bims-supasi Biomed News
on Sulfation pathways and signalling
Issue of 2023–05–21
sixteen papers selected by
Jonathan Wolf Mueller, University of Birmingham



  1. Carbohydr Polym. 2023 Aug 01. pii: S0144-8617(23)00312-0. [Epub ahead of print]313 120847
      The structural and functional relationships of glycosaminoglycans (GAGs) derived from marine organisms have been investigated, suggesting that marine invertebrates, particularly Bivalvia, are abundant sources of highly sulfated or branched GAGs. In this study, we identified a novel fucosylated heparan sulfate (Fuc-HS) from the midgut gland of the Japanese scallop, Patinopecten yessoensis. Scallop HS showed resistance to GAG-degrading enzymes, including chondroitinases and heparinases, and susceptibility to heparinases increased when scallop HS was treated with mild acid hydrolysis, which removes the fucosyl group. Moreover, 1H NMR detected significant signals near 1.2-1.3 ppm corresponding to the H-6 methyl proton of fucose residues and small H-3 (3.59 ppm) or H-2 (3.39 ppm) signals of glucuronate (GlcA) were detected, suggesting that the fucose moiety is attached to the C-3 position of GlcA in scallop HS. GC-MS detected peaks corresponding to 1, 3, 5-tri-O-acetyl-2, 4-di-O-methyl-L-fucitol and 1, 4, 5-tri-O-acetyl-2, 3-di-O-methyl-L-fucitol, suggesting that the fucose moiety is 3-O- or 4-O-sulfated. Furthermore, scallop HS showed anti-coagulant and neurite outgrowth-promoting (NOP) activities. These results suggest that the midgut gland of scallops is a valuable source of Fuc-HS with biological activities.
    Keywords:  Fucosylated chondroitin sulfate; Fucosylation; Heparan sulfate; Patinopecten yessoensis
    DOI:  https://doi.org/10.1016/j.carbpol.2023.120847
  2. Exp Neurol. 2023 May 15. pii: S0014-4886(23)00129-2. [Epub ahead of print] 114444
      Axons of terminally differentiated neurons in the mammalian central nervous system (CNS) are unable to regenerate after dissection. One of the mechanisms underlying this is the inhibition of axonal regeneration by chondroitin sulfate (CS) and its neuronal receptor, PTPσ. Our previous results demonstrated that the CS-PTPσ axis disrupted autophagy flux by dephosphorylating cortactin, which led to the formation of dystrophic endballs and to the inhibition of axonal regeneration. In contrast, juvenile neurons vigorously extend axons toward their targets during development and maintain regenerative activity for axons even after injury. Although several intrinsic and extrinsic mechanisms have been reported to mediate the differences, the detailed mechanisms are still elusive. Here, we report that Glypican-2, a member of heparan sulfate proteoglycans (HSPG), which are able to antagonize CS-PTPσ by competing with the receptor, is specifically expressed in the axonal tips of embryonic neurons. Glypican-2 overexpression in adult neurons rescues the dystrophic endball back to a healthy growth cone on the CSPG gradient. Consistently, Glypican-2 restored cortactin phosphorylation in the axonal tips of adult neurons on CSPG. Taken together, our results clearly demonstrated Glypican-2's pivotal role in defining the axonal response to CS and provided a new therapeutic target for axonal injury.
    Keywords:  Autophagy; Chondroitin sulfate; Embryonic neuron; Glypican-2; Heparan sulfate; Neuronal injury; PTPσ
    DOI:  https://doi.org/10.1016/j.expneurol.2023.114444
  3. Carbohydr Res. 2023 May 11. pii: S0008-6215(23)00094-0. [Epub ahead of print]529 108832
      Heparin-like sulfated polysaccharide, acharan sulfate, was purified from the mucus of an African giant snail with unique sulfated glycosaminoglycans (GAGs). This study reported on finding novel and safe heparin resources from Achatina fulica for further use as well as easy isolation and purification of the active fraction from the initial raw material. Its structure was characterised by a strong-anion exchange combined with high-performance liquid chromatography (HPLC) and nuclear magnetic resonance (NMR) spectroscopy. The results indicated that the potential acharan sulfate fraction is a glycosaminoglycan composed of several repeating disaccharide units, namely, of →4)-α-IdoA(2S)(1→4)-α-GlcNAc/GlcNAc(6S)/GlcNSO3(6S)(1→, and hence, presents heterogeneity regarding negative net charge density. Furthermore, the heparinase digests inhibit the binding of SARS-CoV-2 spike protein to the ACE2 receptor. In summary, the acharan sulfate presented in this work has shown its great potential for application in the preparation of sulfated polysaccharides as an alternative to heparin with important biological activity.
