Activation of protein kinase C stimulates the dephosphorylation of natriuretic peptide receptor-B at a single serine residue: a possible mechanism of heterologous desensitization.
The binding of atrial natriuretic peptide and C-type natriuretic peptide (CNP) to the guanylyl cyclase-linked natriuretic peptide receptors A and B (NPR-A and -B), respectively, stimulates increases in intracellular cGMP concentrations. The vasoactive peptides vasopressin, angiotensin II, and endothelin inhibit natriuretic peptide-dependent cGMP elevations by activating protein kinase C (PKC). Recently, we identified six in vivo phosphorylation sites for NPR-A and five sites for NPR-B and demonstrated that the phosphorylation of these sites is required for ligand-dependent receptor activation. Here, we show that phorbol 12-myristate 13-acetate, a direct activator of PKC, causes the dephosphorylation and desensitization of NPR-B. In contrast to the CNP-dependent desensitization process, which results in coordinate dephosphorylation of all five sites in the receptor, phorbol 12-myristate 13-acetate treatment causes the dephosphorylation of only one site, which we have identified as Ser(523). The conversion of this residue to alanine or glutamate did not reduce the amount of mature receptor protein as indicated by detergent-dependent guanylyl cyclase activities or Western blot analysis but completely blocked the ability of PKC to induce the dephosphorylation and desensitization of NPR-B. Thus, in contrast to previous reports suggesting that PKC directly phosphorylates and inhibits guanylyl cyclase-linked natriuretic peptide receptors, we show that PKC-dependent dephosphorylation of NPR-B at Ser(523) provides a possible molecular explanation for how pressor hormones inhibit CNP signaling.
Molecular Biology and Virology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037, USA. Potter@tc.umn.edu
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D000409:Alanine / Q000737:chemistry; D001665:Binding Sites; D015153:Blotting, Western; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D003902:Detergents / Q000494:pharmacology; D004789:Enzyme Activation; D018698:Glutamic Acid / Q000737:chemistry; D006162:Guanylate Cyclase / Q000378:metabolism; D006801:Humans; D008024:Ligands; D016297:Mutagenesis, Site-Directed; D010449:Peptide Mapping; D010455:Peptides / Q000138:chemical synthesis; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism*; D017461:Receptors, Atrial Natriuretic Factor / Q000378:metabolism*; D012694:Serine / Q000737:chemistry / Q000378:metabolism*; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection; D000099242:Atrial Natriuretic Factor Receptor B
D000409:Alanine; D006152:Cyclic GMP; D003902:Detergents; D018698:Glutamic Acid; D006162:Guanylate Cyclase; D008024:Ligands; D010455:Peptides; D011493:Protein Kinase C; D017461:Receptors, Atrial Natriuretic Factor; D012694:Serine; D013755:Tetradecanoylphorbol Acetate; D000099242:Atrial Natriuretic Factor Receptor B