Regulation of transferrin receptor recycling by protein phosphorylation.
The effect of the protein phosphatase inhibitor okadaic acid on transferrin receptor internalization and recycling was examined in HeLa and K562 cells. Okadaic acid inhibited receptor uptake by more than 85% in both cell lines, whereas it affected transferrin recycling to differing degrees: recycling in HeLa cells was inhibited by greater than 90%, compared with only 65% in K562 cells. Okadaic acid also caused a marked redistribution of receptors in each cell line, which was accounted for by the difference in the extent to which transferrin uptake and recycling were inhibited. These effects were most likely mediated by a protein kinase, as they were delayed by 10-15 min and could be suppressed by prior incubation with certain protein kinase inhibitors. In addition, it was found that specific kinase inhibitors affected basal rates of transferrin uptake and recycling, although the extent of these effects differed between cell lines. Together, these results suggest that a complex pattern of protein phosphorylation influences the flux of the endocytic pathway in interphase cells.
Division of Biochemistry, School of Biological Sciences, University of Manchester Medical School, U.K.
J R
JR
Beauchamp
P G
PG
Woodman
D000255:Adenosine Triphosphate / Q000378:metabolism; D000470:Alkaloids / Q000494:pharmacology; D001665:Binding Sites; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004247:DNA / Q000378:metabolism; D003676:Deferoxamine / Q000494:pharmacology; D004705:Endocytosis / Q000187:drug effects; D004988:Ethers, Cyclic / Q000378:metabolism / Q000494:pharmacology*; D006367:HeLa Cells; D006801:Humans; D007553:Isotope Labeling; D019319:Okadaic Acid; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors*; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000378:metabolism; D011990:Receptors, Transferrin / Q000187:drug effects* / Q000378:metabolism; D019311:Staurosporine; D014168:Transferrin / Q000378:metabolism
D000470:Alkaloids; D004988:Ethers, Cyclic; D047428:Protein Kinase Inhibitors; D011990:Receptors, Transferrin; D014168:Transferrin; D019319:Okadaic Acid; D000255:Adenosine Triphosphate; D004247:DNA; D011494:Protein Kinases; D010749:Phosphoprotein Phosphatases; D019311:Staurosporine; D003676:Deferoxamine