    Keywords:  Acharan sulfate; Achatina fulica; Antiviral screening; Heparin; Snail mucus; Strong-anion exchange chromatography; Sulfated glycosaminoglycans
    DOI:  https://doi.org/10.1016/j.carres.2023.108832
  4. Biotechnol Bioeng. 2023 May 19.
      Chondroitin sulfate A (CSA) is a valuable glycosaminoglycan that has great market demand. However, current synthetic methods are limited by requiring the expensive sulfate group donor 3'-phosphoadenosine-5'-phosphosulfate (PAPS) and inefficient enzyme carbohydrate sulfotransferase 11 (CHST11). Herein, we report the design and integration of the PAPS synthesis and sulfotransferase pathways to realize whole-cell catalytic production of CSA. Using mechanism-based protein engineering, we improved the thermostability and catalytic efficiency of CHST11; its Tm and half-life increased by 6.9°C and 3.5 h, respectively, and its specific activity increased 2.1-fold. Via cofactor engineering, we designed a dual-cycle strategy of regenerating ATP and PAPS to increase the supply of PAPS. Through surface display engineering, we realized the outer membrane expression of CHST11 and constructed a whole-cell catalytic system of CSA production with an 89.5% conversion rate. This whole-cell catalytic process provides a promising method for the industrial production of CSA.
    Keywords:  chondroitin sulfate A; cofactor engineering; protein engineering; surface display engineering; whole-cell catalyst
    DOI:  https://doi.org/10.1002/bit.28423
  5. Molecules. 2023 Apr 26. pii: 3742. [Epub ahead of print]28(9):
      Versican is a chondroitin sulfate proteoglycan (CSPG), which deposits in perineurium as a physical barrier and prevents the growth of axons out of the fascial boundary. Several studies have indicated that the chondroitin sulfate (CS) chains on versican have several possible functions beyond the physical barrier, including the ability to stabilize versican core protein in the extracellular matrix. As chondroitin sulfate synthase 1 (Chsy1) is a crucial enzyme for CS elongation, we hypothesized that in vivo knockdown of Chsy1 at peripheral nerve lesion site may decrease CS and versican accumulation, and result in accelerating neurite regeneration. In the present study, end-to-side neurorrhaphy (ESN) in Wistar rats was used as an in vivo model of peripheral nerve injury to evaluate nerve regeneration after surgical intervention. The distribution and expression of versican and Chsy1 in regenerating axons after ESN was studied using confocal microscopy and western blotting. Chsy1 was silenced at the nerve lesion (surgical) site using in vivo siRNA transfection. The results indicated that Chsy1 was successfully silenced in nerve tissue, and its downregulation was associated with functional recovery of compound muscle action potential. Silencing of Chsy1 also decreased the accumulation of versican core protein, suggesting that transient treating of Chsy1-siRNA may be an alternative and an effective strategy to promote injured peripheral nerve regeneration.
    Keywords:  Chsy1; Schwann cells; end-to-side neurorrhaphy; nerve regeneration; peripheral nerve injury; versican
    DOI:  https://doi.org/10.3390/molecules28093742
  6. Matrix Biol. 2023 May 16. pii: S0945-053X(23)00062-8. [Epub ahead of print]
      Multiple myeloma is a hematological neoplasm derived from plasma cells invariably developing in the bone marrow (BM). The persisting clinical challenge in MM resides in its high ability to resist drugs as shown by the frequent relapses observed in patients regardless of the treatment applied. In a mouse model of MM, we identified a subpopulation of cells harboring increased resistance to current MM drugs. These cells bound a proliferation inducing ligand (APRIL), a key MM promoting/survival factor. APRIL binding involved the heparan sulfate (HS) chain present on syndecan-1 (SDC-1), and correlated with reactivity to the anti-HS antibody 10e4. 10e4+ cells had a high proliferation activity, and were able to form colonies in 3-D cultures. 10e4+ cells were the only cells able to develop in BM after intravenous injection. They also resisted drugs in vivo, since their number increased after treatment in BM. Notably, 10e4+ cells differentiated into 10e4- cells upon in vitro and in vivo expansion. Expression of one sulfotransferase, HS3ST3a1, allowed modification of syndecan-1 to confer reactivity to 10e4 and binding to APRIL. HS3ST3a1 deletion inhibited tumorigenesis in BM. Notably, the two populations coexisted at a variable frequency in the BM of MM patients at diagnosis. In total, our results indicate that 3-O-sulfation on SDC-1 carried out by HS3ST3a1 defines aggressive MM cells, and that targeting of this enzyme could possibly be used to better control drug resistance.
    Keywords:  APRIL; Multiple myeloma; drug resistance; heparan sulfate proteoglycan; syndecan-1
    DOI:  https://doi.org/10.1016/j.matbio.2023.05.005
  7. Int J Mol Sci. 2023 Apr 28. pii: 8031. [Epub ahead of print]24(9):
      In this study, we investigated the impact of the uremic toxin indoxyl sulfate on macrophages and tubular epithelial cells and its role in modulating the response to lipopolysaccharide (LPS). Indoxyl sulfate accumulates in the blood of patients with chronic kidney disease (CKD) and is a predictor of overall and cardiovascular morbidity/mortality. To simulate the uremic condition, primary macrophages and tubular epithelial cells were incubated with indoxyl sulfate at low concentrations as well as concentrations found in uremic patients, both alone and upon LPS challenge. The results showed that indoxyl sulfate alone induced the release of reactive oxygen species and low-grade inflammation in macrophages. Moreover, combined with LPS (proinflammatory conditions), indoxyl sulfate significantly increased TNF-α, CCL2, and IL-10 release but did not significantly affect the polarization of macrophages. Pre-treatment with indoxyl sulfate following LPS challenge induced the expression of aryl hydrocarbon receptor (Ahr) and NADPH oxidase 4 (Nox4) which generate reactive oxygen species (ROS). Further, experiments with tubular epithelial cells revealed that indoxyl sulfate might induce senescence in parenchymal cells and therefore participate in the progression of inflammaging. In conclusion, this study provides evidence that indoxyl sulfate provokes low-grade inflammation, modulates macrophage function, and enhances the inflammatory response associated with LPS. Finally, indoxyl sulfate signaling contributes to the senescence of tubular epithelial cells during injury.
    Keywords:  CKD; indoxyl sulfate; inflammaging; inflammation; macrophage; senescence; uremic toxins
    DOI:  https://doi.org/10.3390/ijms24098031
  8. Steroids. 2023 May 17. pii: S0039-128X(23)00077-6. [Epub ahead of print] 109249
      Cytochrome P450 aromatase (AROM) and steroid sulfatase (STS) are the two key enzymes for the biosynthesis of estrogens in human, and maintenance of the critical balance between androgens and estrogens. Human AROM, an integral membrane protein of the endoplasmic reticulum, is a member of the cytochrome P450 superfamily. It is the only enzyme to catalyze the conversion of androgens with non-aromatic A-rings to estrogens characterized by the aromatic A-ring. Human STS, also an integral membrane protein of the endoplasmic reticulum, is a Ca2+-dependent enzyme that catalyzes the hydrolysis of sulfate esters of estrone and dehydroepiandrosterone to the unconjugated steroids, the precursors of the most potent forms of estrogens and androgens, namely, 17β-estradiol, 16α,17β-estriol, testosterone and dihydrotestosterone. Expression of these steroidogenic enzymes locally within organs and tissues of the endocrine, reproductive, and central nervous systems is the key for maintaining high levels of the reproductive steroids. The enzymes have been drug targets for the prevention and treatment of diseases associated with steroid hormone excesses, especially in breast, endometrial and prostate malignancies. Both enzymes have been the subjects of vigorous research for the past six decades. In this article, we review the important findings on their structure-function relationships, specifically, the work that began with unravelling of the closely guarded secrets, namely, the 3-D structures, active sites, mechanisms of action, origins of substrate specificity and the basis of membrane integration. Remarkably, these studies were conducted on the enzymes purified in their pristine forms from human placenta, the discarded and their most abundant source. The purification, assay, crystallization, and structure determination methodologies are described. Also reviewed are their functional quaternary organizations, post-translational modifications and the advancements made in the structure-guided inhibitor design efforts. Outstanding questions that still remain open are summarized in closing.
    Keywords:  aromatase; breast cancer; conjugated steroid; dehydroepiandrosterone; dihydrotestosterone; endometriosis; estradiol; estriol; estrone; prostate cancer; reproductive steroid hormone; sex steroid hormone; steroid sulfate; structure-function relationship; testosterone
    DOI:  https://doi.org/10.1016/j.steroids.2023.109249
  9. J Diabetes Res. 2023 ;2023 2082940
       Objective: There is a bidirectional interaction between circulating testosterone and blood glucose levels. We aim to investigate the testosterone levels in men with early-onset type 2 diabetes (T2DM).
    Methods: A total of 153 drug naive men with T2DM were enrolled in the study. Early- (n = 63) and late-onset (n = 90) T2DM was classified according to age 40 years old. Clinical characteristics and plasma for biochemical criterions were collected. Gonadal hormones were measured using chemiluminescent immunometric assay. The concentrations of 3β- and 17β-HSD were determined using ELISA.
    Results: Compared with men with late-onset T2DM, those with early-onset T2DM had lower serum total testosterone (TT), sex hormone-binding globulin (SHBG), and FSH, but higher dehydroepiandrosterone sulfate (DHEA-S) level (p < 0.05). The mediating effect analysis showed that the decreased TT levels in patients with early-onset T2DM were associated with the higher HbA1c, BMI, and triglyceride in these patients (both p < 0.05). The early-onset of T2DM directly correlated with increased DHEA-S (both p < 0.01). The 3β-HSD concentration in the early-onset T2DM group was lower than that in the late-onset T2DM group (11.07 ± 3.05 vs. 12.40 ± 2.72 pg/mL, p = 0.048) and was positively correlated with fasting C-peptide, while negatively correlated with HbA1c and fasting glucagon (p all < 0.05).
    Conclusions: Patients with early-onset T2DM showed inhibition of conversion from DHEA to testosterone, which may attribute to the low level of 3β-HSD and high blood glucose in these patients.
    DOI:  https://doi.org/10.1155/2023/2082940
  10. J Food Sci Technol. 2023 Jun;60(6): 1711-1722
      Chondroitin sulfate (ChS) from marine sources is gaining attention. The purpose of this study was to extract ChS from jumbo squid cartilage (Dosidicus gigas) using ultrasound-assisted enzymatic extraction (UAEE). An ultrasound with protease assistance, including either alcalase, papain or Protin NY100 was used to extract ChS. The results showed that alcalase had the best extraction efficiency. The response surface methodology was employed to evaluate the relationship between extraction conditions and extraction yield of ChS. The ridge max analysis revealed a maximum extraction yield of 11.9 mg ml- 1 with an extraction temperature of 59.40 °C, an extraction time of 24.01 min, a pH of 8.25, and an alcalase concentration of 3.60%. Compared to ethanol precipitation, purification using a hollow fiber dialyzer (HFD) had a higher extraction yield of 62.72% and purity of 85.96%. The structure characteristics of ChS were identified using FTIR, 1 H-NMR, and 13 C-NMR to confirm that the purified ChS structure was present in the form of chondroitin-4-sulfate and chondroitin-6-sulfate. The results of this study provide a green and efficient process for extraction and purification of ChS and are essential for the use of ChS for the development and production of nutrient food products or pharmaceuticals.
    Supplementary Information: The online version contains supplementary material available at 10.1007/s13197-023-05701-7.
    Keywords:  Chondroitin sulfate; Hollow fiber dialyzer; Jumbo squid cartilage; Protease; Response surface methodology; Ultrasound-assisted enzymatic extraction
    DOI:  https://doi.org/10.1007/s13197-023-05701-7
  11. Carbohydr Polym. 2023 Aug 15. pii: S0144-8617(23)00402-2. [Epub ahead of print]314 120937
      Diabetic foot (DF) is difficult to heal due to the formation of drug-resistant bacterial biofilms and dysregulation of the wound microenvironment. To solve this problem, multifunctional hydrogels were prepared by in situ or spraying with 3-aminophenylboronic acid modified oxidized chondroitin sulfate (APBA-g-OCS), polyvinyl alcohol (PVA) and black phosphorus/bismuth oxide/ε-polylysine (BP/Bi2O3/ε-PL) as precursors for promoting infected diabetic wounds healing. The hydrogels display multiple stimulus responsiveness, strong adhesion and rapid self-healing ability owing to the dynamic borate ester bonds, hydrogen bonds and π-π conjugation cross-link points, remain synergistic chemo-photothermal antibacterial effect and anti-biofilm formation ability due to the doping of BP/ Bi2O3/ε-PL into the hydrogel by dynamic imine bonds crosslinking and possess anti-oxidation and inflammatory chemokine adsorption ability attributing to the presence of APBA-g-OCS. Most importantly, as a result of the above functions, the hydrogels can not only respond to the wound microenvironment to conduct combined PTT and chemotherapy for efficient anti-inflammation, but also improve the wound microenvironment by scavenging ROS and regulating the expression of cytokines, thus further accelerating collagen deposition, promoting granulation tissue formation and angiogenesis, finally promoting the healing of infected wounds in diabetic rats.
