Differential requirement for NMDAR activity in SAP97 -mediated regulation of the number and strength of glutamatergic AMPAR-containing synapses

PSD-95-like, disc-large (DLG) family membrane-associated guanylate kinase proteins (PSD/DLG-MAGUKs) are essential for regulating synaptic AMPA receptor (AMPAR) function and activity-dependent trafficking of AMPARs. Using a molecular replacement strategy to replace endogenous PSD-95 with SAP97β, we show that the prototypic β-isoform of the PSD-MAGUKs, SAP97β, has distinct NMDA receptor (NMDAR)-dependent roles in regulating basic properties of AMPAR-containing synapses. SAP97β enhances the number of AMPAR-containing synapses in an NMDAR-dependent manner, whereas its effect on the size of unitary synaptic response is not fully dependent on NMDAR activity. These effects contrast with those of PSD-95α, which increases both the number of AMPAR-containing synapses and the size of unitary synaptic responses, with or without NMDAR activity. Our results suggest that SAP97β regulates synaptic AMPAR content by increasing surface expression of GluA1-containing AMPARs, whereas PSD-95α enhances synaptic AMPAR content presumably by increasing the synaptic scaffold capacity for synaptic AMPARs. Our approach delineates discrete effects of different PSD-MAGUKs on principal properties of glutamatergic synaptic transmission. Our results suggest that the molecular diversity of PSD-MAGUKs can provide rich molecular substrates for differential regulation of glutamatergic synapses in the brain.National Institutes of Health (U.S.) (Grant MH080310)National Institutes of Health (U.S.) (Transformative Research Award R01 GM104948-02

Whole cell screen for inhibitors of pH homeostasis in Mycobacterium tuberculosis

Bacterial pathogens like Mycobacterium tuberculosis (Mtb) encounter acidic microenvironments in the host and must maintain their acid-base homeostasis to survive. A genetic screen identified two Mtb strains that cannot control intrabacterial pH (pHIB) in an acidic environment; infection with either strain led to severe attenuation in mice. To search for additional proteins that Mtb requires to survive at low pH, we introduced a whole-cell screen for compounds that disrupt pHIB, along with counter-screens that identify ionophores and membrane perturbors. Application of these methods to a natural product library identified four compounds of interest, one of which may inhibit novel pathway(s). This approach yields compounds that may lead to the identification of pathways that allow Mtb to survive in acidic environments, a setting in which Mtb is resistant to most of the drugs currently used to treat tuberculosis

Sunshine Duration Variability in Haihe River Basin, China, during 1966–2015

Sunshine can have a profound impact on the systematic change in climate elements, such as temperature and wind speed, and in turn affects many aspects of the human society. In recent years, there has been a substantial interest in the variation of sunshine duration due to the dramatic global climate change. Hence, there is a need to better understand the variation of sunshine duration in order to cope with climate change. This study aimed to analyze the variation of sunshine duration in Haihe River basin, China, and its relationship with temperature, wind speed and low-level cloudiness. The annual, seasonal and monthly changes of sunshine duration were analyzed based on the data collected from 33 meteorological stations over the Haihe River basin during 1966–2015. It is evident that the annual, seasonal and monthly sunshine duration shows a decreasing trend over time. In addition, the annual sunshine duration is lower with a higher climate tendency rate in the southern and eastern coastal regions than that in the northwestern regions. It is negatively correlated with temperature (r = −0.50) and low-level cloudiness (r = −0.29), but positively with wind speed (r = 0.61). Wind speed may be one of the important causes of the decrease of sunshine duration in the Haihe River basin during 1966–2015. These changes may have significant implications for the hydrological cycle in the area

Regioselective oxidation of heterocyclic aromatic hydrocarbons catalyzed by cytochrome P450: A case study of carbazole

Recently there are increasing interests in accurately evaluating the health effects of heterocyclic PAHs. However, the activation mechanism and possible metabolites of heterocyclic PAHs catalyzed by human CYP1A1 is still elusive to a great extent. Here, leveraged to high level QM/MM calculations, the corresponding activation pathways of a representative heterocyclic PAHs, carbazole, were systematically explored. The first stage is electrophilic addition or hydrogen abstraction from N-H group. Electrophilic addition was evidenced to be more feasible and regioselectivity at C3 and C4 sites were identified. Correlations between energy barriers and key structural/electrostatic parameters reveal that O-Cα distance and Fe-O-Cα angle are the main origin for the catalytic regioselectivity. Electrophilic addition was determined as the rate-determining step and the subsequent possible reactions include epoxidation, NIH shift (the hydrogen migration from the site of hydroxylation to the adjacent carbon) and proton shuttle. The corresponding products are epoxides, ketones and hydroxylated carbazoles, respectively. The main metabolites (hydroxylated carbazoles) are estimated to be more toxic than carbazole. The regioselectivity of carbazole activated by CYP1A1 is different from the environmental processes (gas and aqueous phase). Collectively, these results will inform the in-depth understanding the metabolic processes of heterocyclic PAHs and aid the accurate evaluation of their health effects

Fitting characteristics of N95 filtering-facepiece respirators used widely in China.

