Protein kinase C-mediated desensitization of the neurokinin 1 receptor.
An understanding of the mechanisms that regulate signaling by the substance P (SP) or neurokinin 1 receptor (NK1-R) is of interest because of their role in inflammation and pain. By using activators and inhibitors of protein kinase C (PKC) and NK1-R mutations of potential PKC phosphorylation sites, we determined the role of PKC in desensitization of responses to SP. Activation of PKC abolished SP-induced Ca(2+) mobilization in cells that express wild-type NK1-R. This did not occur in cells expressing a COOH-terminally truncated NK1-R (NK1-Rdelta324), which may correspond to a naturally occurring variant, or a point mutant lacking eight potential PKC phosphorylation sites within the COOH tail (NK1-R Ser-338, Thr-339, Ser-352, Ser-387, Ser-388, Ser-390, Ser-392, Ser-394/Ala, NK1-RKC4). Compared with wild-type NK1-R, the t(1/2) of SP-induced Ca(2+) mobilization was seven- and twofold greater in cells expressing NK1-Rdelta324 and NK1-RKC4, respectively. In cells expressing wild-type NK1-R, inhibition of PKC caused a 35% increase in the t(1/2) of SP-induced Ca(2+) mobilization. Neither inhibition of PKC nor receptor mutation affected desensitization of Ca(2+) mobilization to repeated challenge with SP or SP-induced endocytosis of the NK1-R. Thus PKC regulates SP-induced Ca(2+) mobilization by full-length NK1-R and does not regulate a naturally occurring truncated variant. PKC does not mediate desensitization to repeated stimulation or endocytosis of the NK1-R.
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Departments of Surgery and Physiology, University of California San Francisco, San Francisco, California 94143-0660, USA.
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Bunnett
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D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001483:Base Sequence; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002460:Cell Line; D017931:DNA Primers; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007211:Indoles; D007668:Kidney; D008301:Maleimides; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism; D010769:Phosphothreonine / Q000378:metabolism; D011487:Protein Conformation; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D018040:Receptors, Neurokinin-1 / Q000737:chemistry / Q000187:drug effects / Q000502:physiology*; D011994:Recombinant Proteins / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D017384:Sequence Deletion; D013373:Substance P / Q000494:pharmacology*; D014162:Transfection
D017931:DNA Primers; D004791:Enzyme Inhibitors; D007211:Indoles; D008301:Maleimides; D018040:Receptors, Neurokinin-1; D011994:Recombinant Proteins; D010769:Phosphothreonine; D010768:Phosphoserine; D013373:Substance P; D015240:Phorbol 12,13-Dibutyrate; D011493:Protein Kinase C; C070515:bisindolylmaleimide I