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Dive into the research topics where G. Jayarama Bhat is active.

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Featured researches published by G. Jayarama Bhat.


Molecular and Biochemical Parasitology | 1992

Transcript-specific developmental regulation of polyadenylation in Trypanosoma brucei mitochondria

G. Jayarama Bhat; Augustine E. Souza; Jean E. Feagin; Kenneth Stuart

Transcripts from many mitochondrial genes in kinetoplastids are heterogeneous in size, often occurring as 2 distinct size classes, but this cannot be accounted for by RNA editing alone. Analyses of transcripts from 6 mitochondrial genes of Trypanosoma brucei indicates that the size variation is due to poly(A) tail length. A larger fraction of CYb, COI and COII transcripts have longer poly(A) tails in procyclic than in bloodstream forms. These transcripts are also more abundant in the procyclic forms. In contrast, a more substantial fraction of CR1 transcripts have longer poly(A) tails in bloodstream than in procyclic forms and these transcripts tend to be more abundant in bloodstream forms. Both ND4 and MURF1 transcripts show a similar size distribution of poly(A) tail lengths in these life cycle states although both transcripts are more abundant in bloodstream forms. Furthermore, genes with edited transcripts tend to have longer poly(A) tails than unedited transcripts. Transcript abundance is not strictly correlated with longer poly(A) tails. Thus, poly(A) length variation appears to be developmentally regulated in a transcript-specific fashion in T. brucei. This regulation of polyadenylation may influence mitochondrial gene expression as polyadenylation can regulate cytoplasmic gene expression in eukaryotes.


Journal of Pharmacology and Experimental Therapeutics | 2009

A Functional Role for Sodium-Dependent Glucose Transport across the Blood-Brain Barrier during Oxygen Glucose Deprivation

Sharanya Vemula; Karen E. Roder; Tianzhi Yang; G. Jayarama Bhat; Thomas J. Thekkumkara; Thomas J. Abbruscato

In the current study, we determined the functional significance of sodium-dependent/-independent glucose transporters at the neurovasculature during oxygen glucose deprivation (OGD). Confluent brain endothelial cells cocultured with astrocytes were exposed to varying degrees of in vitro stroke conditions. Glucose transporter (GLUT) 1 and sodium glucose cotransporter (SGLT) activity were investigated by luminal membrane uptake and transport studies using [3H]d-glucose and also by [14C]α-methyl d-glucopyranoside (AMG), a specific, nonmetabolized substrate of SGLT. In vivo middle cerebral artery occlusion experiments were tested to determine whether blood-brain barrier (BBB) SGLT activity was induced during ischemia. Increases in luminal d-glucose and AMG uptake and transport were observed with in vitro stroke conditions. Specific inhibitor experiments suggest a combined role for both SGLT and GLUT1 at the BBB during OGD. A time-dependent increase in the uptake of AMG was also seen in mice exposed to permanent focal ischemia, and this increase was sensitive to the SGLT inhibitor, phlorizin. Infarct and edema ratio during ischemia were significantly decreased by the inhibition of this transporter. These results show that both GLUT1 and SGLT play a role at the BBB in the blood-to-brain transport of glucose during ischemic conditions, and inhibition of SGLT during stroke has the potential to improve stroke outcome. Pharmacological modulation of this novel BBB transporter could prove to be a brain vascular target in stroke.


Free Radical Biology and Medicine | 2010

Cys-141 glutathionylation of human p53: Studies using specific polyclonal antibodies in cancer samples and cell lines.

Moh D. A. Yusuf; Tri Nette Chuang; G. Jayarama Bhat; Kalkunte S. Srivenugopal

Previously, we reported that human p53 is functionally inactivated by S-glutathionylation at Cys-141 during oxidative and DNA-damaging treatments. Here, we describe the presence of thiolated p53 and the dynamic nature of this modification in human tissues using unique and specific polyclonal antibodies raised against a 12-residue p53 peptide bearing a mixed disulfide at Cys-141. The affinity- purified antibodies (glut-p53) were sequence-specific in that they recognized the antigenic peptide but not the unthiolated peptide or a scrambled glutathionylated peptide in ELISAs. On immunoblots, the purified antibodies did not react with native p53 or recombinant p53 (rp53), but readily detected the glutathionylated or cysteinylated or ethanethiol-treated rp53 only under nonreducing conditions. Untreated HCT116 cells showed low levels of glut-p53, which increased markedly after H(2)O(2), diamide, cisplatin, and doxorubicin treatments. Glut-p53 levels decreased sharply after cells were passed into oxidant-free medium, suggesting efficient dethiolation. The mutant p53 present in HT29 and T47D human cancer cells was also recognized. In vitro, the glut-p53 was rapidly degraded by rabbit reticulocyte lysates. Human prostate and prostate cancer tissues showed an abundant presence of glut-p53 in luminal epithelium, a site well known to generate ROS. Melanoma and colon cancer samples were also positive for glut-p53. The availability of the thiolation-specific antibodies should enhance our knowledge of p53 regulation in redox-perturbed states found in various diseases including cancer.


