Golgi export of the Kir2.1 channel is driven by a trafficking signal located within its tertiary structure.

Mechanisms that are responsible for sorting newly synthesized proteins for traffic to the cell surface from the Golgi are poorly understood. Here, we show that the potassium channel Kir2.1, mutations in which are associated with Andersen-Tawil syndrome, is selected as cargo into Golgi export carriers in an unusual signal-dependent manner. Unlike conventional trafficking signals, which are typically comprised of short linear peptide sequences, Golgi exit of Kir2.1 is dictated by residues that are embedded within the confluence of two separate domains. This signal patch forms a recognition site for interaction with the AP1 adaptor complex, thereby marking Kir2.1 for incorporation into clathrin-coated vesicles at the trans-Golgi. The identification of a trafficking signal in the tertiary structure of Kir2.1 reveals a quality control step that couples protein conformation to Golgi export and provides molecular insight into how mutations in Kir2.1 arrest the channels at the Golgi.

Attention-deficit hyperactivity disorder in adults with epilepsy: An indirect relationship with suicide risk.

PURPOSE: Studies on attention-deficit hyperactivity disorder (ADHD) are scarce in adults with epilepsy. This study aimed to investigate the risk factors for ADHD and determine whether ADHD is directly associated with the risk of suicide in adults with epilepsy. METHODS: ADHD was assessed using the Structured Clinical Interview for the DSM-5 Disorders Clinical Version. The Mini International Neuropsychiatric Interview (MINI) Plus 5.0.0, Neurological Disorders Depression Inventory for Epilepsy (NDDIE), and Generalized Anxiety Disorder-7 (GAD-7) were also used. Suicide risk was defined as a MINI suicidality score of ≥ 1. Stepwise logistic regression and mediation analyses were conducted. RESULTS: Of the 157 adults with epilepsy, 19 (12.1 %) were diagnosed with ADHD, including inattentive (5.7 %), hyperactive (3.8 %), and combined (2.5 %) types. Thirty-two subjects (20.4 %) had a risk of suicide. ADHD was insignificantly associated with any epilepsy-related factors. The diagnosis of ADHD was not associated with suicide risk independent of NDDIE ≥ 14 and GAD-7 ≥ 7. Mediation effects of ADHD on suicidality using NDDIE ≥ 14 (odds ratio [OR] 2.850, 95 % confidence interval [CI] 1.398-5.811, p = 0.004) or GAD-7 ≥ 7 (OR 3.240, 95 % CI 1.537-6.828, p = 0.002) were statistically significant, with the proportion mediated being 84.5 % or 92.0 % of the total ADHD effect, respectively. These models were adjusted for age, sex, and composite epilepsy severity scores. CONCLUSIONS: ADHD was diagnosed in 12.1% of adults with epilepsy and was not associated with any epilepsy-related factors. ADHD was indirectly associated with the risk of suicide resulting from depression and anxiety in adults with epilepsy.

Differences in factors associated with insomnia symptoms between patients with epilepsy with and without depressive symptoms.

OBJECTIVE: To determine if insomnia-related factors differ depending on the presence of depression in patients with epilepsy. METHODS: This cross-sectional multicenter study collected data on depressive symptoms, insomnia symptoms, and excessive daytime sleepiness, which were defined as a Patient Health Questionnaire-9 (PHQ-9) score of ≥ 10, an Insomnia Severity Index (ISI) score of ≥ 15, and an Epworth Sleepiness Scale (ESS) of ≥ 11, respectively. Further, uncontrolled seizures were defined as one or more seizures per month during antiseizure medications treatment. A stepwise logistic regression analysis was conducted, with a logistic regression with interaction terms performed to identify differences in insomnia-related factors depending on depressive symptoms. RESULTS: Of 282 adults with epilepsy (men, 58 %; mean age, 40.4 ± 13.9 years), a PHQ-9 score ≥ 10, an ISI score ≥ 15, an ESS score ≥ 11 were noted in 23.4 % (n = 66), 20.2 % (n = 57), and 12.8 % (n = 36), respectively. More patients with depressive symptoms had an ISI score ≥ 15 (56.1 % vs. 9.3 %; p < 0.001) than those without. In multiple logistic regression, uncontrolled seizures (odds ratio [OR], 4.896; p < 0.01), daytime sleepiness (OR, 5.369; p < 0.05), and a history of psychiatric disorders (OR, 3.971; p < 0.05) were identified as significant factors that were more likely to be associated with an ISI score ≥ 15; however, this was only true in patients without depressive symptoms. In contrast, use of perampanel (OR, 0.282; p < 0.05) was less likely associated, while female sex (OR, 3.178; p < 0.05) was more likely associated with an ISI score ≥ 15 only in patients with depressive symptoms. CONCLUSIONS: Insomnia-related factors in patients with epilepsy may differ between patients with and without depression. Our findings of different insomnia-related factors based on the presence of depression may facilitate the management of patients with epilepsy.

