Nishank Shah

Bio: Nishank Shah is an academic researcher from Australian National University. The author has contributed to research in topics: Binding site & Transporter. The author has an hindex of 3, co-authored 3 publications receiving 53 citations.

Identification of novel inhibitors of the amino acid transporter B0AT1 (SLC6A19), a potential target to induce protein restriction and to treat type 2 diabetes

Abstract: Background and Purpose The neutral amino acid transporter B0AT1 (SLC6A19) has recently been identified as a possible target to treat type 2 diabetes and related disorders. B0AT1 mediates the Na+-dependent uptake of all neutral amino acids. For surface expression and catalytic activity, B0AT1 requires coexpression of collectrin (TMEM27). In this study, we established tools to identify and evaluate novel inhibitors of B0AT1. Experimental Approach A CHO-based cell line was generated, stably expressing collectrin and B0AT1. Using this cell line, a high-throughput screening assay was developed, which uses a fluorescent dye to detect depolarisation of the cell membrane during amino acid uptake via B0AT1. In parallel to these functional assays, we ran a computational compound screen using AutoDock4 and a homology model of B0AT1 based on the high-resolution structure of the highly homologous Drosophila dopamine transporter. Key Results We characterized a series of novel inhibitors of the B0AT1 transporter. Benztropine was identified as a competitive inhibitor of the transporter showing an IC50 of 44 ± 9 μM. The compound was selective with regard to related transporters and blocked neutral amino acid uptake in inverted sections of mouse intestine. Conclusion And Implications The tools established in this study can be widely used to identify new transport inhibitors. Using these tools, we were able to identify compounds that can be used to study epithelial transport, to induce protein restriction, or be developed further through medicinal chemistry.

Heteromeric Solute Carriers: Function, Structure, Pathology and Pharmacology.

Abstract: Solute carriers form one of three major superfamilies of membrane transporters in humans, and include uniporters, exchangers and symporters. Following several decades of molecular characterisation, multiple solute carriers that form obligatory heteromers with unrelated subunits are emerging as a distinctive principle of membrane transporter assembly. Here we comprehensively review experimentally established heteromeric solute carriers: SLC3-SLC7 amino acid exchangers, SLC16 monocarboxylate/H+ symporters and basigin/embigin, SLC4A1 (AE1) and glycophorin A exchanger, SLC51 heteromer Ost α-Ost β uniporter, and SLC6 heteromeric symporters. The review covers the history of the heteromer discovery, transporter physiology, structure, disease associations and pharmacology - all with a focus on the heteromeric assembly. The cellular locations, requirements for complex formation, and the functional role of dimerization are extensively detailed, including analysis of the first complete heteromer structures, the SLC7-SLC3 family transporters LAT1-4F2hc, b0,+AT-rBAT and the SLC6 family heteromer B0AT1-ACE2. We present a systematic analysis of the structural and functional aspects of heteromeric solute carriers and conclude with common principles of their functional roles and structural architecture.

Novel Chemical Scaffolds to Inhibit the Neutral Amino Acid Transporter B0AT1 (SLC6A19), a Potential Target to Treat Metabolic Diseases.

Abstract: Lack of B0AT1 (SLC6A19) partially protects mice against the onset of non-alcoholic steatohepatitis (NASH). To achieve a similar outcome through pharmacological treatment, we improved previously identified inhibitors of B0AT1 by medicinal chemistry and identified second generation inhibitors by high through-put screening. Modified diarylmethine compounds inhibited B0AT1 with IC50 values ranging from 8-90 μM. A second generation of inhibitors was derived from high-throughput screening and showed higher affinity (IC50 of 1-15 μM) and strong selectivity against amino acid transporters with similar substrate specificity, such as ASCT2 (SLC1A5) and LAT1 (SLC7A5). All compounds were unrelated to B0AT1 substrates, but were likely to bind in the vicinity of the substrate binding site.

Absence of S6K1 protects against age- and diet-induced obesity while enhancing insulin sensitivity. [Erratum: 2004 Sept. 23, v. 431, no. 7007, p. 485.]

Abstract: Elucidating the signalling mechanisms by which obesity leads to impaired insulin action is critical in the development of therapeutic strategies for the treatment of diabetes. Recently, mice deficient for S6 Kinase 1 (S6K1), an effector of the mammalian target of rapamycin (mTOR) that acts to integrate nutrient and insulin signals, were shown to be hypoinsulinaemic, glucose intolerant and have reduced β-cell mass. However, S6K1-deficient mice maintain normal glucose levels during fasting, suggesting hypersensitivity to insulin, raising the question of their metabolic fate as a function of age and diet. Here, we report that S6K1-deficient mice are protected against obesity owing to enhanced β-oxidation. However on a high fat diet, levels of glucose and free fatty acids still rise in S6K1-deficient mice, resulting in insulin receptor desensitization. Nevertheless, S6K1-deficient mice remain sensitive to insulin owing to the apparent loss of a negative feedback loop from S6K1 to insulin receptor substrate 1 (IRS1), which blunts S307 and S636/S639 phosphorylation; sites involved in insulin resistance. Moreover, wild-type mice on a high fat diet as well as K/K Ay and ob/ob (also known as Lep/Lep) micetwo genetic models of obesityhave markedly elevated S6K1 activity and, unlike S6K1-deficient mice, increased phosphorylation of IRS1 S307 and S636/S639. Thus under conditions of nutrient satiation S6K1 negatively regulates insulin signalling.