Hypertension | 1999

Angiotensin II–Stimulated Induction of sis-Inducing Factor Is Mediated by Pertussis Toxin–Insensitive Gq Proteins in Cardiac Myocytes

Rachel A. Hunt; G. Jayarama Bhat; Kenneth M. Baker

The Janus kinase-signal transducers and activators of transcription (JAK-STAT) pathway is stimulated by angiotensin II (Ang II) via the type 1 receptor after acute pressure overload in the heart. The purpose of this study was to determine whether activation of the JAK-STAT pathway by Ang II is dependent on G proteins. Ang II (100 nmol/L for 120 minutes) caused formation of sis-inducing factor (SIF) complexes and tyrosine phosphorylation of STAT proteins in neonatal rat ventricular myocytes. The percentage of change in Ang II-stimulated SIF induction was not affected by pertussis toxin (PTX) or GP antagonist-2A, compounds that inhibit activation of G(i) and G(o) proteins. In contrast, GP antagonist-2A, a peptide that selectively inhibits activation of G(q) proteins, completely abolished Ang II-stimulated SIF induction and STAT3 tyrosine phosphorylation. Pretreatment of cardiac myocytes with U73122, an inhibitor of phosphatidylinositol-specific phospholipase C (PLC) activity, decreased Ang II-stimulated SIF induction and STAT3 tyrosine phosphorylation in a dose-dependent manner. Chelation of intracellular Ca(2+) with BAPTA-AM did not alter Ang II-stimulated SIF induction. In contrast, pretreatment of cardiac myocytes with Ro-31-8220, a potent and specific inhibitor of protein kinase C (PKC), decreased Ang II-stimulated SIF induction in a dose-dependent manner. Ang II-stimulated SIF induction was abolished in cardiac myocytes after downregulation of PKC by treatment with PMA. From these data, we conclude that Ang II-stimulated SIF induction and STAT3 tyrosine phosphorylation is mediated by PTX-insensitive G proteins through a G(q)-PLC-PKC-mediated pathway in neonatal rat ventricular myocytes.


American Journal of Physiology-lung Cellular and Molecular Physiology | 1999

Urokinase-type plasminogen activator induces tyrosine phosphorylation of a 78-kDa protein in H-157 cells.

G. Jayarama Bhat; Jagadambika J. Gunaje; Steven Idell

Studies from our laboratory have shown that exposure of human lung epithelial cells to urokinase plasminogen activator (uPA) induces their proliferation. This effect of uPA is likely to occur via activation of signal transduction pathways. To elucidate uPA-induced signal transduction mechanisms, we exposed H-157 cells to uPA and determined the induced tyrosine phosphorylation profile of proteins. We demonstrate that, in these cells, uPA prominently induced tyrosine phosphorylation of a 78-kDa protein. This effect was observed as early as 30 min and was sustained for at least 24 h. Treatment of cells with agents that abrogate uPA receptor (uPAR) function, including neutralizing anti-uPAR antibody, phosphatidylinositol-specific phospholipase C, or a selective antagonist that blocks the association of uPA with uPAR (Å5 compound), all failed to prevent uPA-induced tyrosine phosphorylation. B-428, an active site inhibitor of uPA activity, prevented the uPA effect. Treatment of cells with hepatocyte growth factor, vascular endothelial growth factor, or transforming growth factor-β, all of which are known to be activated by a uPA-dependent pathway, did not stimulate tyrosine phosphorylation of the 78-kDa protein. uPA induced an increase in [3H]thymidine incorporation into DNA, and cell numbers were unaffected in the presence of Å5. These results demonstrate that, in H-157 cells, uPA induces tyrosine phosphorylation of a 78-kDa protein via a proteolysis-dependent but uPAR-independent mechanism. This novel signaling pathway represents a putative mechanism by which uPA could influence epithelial cell proliferation.Studies from our laboratory have shown that exposure of human lung epithelial cells to urokinase plasminogen activator (uPA) induces their proliferation. This effect of uPA is likely to occur via activation of signal transduction pathways. To elucidate uPA-induced signal transduction mechanisms, we exposed H-157 cells to uPA and determined the induced tyrosine phosphorylation profile of proteins. We demonstrate that, in these cells, uPA prominently induced tyrosine phosphorylation of a 78-kDa protein. This effect was observed as early as 30 min and was sustained for at least 24 h. Treatment of cells with agents that abrogate uPA receptor (uPAR) function, including neutralizing anti-uPAR antibody, phosphatidylinositol-specific phospholipase C, or a selective antagonist that blocks the association of uPA with uPAR (A5 compound), all failed to prevent uPA-induced tyrosine phosphorylation. B-428, an active site inhibitor of uPA activity, prevented the uPA effect. Treatment of cells with hepatocyte growth factor, vascular endothelial growth factor, or transforming growth factor-beta, all of which are known to be activated by a uPA-dependent pathway, did not stimulate tyrosine phosphorylation of the 78-kDa protein. uPA induced an increase in [(3)H]thymidine incorporation into DNA, and cell numbers were unaffected in the presence of A5. These results demonstrate that, in H-157 cells, uPA induces tyrosine phosphorylation of a 78-kDa protein via a proteolysis-dependent but uPAR-independent mechanism. This novel signaling pathway represents a putative mechanism by which uPA could influence epithelial cell proliferation.