    Keywords:  Combined PTT and chemotherapy; Diabetic foot; Inflammatory chemokine adsorption; Multifunctional hydrogel; Wounds healing
    DOI:  https://doi.org/10.1016/j.carbpol.2023.120937
  12. Cell Mol Gastroenterol Hepatol. 2023 May 14. pii: S2352-345X(23)00066-8. [Epub ahead of print]
       BACKGROUND & AIMS: Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer deaths in the United States. Tyrosine sulfation, catalyzed by the tyrosylprotein sulfotransferase 2 (TPST2), is a post-translational modification essential for protein-protein interactions and cellular functions. SLC35B2 is a key transporter that transports the universal sulfate donor 3'-phosphoadenosine 5'-phosphosulfate (PAPS) into the Golgi apparatus where the protein sulfation occurs. The goal of this study is to determine whether and how SLC35B2-TPST2 axis of tyrosine sulfation plays a role in PDAC.
    METHODS: Gene expression was analyzed in PDAC patients and mice. Human PDAC MIA PaCa-2 and PANC-1 cells were used for in vitro studies. TPST2 deficient MIA PaCa-2 cells were generated to assess xenograft tumor growth in vivo. Mouse PDAC cells derived from the KrasLSL-G12D/+;Tp53L/+;Pdx1-Cre (KPC) mice were used to generate Tpst2 KO KPC cells to evaluate tumor growth and metastasis in vivo.
    RESULTS: High expressions of SLC35B2 and TPST2 were correlated with poor PDAC patient survival. Knockdown of SLC35B2 or TPST2, or pharmacological inhibition of sulfation inhibited PDAC cell proliferation and migration in vitro. TPST2 deficient MIA PaCa-2 cells exhibited inhibited xenograft tumor growth. Orthotopic inoculation of Tpst2 KO KPC cells in mice showed inhibition of primary tumor growth, local invasion, and metastasis. Mechanistically, the integrin ITGB4 was found to be a novel substrate of TPST2. Inhibition of sulfation destabilizes ITGB4 protein, which may have accounted for the suppression of metastasis.
    CONCLUSIONS: Targeting the SLC35B2-TPST2 axis of tyrosine sulfation may represent a novel approach for therapeutic intervention of PDAC.
    Keywords:  Pancreatic cancer; SLC35B2; TPST2; tyrosine sulfation
    DOI:  https://doi.org/10.1016/j.jcmgh.2023.05.003
  13. Nat Commun. 2023 May 16. 14(1): 2805
      Indoxyl sulfate is a protein-bound uremic toxin synthesized from indole that cannot be efficiently removed by the hemodialysis method and thus becomes a key risk factor for the progression of chronic kidney disease. Here, we develop a non-dialysis treatment strategy to fabricate an ultramicroporous olefin-linked covalent organic framework with high crystallinity in a green and scalable fashion for selectively removing the indoxyl sulfate precursor (i.e., indole) from the intestine. Various analyses show that the resulting material exhibits excellent gastrointestinal fluid stability, high adsorption efficiency, and good biocompatibility. Notably, it realizes the efficient and selective removal of indole from the intestine and significantly attenuates serum indoxyl sulfate level in vivo. More importantly, the selective removal efficacy of indole is substantially higher than that of the commercial adsorbent AST-120 used in the clinic. The present study opens up a new avenue to eliminate indoxyl sulfate by a non-dialysis strategy and further expands the in vivo applications of covalent organic frameworks.
