A straightforward experimental approach to expression, purification, refolding, and enzymatic analysis of recombinant dengue virus NS2B(H)-NS3pro protease.

Dengue virus threatens around 2.5 billion people worldwide; about 50 million become infected every year, and yet no vaccine or drug is available for prevention and/or treatment. The flaviviral NS2B-NS3pro complex is indispensable for flaviviral replication and is considered to be an important drug target. The aim of this study was to develop a simple and generally applicable experimental strategy to construct, purify, and assay a highly active recombinant NS2B(H)-NS3pro complex that would be useful for high-throughput screening of potential inhibitors. The sequence of NS2B(H)-NS3pro was generated by overlap extension PCR (SOE-PCR) and cloned into the pTrcHisA vector. Hexahistidine-tagged NS2B(H)-NS3pro complex was expressed in E. coli predominantly as insoluble protein and purified to >95% purity by single-step immobilized metal affinity chromatography. SDS-PAGE followed by immunoblotting of the purified enzyme demonstrated the presence of the NS2B(H)-NS3pro precursor and its autocleavage products, NS3pro and NS2B(H), as 37, 21, and 10 kDa bands, respectively. Kinetic parameters, Km, kcat, and kcat/Km for the fluorophore-linked protease model substrate Ac-nKRR-amc were obtained using inner-filter effect correction. The kinetic parameters Km, kcat, and kcat/Km for Ac-nKRR-amc substrate were 100 µM, 0.112 s(-1), and 1120 M(-1)·s(-1), respectively. A simplified procedure for the cloning, overexpression, and purification of the NS2B(H)-NS3pro complex was applied, and a highly active recombinant NS2B(H)-NS3pro complex was obtained that could be useful for the design of high-throughput assays aimed at flaviviral inhibitor discovery.

Modulation of enzymatic activity of dengue virus nonstructural protein NS3 nucleoside triphosphatase/helicase by poly(U).

The nonstructural protein 3 (NS3) appears to be the most promising target for anti-flavivirus therapy because of its multiple enzymatic activities that are indispensable for virus replication. NS3 of dengue virus type 2 (DEN2) is composed of two domains, a serine protease in the N-terminal domain (NS3pro) and RNA-stimulated nucleoside triphosphatase (NTPase)/RNA helicase at the C-terminus (NS3h). NS3 plays an important role in viral replication and the coordinated regulation of all the catalytic activities in the full-length NS3 protein. In this study, a plasmid harboring the NS3 helicase domain (NS3h) was constructed by PCR. The 56.5 kDa NS3h protein was purified by metal-chelate affinity chromatography followed by renaturation, mediated by artificial chaperone-assisted refolding, which yielded the active helicase. NTPase activity was assayed with Malachite Green. The NTPase activity in the presence of poly(U) showed a higher turnover number (kcat) and a lower Km value than without poly(U). The activity increased approximately fourfold in the presence of polynucleotides. This indicates that NTPase activity of dengue NS3 can be stimulated by polynucleotides. A helicase assay based on internal fluorescence quenching was conducted using short internally quenched DNA oligonucleotides as substrates. Significant fluorescence signaling increase was observed in the absence of polynucleotides such as poly(U). No unwinding activity was observed with addition of poly(U). The approach we describe here is useful for the further characterization of substrate specificity and for the design of high-throughput assays aimed at discovery of inhibitors against NS3 NTPase/helicase activities.

Dermal melanocortin receptor rebound in diffuse systemic sclerosis after anti-TGFß1 antibody therapy.

Disturbed transforming growth factor beta (TGFß) signalling leads to enhanced synthesis of extracellular matrix (ECM), which is manifested as systemic sclerosis (SSc), but this may be attenuated by the melanocortin system. Here, we report of rebound reaction in the gene expression of melanocortin receptor (MCR) subtypes and of the precursor of these receptors' ligands, the pro-opio-melanocortin protein (POMC), in the acute skin lesion of diffuse systemic sclerosis (dSSc) after treatment with a recombinant human anti-TGFß1 antibody. Biopsies, taken from the leading edge of the skin lesion, before and after treatment of a patient with recent onset dSSc, were examined. Before treatment, increased levels of TGFß mRNA and suppressed levels of POMC mRNA and MCR subtypes MC(1-3, 5) R mRNAs were seen in the lesion, compared with healthy controls. After treatment, there was a rebound expression of POMC, MC(2, 3, 5) R mRNAs. As the melanocortin system regulates collagen and melanin production, our findings add a new understanding to the pathogenetic mechanisms involved in the acute skin lesion of dSSc, which is characterized by enhanced ECM formation and changes in skin pigmentation.

Quantitative measurement of the levels of melanocortin receptor subtype 1, 2, 3 and 5 and pro-opio-melanocortin peptide gene expression in subsets of human peripheral blood leucocytes.

