title: Protein kinase C in the human erythrocyte. Translocation to the plasma membrane and phosphorylation of bands 4.1 and 4.9 and other membrane proteins.
abstract: Protein kinase C (PK-C) was demonstrated in human erythrocytes using the exogenous substrate histone H1. The enzyme was dependent on the simultaneous presence of micromolar Ca2+ and phosphatidylserine. The Ca2+ requirement was reduced in the presence of the tumor promoter 12-O-tetradecanoylphorbol 13-acetate (TPA). Activity was normally recovered in cytoplasmic extracts, but treatment of intact cells with TPA (EC50 = 40 nM) prior to lysis caused a rapid translocation of activity from the cytoplasm to the membrane. Following translocation, PK-C activity in the isolated membrane was independent of Ca2+ and phosphatidylserine and could not be removed by manipulating ionic strength. Ghosts from TPA-treated cells showed a marked increase in the phosphorylation of five proteins (termed PK-C-1-5) of Mr 120,000, 110,000, 80,000, 78,000, and 49,000. Addition of purified bovine brain PK-C to ghosts from untreated cells resulted in the phosphorylation of the same five proteins. PK-C-3/4 corresponded to Band 4.1 and PK-C-5 to Band 4.9. Both proteins were isolated from ghosts and shown to be substrates for PK-C in vitro. PK-C-1 and -2 appear to be minor peripheral membrane proteins as both were released from the membrane by alkaline solutions. Incubation of 32P-prelabeled erythrocytes with TPA (EC50 = 40 nM) also resulted in a dose-dependent phosphorylation of PK-C-1-5. These results suggest that PK-C may play an important role in erythrocyte membrane function.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D001798:Blood Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology; D003598:Cytoskeletal Proteins; D004912:Erythrocytes / Q000201:enzymology*; D006657:Histones / Q000378:metabolism; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D008840:Microfilament Proteins; D008970:Molecular Weight; D009479:Neuropeptides; D010718:Phosphatidylserines / Q000378:metabolism; D010750:Phosphoproteins; D010766:Phosphorylation; D011493:Protein Kinase C / Q000097:blood*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D000596:Amino Acids; D001798:Blood Proteins; D003598:Cytoskeletal Proteins; C044805:DMTN protein, human; D006657:Histones; D008565:Membrane Proteins; D008840:Microfilament Proteins; D009479:Neuropeptides; D010718:Phosphatidylserines; D010750:Phosphoproteins; C028841:erythrocyte membrane band 4.1 protein; C120557:erythrocyte membrane protein band 4.1-like 1; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate