Chaperone Mediated Protective Protein Aggregation and Spatial Quality Control

The accumulation of amyloid-like aggregates is a characteristic of protein conformational disorders such as Huntington Disease, but whether amyloid-like aggregation is causative or a cytoprotective mechanism remains unclear. Molecular chaperones act as the front line of defense against proteotoxicity, as they protect cells by partitioning misfolded proteins towards refolding, degradation, or assembly into large benign aggregates. Herein, a yeast model of proteotoxicity was utilized to study cellular mechanisms for protective aggregation. Ectopic expression of polyglutamine (polyQ) expanded Huntingtin (Htt103Q) is toxic in yeast, and targeting it to the nucleus enhances toxicity while decreasing SDS-resistant aggregation. I utilized this nuclear Htt103Q as the substrate for a high copy toxicity suppressor screen in yeast which identified Sti1 as a molecule that promotes protective aggregation of Htt103Q. The Hsp70 co-chaperone Sti1 regulates spatial quality control of amyloid-like proteins as it induces formation of perinuclear foci containing SDS-resistant material. Accumulation of distinct perinuclear foci correlates with suppression of toxicity and increased complex formation with the Hsp70/Hsp40 chaperone machinery. Endogenous Sti1 appears to be a crucial player in a chaperone-facilitated protective aggregation pathway, because deletion of Sti1 enhances Htt103Q toxicity while decreasing aggregation. In addition to Sti1, the screen produced a group of polyQ-rich proteins, Nab3, Pop2 and Cbk1, as high-copy suppressors of Htt103Q toxicity. PolyQ proteins play different roles in Htt103Q toxicity, either to a detrimental outcome where a Q-rich protein is titrated away from its normal function, or beneficially via interactions that promote protective aggregation. Over-expression of Nab3 appears to suppress Htt103Q toxicity by replacing a functional pool of Nab3 that was lost to aberrant polyQ interaction. Over-expression of Pop2 and Cbk1each suppresses toxicity and promotes aggregation of Htt103Q in a slightly different way, but neither can carry out this function in the absence of Sti1. Therefore, Pop2 and Cbk1 act upstream of Sti1 in pathway which promotes protective aggregation of amyloid-like assemblies. These proteins alter the cellular outcome of proteotoxic insult caused by Htt103Q by modulating spatial quality control.Doctor of Philosoph

The Evolution of Luminous Compact Blue Galaxies: Disks or Spheroids?

Luminous compact blue galaxies (LCBGs) are a diverse class of galaxies characterized by high luminosity, blue color, and high surface brightness that sit at the critical juncture of galaxies evolving from the blue to the red sequence. As part of our multi-wavelength survey of local LCBGs, we have been studying the HI content of these galaxies using both single-dish telescopes and interferometers. Our goals are to determine if single-dish HI observations represent a true measure of the dynamical mass of LCBGs and to look for signatures of recent interactions that may be triggering star formation in LCBGs. Our data show that while some LCBGs are undergoing interactions, many appear isolated. While all LCBGs contain HI and show signatures of rotation, the population does not lie on the Tully-Fisher relation nor can it evolve onto it. Furthermore, the HI maps of many LCBGs show signatures of dynamically hot components, suggesting that we are seeing the formation of a thick disk or spheroid in at least some LCBGs. There is good agreement between the HI and H-alpha kinematics for LCBGs, and both are similar in appearance to the H-alpha kinematics of high redshift star-forming galaxies. Our combined data suggest that star formation in LCBGs is primarily quenched by virial heating, consistent with model predictions.Comment: 4 pages, 2 figures, to appear in the proceedings of IAU Symposium 277, "Tracing the Ancestry of Galaxies on the Land of our Ancestors", eds. C. Carignan, K.C. Freeman, and F. Combe

Domains of Vulnerability, Resilience, Health Habits, and Mental and Physical Health for Health Disparities Research

Health disparities associated with severe mental illness (SMI) have become a major public health concern. The disparities are not directly due to the SMI. They involve the same leading causes of premature death as in the general population. The causes of the disparities are therefore suspected to reflect differences in health-related behavior and resilience. As with other problems associated with SMI, studying non-clinical populations at risk for future onset provides important clues about pathways, from vulnerability to unhealthy behavior and compromised resilience, to poor health and reduced quality of life. The purpose of this study was to identify possible pathways in a sample of public university students. Four domains of biosystemic functioning with a priori relevance to SMI-related vulnerability and health disparities were identified. Measures reflecting various well-studied constructs within each domain were factor-analyzed to identify common sources of variance within the domains. Relationships between factors in adjacent domains were identified with linear multiple regression. The results reveal strong relationships between common factors across domains that are consistent with pathways from vulnerability to health disparities, to reduced quality of life. Although the results do not provide dispositive evidence of causal pathways, they serve as a guide for further, larger-scale, longitudinal studies to identify causal processes and the pathways they follow to health consequences

Amyloid in neurodegenerative diseases: Friend or foe?

