Inhibitor-Induced Conformational Stabilization and Structural Alteration of a Mip-Like Peptidyl Prolyl cis-trans Isomerase and Its C-Terminal Domain

FKBP22, an Escherichia coli-encoded PPIase (peptidyl-prolyl cis-trans isomerase) enzyme, shares substantial identity with the Mip-like pathogenic factors, caries two domains, exists as a dimer in solution and binds some immunosuppressive drugs (such as FK506 and rapamycin) using its C-terminal domain (CTD). To understand the effects of these drugs on the structure and stability of the Mip-like proteins, rFKBP22 (a chimeric FKBP22) and CTD⁺ (a CTD variant) have been studied in the presence and absence of rapamycin using different probes. We demonstrated that rapamycin binding causes minor structural alterations of rFKBP22 and CTD⁺. Both the proteins (equilibrated with rapamycin) were unfolded via the formation of intermediates in the presence of urea. Further study revealed that thermal unfolding of both rFKBP22 and rapamycin-saturated rFKBP22 occurred by a three-state mechanism with the synthesis of intermediates. Intermediate from the rapamycin-equilibrated rFKBP22 was formed at a comparatively higher temperature. All intermediates carried substantial extents of secondary and tertiary structures. Intermediate resulted from the thermal unfolding of rFKBP22 existed as the dimers in solution, carried an increased extent of hydrophobic surface and possessed relatively higher rapamycin binding activity. Despite the formation of intermediates, both the thermal and urea-induced unfolding reactions were reversible in nature. Unfolding studies also indicated the considerable stabilization of both proteins by rapamycin binding. The data suggest that rFKBP22 or CTD⁺ could be exploited to screen the rapamycin-like inhibitors in the future.     

α‐synuclein‐induced mitochondrial dysfunction in isolated preparation and intact cells: Implications in the pathogenesis of Parkinson's disease

This study has shown that purified recombinant human α‐synuclein (20 μM) causes membrane depolarization and loss of phosphorylation capacity of isolated purified rat brain mitochondria by activating permeability transition pore complex. In intact SHSY5Y (human neuroblastoma cell line) cells, lactacystin (5 μM), a proteasomal inhibitor, causes an accumulation of α‐synuclein with concomitant mitochondrial dysfunction and cell death. The effects of lactacystin on intact SHSY5Y cells are, however, prevented by knocking down α‐synuclein expression by specific siRNA. Furthermore, in wild‐type (non‐transfected) SHSY5Y cells, the effects of lactacystin on mitochondrial function and cell viability are also prevented by cyclosporin A (1 μM) which blocks the activity of the mitochondrial permeability transition pore. Likewise, in wild‐type SHSY5Y cells, typical mitochondrial poison like antimycin A (50 nM) produces loss of cell viability comparable to that of lactacystin (5 μM). These data, in combination with those from isolated brain mitochondria, strongly suggest that intracellularly accumulated α‐synuclein can interact with mitochondria in intact SHSY5Y cells causing dysfunction of the organelle which drives the cell death under our experimental conditions. The results have clear implications in the pathogenesis of sporadic Parkinson's disease.

     

Gut physiology mediates a trade‐off between adaptation to malnutrition and susceptibility to food‐borne pathogens

The animal gut plays a central role in tackling two common ecological challenges, nutrient shortage and food‐borne parasites, the former by efficient digestion and nutrient absorption, the latter by acting as an immune organ and a barrier. It remains unknown whether these functions can be independently optimised by evolution, or whether they interfere with each other. We report that Drosophila melanogaster populations adapted during 160 generations of experimental evolution to chronic larval malnutrition became more susceptible to intestinal infection with the opportunistic bacterial pathogen Pseudomonas entomophila. However, they do not show suppressed immune response or higher bacterial loads. Rather, their increased susceptibility to P. entomophila is largely mediated by an elevated predisposition to loss of intestinal barrier integrity upon infection. These results may reflect a trade‐off between the efficiency of nutrient extraction from poor food and the protective function of the gut, in particular its tolerance to pathogen‐induced damage.     

