, as assayed with the mink lung epithelial cell bioassay system.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Medicine, VA Medical Center, Pittsburgh, Pennsylvania, USA.
authors.forename: R K
authors.initials: RK
authors.lastname: Studer
authors.forename: H
authors.initials: H
authors.lastname: Negrete
authors.forename: P A
authors.initials: PA
authors.lastname: Craven
authors.forename: F R
authors.initials: FR
authors.lastname: DeRubertis
mesh_terms: D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D000818:Animals; D002478:Cells, Cultured; D005260:Female; D005353:Fibronectins / Q000096:biosynthesis*; D005920:Glomerular Mesangium / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D008301:Maleimides / Q000494:pharmacology; D010703:Phorbol Esters / Q000494:pharmacology; D011450:Prostaglandin Endoperoxides, Synthetic / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology*; D011817:Rabbits; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D013928:Thromboxane A2 / Q000031:analogs & derivatives / Q000494:pharmacology; D013931:Thromboxanes / Q000502:physiology*; D016212:Transforming Growth Factor beta / Q000378:metabolism*
chemical_list: D005353:Fibronectins; D007211:Indoles; D008301:Maleimides; D010703:Phorbol Esters; D011450:Prostaglandin Endoperoxides, Synthetic; D013931:Thromboxanes; D016212:Transforming Growth Factor beta; D013928:Thromboxane A2; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D011493:Protein Kinase C; C070515:bisindolylmaleimide I