No description available.

No description available.

Protein phosphorylation is a reversible post-translation modification that is essential in cell signaling. It is estimated that a third of all cellular proteins are phosphorylated (reviewed in Ficarro et al., 2002), with more than 98% of those phosphorylation events occurring on serine and threonine residues (Olsen et al., 2006). Kinases are the necessary enzymes for phosphorylation and protein phosphatases dynamically reverse this action. While the mechanisms of substrate recognition for kinases have been well-characterized to date, the same is not true for phosphatases that play an equally important role in opposing kinase function and determining global phosphorylation levels in cells. This dichotomy has also translated into the clinic, where there has been a persistently narrow research focus on the development of small-molecule kinase inhibitors for use as chemotherapeutic agents, without an equal effort being placed into the generation of the analogous phosphatase activators (reviewed in Westermarck, 2018). Members of the phosphoprotein phosphatase (PPP) family of serine/threonine phosphatases are responsible for the majority of dephosphorylation in eukaryotic cells, with protein phosphatase 1 (PP1) and protein phosphatase 2A (PP2A) accounting for more than 90% of the total phosphatase activity (Moorhead et al., 2007; Virshup and Shenolikar, 2009). Structurally, PP2A is a trimeric holoenzyme consisting of a scaffold (A) subunit, a regulatory (B) subunit, and a catalytic (C) subunit. B55α is a ubiquitous regulatory subunit that is reported to target many substrates with critical functions in processes including cell division. A long-standing question that has persisted in the field of cellular signaling is as to how the most abundant serine/threonine PP2A holoenzyme, PP2A/B55α, specifically recognizes substrates and presents them to the enzyme active site for subsequent dephosphorylation. Such critical data have only recently become well understood for the B56 family of ‘B’ regulatory subunits, where an LxxIxE short linear motif (or SLiM) has been identified in a subset of protein targets and shown via crystal structure analysis to dock into a 100% conserved binding pocket on the B56 surface (Hertz et al., 2016; Wang et al., 2016a; Wang et al., 2016b; Wu et al., 2017). Here, we show how B55α recruits p107, a pRB-related tumor suppressor and B55α substrate. Using molecular and cellular approaches, we identified a conserved region 1 (R1, residues 615-626) encompassing the strongest p107 binding site. This enabled us to identify an “HxRVxxV619-625” SLiM in p107 as necessary for B55α binding and dephosphorylation of the proximal pSer-615 in vitro and in cells. Numerous additional PP2A/B55α substrates, including TAU, contain a related SLiM C-terminal from a proximal phosphosite, allowing us to propose a consensus SLiM sequence, “p[ST]-P-x(5-10)-[RK]-V-x-x-[VI]-R”. In support of this, mutation of conserved SLiM residues in TAU dramatically inhibits dephosphorylation by PP2A/B55α, validating its generality. Moreover, a data-guided computational model details the interaction of residues from the conserved p107 SLiM, the B55α groove, and phosphosite presentation to the PP2A/C active site. Altogether, these data provide key insights into PP2A/B55α mechanisms of substrate recruitment and active site engagement, and also facilitate identification and validation of new substrates, a key step towards understanding the role of PP2A/B55α in many key cellular processes. As a parallel continuation of our efforts to identify novel B55α substrates/regulators, we generated mutant B55α constructs that occlude PP2A/A-C dimer engagement but retain substrate binding to the β-propeller structure (allowing us to interrogate direct interactors). Our preliminary AP-MS data led to the identification of several proteins that bound better to our “monomeric B55α” mutant compared to wild-type B55α in the context of the PP2A/B55α heterotrimer, including the centrosomal proteins HAUS6 and CEP170 (two substrates previously validated in a phosphoproteomic screen by our lab), suggesting that these mutants trap substrates as they cannot be dephosphorylated by PP2A/C. These analyses also identified an enrichment of T-complex protein 1 subunits in the “monomeric B55α” mutant elutions, further supporting the notion that these mutants may function as dominant negatives. Several additional proteins of interest were identified in the two independent rounds of mass spectrometry, including subunits of the DNA-directed RNA polymerases I, II, and IV, as well as the double-strand break repair protein MRE11, which can be followed up as potential novel B55α substrates. These studies can contribute to significant advances in our understanding of the network of proteins that B55α interacts with, and thus the signaling pathways that can be modulated by PP2A/B55α complexes in cells. Moreover, these advances can also provide translational benefits as has been demonstrated through the study of PP2A activators termed SMAPs, which demonstrate selective stabilization of PP2A/B56α complexes in cells that result in selective dephosphorylation of substrates including the oncogenic target c-MYC. / Biomedical Sciences

