Site-specific effects of neurosteroids on GABAA receptor activation and desensitization

Sugasawa, Y.; Cheng, W. W.; Bracamontes, J.; Chen, Z.-W.; Wang, L.; Germann, A. L.; Pierce, S. R.; Senneff, T. C.; Krishnan, K.; Reichert, D. E.; Covey, D. F.; Akk, G.; Evers, A.

doi:10.1101/2020.04.27.063404

bioRxiv · 10.1101/2020.04.27.063404

Site-specific effects of neurosteroids on GABAA receptor activation and desensitization

Sugasawa, Y.·Cheng, W. W.·Bracamontes, J.·Chen, Z.-W.·Wang, L.·Germann, A. L.·Pierce, S. R.·Senneff, T. C.·Krishnan, K.·Reichert, D. E.·Covey, D. F.·Akk, G.·Evers, A.

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Abstract

This study examines how site-specific binding to the three identified neurosteroid binding sites in the 1{beta}3 GABAA receptor (GABAAR) contributes to neurosteroid allosteric modulation. We found that the potentiating neurosteroid, allopregnanolone, but not its inhibitory 3{beta}-epimer epi-allopregnanolone, binds to the canonical {beta}3(+)-1(-) intersubunit site that mediates receptor activation by neurosteroids. In contrast, both allopregnanolone and epi-allopregnanolone bind to intrasubunit sites in the {beta}3 subunit, promoting receptor desensitization and the 1 subunit promoting ligand-specific effects. Two neurosteroid analogues with diazirine moieties replacing the 3-hydroxyl (KK148 and KK150) bind to all three sites, but do not potentiate GABAAR currents. KK148 is a desensitizing agent, whereas KK150 is devoid of allosteric activity. These compounds provide potential chemical scaffolds for site-specific and general neurosteroid antagonists. Collectively, these data show that differential occupancy and efficacy at three discrete neurosteroid binding sites determine whether a neurosteroid has potentiating, inhibitory, or competitive antagonist activity on GABAARs.

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Sugasawa, Y., Cheng, W. W., Bracamontes, J., Chen, Z.-W., Wang, L., Germann, A. L., Pierce, S. R., Senneff, T. C., Krishnan, K., Reichert, D. E., Covey, D. F., Akk, G., Evers, A.. 2020-04-28. Site-specific effects of neurosteroids on GABAA receptor activation and desensitization. https://doi.org/10.1101/2020.04.27.063404

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