    DOI:  https://doi.org/10.1038/s41467-023-38427-3
  14. Sci Rep. 2023 May 15. 13(1): 7865
      Mucopolysaccharidosis type II (MPS II) is a lysosomal storage disorder characterized by an accumulation of glycosaminoglycans (GAGs), including heparan sulfate, in the body. Major manifestations involve the central nerve system (CNS), skeletal deformation, and visceral manifestations. About 30% of MPS II is linked with an attenuated type of disease subtype with visceral involvement. In contrast, 70% of MPS II is associated with a severe type of disease subtype with CNS manifestations that are caused by the human iduronate-2-sulfatase (IDS)-Pro86Leu (P86L) mutation, a common missense mutation in MPS II. In this study, we reported a novel Ids-P88L MPS II mouse model, an analogous mutation to human IDS-P86L. In this mouse model, a significant impairment of IDS enzyme activity in the blood with a short lifespan was observed. Consistently, the IDS enzyme activity of the body, as assessed in the liver, kidney, spleen, lung, and heart, was significantly impaired. Conversely, the level of GAG was elevated in the body. A putative biomarker with unestablished nature termed UA-HNAc(1S) (late retention time), one of two UA-HNAc(1S) species with late retention time on reversed-phase separation,is a recently reported MPS II-specific biomarker derived from heparan sulfate with uncharacterized mechanism. Thus, we asked whether this biomarker might be elevated in our mouse model. We found a significant accumulation of this biomarker in the liver, suggesting that hepatic formation could be predominant. Finally, to examine whether gene therapy could enhance IDS enzyme activity in this model, the efficacy of the nuclease-mediated genome correction system was tested. We found a marginal elevation of IDS enzyme activity in the treated group, raising the possibility that the effect of gene correction could be assessed in this mouse model. In conclusion, we established a novel Ids-P88L MPS II mouse model that consistently recapitulates the previously reported phenotype in several mouse models.
    DOI:  https://doi.org/10.1038/s41598-023-34541-w
  15. Carbohydr Polym. 2023 Aug 15. pii: S0144-8617(23)00421-6. [Epub ahead of print]314 120956
      Chlorella is one of the most widely cultivated species of microalgae and has been consumed as a "green healthy food". In this study, a novel polysaccharide (CPP-1) was isolated from Chlorella pyrenoidosa, structurally analyzed, and sulfated as a promising anticoagulant. Structural analyses by chemical and instrumental methods such as monosaccharide composition, methylation-GC-MS and 1D/2D NMR spectroscopy analysis revealed that CPP-1 had a molecular weight of ~13.6 kDa, and mainly consisted of d-mannopyranose (d-Manp), 3-O-methylated d-Manp (3-O-Me-d-Manp), and d-galactopyranose (d-Galp). The molar ratio of d-Manp and d-Galp was 1.0:2.3. CPP-1 consisted of a (1→6)-linked β-d-Galp backbone substituted at C-3 by the d-Manp and 3-O-Me-d-Manp residues in a molar ratio of 1:1, which was a regular mannogalactan. The sulfated Chlorella mannogalactan (SCM) with sulfated group content of 40.2 % equivalent to that of unfractionated heparin was prepared and analyzed. NMR analysis confirmed its structure, indicating that most free hydroxyl groups in the side chains and partial hydroxyl groups in the backbone were sulfated. Anticoagulant activity assays indicated that SCM exhibited strong anticoagulant activity by inhibiting intrinsic tenase (FXase) with IC50 of 13.65 ng/mL, which may be a safer anticoagulant as an alternative to heparin-like drugs.
    Keywords:  3-Methyl-1-phenyl-2-pyrazolin-5-one (PubChem CID: 4021); Anticoagulant activity; Chlorella; Deuterium oxide (PubChem CID: 24602); Dimethyl sulfoxide (PubChem CID: 679); Enoxaparin sodium (PubChem CID: 16667706); Heparin sodium (PubChem CID: 92044406); Mannogalactan; Polysaccharide; Structure; Sulfur trioxide pyridine complex (PubChem CID: 168533); Trifluoroacetic acid (PubChem CID: 6422); d-Galactose (PubChem CID: 6036); d-Glucose (PubChem CID: 5793); d-Mannose (PubChem CID: 18950)
    DOI:  https://doi.org/10.1016/j.carbpol.2023.120956
  16. Br J Pharmacol. 2023 May 17.
       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 by analogues of the endogenous inhibitory neurosteroid, pregnenolone sulfate.
    EXPERIMENTAL APPROACH: New pregnenolone sulfate analogues were synthesized 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 the analogues to specific states of the GABAA receptor, are the likeliest cause of the distinctive functional profiles.
    CONCLUSION AND IMPLICATIONS: Our findings reveal that heterocyclic addition to inhibitory neurosteroids affected not only 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.
    Keywords:  GABA; GABAA receptor; chemical analogues; electrophysiology; human embryonic kidney cells; kinetic modeling; molecular dynamic simulations; organic chemistry; pregnenolone sulfate; recombinant expression; synthesis
    DOI:  https://doi.org/10.1111/bph.16143