Shridhar Bhat - Academia.edu (original) (raw)

Papers by Shridhar Bhat

Molecular Cell, 2009

In a recent issue of Molecular Cell, Rodríguez et al. (2009) identified the NFAT LxVP motif bindi... more In a recent issue of Molecular Cell, Rodríguez et al. (2009) identified the NFAT LxVP motif binding site as the same composite surface formed by the two calcineurin subunits that is recognized by the cyclophilin-CsA and FKBP-FK506 complexes.

Acs Medicinal Chemistry Letters, 2010

Itraconazole is used clinically as an antifungal agent and has recently been shown to possess ant... more Itraconazole is used clinically as an antifungal agent and has recently been shown to possess antiangiogenic acitivity. Itraconazole has three chiral centers that give rise to eight stereoisomers. The complete role of stereochemistry in the two activities of itraconazole, however, has not been addressed adequately. For the first time, all eight stereoisomers of itraconazole (1a-h) have been synthesized and evaluated for activity against human endothelial cell proliferation and for antifungal activity against five fungal strains. Distinct antiangiogenic and antifungal activity profiles of the trans stereoisomers, especially 1e and 1f, suggest different molecular mechanisms underlying the antiangiogenic and antifungal activities of itraconazole.

Tuberculosis

Mycobacterium tuberculosis (Mtb) Tuberculosis (TB) Methionine aminopeptidase (MetAP) Clioquinol (... more Mycobacterium tuberculosis (Mtb) Tuberculosis (TB) Methionine aminopeptidase (MetAP) Clioquinol (CQ) 7-bromo-5-chloroquinolin-8-ol (CLBQ14) s u m m a r y Mycobacterium tuberculosis, the causative agent of tuberculosis claims about five thousand lives daily world-wide, while one-third of the world is infected with dormant tuberculosis. The increased emergence of multi-and extensively drug-resistant strains of M. tuberculosis (Mtb) has heightened the need for novel antimycobacterial agents. Here, we report the discovery of 7-bromo-5-chloroquinolin-8-ol (CLBQ14)-a congener of clioquinol (CQ) as a potent and selective inhibitor of two methionine aminopeptidases (MetAP) from M. tuberculosis: MtMetAP1a and MtMetAP1c. MetAP is a metalloprotease that removes the N-terminal methionine during protein synthesis. N-terminal methionine excision (NME) is a universally conserved process required for the post-translational modification of a significant part of the proteome. The essential role of MetAP in microbes makes it a promising target for the development of new therapeutics. Using a target-based approach in a high-throughput screen, we identified CLBQ14 as a novel MtMetAP inhibitor with higher specificity for both MtMetAP1s relative to their human counterparts. We also found that CLBQ14 is potent against replicating and aged non-growing Mtb at low micro molar concentrations. Furthermore, we observed that the antimycobacterial activity of this pharmacophore correlates well with in vitro enzymatic inhibitory activity. Together, these results revealed a new mode of action of clioquinol and its congeners and validated the therapeutic potential of this pharmacophore for TB chemotherapy.

Nature Chemical Biology, 2011

Tetrahedron Letters, 2011

a b s t r a c t A simple and highly efficient route to the FKBP-binding domain (FKBD) from the na... more a b s t r a c t A simple and highly efficient route to the FKBP-binding domain (FKBD) from the natural product rapamycin has been developed, which entails a sequence of ozonolysis/Baeyer-Villiger/Wittig reactions. The newly synthesized FKBD may serve as a core to assemble hybrid macrocyclic libraries for the discovery of novel probes of protein function and to synthesize new ligands for the FKBP family of proteins.

Chemistry & Biology, 2007

Central to cap-dependent eukaryotic translation initiation is the eIF4F complex, which is compose... more Central to cap-dependent eukaryotic translation initiation is the eIF4F complex, which is composed of the three eukaryotic initiation factors eIF4E, eIF4G, and eIF4A. eIF4A is an RNAdependent ATPase and an ATP-dependent helicase that unwinds local secondary structure in mRNA to allow binding of the 43S ribosomal complex. The marine natural product pateamine A (PatA) has been demonstrated to inhibit capdependent initiation by targeting eIF4A and disrupting its protein-protein interactions while increasing its enzymatic activities. Here we demonstrate that the increased activity is caused by the induction of global conformational changes within eIF4A. Furthermore, binding of PatA is dependent on substrate (RNA and ATP) binding, and the increased activity upon PatA binding is caused by relief of a negative regulatory function of the eIF4A unique domain linker.

