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The aggregation of aminoacyl transfer RNA synthetase complex-interacting multifunctional protein-2 (AIMP2) accelerates α-synuclein aggregation via direct interaction, leading to enhanced dopaminergic neurotoxicity in Parkinson's disease (PD). Thus, it would be beneficial to prevent AIMP2 aggregation to suppress α-synucleinopathy in PD. In this study, we screened small compounds that could inhibit the in vitro aggregation of AIMP2 using a 1909 small-compound library. The AIMP2 inhibitors (SAI-04, 06, and 08) with the most effective inhibition of AIMP2 aggregation bind to AIMP2, disaggregate the pre-formed AIMP2 aggregates, and prevented AIMP2/α-synuclein coaggregation and cytotoxicity in SH-SY5Y cells. Moreover, AIMP2 inhibitors prevented α-synuclein preformed fibril (PFF)-induced pathological AIMP2 aggregation in both mouse cortical and embryonic stem cell-derived human dopaminergic neurons, thereby blocking PFF-induced α-synuclein aggregation and neurotoxicity. Collectively, our results suggest that the use of brain-permeable AIMP2 aggregation inhibitors may serve as an effective therapeutic strategy for α-synucleinopathy in PD.

Grain boundaries (GBs) in polycrystalline materials act as impediments to dislocation motion and result in strengthening. Understanding slip transmission through GBs, specifically twin boundaries, is essential to understand the plastic deformation behavior of polycrystalline fcc materials. In this study the interaction between a glide dislocation and Σ 3 { 112 } incoherent twin boundary (ITB) in copper is investigated using a combined atomistic and mesoscale approach. The material parameters and structure of the GB in the mesoscale phase field dislocation dynamics (PFDD) model are informed from Molecular Statics (MS) simulations. The structural unit of the ITB consists of an array of three partial dislocations. The interaction between a glide dislocation impinging on each of the GB partial dislocations is investigated using both PFDD and Molecular Dynamics (MD) with two boundary conditions. Transmission planes predicted by both PFDD and MD (NVT) are in agreement, and show that not all transmission events are direct. Critical transmission stresses predicted by PFDD are in the range of 276 MPa to 1380 MPa, while MD predictions are in the range from 100 MPa to 700 MPa. The PFDD and MD predictions of slip transmission are explained using dislocation theory based on isotropic linear elasticity.

With the anticipation for a more connected world through the Internet of Things, there is still a strong demand for miniaturized chemical sensors. Here, we report on a miniaturized resonant chemical sensor based on a Capacitive Micromachined Ultrasonic Transducer (CMUT) with a low operating voltage suitable for portable gas sensor applications. Previously reported CMUT chemical sensors required a DC operating voltage (16∼50 V) higher than the supply voltages of common circuits (e.g., 1.8–5 V). Thus, additional circuitry such as a charge pump circuit often was required as a part of the sensor interface circuits to supply the DC voltage to CMUT. This resulted in additional power consumption and a larger footprint. In this work, the vacuum gap of the CMUT which determines the operating voltage was reduced to 50 nm through the development of a double oxidation process with a high wafer-level yield. We achieved a significantly smaller pull-in voltage (

Protoheme (hereafter referred to as heme) is an essential cellular cofactor and signaling molecule that is also potentially cytotoxic. To mitigate heme toxicity, heme synthesis and degradation are tightly coupled to heme utilization in order to limit the intracellular concentration of “free” heme. Such a model, however, would suggest that a readily accessible steady-state, bioavailable labile heme (LH) pool is not required for supporting heme-dependent processes. Using the yeast Saccharomyces cerevisiae as a model and fluorescent heme sensors, site-specific heme chelators, and molecular genetic approaches, we found here that 1) yeast cells preferentially use LH in heme-depleted conditions; 2) sequestration of cytosolic LH suppresses heme signaling; and 3) lead (Pb(2+)) stress contributes to a decrease in total heme, but an increase in LH, which correlates with increased heme signaling. We also observed that the proteasome is involved in the regulation of the LH pool and that loss of proteasomal activity sensitizes cells to Pb(2+) effects on heme homeostasis. Overall, these findings suggest an important role for LH in supporting heme-dependent functions in yeast physiology.

