Role of Chikungunya nsP3 in Regulating G3BP1 Activity, Stress Granule Formation and Drug Efficacy.

BACKGROUND: Ras-GTPase activating protein SH3-domain-binding proteins (G3BP) are a small family of RNA-binding proteins implicated in regulating gene expression. Changes in expression of G3BPs are correlated to several cancers including thyroid, colon, pancreatic and breast cancer. G3BPs are important regulators of stress granule (SG) formation and function. SG are ribonucleoprotein (RNP) particles that respond to cellular stresses to triage mRNA resulting in transcripts being selectively degraded, stored or translated resulting in a change of gene expression which confers a survival response to the cell. These changes in gene expression contribute to the development of drug resistance. Many RNA viruses, including Chikungunya (and potentially Coronavirus), dismantle SG so that the cell cannot respond to the viral infection. Non-structural protein 3 (nsP3), from the Chikungunya virus, has been shown to translocate G3BP away from SG. Interestingly in cancer cells, the formation of SG is correlated to drug-resistance and blocking SG formation has been shown to reestablish the efficacy of the anticancer drug bortezomib. METHODS: Chikungunya nsP3 was transfected into breast cancer cell lines T47D and MCF7 to disrupt SG formation. Changes in the cytotoxicity of bortezomib were measured. RESULTS: Bortezomib cytotoxicity in breast cancer cell lines changed with a 22 fold decrease in its IC50 for T47D and a 7 fold decrease for MCF7 cells. CONCLUSIONS: Chikungunya nsP3 disrupts SG formation. As a result, it increases the cytotoxicity of the FDA approved drug, bortezomib. In addition, the increased cytotoxicity appears to correlate to improved bortezomib selectivity when compared to control cell lines.

G3BP1 and G3BP2 regulate translation of interferon-stimulated genes: IFITM1, IFITM2 and IFITM3 in the cancer cell line MCF7.

G3BPs are members of an RNA-binding protein family and their aberrant expression is common in various cancers and there is growing evidence that G3BPs possess antiviral activities and are targeted by various viruses. G3BPs have also been implicated in both stabilization and degradation of specific mRNAs as well as translational control of mRNA targets. G3BPs have been shown to control translation of interferon-stimulated genes (ISGs), implying that G3BPs are involved in the regulation of the interferon system in response to viral infections and/or cellular stress. The interferon induced transmembrane (IFITM1, IFITM2 and IFITM3) proteins are antiviral proteins, and are also involved in cancer progression and metastasis. Therefore, these genes were selected in the studies reported here as potential transcript targets of G3BPs. Furthermore, G3BPs are involved in the regulation of the MEK pathway which also impacts on the translation of ISGs. Therefore, the role of this pathway was also analysed in regulation of IFITM1-3 proteins. Overall, this research study suggests that G3BPs are essential for the accumulation of IFITM1-3 proteins and intersect twice in the regulation of IFITM1-3 expression, first through MEK pathway and then through an interaction with the 3'-UTRs of its target transcripts. However, it is still to be determined whether the two apparent functions are part of a single control mechanism or the two functions are mutually exclusive.

Rasputin a decade on and more promiscuous than ever? A review of G3BPs.

Ras-GTPase-activating protein (SH3 domain)-binding proteins (G3BPs, also known as Rasputin) are a family of RNA binding proteins that regulate gene expression in response to environmental stresses by controlling mRNA stability and translation. G3BPs appear to facilitate this activity through their role in stress granules for which they are considered a core component, however, it should be noted that not all stress granules contain G3BPs and this appears to be contextual depending on the environmental stress and the cell type. Although the role of G3BPs in stress granules appears to be one of its major roles, data also strongly suggests that they interact with mRNAs outside of stress granules to regulate gene expression. G3BPs have been implicated in several diseases including cancer progression, invasion, and metastasis as well as virus survival. There is now a body of evidence that suggests targeting of G3BPs could be explored as a form of cancer therapeutic. This review discusses the important discoveries and advancements made in the field of G3BPs biology over the last two decades including their roles in RNA stability, translational control of cellular transcripts, stress granule formation, cancer progression and its interactions with viruses during infection. An emerging theme for G3BPs is their ability to regulate gene expression in response to environmental stimuli, disease progression and virus infection making it an intriguing target for disease therapies.

Synthesis, enzyme inhibition and molecular docking studies of 1-Arylsulfonyl-4-phenylpiperazine derivatives.

