POST-TRANSLATIONAL MODIFICATION AND DEGRADATION MECHANISMS OF THE ARYL HYDROCARBON RECEPTOR

The aryl hydrocarbon receptor (AHR) is a transcription factor first discovered to be activated by exogenous ligands, such as dioxins, and helps promote downstream gene (e.g. CYP1A1) transcription to metabolize the toxicants. With the reports of various AHR targets genes, the expression levels and activities of AHR have been implicated in many physiological and pathological situations. Understanding how AHR protein level is regulated would provide more information to target AHR. AHR stays in the cytosol in the absence of ligand in a complex with HSP90, p23 and XAP2. After ligand activation, AHR translocates into the nucleus, fulfilling its transactivation function and then is finally degraded by proteasomes. Here, we discovered a new mechanism that controls basal AHR protein level: the selective autophagy. Loss of AHR co-chaperone p23 leads to increased protein degradation of AHR through autophagy in HeLa cells. Inhibition of autophagy using several inhibitors (chloroquine, bafilomycin A1 or 3-methyladenine) increased AHR protein levels. Knocking down of key macroautophagy protein LC3B increases AHR protein levels and decreases the responsiveness of AHR to CQ treatment. The interaction between AHR and LC3B as well as AHR and autophagy receptor p62 were confirmed in vitro and in situ. AHR is found to be lysine (K) 63-ubiquitinated in HeLa cells, which is a common signal for the autophagy-lysosomal degradation.6 We also discovered that AHR is controlled by glycogen synthase kinase 3β (GSK3β) phosphorylation. Inhibition of GSK3β activity or its expression level increased AHR protein levels while expression of HA tagged-GSK3β lowers AHR protein levels. AHR protein level is regulated through autophagy. We confirmed the GSK3β-mediated phosphorylation of AHR by phos-tag gel electrophoresis couples with Western blot analysis and identified three putative phosphorylation sites of AHR in the C-terminal half of AHR sequence. Moreover, phosphorylated AHR constitutes the active pool for transactivation and phosphorylation tagged AHR for the autophagy-lysosomal degradation, which may act as way to limit its function

English Teaching Reform in Local Undergraduate Colleges Based on Interlanguage Fossilization

The interlanguage fossilization is a distinguishing characteristic of second language acquisition and plays an important role in promoting the foreign language teaching in China. According to survey four main problems of English teaching in local undergraduate colleges have been found, involving language environment, teaching methods, teacher-student relationship and test mode. Therefore, this paper expounds the characteristics, classification and basic causes of interlanguage petrochemical phenomena, and proposes the main measures of English teaching reform in local undergraduate colleges from the perspective of theory of interlanguage fossilization. The reform measures are as follows (a)foster a good language learning environment, (b) emphasize learning strategy in the teaching process, (c) innovate teaching concepts and teaching models,(d) select high-quality teaching materials and strengthen teacher promotion

Glycogen Synthase Kinase 3 Beta Regulates the Human Aryl Hydrocarbon Receptor Cellular Content and Activity

The aryl hydrocarbon receptor (AHR) is a cytosolic receptor which is involved in diverse cellular events in humans. The most well-characterized function of AHR is its ability to upregulate gene transcription after exposure to its ligands, such as environmental toxicants, dietary antioxidants, drugs, and endogenous ligands. The cellular content of AHR is partly controlled by its degradation via the ubiquitin–proteasome system and the lysosome-dependent autophagy. We used human cervical cancer (HeLa) cells to investigate how AHR undergoes protein degradation and how its activity is modulated. Since the glycogen synthase kinase 3 beta (GSK3β)-mediated phosphorylation can trigger protein degradation and substrates of GSK3β contain stretches of serine/threonine residues which can be found in AHR, we examined whether degradation and activity of AHR can be controlled by GSK3β. We observed that AHR undergoes the GSK3β-dependent, LC3-mediated lysosomal degradation without ligand treatment. The AHR can be phosphorylated in a GSK3β-dependent manner at three putative sites (S436/S440/S444, S689/S693/T697, and S723/S727/T731), which leads to lysosomal degradation of the AHR protein. Inhibition of the GSK3β activity suppresses the ligand-activated transcription of an AHR target gene in HeLa, human liver cancer (Hep3B), and human breast cancer (MCF-7) cells. Collectively, our findings support that phosphorylation of AHR by GSK3β is essential for the optimal activation of its target gene transcription and this phosphorylation may partake as an “off” switch by subjecting the receptor to lysosomal degradation

Ekelandʼs variational principle for an L¯0-valued function on a complete random metric space