Mechanistic details of intramembrane aspartyl protease (IAP) chemistry, which is central to many biological and pathogenic processes, remain largely obscure. Here, we investigated the in vitro kinetics of a microbial intramembrane aspartyl protease (mIAP) fortuitously acting on the renin substrate angiotensinogen and the C-terminal transmembrane segment of amyloid precursor protein (C100), which is cleaved by the presenilin subunit of γ-secretase, an Alzheimer disease (AD)-associated IAP. mIAP variants with substitutions in active-site and putative substrate-gating residues generally exhibit impaired, but not abolished, activity toward angiotensinogen and retain the predominant cleavage site (His–Thr). The aromatic ring, but not the hydroxyl substituent, within Tyr of the catalytic Tyr–Asp (YD) motif plays a catalytic role, and the hydrolysis reaction incorporates bulk water as in soluble aspartyl proteases. mIAP hydrolyzes the transmembrane region of C100 at two major presenilin cleavage sites, one corresponding to the AD-associated Aβ42 peptide (Ala–Thr) and the other to the non-pathogenic Aβ48 (Thr–Leu). For the former site, we observed more favorable kinetics in lipid bilayer–mimicking bicelles than in detergent solution, indicating that substrate–lipid and substrate–enzyme interactions both contribute to catalytic rates. High-resolution MS analyses across four substrates support a preference for threonine at the scissile bond. However, results from threonine-scanning mutagenesis of angiotensinogen demonstrate a competing positional preference for cleavage. Our results indicate that IAP cleavage is controlled by both positional and chemical factors, opening up new avenues for selective IAP inhibition for therapeutic interventions.

Body-Centered Cubic (BCC) metals exhibit anomalous mechanical properties such as twinning/anti-twinning and tension/compression asymmetry, which are attributed to asymmetric behavior of screw dislocations. Unlike Face-Centered Cubic (FCC) metals, the Critical Resolved Shear Stress (CRSS) of BCC metals deviates from the Schmid law. We use a mesoscale modeling approach called Phase Field Dislocation Dynamics (PFDD) to understand the critical factors that control this non-Schmid behavior and reproduce atomistic predictions of the CRSS (Peierls stress). All inputs to the PFDD model are obtained from Molecular Statics (MS) simulations. Multiple pathways for modeling the non-Schmid behavior are investigated by incorporating the representative dislocation properties into different energy terms in the PFDD model. One way to understand non-Schmid behavior is to incorporate stress components projected on inclined planes into the external energy term within PFDD. Alternatively, we propose that non-Schmid behavior can also be accounted for by considering the variation of the { 110 } unstable stacking fault energy and the dislocation core width as a function of the applied tensorial stress field. The CRSS predicted using PFDD modeling is in excellent agreement with MS predictions.

Limited knowledge is available on the regeneration of Korean fir ( Abies koreana Wilson), an endemic plant species, growing on the upper part of Mt. Hallasan, a volcanic mountain, located in the central part of Jeju Island, Korea. A forest stand with the size of 1 ha dominated by Korean fir trees was established and all the trees with DBH 2 cm or larger were mapped and surveyed. Initial analysis indicated that the numbers of saplings with their DBHs between 2 cm and 10 cm were very small and that there was a big gap in the frequency of the number of saplings regenerated from the forest stand. It seems clear that the regeneration of the Korean fir trees was disturbed for longer than the last two decades, potentially by the browsing of the seedlings by ungulate including Siberian roe deer and by the physical hindrance of the dwarf bamboo to the development of the saplings of the Korean fir. Urgent measures and extensive studies are needed to promote the natural regeneration of the tree species on the dynamics of the forest regeneration and the mechanism of forest development of the forests on the Mt. Hallasan, Jeju Island, Korea.

