title: Phosphorylation of the human transferrin receptor by protein kinase C is not required for endocytosis and recycling in mouse 3T3 cells.
abstract: We have investigated the role of phosphorylation in the endocytosis of the human transferrin receptor (TR) by replacing its phosphorylation site, Ser24, with Ala through site-directed mutagenesis of the TR cDNA. The TR Ala24 mutant expressed in mouse 3T3 cells was not phosphorylated, even following stimulation of protein kinase C by phorbol ester. However, in spite of this defect the mutant was efficiently endocytosed and recycled back to the plasma membrane with kinetics similar to those of TR and a control mutant TR Ala63. Thus, these results confirm earlier results by Davis et al. (1986, J. Biol. Chem., 261-9034-9041) that Ser24 of human TR is the phosphorylation site for protein kinase C but do not support a role of this modification as a signal for TR endocytosis and recycling.
mesh_terms: D000818:Animals; D002460:Cell Line; D002478:Cells, Cultured; D004705:Endocytosis; D006801:Humans; D009154:Mutation; D015240:Phorbol 12,13-Dibutyrate; D010703:Phorbol Esters / Q000494:pharmacology; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D011990:Receptors, Transferrin / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D014168:Transferrin / Q000378:metabolism
chemical_list: D010703:Phorbol Esters; D011990:Receptors, Transferrin; D014168:Transferrin; D015240:Phorbol 12,13-Dibutyrate; D011493:Protein Kinase C