Fibroblast growth factor phosphorylation and receptors in rod outer segments.
Acidic and basic fibroblast growth factors (aFGF and bFGF) have been isolated and purified from rod outer segments (ROS). aFGF is tightly bound to ROS membranes and can be specifically released by ATP. We show that this mechanism is dependent on the phosphorylation of aFGF itself. Phorbol 12-myristate 13-acetate (PMA) enhances this phenomenon independently of rhodopsin phosphorylation. This demonstrates that aFGF release from ROS membranes is dependent on its phosphorylation by endogenous kinase C. In addition specific binding sites for exogenous FGFs have been identified on ROS and disc membranes. A single high affinity site with a Kd of 40 pM was present in intact ROS while an additional low affinity site with a Kd of 300-600 pM was present in leaky ROS or in disc membranes. Light or ATP modified neither these Kd nor the apparent number of sites. The presence of specific receptors for FGFs and the kinase C dependent release of endogenous membrane bound aFGF suggest an autocrine mechanism which may be involved in photoreceptor cell biology.
Mascarelli
F
F
INSERM U. 118, Centre de Gérontologie Claude-Bernard, Paris, France.
Raulais
D
D
Courtois
Y
Y
D000818:Animals; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D003432:Cross-Linking Reagents; D004591:Electrophoresis, Polyacrylamide Gel; D005136:Eye Proteins / Q000378:metabolism; D005346:Fibroblast Growth Factors / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010766:Phosphorylation; D010786:Photoreceptor Cells / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D017468:Receptors, Fibroblast Growth Factor; D012243:Rhodopsin / Q000378:metabolism; D012374:Rod Cell Outer Segment / Q000378:metabolism*; D017299:Rod Opsins; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D003432:Cross-Linking Reagents; D005136:Eye Proteins; D011956:Receptors, Cell Surface; D017468:Receptors, Fibroblast Growth Factor; D017299:Rod Opsins; D005346:Fibroblast Growth Factors; D012243:Rhodopsin; D013755:Tetradecanoylphorbol Acetate