Turnover of functional basic fibroblast growth factor receptors on the surface of BHK and NIH 3T3 cells.
The recovery of functional cell-surface bFGF receptors after trypsin treatment was studied in BHK cells and NIH 3T3 cells. Restoration of functional bFGF receptors occurred at an approximately linear rate with 50% of the high-affinity binding capacity restored after 4 hr. Restoration of functional receptors required protein synthesis but not RNA synthesis. Upon exposure of BHK cells to bFGF, cell-surface receptors were rapidly lost, with only 25% remaining after 1 hr. When the bFGF was removed, down-regulated BHK and NIH 3T3 cells recovered cell-surface receptors at about the same rate observed in trypsin-treated cells. The recovery of receptors after down-regulation was inhibited by protein synthesis inhibitors. Addition of the protein synthesis inhibitor cycloheximide to unperturbed cultures of BHK or NIH 3T3 cells resulted in a time-dependent loss of cell-surface bFGF receptors, demonstrating that the receptors turn over constantly in the absence of ligand. These results suggest that bFGF receptors do not recycle and must be continuously synthesized.
Moscatelli
D
D
Department of Cell Biology and Kaplan Cancer Center, New York University Medical Center, New York 10016.
Devesly
P
P
D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D015536:Down-Regulation; D005346:Fibroblast Growth Factors / Q000378:metabolism*; D007700:Kinetics; D008970:Molecular Weight; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000378:metabolism*; D017468:Receptors, Fibroblast Growth Factor; D014357:Trypsin / Q000494:pharmacology
D011956:Receptors, Cell Surface; D017468:Receptors, Fibroblast Growth Factor; D005346:Fibroblast Growth Factors; D003513:Cycloheximide; D014357:Trypsin