Stereo-selective inhibition of transient receptor potential TRPC5 cation channels by neuroactive steroids.
OBJECTIVE
Transient receptor potential canonical 5 (TRPC5) channels are widely expressed, including in the CNS, where they potentiate fear responses. They also contribute to other non-selective cation channels that are stimulated by G-protein-coupled receptor agonists and lipid and redox factors. Steroids are known to modulate fear and anxiety states, and we therefore investigated whether TRPC5 exhibited sensitivity to steroids.


METHODS
Human TRPC5 channels were conditionally expressed in HEK293 cells and studied using intracellular Ca2+ measurement, whole-cell voltage-clamp and excised patch techniques. For comparison, control experiments were performed with cells lacking TRPC5 channels or expressing another TRP channel, TRPM2. Native TRPC channel activity was recorded from vascular smooth muscle cells.


RESULTS
Extracellular application of pregnenolone sulphate, pregnanolone sulphate, pregnanolone, progesterone or dihydrotestosterone inhibited TRPC5 activity within 1-2min. Dehydroepiandrosterone sulphate or 17β-oestradiol had weak inhibitory effects. Pregnenolone, and allopregnanolone, a progesterone metabolite and stereo-isomer of pregnanolone, all had no effects. Progesterone was the most potent of the steroids, especially against TRPC5 channel activity evoked by sphingosine-1-phosphate. In outside-out patch recordings, bath-applied progesterone and dihydrotestosterone had strong and reversible effects, suggesting relatively direct mechanisms of action. Progesterone inhibited native TRPC5-containing channel activity, evoked by oxidized phospholipid.


CONCLUSIONS
Our data suggest that TRPC5 channels are susceptible to relatively direct and rapid stereo-selective steroid modulation, leading to channel inhibition. The study adds to growing appreciation of TRP channels as non-genomic steroid sensors.
Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, UK.
Y
Y
Majeed
M S
MS
Amer
A K
AK
Agarwal
L
L
McKeown
K E
KE
Porter
D J
DJ
O'Regan
J
J
Naylor
C W G
CW
Fishwick
K
K
Muraki
D J
DJ
Beech
D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D013196:Dihydrotestosterone / Q000494:pharmacology; D004958:Estradiol / Q000494:pharmacology; D012739:Gonadal Steroid Hormones / Q000494:pharmacology*; D057809:HEK293 Cells; D006801:Humans; D008246:Lysophospholipids / Q000494:pharmacology; D032389:Myocytes, Smooth Muscle / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010743:Phospholipids / Q000378:metabolism; D011284:Pregnenolone / Q000494:pharmacology; D011374:Progesterone / Q000494:pharmacology; D013110:Sphingosine / Q000031:analogs & derivatives / Q000494:pharmacology; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D050052:TRPC Cation Channels / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
D012739:Gonadal Steroid Hormones; D008246:Lysophospholipids; D010743:Phospholipids; D050052:TRPC Cation Channels; C491780:TRPC5 protein, human; C018370:pregnenolone sulfate; D013196:Dihydrotestosterone; C060506:sphingosine 1-phosphate; D011374:Progesterone; D004958:Estradiol; D011284:Pregnenolone; D013110:Sphingosine; D002118:Calcium