Kinetic characterization of ebselen, chelerythrine and apomorphine as glutaminase inhibitors

Abstract

Glutaminase catalyzes the hydrolysis of glutamine to glutamate and plays a central role in the proliferation of neoplastic cells via glutaminolysis, as well as in the generation of excitotoxic glutamate in central nervous system disorders such as HIV-associated dementia (HAD) and multiple sclerosis. Both glutaminase siRNA and glutaminase inhibition have been shown to be effective in in vitro models of cancer and HAD, suggesting a potential role for small molecule glutaminase inhibitors. However, there are no potent, selective inhibitors of glutaminase currently available. The two prototypical glutaminase inhibitors, BPTES and DON, are either insoluble or non-specific. In a search for more drug-like glutaminase inhibitors, we conducted a screen of 1280 in vivo active drugs (Library of Pharmacologically Active Compounds (LOPAC1280)) and identified ebselen, chelerythrine and (R)-apomorphine. The newly identified inhibitors exhibited 10 to 1500-fold greater affinities than DON and BPTES and over 100-fold increased efficiency of inhibition. Although non-selective, it is noteworthy that the affinity of ebselen for glutaminase is more potent than any other activity yet described. It is possible that the previously reported biological activity seen with these compounds is due, in part, to glutaminase inhibition. Ebselen, chelerythrine and apomorphine complement the armamentarium of compounds to explore the role of glutaminase in disease.

Preventing Allograft Rejection by Targeting Immune Metabolism

“…To explore the role of glutaminase activity in T cell activation, naïve CD4 + T cells were stimulated with anti-CD3/CD28 in medium with or without metabolic inhibitors for 24 hrs. The glutaminase activity of these CD4 + T cells was determined using a radiolabeled assay as described (Thomas et al, 2013). We observed that activated T cells exhibited increased glutaminase activity compared to naïve T cells (Figure 2A), indicating metabolic reprogramming toward glutaminolysis.…”

Ebselen, a Small-Molecule Capsid Inhibitor of HIV-1 Replication

“…(27)(28)(29), ebselen forms a selenylsulfide (-Se-S-) linkage with cysteine residues. To confirm the importance of the selenium atom in ebselen, we analyzed analogs with selenium replaced by sulfur (S-ebselen), oxygen (O-ebselen), carbon (C-ebselen) (40), or a selenoxide group (ebselen oxide) or with the phenyl ring converted to pyridine (2pyr-ebselen and 3pyr-ebselen) (41) ( Table 1). The inhibitory activity of these analogs on CTD dimerization was evaluated by TR-FRET assay.…”

Combination therapy with BPTES nanoparticles and metformin targets the metabolic heterogeneity of pancreatic cancer

“…The first step of glutamine metabolism is the conversion of glutamine to glutamate and ammonia, which is catalyzed by glutaminase (GLS). Bis-2-(5-phenylacetamido-1,2,4-thiadiazol-2-yl)ethyl sulfide (BPTES), which is an allosteric, time-dependent (9), and specific inhibitor of GLS1, exhibits unique binding at the oligomerization interface of the glutaminase tetramer (10,11). Although BPTES is more selective than other prototype glutaminase inhibitors, such as 6-diazo-5-oxo-L-norleucine (12) or ebselen (9), and can effectively inhibit GLS1 (13) and tumor growth (13)(14)(15), poor solubility (0.144 μg/mL) (16) has limited its clinical development.…”