TMEM43 Mutation p.S358L Alters Intercalated Disc Protein Expression and Reduces Conduction Velocity in Arrhythmogenic Right Ventricular Cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a myocardial disease characterized by fibro-fatty replacement of myocardium in the right ventricular free wall and frequently results in life-threatening ventricular arrhythmias and sudden cardiac death. A heterozygous missense mutation in the transmembrane protein 43 (TMEM43) gene, p.S358L, has been genetically identified to cause autosomal dominant ARVC type 5 in a founder population from the island of Newfoundland, Canada. Little is known about the function of the TMEM43 protein or how it leads to the pathogenesis of ARVC. We sought to determine the distribution of TMEM43 and the effect of the p.S358L mutation on the expression and distribution of various intercalated (IC) disc proteins as well as functional effects on IC disc gap junction dye transfer and conduction velocity in cell culture. Through Western blot analysis, transmission electron microscopy (TEM), immunofluorescence (IF), and electrophysiological analysis, our results showed that the stable expression of p.S358L mutation in the HL-1 cardiac cell line resulted in decreased Zonula Occludens (ZO-1) expression and the loss of ZO-1 localization to cell-cell junctions. Junctional Plakoglobin (JUP) and α-catenin proteins were redistributed to the cytoplasm with decreased localization to cell-cell junctions. Connexin-43 (Cx43) phosphorylation was altered, and there was reduced gap junction dye transfer and conduction velocity in mutant TMEM43-transfected cells. These observations suggest that expression of the p.S358L mutant of TMEM43 found in ARVC type 5 may affect localization of proteins involved in conduction, alter gap junction function and reduce conduction velocity in cardiac tissue.     

Biodiversity banking: a strategic conservation mechanism

Among the conservation initiatives, biodiversity banking is a strategic new concept that calls for advocacy by the researchers, conservationists, policy planners and business corporate houses to enhance the conservational behaviour of the stakeholders. The concept has dual benefits of restoration of livelihood support systems and conservation of biodiversity that provides ecological services and economic benefits to civil society. Currently, lack of defined guidelines with robust valuation and incentive mechanism for biodiversity banking has resulted in ‘business as usual’ situation especially in developing and under developed countries. There is need for re-defining the country level biodiversity banking guidelines for the effective private-government-stakeholder participation. Furthermore, the mechanism must consider using robust scientific database of inter-disciplinary nature and suitably adopt the modalities of successful case studies to overcome the flaws/risks. Biodiversity banking is a realizable concept in developing and resource poor countries as additional livelihood support system through the market of accrued ecosystem services linked to conservation behaviour of stakeholders.     

Quinazolinone fungal efflux pump inhibitors. Part 3: (N-methyl)piperazine variants and pharmacokinetic optimization

Further structure-activity relationships of a novel series of fungal efflux pump inhibitors with respect to potentiation of the activity of fluconazole against strains of C. albicans and C. glabrata over-expressing ABC-type efflux pumps are systematically explored. Rat protein binding and pharmacokinetics of selected analogues are reported.     

Spatial distribution of methane-oxidizing activity in a flooded rice soil

In a study on spatial distribution of methane oxidation in an unplanted flooded field, methane-oxidizing activity, analysed in soil samples under laboratory conditions, decreased with increasing depth (25 cm and beyond). In a flooded field planted to rice, rates of methane oxidation followed the order : rhizosphere (collected from roots at 10-20 cm depth) > surface soil at (0-1 cm) > subsurface soil at 10-20 cm depth, diagonally 10-15 cm away from the centre of hill. Application of ammonium sulfate and, to a lesser extent, urea to surface, rhizosphere and subsurface soil samples from flooded field planted to rice effected a distinct inhibition of methane oxidation. Nitrification inhibitors (thiourea, sodium thiosulfate and dicyandiamide) were also effective in inhibiting methane oxidation. Both surface and rhizosphere soil samples harbored higher populations of methane-oxidizing bacteria than the subsurface soil. Inhibition of methane oxidation in surface and rhizosphere soil samples concomitant with the suppression of autotrophic ammonium oxidizers by nitrification inhibitors implicates an active involvement of autotrophic ammonium oxidizers in methane oxidation.     

