title: Neurokinin 1 receptors trigger overlapping stimulation and inhibition of CaV2.3 (R-type) calcium channels.
abstract: Neurokinin (NK) 1 receptors and CaV2.3 calcium channels are both expressed in nociceptive neurons, and mice lacking either protein display altered responses to noxious stimuli. Here, we examined modulation of CaV2.3 through NK1 receptors expressed in human embryonic kidney 293 cells. We find that NK1 receptors generate complex modulation of CaV2.3. In particular, weak activation of these receptors evokes mainly stimulation of CaV2.3, whereas strong receptor activation elicits profound inhibition that overlaps with channel stimulation. Unlike R-type channels encoded by CaV2.3, L-type (CaV1.3), N-type (CaV2.2), and P/Q-type (CaV2.1) channels are inhibited, but not stimulated, through NK1 receptors. Pharmacological experiments show that protein kinase C (PKC) mediates stimulation of CaV2.3 through NK1 receptors. The signaling mechanisms underlying inhibition were explored by expressing proteins that buffer either Galpha(q/11) (regulator of G protein signaling protein 3T and carboxyl-terminal region of phospholipase C-beta1) or Gbeta gamma subunits (transducin and the carboxyl-terminal region of bovine G-protein-coupled receptor kinase). A fast component of inhibition was attenuated by buffering Gbeta gamma, whereas a slow component of inhibition was reduced by buffering Galpha(q/11). When both Gbeta gamma and Galpha(q/11) were simultaneously buffered in the same cells, inhibition was virtually eliminated, but receptor activation still triggered substantial stimulation of CaV2.3. We also report that NK1 receptors accelerate the inactivation kinetics of CaV2.3 currents. Altogether, our results indicate that NK1 receptors modulate CaV2.3 using three different signaling mechanisms: a fast inhibition mediated by Gbeta gamma, a slow inhibition mediated by Galpha(q/11), and a slow stimulation mediated by PKC. This new information concerning R-type calcium channels and NK1 receptors may help in understanding nociception, synaptic plasticity, and other physiological processes.
authors.affiliation: Department of Biology, Utah State University, 5305 Old Main Hill, Logan, UT 84322, USA.
authors.forename: Ulises
authors.initials: U
authors.lastname: Meza
authors.forename: Ashish
authors.initials: A
authors.lastname: Thapliyal
authors.forename: Roger A
authors.initials: RA
authors.lastname: Bannister
authors.forename: Brett A
authors.initials: BA
authors.lastname: Adams
mesh_terms: D000818:Animals; D001921:Brain / Q000502:physiology*; D020908:Calcium Channels, R-Type / Q000235:genetics / Q000502:physiology*; D027682:Cation Transport Proteins / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D004594:Electrophysiology; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000378:metabolism; D044387:GTP-Binding Protein beta Subunits / Q000378:metabolism; D006801:Humans; D007668:Kidney; D007700:Kinetics; D008564:Membrane Potentials; D018408:Patch-Clamp Techniques; D010957:Plasmids; D011493:Protein Kinase C / Q000378:metabolism; D011817:Rabbits; D018040:Receptors, Neurokinin-1 / Q000502:physiology*; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection
chemical_list: C423009:CACNA1E protein, human; D020908:Calcium Channels, R-Type; D027682:Cation Transport Proteins; D044387:GTP-Binding Protein beta Subunits; D018040:Receptors, Neurokinin-1; D011994:Recombinant Proteins; D011493:Protein Kinase C; D043802:GTP-Binding Protein alpha Subunits, Gq-G11