Molecular and Cellular Biochemistry | 1997

Angiotensin II stimulates rapid serine phosphorylation of transcription factor Stat3

G. Jayarama Bhat; Kenneth M. Baker

In rat neonatal cardiac fibroblasts and CHO-K1 cells expressing angiotensin type 1 receptors, angiotensin II (AII) rapidly caused a time dependent reduction in the SDS-polyacrylamide gel electrophoretic mobility of Stat3 (Signal Transducer and Activator of Transcription). This was concentration dependent and detected at a low/physiological concentration of AII (1 nM), with initial effect observed as early as 2 min; and maximal at 5 min. The rapid stimulation of Stat3 mobility retardation by AII, paralleled the rapid activation of MAP kinases (mitogen-activated protein kinases), and both were sensitive to the MAP kinase kinase 1 inhibitor, PD98059. Immunoprecipitation of Stat3 from [32P] labeled cells demonstrated a 4-fold increase in Stat3 phosphorylation in response to AII, and phosphoamino acid analysis indicated that phosphorylation occurred on serine residues. Angiotensin II-induced rapid phosphorylation of Stat3 was also sensitive to the MAP kinase kinase 1 inhibitor, PD98059. Treatment of immunoprecipitated Stat3 from AII-treated cells with protein phosphatase- PP-2A, reversed the AII-induced retardation of Stat3 mobility. These results demonstrate that AII rapidly induces Stat3 serine phosphorylation through a MAP kinase kinase 1 dependent pathway. Rapid stimulation of Stat3 serine phosphorylation by AII may have implications in the modulation of its transcriptional activity and gene expression.


Molecular Cancer Research | 2016

Cyclin A2 and CDK2 as Novel Targets of Aspirin and Salicylic Acid: A Potential Role in Cancer Prevention

Rakesh Dachineni; Guoqiang Ai; D. Ramesh Kumar; Satya S. Sadhu; Hemachand Tummala; G. Jayarama Bhat

Data emerging from the past 10 years have consolidated the rationale for investigating the use of aspirin as a chemopreventive agent; however, the mechanisms leading to its anticancer effects are still being elucidated. We hypothesized that aspirins chemopreventive actions may involve cell-cycle regulation through modulation of the levels or activity of cyclin A2/cyclin-dependent kinase-2 (CDK2). In this study, HT-29 and other diverse panel of cancer cells were used to demonstrate that both aspirin and its primary metabolite, salicylic acid, decreased cyclin A2 (CCNA2) and CDK2 protein and mRNA levels. The downregulatory effect of either drugs on cyclin A2 levels was prevented by pretreatment with lactacystin, an inhibitor of proteasomes, suggesting the involvement of 26S proteasomes. In-vitro kinase assays showed that lysates from cells treated with salicylic acid had lower levels of CDK2 activity. Importantly, three independent experiments revealed that salicylic acid directly binds to CDK2. First, inclusion of salicylic acid in naïve cell lysates, or in recombinant CDK2 preparations, increased the ability of the anti-CDK2 antibody to immunoprecipitate CDK2, suggesting that salicylic acid may directly bind and alter its conformation. Second, in 8-anilino-1-naphthalene-sulfonate (ANS)-CDK2 fluorescence assays, preincubation of CDK2 with salicylic acid dose-dependently quenched the fluorescence due to ANS. Third, computational analysis using molecular docking studies identified Asp145 and Lys33 as the potential sites of salicylic acid interactions with CDK2. These results demonstrate that aspirin and salicylic acid downregulate cyclin A2/CDK2 proteins in multiple cancer cell lines, suggesting a novel target and mechanism of action in chemoprevention. Implications: Biochemical and structural studies indicate that the antiproliferative actions of aspirin are mediated through cyclin A2/CDK2. Mol Cancer Res; 14(3); 241–52. ©2015 AACR.


