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The Sulfated Steroids Pregnenolone Sulfate and Dehydroepiandrosterone Sulfate Inhibit the α1β3γ2L GABA_A Receptor by Stabilizing a Novel Nonconducting State.

ABSTRACT: The GABA_A receptor is inhibited by the endogenous sulfated steroids pregnenolone sulfate (PS) and dehydroepiandrosterone sulfate (DHEAS). It has been proposed in previous work that these steroids act by enhancing desensitization of the receptor. Here, we have investigated the modulatory effects of the steroids on the human α1β3γ2L GABA_A receptor. Using electrophysiology and quantitative model-based data analysis, we show that exposure to the steroid promotes occupancy of a nonconducting state that retains high affinity to the transmitter but whose properties differ from those of the classic, transmitter-induced desensitized state. From the analysis of the inhibitory actions of two combined steroids, we infer that PS and DHEAS act through shared or overlapping binding sites. SIGNIFICANCE STATEMENT: Previous work has proposed that sulfated neurosteroids inhibit the GABA_A receptor by enhancing the rate of entry into the desensitized state. This study shows that the inhibitory steroids pregnenolone sulfate and dehydroepiandrosterone sulfate act through a common interaction site by stabilizing a distinct nonconducting state.

SUBMITTER: Pierce SR

PROVIDER: S-EPMC8969134 | biostudies-literature | 2022 Feb

REPOSITORIES: biostudies-literature

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The Sulfated Steroids Pregnenolone Sulfate and Dehydroepiandrosterone Sulfate Inhibit the α1β3γ2L GABAA Receptor by Stabilizing a Novel Nonconducting State.

Pierce Spencer R SR Germann Allison L AL Steinbach Joe Henry JH Akk Gustav G

Molecular pharmacology 20211201 2

The GABAA receptor is inhibited by the endogenous sulfated steroids pregnenolone sulfate (PS) and dehydroepiandrosterone sulfate (DHEAS). It has been proposed in previous work that these steroids act by enhancing desensitization of the receptor. Here, we have investigated the modulatory effects of the steroids on the human α1β3γ2L GABAA receptor. Using electrophysiology and quantitative model-based data analysis, we show that exposure to the steroid pro ...[more]

PMID: 34853153

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Project description:BackgroundNeurosteroids have various physiological and neuropsychopharmacological effects. In addition to the genomic effects of steroids, some neurosteroids modulate several neurotransmitter receptors and channels, such as N-methyl-D-aspartate receptors, gamma-aminobutyric acid type A (GABA(A)) receptors, and sigma(1) receptors, and voltage-gated Ca(2+) and K(+) channels. However, the molecular mechanisms underlying the various effects of neurosteroids have not yet been sufficiently clarified. In the nervous system, inwardly rectifying K(+) (Kir) channels also play important roles in the control of resting membrane potential, cellular excitability and K(+) homeostasis. Among constitutively active Kir2 channels in a major Kir subfamily, Kir2.3 channels are expressed predominantly in the forebrain, a brain area related to cognition, memory, emotion, and neuropsychiatric disorders.Methodology/principal findingsThe present study examined the effects of various neurosteroids on Kir2.3 channels using the Xenopus oocyte expression assay. In oocytes injected with Kir2.3 mRNA, only pregnenolone sulfate (PREGS), among nine neurosteroids tested, reversibly potentiated Kir2.3 currents. The potentiation effect was concentration-dependent in the micromolar range, and the current-voltage relationship showed inward rectification. However, the potentiation effect of PREGS was not observed when PREGS was applied intracellularly and was not affected by extracellular pH conditions. Furthermore, although Kir1.1, Kir2.1, Kir2.2, and Kir3 channels were insensitive to PREGS, in oocytes injected with Kir2.1/Kir2.3 or Kir2.2/Kir2.3 mRNA, but not Kir2.1/Kir2.2 mRNA, PREGS potentiated Kir currents. These potentiation properties in the concentration-response relationships were less potent than for Kir2.3 channels, suggesting action of PREGS on Kir2.3-containing Kir2 heteromeric channels.Conclusions/significanceThe present results suggest that PREGS acts as a positive modulator of Kir2.3 channels. Kir2.3 channel potentiation may provide novel insights into the various effects of PREGS.

Project description:Cirrhotic patients are susceptible to sepsis and critical illness-related corticosteroid insufficiency (CIRCI). Dehydroepiandrosterone sulfate (DHEAS) is a corticotropin-dependent adrenal androgen, which has immunostimulating and antiglucocorticoid effects. Considering the synchronized synthesis of cortisol and DHEAS and their opposing effects to each other, investigators have proposed measuring these two hormones as a ratio. Severe sepsis has been associated with low DHEAS, especially relative to high cortisol. Despite growing interest in the role of adrenal androgen replacement in critical illness, there have been no data about DHEAS and the DHEAS/cortisol ratio in patients with liver cirrhosis. We studied whether low concentrations of DHEAS and decreased DHEAS/cortisol ratio are associated with poor outcome in patients with liver cirrhosis and septic shock.We recruited 46 cirrhotic patients with septic shock, and 46 noncirrhotic counterparts matched by age and sex. We evaluated adrenal function using the short corticotropin stimulation test and analyzed the relation between DHEAS and cortisol.While the nonsurvivors in the cirrhotic group had significantly lower baseline DHEAS, lower baseline DHEAS/cortisol ratio, and reduced increments of both DHEAS and cortisol upon corticotropin stimulation, the survivors had lower baseline cortisol. Cirrhotic patients with lower DHEAS/cortisol ratio (<1.50) had higher levels of interleukin-6 and tumor necrosis factor alpha, higher Sequential Organ Failure Assessment scores, and higher rates of CIRCI and hospital mortality. Using the area under the receiver operating characteristic (AUROC) curve, both DHEAS and the DHEAS/cortisol ratio demonstrated a good discriminative power for predicting hospital survival (AUROC 0.807 and 0.925 respectively). The cirrhotic group had lower DHEAS and DHEAS/cortisol ratio but higher rates of CIRCI and hospital mortality, compared to the noncirrhotic group.There is dissociation between cortisol (increased) and DHEAS (decreased) in those cirrhotic patients who succumb to septic shock. Low DHEAS/cortisol ratios are associated with more severe diseases, inflammation, and CIRCI and can serve as a prognostic marker. More investigations are needed to evaluate the role of adrenal androgen in this clinical setting.

Dataset Information

The Sulfated Steroids Pregnenolone Sulfate and Dehydroepiandrosterone Sulfate Inhibit the α1β3γ2L GABA_A Receptor by Stabilizing a Novel Nonconducting State.

Publications

The Sulfated Steroids Pregnenolone Sulfate and Dehydroepiandrosterone Sulfate Inhibit the <i>α</i>1<i>β</i>3<i>γ</i>2L GABA<sub>A</sub> Receptor by Stabilizing a Novel Nonconducting State.

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