Neurosteroids differentially modulate P2X ATP-gated channels through non-genomic interactions.
As neuroactive steroids modulate several ionotropic receptors, we assessed whether the ATP-gated currents elicited by P2X(4) receptors are modulated by these compounds. We transfected HEK293 cells or injected Xenopus laevis oocytes with the cDNA coding for rat P2X(4) receptor. Application of 0.1-10 microM alfaxolone potentiated within 60-s the 1 microM ATP-evoked currents with a maximal potentiation of 1.8 and 2.6-fold in HEK293 or oocytes cells respectively. Allopregnalolone or 3alpha, 21-dihydroxy-5alpha-pregnan-20-one (THDOC) also potentiated the ATP-gated currents but with a maximal effect only averaging 1.25 and 1.35-fold respectively. In contrast, 0.3-10 microM pregnanolone, but not its sulfated derivative, inhibited the ATP-gated currents; the maximal inhibition reached 40% in both cell types. THDOC, but not other neurosteroids increased significantly the tau(off) of the ATP-evoked currents, revealing another mode of neurosteroid modulation. Sexual steroids such as 17beta-estradiol or progesterone were inactive revealing explicit structural requirements. Alfaxolone or THDOC at concentrations 30- to 100-fold larger than required to modulate the receptor, gated the P2X(4) receptor eliciting ATP-like currents that were reduced with suramin or brilliant blue G, but potentiated the P2X(4) receptor more than 10-fold by 10 microM zinc. In conclusion, neurosteroids rapidly modulate via non-genomic mechanisms and with nanomolar potencies, the P2X4 receptor interacting likely at distinct modulator sites.
Codocedo
Juan Francisco
JF
Departamento de Fisiología, Centro de Regulación Celular y Patología, Instituto Milenio de Biología Fundamental y Aplicada, MIFAB, Pontificia Universidad Católica de Chile, Santiago, Chile.
Rodríguez
Felipe E
FE
Huidobro-Toro
Juan Pablo
JP
D000255:Adenosine Triphosphate / Q000502:physiology*; D000818:Animals; D002460:Cell Line; D003900:Desoxycorticosterone / Q000031:analogs & derivatives / Q000502:physiology; D004347:Drug Interactions; D004958:Estradiol / Q000502:physiology; D005260:Female; D023281:Genomics; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects* / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D009865:Oocytes / Q000378:metabolism; D011277:Pregnanediones / Q000494:pharmacology; D011280:Pregnanolone / Q000502:physiology; D011374:Progesterone / Q000502:physiology; D058910:Purinergic P2 Receptor Agonists; D051381:Rats; D018048:Receptors, Purinergic P2 / Q000378:metabolism* / Q000502:physiology; D058848:Receptors, Purinergic P2X4; D014982:Xenopus laevis
D018377:Neurotransmitter Agents; C548226:P2RX4 protein, human; C548228:P2rx4 protein, rat; D011277:Pregnanediones; D058910:Purinergic P2 Receptor Agonists; D018048:Receptors, Purinergic P2; D058848:Receptors, Purinergic P2X4; D003900:Desoxycorticosterone; C009413:tetrahydrodeoxycorticosterone; D011374:Progesterone; D004958:Estradiol; D000255:Adenosine Triphosphate; C006477:alphaxalone; D011280:Pregnanolone