Levels of the melanocortin receptor (MCR) 1, 2, 3 and 5 subtypes and pro-opio-melanocortin (POMC) protein mRNA were measured by the real-time quantitative reverse transcriptase polymerase chain reaction method in CD4+ T helper (Th) cells, CD8+ T cytotoxic cells, CD19+ B cells, CD56+ natural killer (NK) cells, CD14+ monocytes and CD15+ granulocytes from healthy donors. We found high levels of all of the MC1, 2, 3 and 5R subtype mRNA in Th cells and moderate levels in NK cells, monocytes and granulocytes. POMC peptide mRNA was found in all examined leucocyte subsets, but only low levels were present in granulocytes. Our findings suggest a co-ordinating role for MCR subtypes and their naturally occurring ligands in the co-operation between innate and adaptive immunity. Moreover, our findings are compatible with earlier finding of MCR-mediated tolerance induction in Th cells.

In vivo measurements of the cerebral perfusion and cardiovascular effects of the novel guanidine ME10092 in the non-human primate, Papio ursinus.

The novel guanidines N-(3,4-dimethoxy-2-chlorobenzylideneamino)-guanidine (ME 10092) and N-(3,4-dimethoxy-2-chlorobenzylideneamino)-N1-hydroxyguanidine (PR5) were recently reported to exhibit promising cardioprotective activities in myocardial ischaemia and reperfusion in rats. The current study investigated for the first time pharmacological effects of ME10092 in the primate, viz. the Cape baboon Papio ursinus. The effects of ME10092 (1 and 2 mg/kg doses) on the cerebral blood flow, heart rates and the systolic and diastolic blood pressure were investigated after intravenous injection to the baboon under anaesthesia. The cerebral perfusion effects of ME10092 were assessed using Single Photon Emission Computed Tomography according to the split-dose approach and 99mTc-hexamethyl-propylene amine oxime as brain perfusion tracer. The observation that the recovery times from the anaesthesia were unacceptably prolonged excluded doses beyond 2 mg/kg. The data indicate that no cerebral perfusion changes were induced at both the 1 and 2 mg/kg doses of ME10092. Both these doses of ME10092 showed blood pressure and heart rate effects, with the latter being more significant. Decreases in heart rate were seen directly after ME10092 administration reaching levels of about 20% for the 2 mg/kg dose and about 15% for the 1 mg/kg dose at around 6 min post drug administration. A transient decrease in both systolic and diastolic blood pressure was observed for the higher dose. The blood pressure data further suggest an attenuation of the anaesthesia induced increase in pressure usually present in non-intervention studies. ME10092 clearly exhibits mycocardial effects in the non-human primate, similar to the effects previously observed in the ischaemia-reperfusion rat model, where ME10092 showed strong protection.

EPR investigation of in vivo inhibitory effect of guanidine compounds on nitric oxide production in rat tissues.

The aim of the present study was to evaluate in vivo effects on NO production of pharmacologically widely used, commercially available NOS inhibitors, structurally related to guanidine. We compared the NO inhibitory potency and selectivity of L-NAME, aminoguanidine and guanabenz in tissues of normal and LPS-stimulated rats using ex vivo EPR measurements of the NO radical in its complex with dithiocarbamate-Fe(II). The tissues studied were the brain cortex, kidney, liver, heart and testis. Differential inhibitory effects were seen for L-NAME, aminoguanidine and guanabenz when applied during basal or LPS-stimulated conditions. Aminoguanidine exerted inhibition of NO only after stimulation with LPS. Guanabenz had little effect on NO in liver, kidney, testis and heart under normal conditions, while it reduced the basal NO in brain cortex. After stimulation with LPS guanabenz afforded a partial inhibition of the NO formation in all tissues studied. L-NAME was a potent inhibitor of NO synthesis in all tested tissues, both during basal and LPS stimulated conditions. Our results show that compounds containing a guanidine moiety might possess different NOS inhibitory profiles in vivo.

Melanocortin receptors: ligands and proteochemometrics modeling.

The melanocortin receptors exist in five subtypes, MC(1-5)R. These receptors participate in important regulations of the immune system, central behavior, and endocrine and exocrine glands. Here we provide a short review on MCR subtype selective peptides and organic compounds with activity on the MCRs, developed in our laboratory. Also provided is an overview of our new proteochemometric modeling technology, which has been applied to model the interaction of MSH peptides with the MCRs.

Alcohol-preferring AA rats show a derangement in their central melanocortin signalling system.

The AA (Alko, Alcohol) rats are selectively bred for their preference of alcohol to water, contrasting to ANA rats that avoid alcohol. They also exhibit a lower growth rate compared to ANA rats, as well as differences in their response to substances affecting food intake. The melanocortin (MC) system is involved in the regulation of feeding behaviour and in mechanisms underlying drug addiction and tolerance. Recently, administration of an MC receptor agonist proved to reduce alcohol intake in AA rats. We predicted that the ratio of endogenous MC receptor agonists (proopiomelanocortin, POMC) and antagonists (agouti-related protein, AgRP) would differ from ANA rats, and that subsequent differences in MC receptor levels would be detectable. We used in situ hybridization to detect an increased ratio of POMC/AgRP mRNA in the arcuate nucleus (Arc) of AA rats. Receptor autoradiography indicated that MC3 receptor binding differed in the nucleus accumbens and several hypothalamic nuclei, possibly reflecting differences in MC peptide transmission in the AA rats. Our results support the claim that AA rats have a high ratio of POMC/AgRP expression, and that this observation is accompanied by differences in MC3 receptor levels.