Heterocyclic molecules have been frequently investigated to possess various biological activities during the last few decades. The present work elaborates the synthesis and enzymatic inhibition potentials of a series of sulfonamides. A series of 1-arylsulfonyl-4-Phenylpiperazine (3a-n) geared up by the reaction of 1-phenylpiperazine (1) and different (un)substituted alkyl/arylsulfonyl chlorides (2a-n), under defined pH control using water as a reaction medium. The synthesized molecules were characterized by 1H-NMR, 13C-NMR, IR and EI-MS spectral data. The enzyme inhibition study was carried on α-glucosidase, lipoxygenase (LOX), acetyl cholinesterase (AChE) and butyryl cholinesterase (BChE) enzymes supported by docking simulation studies and the IC50 values rendered a few of the synthesized molecules as moderate inhibitors of these enzymes where, the compound 3e exhibited comparatively better potency against α-glucosidase enzyme. The synthesized compounds showed weak or no inhibition against LOX, AChE and BChE enzymes.

Novel synthesis of dihydropyrimidines for α-glucosidase inhibition to treat type 2 diabetes: in vitro biological evaluation and in silico docking.

A convenient and efficient new method has been established for the synthesis of dihydropyrimidines by inexpensive and non-toxic N-acetyl glycine (NAG) catalysed reaction of aromatic aldehydes with ethyl acetoacetate and urea/thiourea. This method is applicable for various substituted aldehydes as well as urea and thiourea. It has also been used to synthesize bicyclic oxygen-bridged pyrimidine derivatives (4d, 4j). The biological assay revealed that the majority of compounds synthesized displayed modest inhibitory activity against α-glucosidase at low micro-molar concentrations. Molecular docking studies were also performed on the most active compound, 4f (with IC50 value 112.21±0.97 µM), to show the enzyme - inhibitor interactions.

Discovery of novel oxindole derivatives as potent α-glucosidase inhibitors.

A series of 6-chloro-3-oxindole derivatives 1-25 were synthesized in high yields by the reaction of 6-chlorooxindole with different aromatic aldehydes in the presence of piperidine. All the synthesized compounds were isolated with E configuration. The structures were confirmed using spectroscopic techniques, including (1)H NMR and EIMS. These compounds showed varying degree of yeast α-glucosidase inhibition and seven were found as potent inhibitors of the enzyme. Compounds 2, 3, 4, 5, 6, 23, and 25 exhibited IC50 values 2.71±0.007, 11.41±0.005, 37.93±0.002, 15.19±0.004, 24.71±0.007, 17.33±0.001, and 14.2±0.002µM, respectively, as compared to standard acarbose (IC50, 38.25±0.12µM). Docking studies helped to find interactions between the enzyme and the active compounds. As a result of this study, oxindoles have been discovered as a new class of α-glucosidase inhibitors which have not been reported earlier.

Synthesis of novel indenoquinoxaline derivatives as potent α-glucosidase inhibitors.

A series of new N-(11H-Indeno[1,2-b]quinoxalin-11-ylidene)benzohydrazide derivatives (3a-3p) were synthesized and evaluated for their α-glucosidase inhibitory activity. The synthesized compounds 3d, 3f, 3g, 3k, 3n, 3p and 4 showed significant α-glucosidase inhibitory activity as compared to acrabose, a standard drug used to treat type II diabetes. Structures of the synthesized compounds were determined by using FT-IR, (1)H NMR, (13)C NMR, mass spectrometry and elemental analysis techniques.

Isolation of natural compounds from Phlomis stewartii showing α-glucosidase inhibitory activity.

Stewartiiside (1), a phenylethanoid glycoside and three 28-nortriterpenoids: stewertiisins A-C [(17R)-19(18→17)-abeo-3α,18ß,23,24-tetrahydroxy-28-norolean-12-ene, 2; (17R)-19(18→17)-abeo-2α,16ß,18ß,23,24-pentahydroxy-28-norolean-12-en-3-one, 3; (17R)-19(18→17)-abeo-2α,3α,23,24-tetrahydroxy-28-noroleane-11,13-diene, 4] together with eight known compounds: lunariifolioside (5), notohamosin A (6), phlomispentanol (7), isorhamnetin 3-(6-p-coumaroyl)-ß-D-glucopyranoside (8), tiliroside (9), caffeic acid (10), p-hydrxybenzoic acid (11) and oleanolic acid (12) were isolated from the ethyl acetate soluble fraction of the methanolic extract of whole plant of Phlomis stewartii. The structures of these isolates (1-12) were elucidated by the combination of 1D ((1)H and (13)C NMR), 2D (HMQC, HMBC COSY, NOESY) NMR spectroscopy and mass spectrometry (EIMS, HREIMS, FABMS, HRFABMS) and in comparison with literature data of related compounds. All the isolates (1-12) showed α-glucosidase inhibitory activity with IC50 values ranging between 14.5 and 355.4 µM, whereas, compounds 1, 5, 9 and 10 showed promising α-glucosidase inhibitory activity with IC50 values below 30 µM.