Hsp70 Inhibits Aggregation of IAPP by Binding to the Heterogeneous Prenucleation Oligomers

Molecular chaperone Hsp70 plays important roles in the pathology of amyloid diseases by inhibiting aberrant aggregation of proteins. However, the biophysical mechanism of the interaction of Hsp70 with the intrinsically disordered proteins (IDPs) is unclear. Here, we report that Hsp70 inhibits aggregation of islet amyloid polypeptide (IAPP) at substoichiometric concentrations under diverse solution conditions, including in the absence of ATP. The inhibitory effect is strongest if Hsp70 is added in the beginning of aggregation but progressively less if added later, indicating a role for Hsp70 in preventing nucleation of IAPP. However, ensemble measurement of the binding affinity suggests poor interactions between Hsp70 and IAPP. Therefore, we hypothesize that the interaction must involve a rare species (e.g., the oligomeric intermediates of IAPP). Size exclusion chromatography and field flow fractionation are then used to fractionate the constituent species. Multiangle light scattering and fluorescence correlation spectroscopy measurements indicate that the dominant fraction in size exclusion chromatography contains a few nanomolar Hsp70-IAPP complexes amid several μmoles of free Hsp70. Using single-particle two-color coincidence detection measurements, we detected a minor fraction that exhibits fluorescence bursts arising from heterogeneous oligomeric complexes of IAPP and Hsp70. Taken together, our results indicate that Hsp70 interacts poorly with the monomers but strongly with oligomers of IAPP. This is likely a generic feature of the interactions of Hsp70 chaperones with the amyloidogenic IDPs. Whereas high-affinity interactions with the oligomers prevent aberrant aggregation, poor interaction with the monomers averts interference with the physiological functions of the IDPs.     

Complete Genome Sequence of Penicillium oxalicum Strain SGAir0226 Isolated from Outdoor Tropical Air in Singapore

Mycopathologia - Penicillium oxalicum strain SGAir0226 was isolated from a tropical air sample collected in Singapore. The complete genome was assembled from long reads obtained from...     

Concentration- and stage-specific effects of nitrite on colon cancer cell lines

Colorectal cancer (CRC) is the second leading cause of cancer-related death in the United States. Nitrite in cured meats is thought to contribute to increased incidence of colon cancer. We sought to determine the effect of nitrite on human colon cancer cell lines at different stages. Our results indicate nitrite has no effect on proliferation of stage 1 SW116 colon cancer cells, while nitrite inhibits proliferation of stage 2 SW480 at 10 nM–100 μM and inhibits stage 3 HCT15 proliferation at 100 nM–1 μM, but promotes a significant increase in proliferation on stage 4 COLO205 cells at 100 μM. Furthermore, nitrite inhibited invasion into Matrigel® of stage 3 SW480 colon cancer cells in a concentration-dependent manner. However, it significantly promotes the invasion of stage 4 cells at 100 μM. Our FACS data demonstrated that nitrite decreased cell cycle progression in SW480 and HCT15 with arrested G2/M transition and delayed G1 phase entry in a concentration-dependent manner. However, 100 μM nitrite promoted cell cycle progression in COLO205 cells with increased S-phase entry. Taken together, our data indicate nitrite inhibits cancer cell progression at low concentrations and early stage but promotes cancer cell progression at higher concentrations in cells representing stage 4 colon carcinomas.     

The Phylogeography of Y-Chromosome Haplogroup H1a1a-M82 Reveals the Likely Indian Origin of the European Romani Populations

Linguistic and genetic studies on Roma populations inhabited in Europe have unequivocally traced these populations to the Indian subcontinent. However, the exact parental population group and time of the out-of-India dispersal have remained disputed. In the absence of archaeological records and with only scanty historical documentation of the Roma, comparative linguistic studies were the first to identify their Indian origin. Recently, molecular studies on the basis of disease-causing mutations and haploid DNA markers (i.e. mtDNA and Y-chromosome) supported the linguistic view. The presence of Indian-specific Y-chromosome haplogroup H1a1a-M82 and mtDNA haplogroups M5a1, M18 and M35b among Roma has corroborated that their South Asian origins and later admixture with Near Eastern and European populations. However, previous studies have left unanswered questions about the exact parental population groups in South Asia. Here we present a detailed phylogeographical study of Y-chromosomal haplogroup H1a1a-M82 in a data set of more than 10,000 global samples to discern a more precise ancestral source of European Romani populations. The phylogeographical patterns and diversity estimates indicate an early origin of this haplogroup in the Indian subcontinent and its further expansion to other regions. Tellingly, the short tandem repeat (STR) based network of H1a1a-M82 lineages displayed the closest connection of Romani haplotypes with the traditional scheduled caste and scheduled tribe population groups of northwestern India.     