The impact of fear of falling on health-related quality of life in community-dwelling older adults: mediating effects of depression and moderated mediation effects of physical activity.

BACKGROUND: The fear of falling is a common issue among older adults that negatively affects physical and psychological aspects of health-related quality of life, regardless of actual fall events. Interventions aimed at reducing fear of falling, independent of falls, may improve older adults' quality of life. This study examined the moderated mediation effect of physical activity in how fear of falling affects health-related quality of life through depression in community-dwelling older adults. METHODS: This study used secondary data from the Korea Centers for Disease Control and Prevention's 2019 Community Health Survey. The study included 73,738 adults aged 65 years or older. The researchers used the fear of falling scale, International Physical Activity Questionnaire, Patient Health Questionnaire-9, and EuroQol 5 Dimension as research tools, and performed descriptive statistics, Pearson's correlation coefficient, and SPSS PROCESS macro analysis. The study used the bootstrapping method to assess the adjusted mediating effect by resampling 5,000 times, and determined statistical significance with a 95% confidence interval. RESULTS: In the model in which fear of falling affects health-related quality of life by mediating depression, the moderated mediation effect of physical activity was statistically significant, as the bootstrapping result did not include 0 in the 95% confidence interval (Index of moderated mediation [95% CI] = 0.006 [0.004-0.007], 0.008 [0.006-0.009]). Depression and health-related quality of life impairment decreased as the level of physical activity increased through inactivity, minimal activity, and health promotion activities, as the negative mediating effects decreased. CONCLUSION: Physical activity reduces depression and improves health-related quality of life by influencing older adults' fear of falling. Community-based programs are needed to encourage and support older adults in maintaining moderate physical activity to manage the depression caused by fear of falling, which is common among older adults, and to improve their health-related quality of life.

Oxysterol Induces Expression of 60 kDa Chaperone Protein on Cell Surface of Microglia.

Microglia, essential immune cells in the brain, play crucial roles in neuroinflammation by performing various functions such as neurogenesis, synaptic pruning, and pathogen defense. These cells are activated by inflammatory factors like ß-amyloid (Aß) and oxysterols, leading to morphological and functional changes, including the secretion of inflammatory cytokines and the upregulation of MHC class II molecules. This study focused on identifying specific markers for microglial activation, with a particular emphasis on the roles of oxysterols in this process. We used the HMC3 human microglial cell line to investigate the induction of heat shock protein 60 (HSP60), a chaperonin protein by oxysterols, specifically in the presence of 25-hydroxycholesterol (25OHChol) and 27-hydroxycholesterol (27OHChol). Our findings obtained by the proteomics approach revealed that these oxysterols significantly increased HSP60 expression on microglial cells. This induction was further confirmed using Western blot analysis and immunofluorescence microscopy. Additionally, Aß1-42 also promoted HSP60 expression, indicating its role as a microglial activator. HSP60 involved in protein folding and immune modulation was identified as a potential marker for microglial activation. This study underscores the importance of HSP60 in the inflammatory response of microglia, suggesting its utility as a target for new therapeutic approaches in neuroinflammatory diseases such as Alzheimer's disease (AD).

Ptr1 and ZAR1 immune receptors confer overlapping and distinct bacterial pathogen effector specificities.