Chemistry & Biology, 2009

The fumagillin family of natural products is known to inhibit angiogenesis through irreversible i... more The fumagillin family of natural products is known to inhibit angiogenesis through irreversible inhibition of human type 2 methionine aminopeptidase (MetAP2). Recently, fumagillin and TNP-470 were reported to possess antimalarial activity in vitro, and it was hypothesized that this inhibition was mediated by interaction with the putative malarial ortholog of human MetAP2. In this report, we have overexpressed and purified to near-homogeneity PfMetAP2 from bacteria, yeast, and insect cells. Although none of the recombinant forms of PfMetAP2 exhibited enzymatic activity in existing assays, PfMetAP2 proteins expressed in both yeast and insect cells were able to bind to fumagillin in a pull-down assay. The interaction between fumagillin and analogs with PfMetAP2 was further demonstrated using a newly established mammalian three-hybrid assay incorporating a conjugate between dexamethasone and fumagillin. Unlike human (Hs)MetAP2, it was found that PfMetAP2 is bound to fumagillin noncovalently. Importantly, a new analog of fumagillin, fumarranol, was demonstrated to interact with PfMetAP2 and inhibit the growth of both chloroquine-sensitive and drug-resistant Plasmodium falciparum strains in vitro. Antiparasite activity of fumagillin and fumarranol was also demonstrated in vivo using a mouse malaria model. These findings suggest that PfMetAP2 is a viable target, and fumarranol is a promising lead compound for the development of novel antimalarial agents.

Acs Chemical Biology, 2007

Angiogenesis, the formation of new blood vessels, is implicated in a number of important human di... more Angiogenesis, the formation of new blood vessels, is implicated in a number of important human diseases, including cancer, diabetic retinopathy, and rheumatoid arthritis. To identify clinically useful angiogenesis inhibitors, we assembled and screened a library of mostly Food and Drug Administration-approved drugs for inhibitors of human endothelial cell proliferation. One of the most promising and unexpected hits was itraconazole, a known antifungal drug. Itraconazole inhibits endothelial cell cycle progression at the G1 phase in vitro and blocks vascular endothelial growth factor/basic fibroblast growth factor-dependent angiogenesis in vivo. In attempts to delineate the mechanism of action of itraconazole, we found that human lanosterol 14␣-demethylase (14DM) is essential for endothelial cell proliferation and may partially mediate the inhibition of endothelial cells by itraconazole. Together, these findings suggest that itraconazole has the potential to serve as an antiangiogenic drug and that lanosterol 14DM is a promising new target for discovering new angiogenesis inhibitors.

Molecular Cell, 2009

Acs Medicinal Chemistry Letters, 2010

Tuberculosis

Chemistry & Biology, 2010

Methionine aminopeptidase (MetAP) is a metalloprotease that removes the N-terminal methionine dur... more Methionine aminopeptidase (MetAP) is a metalloprotease that removes the N-terminal methionine during protein synthesis. To assess the importance of the two MetAPs in Mycobacterium tuberculosis, we overexpressed and purified each of the MetAPs to near homogeneity and showed that both were active as MetAP enzymes in vitro. We screened a library of 175,000 compounds against MtMetAP1c and identified 2,3-dichloro-1,4-naphthoquinone class of compounds as inhibitors of both MtMetAPs. It was found that the MtMetAP inhibitors were active against replicating and aged nongrowing M. tuberculosis. Overexpression of either MtMetAP1a or MtMetAP1c in M. tuberculosis conferred resistance of bacterial cells to the inhibitors. Moreover, knockdown of MtMetAP1a, but not MtMetAP1c, resulted in decreased viability of M. tuberculosis. These results suggest that MtMetAP1a is a promising target for developing antituberculosis agents.