AbstractMotivated by the recent work on conditional risk measures, this paper studies the Ekelandʼs variational principle for a proper, lower semicontinuous and lower bounded L¯0-valued function, where L¯0 is the set of equivalence classes of extended real-valued random variables on a probability space. First, we prove a general form of Ekelandʼs variational principle for such a function defined on a complete random metric space. Then, we give a more precise form of Ekelandʼs variational principle for such a local function on a complete random normed module. Finally, as applications, we establish the Bishop–Phelps theorem in a complete random normed module under the framework of random conjugate spaces

Selective Autophagy Maintains the Aryl Hydrocarbon Receptor Levels in HeLa Cells: A Mechanism That Is Dependent on the p23 Co-Chaperone

The aryl hydrocarbon receptor (AHR) is an environmental sensing molecule which impacts diverse cellular functions such as immune responses, cell growth, respiratory function, and hematopoietic stem cell differentiation. It is widely accepted that the degradation of AHR by 26S proteasome occurs after ligand activation. Recently, we discovered that HeLa cells can modulate the AHR levels via protein degradation without exogenous treatment of a ligand, and this degradation is particularly apparent when the p23 content is down-regulated. Inhibition of autophagy by a chemical agent (such as chloroquine, bafilomycin A1, or 3-methyladenine) increases the AHR protein levels in HeLa cells whereas activation of autophagy by short-term nutrition deprivation reduces its levels. Treatment of chloroquine retards the degradation of AHR and triggers physical interaction between AHR and LC3B. Knockdown of LC3B suppresses the chloroquine-mediated increase of AHR. Down-regulation of p23 promotes AHR degradation via autophagy with no change of the autophagy-related gene expression. Although most data in this study were derived from HeLa cells, human lung (A549), liver (Hep3B), and breast (T-47D and MDA-MB-468) cells also exhibit AHR levels sensitive to chloroquine treatment and AHR-p62/LC3 interactions. Here we provide evidence supporting that AHR undergoes the p62/LC3-mediated selective autophagy in HeLa cells

Spatial Analysis of Geographic Variation in Mental Health Visits and Its Association with Social and Built Environment in Toronto Neighbourhoods

Introduction: Mental health is a growing concern in Canada. Existing studies that examine mental health related factors generally focus on individual-level characteristics, which often neglect contextual and spatial effects. This study explores the geographic variation in mental health visits (MHV) in Toronto and identifies the social and built environment factors associated with MHV at the neighbourhood level adopting spatial analytical methods. Methods: MHV are defined as individuals aged 20+ having had a mental health and addictions related primary care visit according to physicians’ billing claims during the 2011 and 2012 fiscal years. MHV data were retrieved from the Toronto Community Health Profiles; social and built environment factors derived from various original data sources were obtained from the Toronto Community Health Profiles and Toronto Open Data. The Global Moran’s I Statistic and Kulldorff’s Spatial Scan Statistic were applied to evaluate the overall geographic variation in MHV and detect the locations of high and low risk clusters for MHV, respectively. This study quantified the effects of social and built environment on MHV fitting two spatial regression models, the spatial error model and the spatial lag model. All-subset selection using BIC as the selection criterion was employed as an ancillary tool to help determine which factors are most important to the relationships between social and built environment and MHV. Results: Overall, the geographic distribution of MHV exhibited a clustering pattern, and the locations of hot and cold spots for MHV were further identified and visualized in Toronto neighbourhoods. Two social factors and two built environment factors were identified as the most salient factors affecting MHV. Income inequality and the proportion of households in need of major repairs were associated with increased MHV, while the proportion of East Asian residents and the number of health providers per 10,000 residents were negatively correlated with MHV. The spatial regression models showed superior performance compared to the non-spatial OLS model, and the spatial lag model provided the best model fit as indicated by BIC. Conclusions: This study indicates that both social and built environment factors can contribute to variation of population mental health. The results can provide useful strategy basis for both locally tailored and general population mental health promotion programs. The cluster maps that visualized specific areas of high mental health concern can be utilized to target neighbourhoods in need of more focused investigations and mental health initiatives. Stakeholders may develop appropriate campaigns that serve to improve mental health in neighbourhoods with high levels of income inequality and deliver culturally tailored mental health services in East Asian communities. The findings also point to the need to improve housing quality and supply of general healthcare providers for addressing population mental health problems. Limitations related to data, the modifiable areal unit problem, and ecological fallacy are also discussed. Future studies can conduct attitude surveys among Toronto residents to gain better understandings of neighbourhood mental health