Identification of a protein transiently phosphorylated by activators of endothelial cell function as the heat-shock protein HSP27. A possible role for protein kinase C.
Several agonists of endothelial cell function (thrombin, histamine, dioctanoylglycerol, phorbol 12-myristate 13-acetate, interleukin-1) have previously been shown to enhance the level of phosphorylation of an undefined 29,000-M(r) protein (P29). Comparison of this protein with other phosphoproteins suggested that it may be related to the mammalian heat-shock protein HSP27. Immunoprecipitation and immunoblot analysis with antibodies specific for human HSP27 demonstrated that P29 was immunochemically identical with HSP27. Further characterization of agonist-induced phosphorylation of HSP27 indicated that phosphorylation occurred exclusively on serine residues, and phosphopeptide analysis of tryptic- and chymotryptic-cleavage products demonstrated that the phosphopeptides generated were identical for each agonist and okadaic acid. Down-regulation of protein kinase C-alpha by prolonged treatment with phorbol esters eliminated the ability of phorbol 12-myristate 13-acetate, dioctanoylglycerol, thrombin and histamine to phosphorylate HSP27 above background levels and deceased interleukin-1-stimulated HSP27 phosphorylation by 60%. These data suggest that the various agonists employed stimulate HSP27 phosphorylation through similar mechanisms and that protein kinase C is probably involved.
Santell
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L
Department of Molecular and Experimental Medicine, Scripps Research Institute, La Jolla, CA 92037.
Bartfeld
N S
NS
Levin
E G
EG
D001345:Autoradiography; D015153:Blotting, Western; D002478:Cells, Cultured; D015180:Electrophoresis, Gel, Two-Dimensional; D004591:Electrophoresis, Polyacrylamide Gel; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D010449:Peptide Mapping; D010710:Phosphates / Q000378:metabolism; D010748:Phosphopeptides / Q000032:analysis; D010750:Phosphoproteins / Q000302:isolation & purification / Q000378:metabolism; D010761:Phosphorus Radioisotopes; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014357:Trypsin; D014471:Umbilical Veins
D006360:Heat-Shock Proteins; D010710:Phosphates; D010748:Phosphopeptides; D010750:Phosphoproteins; D010761:Phosphorus Radioisotopes; D011493:Protein Kinase C; D014357:Trypsin; D013755:Tetradecanoylphorbol Acetate