Two container production studies (nursery area and greenhouse) and a landscape performance study to evaluate bananas and cannas were performed at R. R. Foil Plant Science Research Center on the campus of Mississippi State University. Previous reports determined that there is greater need of K2O fertilization in addition to N for tropical monocot nutrition. Contradictory to previous cultural recommendations for landscapes, it was determined that a N:K2O ratio is not significant for container production of Musa, Ensete, and Canna in pine bark substrate. Nitrogen rate was the most significant variable in the containerized production of Musa, Ensete, and Canna. The purpose of the landscape performance study was to evaluate six cultivars of bananas for growth and cold hardiness. The three cultivars of bananas trialed which showed the greatest cold tolerance and vigor were Musa basjoo, Musella lasiocarpa, and Musa balbisiana ‘Thai Black’.

Since their conception, plastics have been a dominant product due to the versatility of use, and readily available raw materials. However, the production and consumption of synthetic plastics have continued to increase over the years, leading to a significant rise in plastic waste and its associated environmental impacts, such as the detrimental effects plastic waste has on ecosystems, including the presence of toxic microplastics and risks to marine life, are becoming the focus of criticism. Moreover, the contribution of plastic production to global warming through the usage of petroleum as a raw material cannot be understated. Solutions are being sought after to reduce the impact of this plastic waste, with one such solution being the replacement of the raw materials involved in plastic production. If a biologically degradable plastic product can be produced, then even if the dangers associated with plastic waste cannot be removed, they can be reduced. One method is the production of plastics using polyhydroxyalkanoates (PHA) as a replacement as these are shown to have similar properties as synthetic plastics while being 100% degradable. PHA production has existed since the 1960’s, but the process has always been too expensive to be a viable alternative to the cheaper petroleum-based products. A reduction of the production costs is needed for PHA to be an economically viable alternative, and there are two areas that contain the highest costs; The usage of expensive monocultural bacteria, and specially crafted carbon sources used to feed these bacteria to stimulate PHA accumulation. By switching to a multi-cultural bacterium and using readily available organic carbon sources can the costs of production be brought down, allowing the prospective biological plastics a chance to compete in the plastic market.  This thesis focuses on the usage of a multi-cultural bacterium collected from the water purification plant of a papermill, and the filtrate from the hydrothermal carbonisation (HTC) of sludge as the organic carbon source as materials in the production of PHA. The aim of the thesis is to investigate how successful PHA accumulation can occur using these two readily available waste products, and if successful to analyse the characteristics of any biological plastic that could be produced. The trials were performed in a cylindrical tank; one benchmark trial using acetic acid as the carbon source to be used as a reference for successful PHA accumulation, and five trials investigating the PHA accumulation that occurred using the HTC filtrate as the carbon source. The trials were analysed by extraction, TGA, FT-IR, TOC, and SS. During the trials pH, temperature and concentration of diffused oxygen was monitored. The trials indicated that the accumulation of PHA was possible, with various results. The most successful accumulation was observed in trial I-1, where PHA reached 12.45%, only slightly lower than the benchmark trials accumulation of 13.6%. Trials I-2 and I-3 also showed potential for high PHA content according to FTIR analysis. However, trials F-1 and F-2 failed to accumulate any PHA, and the inhibiting factors behind this were not fully understood. Possible reasons included high ammonia levels, incompatible bacteria, or imbalanced nutrient ratios. Various extraction methods were attempted to isolate the polymers found within the biomass for use in plastic production. While one extraction method was successful and used to analyse the PHA content found in the biomass, the amount of polymer that was extracted via this method was too small for use in plastic production, and as such the characteristic investigation of the plastic was unable to be completed. Overall, the study identified successful PHA accumulation in some trials but faced challenges and uncertainties regarding inhibiting factors and extraction methods. Future improvements should focus on standardizing experimental conditions and optimizing extraction techniques for better results.

Microbial community functional diversity enhances the degradation of organic matter and pollutants in the environment, but there is a growing concern that these ecosystem services may be altered by the introduction of emerging environmental contaminants including silver nanoparticles (AgNPs) into aquatic systems. We added 0, 25, 50, 75, 100, and 125 mg L−1 (nominal concentrations) of citrate-AgNP and polyvinylpyrrolidone-AgNP (PVP-AgNP) each to freshwater sediment and examined their antimicrobial effects on microbial communities using community-level physiological profiling. The results showed that citrate-AgNP decreased the overall microbial catabolic activity by 80% from 1.16 ± 0.02 to 0.23 ± 08 while PVP-AgNP decreased the catabolic activity by 51% from 1.25 ± 0.07 to 0.61 ± 0.19 at 125 mg L−1. Citrate-AgNP and PVP-AgNP caused a statistically significant reduction in substrate richness and substrate diversity that decreased microbial functional diversity. AgNPs decreased microbial catabolic capability and functional diversity at concentrations ranging from 0.12 ± 0.04 to 0.43 ± 0.07 mg Ag kg-1 which are lower than the predicted concentrations in freshwater sediment. To our knowledge, this is the first study to demonstrate inhibition of microbial functional diversity by citrate-AgNP and PVP-AgNP in a pathogen impaired stream. Citrate-AgNP caused greater inhibition of carbon substrate utilization but amino acids, carbohydrates, and carboxylic acids were the most affected carbon groups which led to a shift in the metabolic fingerprint pattern of the microbial community. AgNPs decreased the catabolic capability and the ability of the microbial community to degrade organic matter and a variety of pollutants in the environment.