Double strand-breaks (DSBs) of genomic DNA caused by ionizing radiation or mutagenic chemicals are a common source of mutation, recombination, chromosomal aberration, and cell death. Linker histones are DNA packaging proteins with established roles in chromatin compaction, gene transcription, and in homologous recombination (HR)-mediated DNA repair. Using a machine-learning model for functional prioritization of eukaryotic post-translational modifications (PTMs) in combination with genetic and biochemical experiments with the yeast linker histone, Hho1, we discovered that site-specific phosphorylation sites regulate HR and HR-mediated DSB repair. Five total sites were investigated (T10, S65, S141, S173, and S174), ranging from high to low function potential as determined by the model. Of these, we confirmed S173/174 are phosphorylated in yeast by mass spectrometry and found no evidence of phosphorylation at the other sites. Phospho-nullifying mutations at these two sites results in a significant decrease in HR-mediated DSB repair templated either with oligonucleotides or a homologous chromosome, while phospho-mimicing mutations have no effect. S65, corresponding to a mammalian phosphosite that is conserved in yeast, exhibited similar effects. None of the mutations affected base- or nucleotide-excision repair, nor did they disrupt non-homologous end joining or RNA-mediated repair of DSBs when sequence heterology between the break and repair template strands was low. More extensive analysis of the S174 phospho-null mutant revealed that its repression of HR and DSB repair is proportional to the degree of sequence heterology between DSB ends and the HR repair template. Taken together, these data demonstrate the utility of machine learning for the discovery of functional PTM hotspots, reveal linker histone phosphorylation sites necessary for HR and HR-mediated DSB repair, and provide insight into the context-dependent control of DNA integrity by the yeast linker histone Hho1.

Dopamine (DA), an organic chemical neurotransmitter in the human brain, plays important roles in neuronal reward, motor control, and decision making. Thus, accurate quantification of DA concentration is essential for the investigation of various dopaminergic neural circuits and diagnosis of neurological diseases. Herein, we report an overoxidized polypyrrole/sodium dodecyl sulfate (SDS)-modified multi-walled carbon nanotube (OPPy/SDS-CNT) electrode which allows detection of DA with high resolution and selectivity. By using SDS as a dopant and sodium hydroxide (NaOH) as an oxidizing agent, highly sensitive detection of DA down to 5 nM with a detection limit of 136 pM is achieved. Moreover, due to the strong electrostatic interaction between the negatively-charged electrode and the positively-charged DA molecules, selective electrochemical detection of DA is successfully demonstrated in the presence of ascorbic acid (AA) and glucose (Glc). Lastly, by demonstrating in vitro detection of DA secreted from dopaminergic cells (PC12 cells) and examining biocompatibility of the electrode, we show the potential of our OPPy/SDS-CNT electrode as a promising candidate for a functional neural interface for in vitro and in vivo monitoring of DA concentrations.

OBJECTIVES: Antiretroviral therapy has increased life expectancy for HIV infected patients; however, this population is developing chronic illnesses associated with aging. Liver disease is a major cause of non-AIDS mortality, characterized by progressive fibrosis. Infection with HIV and with Hepatitis C Virus (HCV) promotes liver fibrogenesis. Tissue inhibitor of metalloproteinase-1 (TIMP1), inhibits fibrosis regression and is profibrogenic. Association between TIMP1 and liver disease progression in an aging population of HIV/HCV co-infected, HIV mono-infected, HCV mono-infected, and healthy groups from the Miami Adult Studies on HIV (MASH) cohort in Miami, Florida, was investigated. METHODS: Serum TIMP1 levels were determined by ELISA. A non-invasive estimate of liver fibrosis, FIB-4 score was calculated. Liver fibrosis was defined as FIB-4: Low 3.25. ANOVA with Tukey's test assessed the mean differences of FIB-4 score and TIMP1 level between groups, TIMP1 levels between 3 FIB-4 categories, and the effect of age on FIB-4 and TIMP1. Linear regression predicted the association of FIB-4 score and TIMP-1 level. RESULTS: Mean age of the cohort was 54.3 ± 8.1 years with no difference between groups. Mean FIB-4 for HIV/HCV co-infected group was the highest among the 4 groups (P