BACKGROUND: Millions of people rely on N95 filtering facepiece respirators to reduce the risk of airborne particles and prevent them from respiratory infections. However, there are no respirator fit testing and training regulations in China. Meanwhile, no study has been conducted to investigate the fit of various respirators. The objective of this study was to investigate whether people obtained adequate fit when wearing N95 filtering facepiece respirators (FFRs) used widely in China. METHODS: Fifty adult participants selected using the Chinese respirator fit test panel donned 10 common models of N95 FFRs. Fit factors (FF) and inward leakage were measured using the TSI PortaCount Plus. Each subject was tested with three replications for each model. A subject was considered to pass the fit test when at least two of the three FFs were greater than 100. Two models were conducted fit tests before and after training to assess the role of training. RESULTS: The geometric mean FFs for each model and trained subjects ranged from <10 to 74.0. The fifth percentile FFs for only two individual respirator models were greater than 10 which is the expected level of performance for FFRs. The passing rates for these two models of FFRs were 44.7% and 20.0%. The passing rates were less than 10.0% for the other eight models. There were 27 (54%) participants who passed none of the 10 FFRs. The geometric mean FFs for both models when the subjects received training (49.7 and 74.0) were significantly larger than those when the same group of subjects did not receive any training (29.0 and 30.9) (P<0.05). CONCLUSIONS: FFRs used widely in China should be improved according to Chinese facial dimensions. Respirator users could benefit from respirator training and fit testing before using respirators

Long-term monoculture reduces the symbiotic rhizobial biodiversity of peanut

Long-term monoculture (LTM) decreases the yield and quality of peanut, even resulting in changes in the microbial community. However, the effect of LTM on peanut rhizobial communities has still not been elucidated. In this study, we isolated and characterized peanut rhizobia from 6 sampling plots with different monoculture cropping durations. The community structure and diversity index for each sampling site were analyzed, and the correlations between a peanut rhizobium and soil characteristics were evaluated to clarify the effects on peanut rhizobial communities. The competitive abilities among representative strains were also analyzed. A total of 283 isolates were obtained from 6 sampling plots. Nineteen recA haplotypes were defined and were grouped into 8 genospecies of Bradyrhizobium, with B. liaoningense and B. ottawaense as the dominant groups in each sample. The diversity indexes of the rhizobial community decreased, and the dominant groups of B. liaoningense and B. ottawaense were enriched significantly with extended culture duration. Available potassium (AK), available phosphorus (AP), available nitrogen (AN), total nitrogen (TN) and organic carbon (OC) gradually increased with increasing monoculture duration. OC, TN, AP and AK were the main soil characteristics affecting the distribution of rhizobial genospecies in the samples. A competitive nodulation test indicated that B. liaoningense presented an excellent competitive ability, which was congruent with its high isolation frequency. This study revealed that soil characteristics and the competitive ability of rhizobia shape the symbiotic rhizobial community and provides information on community formation and the biogeographic properties of rhizobia. (C) 2020 Elsevier GmbH. All rights reserved

Shank Proteins Differentially Regulate Synaptic Transmission

Shank proteins, one of the principal scaffolds in the postsynaptic density (PSD) of the glutamatergic synapses, have been associated with autism spectrum disorders and neuropsychiatric diseases. However, it is not known whether different Shank family proteins have distinct functions in regulating synaptic transmission, and how they differ from other scaffold proteins in this aspect. Here, we investigate the role of Shanks in regulating glutamatergic synaptic transmission at rat hippocampal SC-CA1 synapses, using lentivirus-mediated knockdown and molecular replacement combined with dual whole-cell patch clamp in hippocampal slice culture. In line with previous findings regarding PSD-MAGUK scaffold manipulation, we found that loss of scaffold proteins via knockdown of Shank1 or Shank2, but not Shank3, led to a reduction of the number but not the unitary response of AMPAR containing synapses. Only when both Shank1 and Shank2 were knocked down, were both the number and the unitary response of active synapses reduced. This reduction was accompanied by a decrease in NMDAR-mediated synaptic response, indicating more profound deficits in synaptic transmission. Molecular replacement with Shank2 and Shank3c rescued the synaptic transmission to the basal level, and the intact sterile _-motif (SAM) of Shank proteins is required for maintaining glutamatergic synaptic transmission. We also found that altered neural activity did not influence the effect of Shank1 or Shank2 knockdown on AMPAR synaptic transmission, in direct contrast to the activity dependence of the effect of PSD-95 knockdown, revealing differential interaction between activity-dependent signaling and scaffold protein families in regulating synaptic AMPAR function. Keywords: ASD; bicuculline; excitatory; hippocampus; mini; Prosap1National Institutes of Health (U.S.) (Grant MH080310