title: Differential phosphorylation of sites in the linker region of P-glycoprotein by protein kinase C isozymes alpha, betaI, betaII, gamma, delta, epsilon, eta, and zeta.
abstract: To determine whether individual protein kinase C (PKC) isozymes differentially phosphorylate sites in the linker region of human P-glycoprotein (P-gp), we used a synthetic peptide substrate, PG-2, exactly corresponding to amino acid residues spanning the region 656-689 of the multidrug resistance gene (MDRI). All tested PKC isozymes phosphorylated PG-2. The maximum phosphate incorporation by calcium-dependent PKC isozymes alpha, betaI, betaII, and gamma was 3, 2, 2, and 3 mol phosphate/mol PG-2, respectively. The maximum phosphate incorporation by calcium-independent isozymes delta, epsilon, eta, and zeta was 1.5, 0.5, 1.5, and 1.5 mol phosphate/mol PG-2, respectively. Two-dimensional tryptic phosphopeptide mapping indicated differential phosphorylation of the PKC consensus sites Ser-661, Ser-667, and Ser-671 by individual isozymes, which may be functionally significant. These data suggest that differential phosphorylation by PKC isoenzymes of PKC sites within the P-gp linker region may play a role in modulating P-gp activity.
authors.affiliation: Department of Medicine, Duke University, Durham, NC, USA.
authors.forename: C W
authors.initials: CW
authors.lastname: Sachs
authors.forename: T C
authors.initials: TC
authors.lastname: Chambers
authors.forename: R L
authors.initials: RL
authors.lastname: Fine
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism*; D000595:Amino Acid Sequence; D006801:Humans; D066298:In Vitro Techniques; D007527:Isoenzymes / Q000378:metabolism*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000378:metabolism; D010449:Peptide Mapping; D010748:Phosphopeptides / Q000032:analysis; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D007527:Isoenzymes; D010446:Peptide Fragments; D010748:Phosphopeptides; D011994:Recombinant Proteins; D011493:Protein Kinase C