The molecular genetic basis of age-related macular degeneration: an overview

Age-related macular degeneration (AMD) is a complex disorder of the eye and the third leading cause of blindness worldwide. With a multifactorial etiology, AMD results in progressive loss of central vision affecting the macular region of the eye in elderly. While the prevalence is relatively higher in the Caucasian populations, it has gradually become a major public health issue among the non-Caucasian populations (including Indians) as well due to senescence, rapidly changing demographics and life-style factors. Recent genome-wide association studies (GWAS) on large case-control cohorts have helped in mapping genes in the complement cascade that are involved in the regulation of innate immunity with AMD susceptibility. Genes involved with mitochondrial oxidative stress and extracellular matrix regulation also play a role in AMD pathogenesis. Majority of the associations observed in complement (CFH, CFB, C2 and C3) and other (ARMS2 and HTRA1) genes have been replicated in diverse populations worldwide. Gene-gene (CFH with ARMS2 and HTRA1) interactions and correlations with environmental traits (smoking and body mass index) have been established as significant covariates in AMD pathology. In this review, we have provided an overview on the underlying molecular genetic mechanisms in AMD worldwide and highlight the AMD-associated-candidate genes and their potential role in disease pathogenesis.     

Polycomb Repressive Complex 2 Regulates MiR-200b in Retinal Endothelial Cells: Potential Relevance in Diabetic Retinopathy

Glucose-induced augmented vascular endothelial growth factor (VEGF) production is a key event in diabetic retinopathy. We have previously demonstrated that downregulation of miR-200b increases VEGF, mediating structural and functional changes in the retina in diabetes. However, mechanisms regulating miR-200b in diabetes are not known. Histone methyltransferase complex, Polycomb Repressive Complex 2 (PRC2), has been shown to repress miRNAs in neoplastic process. We hypothesized that, in diabetes, PRC2 represses miR-200b through its histone H3 lysine-27 trimethylation mark. We show that human retinal microvascular endothelial cells exposed to high levels of glucose regulate miR-200b repression through histone methylation and that inhibition of PRC2 increases miR-200b while reducing VEGF. Furthermore, retinal tissue from animal models of diabetes showed increased expression of major PRC2 components, demonstrating in vivo relevance. This research established a repressive relationship between PRC2 and miR-200b, providing evidence of a novel mechanism of miRNA regulation through histone methylation.     

In vivo sister chromatid differentiation and baseline sister chromatid exchanges in a mouse ascites tumour model.

Induction of differentially stained sister chromatids at G2/M and determination of baseline sister chromatid exchanges (SCEs) in ascites form of mouse sarcoma 180 cell line have been done by in vivo incorporation of 5-bromodeoxyuridine (BrdU) for two consecutive DNA replication cycles. The baseline SCE frequency is 6.24 at log phase of tumour growth.     

Boosted UV Sensitivity of Er-Doped In2O3 Thin Films Using Plasmonic Ag Nanoparticle-Based Surface Texturing

Plasmonics - Ag nanoparticles (NPs) were deposited on the sol-gel-processed Erbium-doped Indium Oxide (In2O3:Er) thin films (TFs) using thermal evaporation cum glancing angle deposition technique...     

Membrane perturbation through novel cell-penetrating peptides influences intracellular accumulation of imatinib mesylate in CML cells

Chronic myeloid leukemia is a stem cell disease with the presence of Philadelphia chromosome generated through reciprocal translocation of chromosome 9 and 22. The use of first- and second-generation tyrosine kinase inhibitors has been successful to an extent. However, resistance against such drugs is an emerging problem. Apart from several drug-resistant mechanisms, drug influx/efflux ratio appears to be one of the key determinants of therapeutic outcomes. In addition, intracellular accumulation of drug critically depends on cell membrane fluidity and lipid raft dynamics. Previously, we reported two novel cell-penetrating peptides (CPPs), namely, cationic IR15 and anionic SR11 present in tryptic digest of Abrus agglutinin. Here, the potential of IR15 and SR11 to influence intracellular concentration of imatinib has been evaluated. Fluorescent correlation spectroscopy and lifetime imaging were employed to map membrane fluidity and lipid raft distribution following peptide-drug co-administration. Results show that IR15 and SR11 are the two CPPs which can modulate membrane fluidity and lipid raft distribution in K562 cells. Both IR15 and SR11 significantly reduce the viability of CML cells in the presence of imatinib by increasing the intracellular accumulation of the drug.     

New Species and New Records of Eriophyoid Mites (Acari: Eriophyoidea) from West Bengal,India

Two new species viz., Acaricalus indicus n. sp. from Fern (indet) and Neooxycenus dilleniae n. sp. from Dillenia pentagyna Roxb. (Dilleniaceae) are described from West Bengal. Four species viz., Acaphyllisa araucuriae Flechtmann (2000), Aculops pretoriensis Smith Meyer and Ueckermann (1990), Tetra tyrohylae Smith Meyer (1992) and Tetra visci Smith Meyer (1992) are recorded for the first time from India. Besides, 23 other species are reported for the first time from West Bengal. An eriophyoid species is recorded for the first time from a species of Fern in India.