Accumulation of amyloid-like aggregates is a hallmark of numerous neurodegenerative disorders such as Alzheimer’s and polyglutamine disease. Yet, whether the amyloid inclusions found in these diseases are toxic or cytoprotective remains unclear. Various studies suggest that the toxic culprit in the amyloid folding pathway is actually a soluble oligomeric species which might interfere with normal cellular function by a multifactorial mechanism including aberrant protein-protein interactions. Molecular chaperones suppress toxicity of amyloidogenic proteins by inhibiting aggregation of non-native disease substrates and targeting them for refolding or degradation. Paradoxically, recent studies also suggest a protective action of chaperones in their promotion of the assembly of large, tightly packed, benign aggregates that sequester toxic protein species

Mand Training: An Examination of Response-Class Structure in Three Children With Autism and Severe Language Delays

Our primary purpose in this study was to examine the structure of a response class when new members are acquired through mand training. To do this, we replaced existing mands (e.g., reaching) in three children with autism with two new functionally equivalent mands. Next, we examined their responding under immediate- and delayed-reinforcement conditions. Then, we assessed generalization to novel social partners. We employed a reversal design to examine the effectiveness of mand training and to assess responding under both immediate- and delayed-reinforcement conditions. Our results suggest that all children acquired the new mands and that two of the children emitted these responses as replacements when the social partner did not provide access to the reinforcer contingent on the child\u27s first mand. Generalization data indicate that all three children emitted the new mands and two of the children alternated between the new mands with novel social partners. We discuss the clinical implications and the conceptual significance of teaching multiple replacement mands to children with autism and severe language delays

Understanding and mitigating thiaminase activity in silver carp

A deficiency of thiamine (vitamin B1), an essential cofactor for enzymes involved in metabolic processes, can be caused by the enzyme thiaminase. Thiaminase in food stocks has been linked to morbidity and mortality due to thiamine depletion in many ecologically and economically important species. Thiaminase activity has been detected in certain bacteria, plants, and fish species, including carp. The invasive silver carp (Hypophthalmichthys molitrix) presents an enormous burden to ecosystems throughout the Mississippi River watershed. Its large biomass and nutritional content offer an attractive possibility as a food source for humans, wild animals, or pets. Additionally, harvesting this fish could alleviate some of the effects of this species on waterways. However, the presence of thiaminase would detract from its value for dietary consumption. Here we confirm the presence of thiaminase in several tissues from silver carp, most notably the viscera, and systematically examine the effects of microwaving, baking, dehydrating, and freeze-drying on thiaminase activity. Certain temperatures and durations of baking and microwaving reduced thiaminase activity to undetectable levels. However, caution should be taken when carp tissue is concentrated by processes without sufficient heat treatment, such as freeze-drying or dehydration, which results in concentration, but not inactivation of the enzyme. The effects of such treatments on the ease of extracting proteins, including thiaminase, and the impact on data interpretation using the 4-nitrothiophenol (4-NTP) thiaminase assay were considered

The Hsp70/90 cochaperone, Sti1, suppresses proteotoxicity by regulating spatial quality control of amyloid-like proteins