Design and docking studies of [diethylenetriaminepentaacetic acid-(amino acid)2] with acetylcholine receptor as a molecular imaging agent for single-photon emission computed tomographic application

The acetylcholine receptor is an essential link between the brain and the muscles, so it is a sensitive location for attack. In this study, some reversible [diethylenetriaminepentaacetic acid-(amino acid)2] have been docked computationally to the active site of the acetylcholine receptor. The induced fit method was employed to perform the automolecular docking for these systems. The result of docking studies generated thermodynamic properties, such as free energy of bindings (Glide score) and their weak electrostatic interactions. On the basis of these results, scintigraphic imaging studies were performed in mice. Among the radiotracers evaluated in this study, compound derived from 5-hydroxytryptophan/tryptophan exhibited remarkable localization in the brain, whereas radiotracer derived from l-histidine shows moderate accumulation in the brain. Preliminary studies with these amino acid-based ligands are encouraging to carrying out further in vivo experiments for targeted imaging.     

Genetic affinities of the central Indian tribal populations

Background

The central Indian state Madhya Pradesh is often called as ‘heart of India’ and has always been an important region functioning as a trinexus belt for three major language families (Indo-European, Dravidian and Austroasiatic). There are less detailed genetic studies on the populations inhabited in this region. Therefore, this study is an attempt for extensive characterization of genetic ancestries of three tribal populations, namely; Bharia, Bhil and Sahariya, inhabiting this region using haploid and diploid DNA markers.

Methodology/Principal Findings

Mitochondrial DNA analysis showed high diversity, including some of the older sublineages of M haplogroup and prominent R lineages in all the three tribes. Y-chromosomal biallelic markers revealed high frequency of Austroasiatic-specific M95-O2a haplogroup in Bharia and Sahariya, M82-H1a in Bhil and M17-R1a in Bhil and Sahariya. The results obtained by haploid as well as diploid genetic markers revealed strong genetic affinity of Bharia (a Dravidian speaking tribe) with the Austroasiatic (Munda) group. The gene flow from Austroasiatic group is further confirmed by their Y-STRs haplotype sharing analysis, where we determined their founder haplotype from the North Munda speaking tribe, while, autosomal analysis was largely in concordant with the haploid DNA results.

Conclusions/Significance

Bhil exhibited largely Indo-European specific ancestry, while Sahariya and Bharia showed admixed genetic package of Indo-European and Austroasiatic populations. Hence, in a landscape like India, linguistic label doesn''t unequivocally follow the genetic footprints.     

Population genetic structure of Penaeus monodon, in relation to monsoon current patterns in Southwest, East and Andaman coastal waters of India

The black tiger shrimp (Penaeus monodon), a commercially important penaeid species, is widely distributed across the Indo-Pacific region. Genetic diversity in P. monodon collected from eight geographical regions in Southwest, East and Andaman coastal waters of India (N = 418) was investigated using 10 polymorphic microsatellite loci. Average observed heterozygosity at sampled loci were high, ranging from 0.643 (Coromandel Coast) to 0.753 (South Andaman). Pairwise F_ST (ranged from 0.005 to 0.078) and R_ST (ranged from 0.005 to 0.171) estimates revealed surprisingly strong and statistically significant genetic structure among tiger shrimp populations. A synthetic map generated by multidimensional scaling shows an apparent cline in allele frequencies paralleling the roughly circular flow of surface currents in the Bay of Bengal. Significant heterozygote deficiencies were noted in most population samples at most loci. Andaman Island sites showed the highest diversity. Recognition of high genetic diversity and distinct population structuring of P. monodon in Indian seas has important implications for future domestication of this species in India, for two reasons: identification of the best wild founding stocks for aquaculture and, subsequently, the potential impacts of release of domesticates to the wild, either accidentally or deliberately (i.e. for stock enhancement).     