Biochemical and Biophysical Research Communications | 1988

Heme regulates cytochrome P-450 gene transcription elongation

G. Jayarama Bhat; Govindarajan Padmanaban

Administration of 3-methylcholanthrene (MC) to rats results in a striking increase in the transcription of cytochrome P-450 (c + d) messenger RNA with isolated nuclei, which is blocked by the simultaneous administration of cobalt chloride, an inhibitor of heme biosynthesis. Transcription of cytochrome P-450 (c + d) mRNAs with nuclei isolated from MC treated rats shows a linear increase with time of incubation, whereas it shows a progressive decrease with incubation time in the case of nuclei isolated from MC+CoCl2 treated rats. Addition of heme in vitro (10(-6)M) to the latter nuclei results in a significant counteraction of the decreased cytochrome P-450 (c + d) mRNA transcription. The inhibition in transcription rates observed in MC+CoCl2 treated rat liver nuclei is more pronounced with the seventh exon probe than with the second exon probe. Once again, in vitro heme addition can counteract the inhibition observed with both the probes. Since run off transcription with isolated nuclei represents essentially elongation of the initiated transcripts, the data obtained can be interpreted on the basis that heme regulates cytochrome P-450 gene transcription elongation.


Tumor Biology | 2016

Aspirin acetylates wild type and mutant p53 in colon cancer cells: identification of aspirin acetylated sites on recombinant p53

Guoqiang Ai; Rakesh Dachineni; D. Ramesh Kumar; Srinivasan Marimuthu; Lloyd F. Alfonso; G. Jayarama Bhat

Aspirin’s ability to inhibit cell proliferation and induce apoptosis in cancer cell lines is considered to be an important mechanism for its anti-cancer effects. We previously demonstrated that aspirin acetylated the tumor suppressor protein p53 at lysine 382 in MDA-MB-231 human breast cancer cells. Here, we extended these observations to human colon cancer cells, HCT 116 harboring wild type p53, and HT-29 containing mutant p53. We demonstrate that aspirin induced acetylation of p53 in both cell lines in a concentration-dependent manner. Aspirin-acetylated p53 was localized to the nucleus. In both cell lines, aspirin induced p21CIP1. Aspirin also acetylated recombinant p53 (rp53) in vitro suggesting that it occurs through a non-enzymatic chemical reaction. Mass spectrometry analysis and immunoblotting identified 10 acetylated lysines on rp53, and molecular modeling showed that all lysines targeted by aspirin are surface exposed. Five of these lysines are localized to the DNA-binding domain, four to the nuclear localization signal domain, and one to the C-terminal regulatory domain. Our results suggest that aspirin’s anti-cancer effect may involve acetylation and activation of wild type and mutant p53 and induction of target gene expression. This is the first report attempting to characterize p53 acetylation sites targeted by aspirin.


European Journal of Pharmaceutical Sciences | 2016

Molecular complexation of curcumin with pH sensitive cationic copolymer enhances the aqueous solubility, stability and bioavailability of curcumin

Sunny Kumar; Siddharth S. Kesharwani; Himanshi Mathur; Mohit Tyagi; G. Jayarama Bhat; Hemachand Tummala

Curcumin is a natural dietary compound with demonstrated potential in preventing/treating several chronic diseases in animal models. However, this success is yet to be translated to humans mainly because of its poor oral bioavailability caused by extremely low water solubility. This manuscript demonstrates that water insoluble curcumin (~1μg/ml) forms highly aqueous soluble complexes (>2mg/ml) with a safe pH sensitive polymer, poly(butyl-methacrylate-co-(2-dimethylaminoethyl) methacrylate-co-methyl-methacrylate) when precipitated together in water. The complexation process was optimized to enhance curcumin loading by varying several formulation factors. Acetone as a solvent and polyvinyl alcohol as a stabilizer with 1:2 ratio of drug to polymer yielded complexes with relatively high loading (~280μg/ml) and enhanced solubility (>2mg/ml). The complexes were amorphous in solid and were soluble only in buffers with pHs less than 5.0. Hydrogen bond formation and hydrophobic interactions between curcumin and the polymer were recorded by infrared spectroscopy and nuclear magnetic resonance spectroscopy, respectively. Molecular complexes of curcumin were more stable at various pHs compared to unformulated curcumin. In mice, these complexes increased peak plasma concentration of curcumin by 6 times and oral bioavailability by ~20 times. This is a simple, economic and safer strategy of enhancing the oral bioavailability of curcumin.

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Rakesh Dachineni

South Dakota State University

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Hemachand Tummala

South Dakota State University

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Thomas J. Thekkumkara

Texas Tech University Health Sciences Center

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D. Ramesh Kumar

South Dakota State University

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Guoqiang Ai

South Dakota State University

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Jagadambika J. Gunaje

University of Texas Health Science Center at Tyler

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Thomas J. Abbruscato

Texas Tech University Health Sciences Center

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Kalkunte S. Srivenugopal

Texas Tech University Health Sciences Center

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