Basic fibroblast growth factor (FGF) has recently been shown to be a phosphoprotein and its receptor affinity is modified by phosphorylation. Since most studies of protein phosphorylation have focused on intracellular protein kinases, a physiologic mechanism of the regulation of basic FGF activity by phosphorylation has been unclear. Evidence for the existence of ecto-protein kinase activity on the surface of several types of cells including human neutrophils has been described. These ecto-protein kinase activities utilize exogenous ATP to phosphorylate exogenous as well as endogenous cell-surface proteins. This report demonstrates that human basic FGF is phosphorylated on serine by human neutrophil ecto-protein kinase activity and this phosphorylation is inhibited by heparin. Regulation of basic FGF activity by phosphorylation may be one of the functions of ecto-protein kinase activity.
|Original language||English (US)|
|Number of pages||7|
|Journal||Biochemical and Biophysical Research Communications|
|State||Published - Jan 15 1991|
Bibliographical noteFunding Information:
*Supported in part by National Institutes of Health Grant CA36248, the Leukemia Task Force, and the Masonic Memorial Hospital Fund, Inc. §To whom correspondences hould be addressed. Abbreviations: FGF, fibroblast growth factor; PKA, CAMP-dependent protein kinase; PKC, calcium-dependent and phospholipid-dependent protein kinase; HBSS, Hanks’ balanced salt solution, pH 7.4; NaCl-HEPES, 145 mM NaCl, 20 mM N-2-hydroxyethylpiperazine-N’-2-ethanesulfonica cid, pH 7.4; PAGE, polyacrylamide gel electrophoresis;P VDF, Immobilon-P, PS, phosphoserine;P -T, phosphothreonine;P -Y, phosphotyrosine.