Biomedical subjects

Pundi N Rangarajan

Publications and source records attributed to Pundi N Rangarajan.

10 recordsLinked to original sources

PubMed2006

Regulation of Ca2+/calmodulin kinase II inhibitor alpha (CaMKIINalpha) in virus-infected mouse brain.

The alpha and beta isoforms of rat Ca(2+)/calmodulin kinase II inhibitor (CaMKIINalpha/beta) expressed in brain or brain and testis, respectively, are potent inhibitors of Ca(2+)/calmodulin kinase II (CaMKII) in vitro. However, the regulation or function of CaMKIINalpha/beta in the central nervous system (CNS) is not known. In this study, we demonstrate that mouse CaMKIINalpha gene encodes a 2.9kb brain-specific transcript whose expression is downregulated in mouse brain during Japanese encephalitis virus (JEV) and rabies virus infection. The downregulation is specific for CaMKIINalpha but not CaMKIINbeta mRNA. In addition to these changes in CaMKIINalpha mRNA, distinct changes are also observed in the phosphorylation as well as subcellular localization of CaMKIIalpha leading to an increase in cytosolic CaMKII activity in JEV-infected mouse brain. The differential regulation of CaMKIIalpha and CaMKIINalpha during JEV infection suggests a possible role for these proteins in viral infection and/or virus-induced neuropathogenesis in the CNS.

Amino Acid Sequence↗

PubMed2006

Isolation of a single-stranded DNA-binding protein from the methylotrophic yeast, Pichia pastoris and its identification as zeta crystallin.

A single-stranded DNA (ssDNA)-binding protein (SSB) that binds to specific upstream sequences of alcohol oxidase (AOX1) promoter of the methylotrophic yeast Pichia pastoris has been isolated and identified as zeta crystallin (ZTA1). The cDNA encoding P.pastoris ZTA1 (PpZTA1) was cloned into an Escherichia coli expression vector, the recombinant PpZTA1 was expressed and purified from E.coli cell lysates. The DNA-binding properties of recombinant PpZTA1 are identical to those of the SSB present in P.pastoris cell lysates. PpZTA1 binds to ssDNA sequences >24 nt and its DNA-binding activity is abolished by NADPH. This is the first report on the characterization of DNA-binding properties of a yeast ZTA1.

Alcohol Oxidoreductases↗

PubMed2006

Identification and characterization of a virus-inducible non-coding RNA in mouse brain.

Infection of mice with Japanese encephalitis virus or Rabies virus results in the activation of a gene encoding a novel, non-coding RNA (ncRNA) in the mouse central nervous system. This transcript, named virus-inducible ncRNA (VINC), is identical to a 3.18 kb transcript expressed in mouse neonate skin (GenBank accession no. AK028745) that, together with a number of unannotated cDNAs and expressed sequence tags, is grouped in the mouse unigene cluster Mm281895. VINC is expressed constitutively in early mouse embryo and several adult non-neuronal mouse tissues, as well as a murine renal adenocarcinoma (RAG) cell line. Northern blotting of nuclear and cytoplasmic RNAs revealed that VINC is localized primarily in the nucleus of RAG cells and is thus a novel member of the nuclear ncRNA family.

Animals↗

PubMed2006

Identification of Japanese encephalitis virus-inducible genes in mouse brain and characterization of GARG39/IFIT2 as a microtubule-associated protein.

Several mouse central nervous system genes have been identified that are differentially regulated during Japanese encephalitis virus (JEV) infection, including those which have not been reported to be induced by any other neurotropic virus. Interestingly, approximately 80 % of JEV-inducible genes identified in this study are also induced by Sindbis virus, indicating activation of common host signalling pathways by these two viruses, despite their diverse life cycles. One of these, the glucocorticoid attenuated response gene 39 (GARG39, also known as IFIT2, ISG54 and MuP54) was characterized further. It was demonstrated that GARG39 protein interacts with microtubules in vitro, co-localizes with beta-tubulin in vivo and is enriched in the mitotic spindle of non-neuronal cells undergoing mitosis. While GARG39 was known for a long time as an inflammation-inducible glucocorticoid attenuated protein, its identification as a microtubule-associated protein in this study suggests a possible role for this protein in cell proliferation, virion assembly/transport and microtubule dynamics.