Some nucleotide-binding and leucine-rich repeat receptors (NLRs) indirectly detect pathogen effectors by monitoring their host targets. In Arabidopsis thaliana, RIN4 is targeted by multiple sequence-unrelated effectors and activates immune responses mediated by RPM1 and RPS2. These effectors trigger cell death in Nicotiana benthamiana, but the corresponding NLRs have yet not been identified. To identify N. benthamiana NLRs (NbNLRs) that recognize Arabidopsis RIN4-targeting effectors, we conducted a rapid reverse genetic screen using an NbNLR VIGS library. We identified that the N. benthamiana homolog of Ptr1 (Pseudomonas tomato race 1) recognizes the Pseudomonas effectors AvrRpt2, AvrRpm1, and AvrB. We demonstrated that recognition of the Xanthomonas effector AvrBsT and the Pseudomonas effector HopZ5 is conferred independently by the N. benthamiana homolog of Ptr1 and ZAR1. Interestingly, the recognition of HopZ5 and AvrBsT is contributed unequally by Ptr1 and ZAR1 in N. benthamiana and Capsicum annuum. In addition, we showed that the RLCK XII family protein JIM2 is required for the NbZAR1-dependent recognition of AvrBsT and HopZ5. The recognition of sequence-unrelated effectors by NbPtr1 and NbZAR1 provides an additional example of convergently evolved effector recognition. Identification of key components involved in Ptr1 and ZAR1-mediated immunity could reveal unique mechanisms of expanded effector recognition.

Outbred Mice with Streptozotocin-Induced Diabetes Show Sex Differences in Glucose Metabolism.

Outbred mice (ICR) with different genotypes and phenotypes have been reported to be more suitable for scientific testing than inbred mice because they are more similar to humans. To investigate whether the sex and genetic background of the mice are important factors in the development of hyperglycemia, we used ICR mice and divided them into male, female, and ovariectomized female (FOVX) groups and treated them with streptozotocin (STZ) for five consecutive days to induce diabetes. Our results show that fasting blood glucose and hemoglobin A1c (HbA1c) levels were significantly higher in diabetes-induced males (M-DM) and ovariectomized diabetes-induced females (FOVX-DM) than in diabetes-induced females (F-DM) at 3 and 6 weeks after STZ treatment. Furthermore, the M-DM group showed the most severe glucose tolerance, followed by the FOVX-DM and F-DM groups, suggesting that ovariectomy affects glucose tolerance in female mice. The size of pancreatic islets in the M-DM and FOVX-DM groups was significantly different from that of the F-DM group. The M-DM and FOVX-DM groups had pancreatic beta-cell dysfunction 6 weeks after STZ treatment. Urocortin 3 and somatostatin inhibited insulin secretion in the M-DM and FOVX-DM groups. Overall, our results suggest that glucose metabolism in mice is dependent on sex and/or genetic background.

Atheroma-Relevant 7-Oxysterols Differentially Upregulate Cd14 Expression.

The expression of CD14 in monocytic cells is elevated in atherosclerotic lesions where 7-oxyterols are abundant. However, it remains unknown whether atheroma-relevant 7-oxysterols are involved in receptor expression. Therefore, we investigated the effects of 7α-hydroxycholesterol (7αOHChol), 7ß-hydroxycholesterol (7ßOHChol), and 7-ketocholesterol (7K) on CD14 levels in THP-1 cells. The three 7-oxysterols increased CD14 transcript levels at a distinct time point, elevated cellular CD14 protein levels, and promoted the release of soluble CD (sCD14) from THP-1 cells. Our data revealed that CD14 expression was most strongly induced after treatment with 7αOHChol. Moreover, 7αOHChol alone upregulated membrane-bound CD14 levels and enhanced responses to lipopolysaccharides, as determined by CCL2 production and monocytic cell migration. The 7-oxysterols also increased the gelatinolytic activity of MMP-9, and a cell-permeable, reversible MMP-9 inhibitor, MMP-9 inhibitor I, significantly impaired sCD14 release. These results indicate that 7-oxysterols differentially induce CD14 expression in vascular cells and contribute to the monocytic cell expression of CD14 via overlapping, but distinct, mechanisms.