Escape of aberrant proteins from protein quality control leads to accumulation of toxic protein species. Sti1 interacts with Hsp70 to mediate spatial PQC of amyloid-like proteins by regulating their distribution in different intracellular protein-handling depots. Sti1 suppresses proteotoxicity by targeting amyloid-like proteins to perinuclear foci.Conformational diseases are associated with the conversion of normal proteins into aggregation-prone toxic conformers with structures similar to that of β-amyloid. Spatial distribution of amyloid-like proteins into intracellular quality control centers can be beneficial, but cellular mechanisms for protective aggregation remain unclear. We used a high-copy suppressor screen in yeast to identify roles for the Hsp70 system in spatial organization of toxic polyglutamine-expanded Huntingtin (Huntingtin with 103Q glutamine stretch [Htt103Q]) into benign assemblies. Under toxic conditions, Htt103Q accumulates in unassembled states and speckled cytosolic foci. Subtle modulation of Sti1 activity reciprocally affects Htt toxicity and the packaging of Htt103Q into foci. Loss of Sti1 exacerbates Htt toxicity and hinders foci formation, whereas elevation of Sti1 suppresses Htt toxicity while organizing small Htt103Q foci into larger assemblies. Sti1 also suppresses cytotoxicity of the glutamine-rich yeast prion [RNQ+] while reorganizing speckled Rnq1–monomeric red fluorescent protein into distinct foci. Sti1-inducible foci are perinuclear and contain proteins that are bound by the amyloid indicator dye thioflavin-T. Sti1 is an Hsp70 cochaperone that regulates the spatial organization of amyloid-like proteins in the cytosol and thereby buffers proteotoxicity caused by amyloid-like proteins

Taxonomic shifts in arbuscular mycorrhizal fungal communities with shade and soil nitrogen across conventionally managed and organic coffee agroecosystems

The composition of arbuscular mycorrhizal fungal (AMF) communities should reflect not only responses to host and soil environments, but also differences in functional roles and costs vs. benefits among arbuscular mycorrhizal fungi. The coffee agroecosystem allows exploration of the effects of both light and soil fertility on AMF communities, because of the variation in shade and soil nutrients farmers generate through field management. We used high-throughput ITS2 sequencing to characterize the AMF communities of coffee roots in 25 fields in Costa Rica that ranged from organic management with high shade and no chemical fertilizers to conventionally managed fields with minimal shade and high N fertilization, and examined relationships between AMF communities and soil and shade parameters with partial correlations, NMDS, PERMANOVA, and partial least squares analysis. Gigasporaceae and Acaulosporaceae dominated coffee AMF communities in terms of relative abundance and richness, respectively. Gigasporaceae richness was greatest in conventionally managed fields, while Glomeraceae richness was greatest in organic fields. While total AMF richness and root colonization did not differ between organic and conventionally managed fields, AMF community composition did; these differences were correlated with soil nitrate and shade. OTUs differing in relative abundance between conventionally managed and organic fields segregated into four groups: Gigasporaceae associated with high light and nitrate availability, Acaulosporaceae with high light and low nitrate availability, Acaulosporaceae and a single relative of Rhizophagus fasciculatus with shade and low nitrate availability, and Claroideoglomus/Glomus with conventionally managed fields but uncorrelated with shade and soil variables. The association of closely related taxa with similar shade and light availabilities is consistent with phylogenetic trait conservatism in AM fungi

Contrasting patterns of functional diversity in coffee root fungal communities associated with organic and conventionally managed fields

The structure and function of fungal communities in the coffee rhizosphere are influenced by crop environment. Because coffee can be grown along a management continuum from conventional application of pesticides and fertilizers in full sun to organic management in a shaded understory, we used coffee fields to hold host constant while comparing rhizosphere fungal communities under markedly different environmental conditions with regard to shade and inputs. We characterized the shade and soil environment in 25 fields under conventional, organic, or transitional management in two regions of Costa Rica. We amplified the internal transcribed spacer 2 (ITS2) region of fungal DNA from coffee roots in these fields and characterized the rhizosphere fungal community via high-throughput sequencing. Sequences were assigned to guilds to determine differences in functional diversity and trophic structure among coffee field environments. Organic fields had more shade, a greater richness of shade tree species, and more leaf litter and were less acidic, with lower soil nitrate availability and higher soil copper, calcium, and magnesium availability than conventionally managed fields, although differences between organic and conventionally managed fields in shade and calcium and magnesium availability depended on region. Differences in richness and community composition of rhizosphere fungi between organic and conventionally managed fields were also correlated with shade, soil acidity, and nitrate and copper availability. Trophic structure differed with coffee field management. Saprotrophs, plant pathogens, and mycoparasites were more diverse, and plant pathogens were more abundant, in organic than in conventionally managed fields, while saprotroph-plant pathogens were more abundant in conventionally managed fields. These differences reflected environmental differences and depended on region