Modulated dispersion of activation and repolarization by premature beats in patients with cardiomyopathy at risk of sudden death

Premature beats can trigger ventricular arrhythmias in heart disease, but the mechanisms are not well defined. We studied the effect of premature beats on activation and repolarization dispersion in seven patients with cardiomyopathy (57 ± 10 yr, left ventricular ejection fraction 31 ± 7%). Activation time (AT), activation-recovery interval (ARI), and total repolarization time (TRT) were measured from 26 unipolar electrograms during right ventricle (RV) endocardial (early) to left ventricle epicardial (late) activation in response to RV apical extrastimulation (S1S2). Early TRT dispersion increased significantly with shorter S1S2 (1.0 ± 0.2 to 2.3 ± 0.4 ms/mm, P < 0.0001), with minimal change in late TRT dispersion (0.8 ± 0.1 to 1.0 ± 0.3 ms, P = 0.02). This was associated with an increase in early AT dispersion (1.0 ± 0.1 to 1.5 ± 0.2 ms/mm, P = 0.05) but no change in late AT dispersion (0.6 ± 0.1 to 0.7 ± 0.2 ms/mm, P = 0.4). Early and late ARI dispersion did not change with shorter S1S2. AT restitution slopes were similar between early and late sites, as was slope heterogeneity. ARI restitution slope was greater in early vs. late sites (1.3 ± 0.6 vs. 0.8 ± 0.6, P = 0.03), but slope heterogeneity was similar. With shorter S1S2, AT-ARI slopes became less negative (flattened) at both early (-0.4 ± 0.1 to +0.04 ± 0.2) and late (-1.5 ± 0.2 to +0.3 ± 0.2) sites, implying less activation-repolarization coupling. There was no difference in AT-ARI slopes between early and late sites at short S1S2. In conclusion, high-risk patients with cardiomyopathy have greater TRT dispersion at tightly coupled S1S2 due to greater AT dispersion and activation-repolarization uncoupling. Modulated dispersion is more pronounced at early vs. late activated sites, which may predispose to reentrant ventricular arrhythmias.     

Comparative analysis of interactions between aryl hydrocarbon receptor ligand binding domain with its ligands: a computational study

Background

Aryl hydrocarbon receptor (AhR) ligands may act as potential carcinogens or anti-tumor agents. Understanding how some of the residues in AhR ligand binding domain (AhRLBD) modulate their interactions with ligands would be useful in assessing their divergent roles including toxic and beneficial effects. To this end, we have analysed the nature of AhRLBD interactions with 2,3,7,8-tetrachlorodibenzo-ρ-dioxin (TCDD), 6-formylindolo[3,2-b]carbazole (FICZ), indole-3-carbinol (I3C) and its degradation product, 3,3′-diindolylmethane (DIM), Resveratrol (RES) and its analogue, Piceatannol (PTL) using molecular modeling approach followed by molecular dynamic simulations.

Results

Results showed that each of the AhR ligands, TCDD, FICZ, I3C, DIM, RES and PTL affect the local and global conformations of AhRLBD.

Conclusion

The data presented in this study provide a structural understanding of AhR with its ligands and set the basis for its functions in several pathways and their related diseases.

     

A conserved domain in prokaryotic bifunctional FAD synthetases can potentially catalyze nucleotide transfer

Biosynthesis of flavin adenine dinucleotides in most prokaryotes is catalyzed by a family of bifunctional flavin adenine dinucleotide (FAD) synthetases. These enzymes carry out the dual functions of phosphorylation of flavin mononucleotide (FMN) and its subsequent adenylylation to generate FAD. Using various sequence analysis methods, a new domain has been identified in the N-terminal region that is well conserved in all the bacterial FAD synthetases. We also identify remote similarity of this domain to the nucleotidyl transferases and, hence, this domain is suggested to be invloved in the adenylylation reaction of FAD synthetases.     

Nitrate-dependent [Fe(II)EDTA]2- oxidation by Paracoccus ferrooxidans sp. nov., isolated from a denitrifying bioreactor

Enrichments with [Fe(II)EDTA]2- as electron donor and nitrate or nitrite as electron acceptor were established using an inoculum from a bioreactor performing denitrification. A nitrate-reducing, [Fe(II)EDTA]2- oxidizing strain was isolated and named strain BDN-1. The G + C content of strain BDN-1 was 67%, and the organism was closely affiliated to Paracoccus denitrificans, P. pantotrophus and P. versutus by 16S rRNA sequence comparison. Results from DNA-DNA hybridization, rep-PCR, and whole cell protein analysis gave congruent results confirming the genotypic and phenotypic differences between strain BDN-1 and the other species of Paracoccus. From these results, we considered strain BDN-1 as a novel species for which we propose the name Paracoccus ferrooxidans. Apart from [Fe(II)EDTA]2-, BDN-1 could also use thiosulfate and thiocyanate as inorganic electron donors. Nitrate, nitrite, N2O, [Fe(II)EDTA.NO]2- and oxygen could be used by strain BDN-1 as electron acceptors. Repeated transfer on a culture medium with bicarbonate as the sole carbon source confirmed that strain BDN-1 was a facultative autotroph. [Fe(II)EDTA]2- oxidation dependent denitrification was also performed by other Paracoccus species, that were closely affiliated to P. ferrooxidans.