Protein kinase C(alpha) is required for vanilloid receptor 1 activation. Evidence for multiple signaling pathways.
Activation of vanilloid receptor (VR1) by protein kinase C (PKC) was investigated in cells ectopically expressing VR1 and primary cultures of dorsal root ganglion neurons. Submicromolar phorbol 12,13-dibutyrate (PDBu), which stimulates PKC, acutely activated Ca(2+) uptake in VR1-expressing cells at pH 5.5, but not at mildly acidic or neutral pH. PDBu was antagonized by bisindolylmaleimide, a PKC inhibitor, and ruthenium red, a VR1 ionophore blocker, but not capsazepine, a vanilloid antagonist indicating that catalytic activity of PKC is required for PDBu activation of VR1 ion conductance, and is independent of the vanilloid site. Chronic PDBu dramatically down-regulated PKC(alpha) in dorsal root ganglion neurons or the VR1 cell lines, whereas only partially influencing PKCbeta, -delta, -epsilon, and -zeta. Loss of PKC(alpha) correlated with loss of response to acute re-challenge with PDBu. Anandamide, a VR1 agonist in acidic conditions, acts additively with PDBu and remains effective after chronic PKC down-regulation. Thus, two independent VR1 activation pathways can be discriminated: (i) direct ligand binding (anandamide, vanilloids) or (ii) extracellular ligands coupled to PKC by intracellular signaling. Experiments in cell lines co-expressing VR1 with different sets of PKC isozymes showed that acute PDBu-induced activation requires PKC(alpha), but not PKC(epsilon). These studies suggest that PKC(alpha) in sensory neurons may elicit or enhance pain during inflammation or ischemia.
Olah
Zoltan
Z
Neuronal Gene Expression Unit, Pain and Neurosensory Mechanisms Branch, NIDCR, National Institutes of Health, Bethesda, Maryland 20892, USA. zoltan.olah@nih.gov
Karai
Laszlo
L
Iadarola
Michael J
MJ
D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D006863:Hydrogen-Ion Concentration; D007211:Indoles / Q000494:pharmacology; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008301:Maleimides / Q000494:pharmacology; D051379:Mice; D008969:Molecular Sequence Data; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051571:Protein Kinase C-alpha; D011955:Receptors, Drug / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012430:Ruthenium Red / Q000494:pharmacology; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D017931:DNA Primers; D007211:Indoles; D007527:Isoenzymes; D008301:Maleimides; D011955:Receptors, Drug; D012430:Ruthenium Red; C496630:Prkca protein, mouse; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha; C088060:bisindolylmaleimide; D013755:Tetradecanoylphorbol Acetate