TY - JOUR

T1 - Pregnenolone sulfate analogues differentially modulate GABAA receptor closed/desensitised states

AU - Mortensen, Martin

AU - Xu, Yue

AU - Shehata, Mohamed A.

AU - Krall, Jacob

AU - Ernst, Margot

AU - Frølund, Bente

AU - Smart, Trevor G.

N1 - Funding Information: This work was supported by the Medical Research Council UK (MR/T002581/1), the Wellcome Trust (217199/Z/19/Z), the Lundbeck Foundation (R303‐2018‐3162) and the Chinese Scholarship Council. We are grateful to the group of Thierry Langer for hosting YX and for the supervision of computational work by Thomas Seidel.

PY - 2023

Y1 - 2023

N2 - Background and Purpose: GABAA receptors are regulated by numerous classes of allosteric modulators. However, regulation of receptor macroscopic desensitisation remains largely unexplored and may offer new therapeutic opportunities. Here, we report the emerging potential for modulating desensitisation with analogues of the endogenous inhibitory neurosteroid, pregnenolone sulfate. Experimental Approach: New pregnenolone sulfate analogues were synthesised incorporating various heterocyclic substitutions located at the C-21 position on ring D. The pharmacological profiles of these compounds were assessed using electrophysiology and recombinant GABAA receptors together with mutagenesis, molecular dynamics simulations, structural modelling and kinetic simulations. Key Results: All seven analogues retained a negative allosteric modulatory capability whilst exhibiting diverse potencies. Interestingly, we observed differential effects on GABA current decay by compounds incorporating either a six- (compound 5) or five-membered heterocyclic ring (compound 6) on C-21, which was independent of their potencies as inhibitors. We propose that differences in molecular charges, and the targeted binding of analogues to specific states of the GABAA receptor, are the most likely cause of the distinctive functional profiles. Conclusions and Implications: Our findings reveal that heterocyclic addition to inhibitory neurosteroids not only affected their potency and macroscopic efficacy but also affected innate receptor mechanisms that underlie desensitisation. Acute modulation of macroscopic desensitisation will determine the degree and duration of GABA inhibition, which are vital for the integration of neural circuit activity. Discovery of this form of modulation could present an opportunity for next-generation GABAA receptor drug design and development.

AB - Background and Purpose: GABAA receptors are regulated by numerous classes of allosteric modulators. However, regulation of receptor macroscopic desensitisation remains largely unexplored and may offer new therapeutic opportunities. Here, we report the emerging potential for modulating desensitisation with analogues of the endogenous inhibitory neurosteroid, pregnenolone sulfate. Experimental Approach: New pregnenolone sulfate analogues were synthesised incorporating various heterocyclic substitutions located at the C-21 position on ring D. The pharmacological profiles of these compounds were assessed using electrophysiology and recombinant GABAA receptors together with mutagenesis, molecular dynamics simulations, structural modelling and kinetic simulations. Key Results: All seven analogues retained a negative allosteric modulatory capability whilst exhibiting diverse potencies. Interestingly, we observed differential effects on GABA current decay by compounds incorporating either a six- (compound 5) or five-membered heterocyclic ring (compound 6) on C-21, which was independent of their potencies as inhibitors. We propose that differences in molecular charges, and the targeted binding of analogues to specific states of the GABAA receptor, are the most likely cause of the distinctive functional profiles. Conclusions and Implications: Our findings reveal that heterocyclic addition to inhibitory neurosteroids not only affected their potency and macroscopic efficacy but also affected innate receptor mechanisms that underlie desensitisation. Acute modulation of macroscopic desensitisation will determine the degree and duration of GABA inhibition, which are vital for the integration of neural circuit activity. Discovery of this form of modulation could present an opportunity for next-generation GABAA receptor drug design and development.

KW - chemical analogues

KW - electrophysiology

KW - GABA

KW - GABA receptor

KW - human embryonic kidney cells

KW - kinetic modelling

KW - molecular dynamics simulations

KW - organic chemistry

KW - pregnenolone sulfate

KW - recombinant expression

KW - synthesis

U2 - 10.1111/bph.16143

DO - 10.1111/bph.16143

M3 - Journal article

C2 - 37194503

AN - SCOPUS:85161372892

VL - 180

SP - 2482

EP - 2499

JO - British Journal of Pharmacology

JF - British Journal of Pharmacology

SN - 0007-1188

IS - 19

ER -