title: Substance P evokes cation currents through TRP channels in HEK293 cells.
abstract: Activation of any of the three known tachykinin receptors (NK1R, -2R, or -3R) can cause a rise in [Ca2+]i via a pertussis toxin-insensitive heterotrimeric G protein, Gq/G11, activation of phospholipase C (PLC), and a membrane depolarization. Tachykinins can depolarize neurons by two distinct mechanisms: 1) they reduce a resting K+ current in many neurons or 2) in parasympathetic and vagal primary sensory neurons, they activate a nonspecific cation current (Icat). Transient receptor potential channels (TRPC) are nonspecific cation channels that can be activated by a rise in [Ca2+]i in a PLC-dependent manner. The present work tests whether NK2R can signal TRPC. We applied standard whole cell patch-clamp recordings to HEK293 cells stably transfected with the human TRP3 channels (TRP3C), and transiently transfected with a functional NK2R-EGFP. Bath applied Substance P (SP, 1 microM) induced an Icat in the cells expressing both TRP3C and NK2R. Icat reached its peak value in approximately 3 min (195 +/- 120.0 s, mean +/- SE, n = 20), had a peak density of 11.3 +/- 3.48 pA/pF (n = 24), and was blocked by an NK2R-specific antagonist (SR48968, 100 nM). The Erev value for the SP current was 6.8 +/- 7.66 mV (n = 6), suggestive of a nonspecific cation channel. Icat was not measurable in TRP3C-expressing HEK293 cells without NK2R expression (n = 6) or in wild-type HEK293 cells with NK2R expression (n = 12). These data indicate that NK2R can be functionally coupled to TRP channels in HEK293 cells and suggest that SP-induced cation currents in vagal primary sensory neurons might be mediated by TRPC.
authors.affiliation: Pharmacology and Experimental Therapeutics, University of Maryland Medical School, Baltimore, Maryland 21201-1559, USA.
authors.forename: E J
authors.initials: EJ
authors.lastname: Oh
authors.forename: T D
authors.initials: TD
authors.lastname: Gover
authors.forename: R
authors.initials: R
authors.lastname: Cordoba-Rodriguez
authors.forename: D
authors.initials: D
authors.lastname: Weinreich
mesh_terms: D015220:Calcium Channels / Q000502:physiology*; D002412:Cations; D002460:Cell Line; D006801:Humans; D007473:Ion Channels / Q000502:physiology; D018041:Receptors, Neurokinin-2 / Q000502:physiology; D013373:Substance P / Q000494:pharmacology*; D050052:TRPC Cation Channels
chemical_list: D015220:Calcium Channels; D002412:Cations; D007473:Ion Channels; D018041:Receptors, Neurokinin-2; D050052:TRPC Cation Channels; C104603:TRPC3 cation channel; D013373:Substance P