A review of hybrid renewable energy systems in mini-grids for off-grid electrification in developing countries

Abstract: Rural communities in developing countries lack access to affordable, reliable, and sustainable forms of energy, which are essential factors for improving living conditions. These communities rely on diesel and kerosene, which are highly polluting compared to renewable energy technologies, to satisfy their energy needs. In this study, hybrid renewable energy systems (HRESs) have been analyzed, which are designed to overcome the fluctuating nature of renewables, for off-grid electrification. The results of this study—which covers many countries and examples—show that the successful integration of HRES is influenced by factors such as government support—and community organization — which is essential to keep these systems operating over the project lifetime. The levelized cost of energy (LCOE) of different mini-grids was compared and analyzed. The results reveal that by comparing the LCOE range of diesel (between USD 0.92/kWh and USD 1.30/kWh), solar photovoltaic (USD 0.40/kWh and USD 0.61/kWh), and hybrid solar photovoltaic/diesel (USD 0.54/kWh to USD 0.77/kWh), diesel is the most expensive technology. Additionally, the study addressed barriers that can hinder the implementation of mini-grids, such as lack of supportive policies and high capital cost. However, governments’ incentives are instrumental in lowering capital costs. These results are of particular importance for developing countries, where electricity supply via HRES is often quicker and cheaper than grid extension. The insights from this paper are a good starting point for in-depth research on optimal local design and ownership models, which can help accelerate the implementation, and lower the costs of sustainable electricity supply in remote areas.

Amino Acid Transporters as Targets for Cancer Therapy: Why, Where, When, and How.

Abstract: Amino acids are indispensable for the growth of cancer cells. This includes essential amino acids, the carbon skeleton of which cannot be synthesized, and conditionally essential amino acids, for which the metabolic demands exceed the capacity to synthesize them. Moreover, amino acids are important signaling molecules regulating metabolic pathways, protein translation, autophagy, defense against reactive oxygen species, and many other functions. Blocking uptake of amino acids into cancer cells is therefore a viable strategy to reduce growth. A number of studies have used genome-wide silencing or knock-out approaches, which cover all known amino acid transporters in a large variety of cancer cell lines. In this review, these studies are interrogated together with other databases to identify vulnerabilities with regard to amino acid transport. Several themes emerge, such as synthetic lethality, reduced redundancy, and selective vulnerability, which can be exploited to stop cancer cell growth.

ACE2 Protein Landscape in the Head and Neck Region: The Conundrum of SARS-CoV-2 Infection.

Abstract: The coronavirus pandemic raging worldwide since December 2019 is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which invades human cells via the angiotensin-converting enzyme 2 (ACE2) receptor. Although it has already been identified in many organs, ACE2 expression remains largely unknown in the head and neck (HN) sphere. Thus, this study aims to investigate its protein expression in several sites of the upper aerodigestive tract in order to highlight potential routes of infection. We compared ACE2 immunohistochemical expression between 70 paraffin-embedded specimens with two different antibodies and reported the quantified expression in each histological location. Surprisingly, we obtained different results depending on the antibody, an absence of labeling having been observed with a monoclonal antibody raised against the extracellular domain, whereas the polyclonal, against the cytoplasmic part of the protein, revealed enriched ACE2 expression, particularly in sinuses, vocal cords, salivary glands and oral cavity epithelial cells. The interpretation of these discordant results has brought several exciting lines of reflection. In conclusion, this study provides possible routes of entry for the SARS-CoV-2 in HN region and, above all, has led us to encourage caution when studying the ACE2 expression which is currently at the center of all attention.

Crystal structure of a substrate-bound amino acid antiporter in the outward open conformation: mechanism of substrate recognintion and transport.

Abstract: This work was supported in part by the Spanish Ministry of Science and Innovation, Grants SAF2009-12606-C02-01 (M.P.), BFU2008-04637 (J.L.V.-I.), and BFU2009-09268 (I.F., X.C.), by the European Commission Frame Program 7 Grant 201924 (EDICT; M.P. and L.K.), by Consolider E-Science Project and Fundacion Marcelino Botin (M.O.), and by the computer resources provided by the Red Espanola de Supercomputacion (M.P.). Additional support from Generalitat de Catalunya SGR2009-1355 (M.P.) and BP-B2008-00239 (X.C.) is also acknowledged.