Browsing by Subject "Medicinal chemistry"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    High-resolution crystal structure of human asparagine synthetase enables analysis of inhibitor binding and selectivity
    (Springer Nature, 2019-09-17) Zhu, Wen; Radadiya, Ashish; Bisson, Claudine; Wenzel, Sabine; Nordin, Brian E.; Martínez-Márquez, Francisco; Imasaki, Tsuyoshi; Sedelnikova, Svetlana E.; Coricello, Adriana; Baumann, Patrick; Berry, Alexandria H.; Nomanbhoy, Tyzoon K.; Kozarich, John W.; Jin, Yi; Rice, David W.; Takagi, Yuichiro; Richards, Nigel G. J.; Biochemistry and Molecular Biology, School of Medicine
    Expression of human asparagine synthetase (ASNS) promotes metastatic progression and tumor cell invasiveness in colorectal and breast cancer, presumably by altering cellular levels of L-asparagine. Human ASNS is therefore emerging as a bona fide drug target for cancer therapy. Here we show that a slow-onset, tight binding inhibitor, which exhibits nanomolar affinity for human ASNS in vitro, exhibits excellent selectivity at 10 μM concentration in HCT-116 cell lysates with almost no off-target binding. The high-resolution (1.85 Å) crystal structure of human ASNS has enabled us to identify a cluster of negatively charged side chains in the synthetase domain that plays a key role in inhibitor binding. Comparing this structure with those of evolutionarily related AMP-forming enzymes provides insights into intermolecular interactions that give rise to the observed binding selectivity. Our findings demonstrate the feasibility of developing second generation human ASNS inhibitors as lead compounds for the discovery of drugs against metastasis.
  • Thumbnail Image
    Item
    The small molecule GAT1508 activates brain-specific GIRK1/2 channel heteromers and facilitates conditioned fear extinction in rodents
    (American Society for Biochemistry and Molecular Biology, 2020-03) Xu, Yu; Cantwell, Lucas; Molosh, Andrei I.; Plant, Leigh D.; Gazgalis, Dimitris; Fitz, Stephanie D.; Dustrude, Erik T.; Yang, Yuchen; Kawano, Takeharu; Garai, Sumanta; Noujaim, Sami F.; Shekhar, Anantha; Logothetis, Diomedes E.; Thakur, Ganesh A.; Psychiatry, School of Medicine
    G-protein-gated inwardly-rectifying K+ (GIRK) channels are targets of Gi/o-protein-signaling systems that inhibit cell excitability. GIRK channels exist as homotetramers (GIRK2 and GIRK4) or heterotetramers with nonfunctional homomeric subunits (GIRK1 and GIRK3). Although they have been implicated in multiple conditions, the lack of selective GIRK drugs that discriminate among the different GIRK channel subtypes has hampered investigations into their precise physiological relevance and therapeutic potential. Here, we report on a highly-specific, potent, and efficacious activator of brain GIRK1/2 channels. Using a chemical screen and electrophysiological assays, we found that this activator, the bromothiophene-substituted small molecule GAT1508, is specific for brain-expressed GIRK1/2 channels rather than for cardiac GIRK1/4 channels. Computational models predicted a GAT1508-binding site validated by experimental mutagenesis experiments, providing insights into how urea-based compounds engage distant GIRK1 residues required for channel activation. Furthermore, we provide computational and experimental evidence that GAT1508 is an allosteric modulator of channel-phosphatidylinositol 4,5-bisphosphate interactions. Through brain-slice electrophysiology, we show that subthreshold GAT1508 concentrations directly stimulate GIRK currents in the basolateral amygdala (BLA) and potentiate baclofen-induced currents. Of note, GAT1508 effectively extinguished conditioned fear in rodents and lacked cardiac and behavioral side effects, suggesting its potential for use in pharmacotherapy for post-traumatic stress disorder. In summary, our findings indicate that the small molecule GAT1508 has high specificity for brain GIRK1/2 channel subunits, directly or allosterically activates GIRK1/2 channels in the BLA, and facilitates fear extinction in a rodent model.
  • Thumbnail Image
    Item
    Structure-Guided Optimization of Replication Protein A (RPA)–DNA Interaction Inhibitors
    (American Chemical Society, 2020-01-02) Gavande, Navnath S.; VanderVere-Carozza, Pamela S.; Pawelczak, Katherine S.; Vernon, Tyler L.; Jordan, Matthew R.; Turchi, John J.; Medicine, School of Medicine
    Replication protein A (RPA) is the major human single stranded DNA (ssDNA)-binding protein, playing essential roles in DNA replication, repair, recombination, and DNA-damage response (DDR). Inhibition of RPA-DNA interactions represents a therapeutic strategy for cancer drug discovery and has great potential to provide single agent anticancer activity and to synergize with both common DNA damaging chemotherapeutics and newer targeted anticancer agents. In this letter, a new series of analogues based on our previously reported TDRL-551 (4) compound were designed to improve potency and physicochemical properties. Molecular docking studies guided molecular insights, and further SAR exploration led to the identification of a series of novel compounds with low micromolar RPA inhibitory activity, increased solubility, and excellent cellular up-take. Among a series of analogues, compounds 43, 44, 45, and 46 hold promise for further development of novel anticancer agents.