Tardive dyskinesia (TD) is a serious side effect of certain antipsychotic medications that are used to treat schizophrenia (SCZ) and other mental illnesses. The methylation status of the insulin receptor substrate 1 (IRS1) gene is reportedly associated with SCZ; however, no study, to the best of the authors' knowledge, has focused on the quantitative DNA methylation levels of the IRS1 gene using pyrosequencing in SCZ with or without TD. The present study aimed to quantify DNA methylation levels of 4 CpG sites in the IRS1 gene using a Chinese sample including SCZ patients with TD and without TD (NTD) and healthy controls (HCs). The general linear model (GLM) was used to detect DNA methylation levels among the 3 proposed groups (TD vs. NTD vs. HC). Mean DNA methylation levels of 4 CpG sites demonstrated normal distribution. Pearson's correlation analysis did not reveal any significant correlations between the DNA methylation levels of the 4 CpG sites and the severity of SCZ. GLM revealed significant differences between the 3 groups for CpG site 1 and the average of the 4 CpG sites (P=0.0001 and P=0.0126, respectively). Furthermore, the TD, NTD and TD + NTD groups demonstrated lower methylation levels in CpG site 1 (P=0.0003, P<0.0001 and P<0.0001, respectively) and the average of 4 CpG sites (P=0.0176, P=0.0063 and P=0.003, respectively) compared with the HC group. The results revealed that both NTD and TD patients had significantly decreased DNA methylation levels compared with healthy controls, which indicated a significant association between the DNA methylation levels of the IRS1 gene with SCZ and TD.

Indiana University-Purdue University Indianapolis (IUPUI) / Tissue cells display mechanosensitivity in their ability to discern and respond to changes in the viscoelastic properties of their surroundings. By anchoring and pulling, cells are capable of translating mechanical stimuli into a biological response through a process known as mechanotransduction, a pathway believed to critically impact cell adhesion, morphology and multiple cellular processes from migration to differentiation. While previous studies on polymeric gels have revealed the influence of substrate elasticity on cellular shape and function, a lack of suitable substrates (i.e. with mobile cell-substrate linkers) has hindered research on the role of substrate viscosity. This work presents the successful design and characterization of lipid-bilayer based cell substrates of tunable viscosity affecting cell-substrate linker mobility through changes in viscous drag. Here, two complementary membrane systems were employed to span a wide range of viscosity. Single polymer-tethered lipid bilayers were used to generate subtle changes in substrate viscosity while multiple, polymer-interconnected lipid bilayer stacks were capable of producing dramatic changes in substrate viscosity. The homogeneity and integrity of these novel multibilayer systems in the presence of adherent cells was confirmed using optical microscopy techniques. Profound changes in cellular growth, phenotype and cytoskeletal organization confirm the ability of cells to sense changes in viscosity. Moreover, increased migration speeds coupled with rapid area fluctuations suggest a transition to a different migration mode in response to the dramatic changes in substrate viscosity.

No description available.

Lithium phosphorus oxy-nitride (LiPON) thin films are widely studied and used as a thin film electrolyte for lithium ion battery applications. LiPON thin films may be prepared by many techniques, but RF sputter deposition is most frequently used and was investigated in this dissertation, in spite of its low deposition rate, because of it offers more reliable and controllable processing. This dissertation includes the methodologies of sputter deposition and materials characterization of the LiPON thin film electrolytes. The LiPON thin films were deposited under varying conditions of process gas, substrate bias, and deposition temperature. To understand the variations in ionic conductivity observed, the films were extensively characterized to examine structural and compositional differences, including examination by x-ray photoelectron spectroscopy (XPS), inductively coupled plasma optical emission spectroscopy (ICP/OES), and spectroscopic ellipsometry. In addition, film density, and the intrinsic stress of the deposited films were also studied. The highest ionic conductivity of 9.8 x 10-6 S/cm was obtained at elevated deposition temperature and is correlated to a reduced density of defects, as indicated from the optical characterization.