Animals↗

PubMed2005

Curcumin for malaria therapy.

Malaria remains a major global health concern. New, inexpensive, and effective antimalarial agents are urgently needed. Here we show that curcumin, a polyphenolic organic molecule derived from turmeric, inhibits chloroquine-resistant Plasmodium falciparum growth in culture in a dose dependent manner with an IC(50) of approximately 5 microM. Additionally, oral administration of curcumin to mice infected with malaria parasite (Plasmodium berghei) reduces blood parasitemia by 80-90% and enhances their survival significantly. Thus, curcumin may represent a novel treatment for malarial infection.

Animals↗

PubMed2004

Localization of ferrochelatase in Plasmodium falciparum.

Our previous studies have demonstrated de novo haem biosynthesis in the malarial parasite (Plasmodium falciparum and P. berghei). It has also been shown that the first enzyme of the pathway is the parasite genome-coded ALA (delta-aminolaevulinate) synthase localized in the parasite mitochondrion, whereas the second enzyme, ALAD (ALA dehydratase), is accounted for by two species: one species imported from the host red blood cell into the parasite cytosol and another parasite genome-coded species in the apicoplast. In the present study, specific antibodies have been raised to PfFC (parasite genome-coded ferrochelatase), the terminal enzyme of the haem-biosynthetic pathway, using recombinant truncated protein. With the use of these antibodies as well as those against the hFC (host red cell ferrochelatase) and other marker proteins, immunofluorescence studies were performed. The results reveal that P. falciparum in culture manifests a broad distribution of hFC and a localized distribution of PfFC in the parasite. However, PfFC is not localized to the parasite mitochondrion. Immunoelectron-microscopy studies reveal that PfFC is indeed localized to the apicoplast, whereas hFC is distributed in the parasite cytoplasm. These results on the localization of PfFC are unexpected and are at variance with theoretical predictions based on leader sequence analysis. Biochemical studies using the parasite cytosolic and organellar fractions reveal that the cytosol containing hFC accounts for 80% of FC enzymic activity, whereas the organellar fraction containing PfFC accounts for the remaining 20%. Interestingly, both the isolated cytosolic and organellar fractions are capable of independent haem synthesis in vitro from [4-14C]ALA, with the cytosol being three times more efficient compared with the organellar fraction. With [2-14C]glycine, most of the haem is synthesized in the organellar fraction. Thus haem is synthesized in two independent compartments: in the cytosol, using the imported host enzymes, and in the organellar fractions, using the parasite genome-coded enzymes.

Animals↗

PubMed2004

Yeast cytochrome c is a sequence-specific DNA-binding protein.

A protein binding to the alcohol oxidase 2 upstream activation sequence (AOX2UAS) of the methylotropic yeast, Pichia pastoris, has been purified and identified as cytochrome c (cyt c). Cyt c purified from P. pastoris or Saccharomyces cerevisiae binds to AOX2UAS. Specific point mutations in AOX2UAS abolish cyt c binding. We conclude that yeast cyt c is a sequence-specific DNA-binding protein and may have a regulatory role in the nucleus.

Amino Acid Sequence↗

PubMed2003

Delta-aminolevulinic acid dehydratase from Plasmodium falciparum: indigenous versus imported.