Deregulated hepatic metabolism exacerbates impaired testosterone production in Mrp4-deficient mice

The physiological role of multidrug resistance protein 4 (Mrp4, Abcc4) in the testes is unknown. We found that Mrp4 is expressed primarily in mouse and human Leydig cells; however, there is no current evidence that Mrp4 regulates testosterone production. We investigated its role in Leydig cells, where testosterone production is regulated by cAMP, an intracellular messenger formed when the luteinizing hormone (LH) receptor is activated. Because Mrp4 regulates cAMP, we compared testosterone levels in Mrp4(-/-) and Mrp4(+/+) mice. Young Mrp4(-/-) mice had significantly impaired gametogenesis, reduced testicular testosterone, and disruption of Leydig cell cAMP homeostasis. Both young and adult mice had impaired testosterone production. In Mrp4(-/-) primary Leydig cells treated with LH, intracellular cAMP production was impaired and cAMP-response element-binding protein (CREB) phosphorylation was strongly attenuated. Notably, expression of CREB target genes that regulate testosterone biosynthesis was reduced in Mrp4(-/-) Leydig cells in vivo. Therefore, Mrp4 is required for normal Leydig cell testosterone production. However, adult Mrp4(-/-) mice are fertile, with a normal circulating testosterone concentration. The difference is that in 3-week-old Mrp4(-/-) mice, disruption of gonadal testosterone production up-regulates hepatic Cyp2b10, a known testosterone-metabolizing enzyme. Therefore, defective testicular testosterone production de-regulates hepatic Cyp-mediated testosterone metabolism to disrupt gametogenesis. These findings have important implications for understanding the side effects of therapeutics that disrupt Mrp4 function and are reported to alter androgen production.     

Measurement of net ecosystem production and ecosystem respiration in a Zoysia japonica grassland,central Japan,by the chamber method

Measuring light, temperature, soil moisture, and growth provides a better understanding of net ecosystem production (NEP), ecosystem respiration (R _eco), and their response functions. Here, we studied the variations in NEP and R _eco in a grassland dominated by a perennial warm-season C₄ grass, Zoysia japonica. We used the chamber method to measure NEP and R _eco from August to September 2007. Biomass and leaf area index (LAI) were also measured to observe their effects on NEP and R _eco. Diurnal variations in NEP and R _eco were predicted well by light intensity (PPFD) and by soil temperature, respectively. Maximum NEP (NEP_max) values on days of year 221, 233, 247, and 262, were 2.44, 2.55, 3.90, and 4.17 μmol m⁻² s⁻¹, respectively. Throughout the growing period, the apparent quantum yield (α) increased with increasing NEP_max that ranged from 0.0154 to 0.0515, and NEP responded to the soil temperature changes by 44% and R _eco changes by 48%, and R _eco responded from 88 to 94% with the soil temperature diurnally. NEP’s light response and R _eco’s temperature response were affected by soil water content; more than 27% of the variation in NEP and 67% of the variation in R _eco could be explained by this parameter. NEP was strongly correlated with biomass and LAI, but R _eco was not, because environmental variables affected R _eco more strongly than growth parameters. Using the light response of NEP, the temperature response of R _eco, and meteorological data, daily NEP and R _eco were estimated at 0.67, 0.81, 1.17, and 1.56 g C m⁻², and at 2.88, 2.50, 3.51, and 3.04 g C m⁻², respectively, on days of year 221, 233, 247, and 262. The corresponding daily gross primary production (NEP + R _eco) was 3.5, 3.3, 4.6, and 4.6 g C m⁻².     

Carbon dynamics and budget in a Zoysia japonica grassland, central Japan

The ecosystem carbon budget was estimated in a Japanese Zoysia japonica grassland. The green biomass started to grow in May and peaked from mid-July to September. Seasonal variations in soil CO₂ flux and root respiration were mediated by changes in soil temperature. Annual soil CO₂ flux was 1,121.4 and 1,213.6 g C m⁻² and root respiration was 471.0 and 544.3 g C m⁻² in 2007 and 2008, respectively. The root respiration contribution to soil CO₂ flux ranged from 33% to 71%. During the growing season, net primary production (NPP) was 747.5 and 770.1 g C m⁻² in 2007 and 2008, respectively. The biomass removed by livestock grazing (GL) was 122.1 and 102.7 g C m⁻², and the livestock returned 28.2 and 25.6 g C m⁻² as fecal input (FI) in 2007 and 2008, respectively. The decomposition of FI (DL, the dry weight loss due to decomposition) was very low, 1.5 and 1.4 g C m⁻², in 2007 and 2008. Based on the values of annual NPP, soil CO₂ flux, root respiration, GL, FI, and DL, the estimated carbon budget of the grassland was 1.7 and 22.3 g C m⁻² in 2007 and 2008, respectively. Thus, the carbon budget of this Z. japonica grassland ecosystem remained in equilibrium with the atmosphere under current grazing conditions over the 2 years of the study.