The heme biosynthetic pathway of the malaria parasite is a drug target and the import of host delta-aminolevulinate dehydratase (ALAD), the second enzyme of the pathway, from the red cell cytoplasm by the intra erythrocytic malaria parasite has been demonstrated earlier in this laboratory. In this study, ALAD encoded by the Plasmodium falciparum genome (PfALAD) has been cloned, the protein overexpressed in Escherichia coli, and then characterized. The mature recombinant enzyme (rPfALAD) is enzymatically active and behaves as an octamer with a subunit Mr of 46,000. The enzyme has an alkaline pH optimum of 8.0 to 9.0. rPfALAD does not require any metal ion for activity, although it is stimulated by 20-30% upon addition of Mg2+. The enzyme is inhibited by Zn2+ and succinylacetone. The presence of PfALAD in P. falciparum can be demonstrated by Western blot analysis and immunoelectron microscopy. The enzyme has been localized to the apicoplast of the malaria parasite. Homology modeling studies reveal that PfALAD is very similar to the enzyme species from Pseudomonas aeruginosa, but manifests features that are unique and different from plant ALADs as well as from those of the bacterium. It is concluded that PfALAD, while resembling plant ALADs in terms of its alkaline pH optimum and apicoplast localization, differs in its Mg2+ independence for catalytic activity or octamer stabilization. Expression levels of PfALAD in P. falciparum, based on Western blot analysis, immunoelectron microscopy, and EDTA-resistant enzyme activity assay reveals that it may account for about 10% of the total ALAD activity in the parasite, the rest being accounted for by the host enzyme imported by the parasite. It is proposed that the role of PfALAD may be confined to heme synthesis in the apicoplast that may not account for the total de novo heme biosynthesis in the parasite.

Amino Acid Sequence↗

PubMed2002

Protective efficacy of a plasmid DNA encoding Japanese encephalitis virus envelope protein fused to tissue plasminogen activator signal sequences: studies in a murine intracerebral virus challenge model.

We report the construction of chimeric DNA vaccine vectors in which secretory signal sequence derived from tissue plasminogen activator (TPA) was fused to the full length (pCMVTE) or 398 amino terminal amino acids (pCMVTdeltaE) of Japanese encephalitis virus (JEV) envelope (E) protein. Transfection studies indicate that E protein expressed from pCMVTdeltaE-transfected cells but not pCMVTE-transfected cells is secreted into the culture medium. Analysis of the potency of various DNA vaccine constructs in a murine intracerebral (i.c.) JEV challenge model indicates that pCMVTdeltaE confers the highest level (71%) of protection. Immunization with pCMVTdeltaE induces a mixed Th1 and Th2 T helper cell response while immunization with plasmids encoding nonsecretory forms of E protein induces a Th1 T helper response. Only low levels (<1:20) of virus neutralizing antibody titres were observed in DNA vaccinated mice which did not increase further after i.c. JEV challenge. Thus, immunization with a plasmid encoding secretory E protein results in an altered cytokine response and better protection against i.c. JEV challenge than that conferred by immunization with plasmids encoding nonsecretory forms of E protein. We also demonstrate that unlike peripheral JEV challenge, i.c. JEV challenge does not result in an increase in anamnestic antibody response suggesting that other components of immune system such as cytotoxic T cells and T helper cells contribute to protection against i.c. JEV challenge of DNA vaccinated mice.

Animals↗

PubMed2001

Emerging targets for antimalarial drugs.

The absence of an effective vaccine against malaria and the ability of the parasite to develop resistance to known antimalarial drugs makes it mandatory to unravel newer drug targets with a view to developing newer pharmacophores. While conventional targets such as the purine, pyrimidine and folate pathways are still being investigated in the light of newer knowledge, a new opportunity has emerged from an understanding of certain unique features of the parasite biology. These include the food vacuole, haemoglobin catabolism, haeme biosynthesis, apicoplasts and their metabolism as well as macromolecular transactions, import of host proteins, parasite induced alterations in the red cell surface and transport phenomena. This review seeks to emphasise the new and emerging targets, while giving a brief account of the targets that have already been exploited.

Journal Article↗