Factors influencing medical and nursing students' willingness to care for COVID-19 patients in South Korea: a cross-sectional study.

BACKGROUND: The COVID-19 pandemic has threatened the stability and adequacy of the global healthcare system. In this situation, authorities have considered engaging medical and nursing students to address the shortage of frontline healthcare workers. This study investigated the effect of COVID-19-related knowledge, attitudes, and preventive behaviors on medical and nursing students' willingness to care for COVID-19 patients. METHODS: Medical and nursing students from universities in two regions of South Korea participated in this cross-sectional study. A total of 330 questionnaires were distributed; of them, 99.3% were collected, and 315 questionnaires were analyzed. Data were collected on participants' general characteristics, COVID-19-related knowledge, attitudes, and preventive behaviors, and willingness to care for COVID-19 patients. RESULTS: In total, 66.3% of the participants were willing to care for patients during the COVID-19 pandemic. Students in higher grades and those with more clinical practice experience showed higher levels of willingness to care. Specifically, willingness to care was correlated with the senior year (OR = 3.58, 95% CI = 1.24 - 10.37, p = .019), a high level of COVID-19-related knowledge (OR = 1.03, 95% CI = 1.00 - 1.05, p = .041), an optimistic attitude that COVID-19 can be overcome (OR = 1.63, 95% CI = 1.24 - 2.14, p < .001), and increased engagement in infection prevention behaviors (OR = 1.41, 95% CI = 1.16 - 1.71, p < .001). CONCLUSIONS: The findings indicated that a high level of knowledge regarding the COVID-19 pandemic, having an optimistic attitude, and engaging in preventive behaviors affected students' willingness to care for COVID-19 patients. Integrating disaster preparedness courses in the early years of their curriculum could increase future healthcare providers' willingness to care for patients.

The impact of fear of COVID-19 on the impact of event and indirect trauma.

This study investigated the mediating effect of fear of COVID-19 on the relationship between the impact of an event and indirect trauma during the pandemic. The study was conducted online from February 8 to 18, 2021, with 215 participants who had never been diagnosed with COVID-19. The collected data were analyzed using SPSS and PROCESS macro software. It was confirmed that fear of COVID-19 partially mediates the relationship between the impact of an event and indirect trauma. This means that the greater the degree of impact of COVID-19, the higher the level of indirect trauma. Additionally, the greater the fear of COVID-19, the higher the level of indirect trauma. These results indicate that the prolonged spread of COVID-19 may vary depending on the country's quarantine systems. Overall, the findings of this study can assist in understanding the psychological problems of people who have experienced COVID-19 and in preparing relevant countermeasures for emotional problems.

Factors Affecting Nurses' Health Promotion Behavior during the COVID-19 Pandemic Based on the Information-Motivation-Behavioral Skills Model.

Background and Objectives: The COVID-19 pandemic has emerged as a major threat to nurses' health. This study aimed to investigate the factors affecting nurses' health promotion behaviors during the coronavirus disease 2019 (COVID-19) pandemic. Material and Methods: The participants were clinical nurses who had direct contact with patients at a university hospital in G province, Korea. Data were collected from March 16 to April 16, 2021, and the final analysis included data from 162 nurses. The general and lifestyle characteristics of the participants were analyzed using descriptive statistics, and the effect on health promotion behavior was analyzed using multiple regression with SPSS/WIN 21.0. Results: The results showed that the factors influencing nurses' health promotion behavior during the COVID-19 pandemic were social support (ß = 0.40, p < 0.001), self-efficacy (ß = 0.27, p = 0.014), being married (ß = 0.18, p = 0.018), having good health (ß = 0.31, p < 0.001), and not skipping meals (ß = 0.20, p = 0.001). The explanatory power of the variables was 51.4%. Therefore, health promotion programs to promote social support and self-efficacy are needed to improve nurses' health promotion behaviors during the COVID-19 pandemic. Conclusions: These results indicate that the development of additional management strategies for health promotion among nurses during the COVID-19 pandemic is necessary. It is necessary to prepare organizational policies and manage self-care to improve nurses' irregular eating habits during the ongoing pandemic.

Development of an Accurate and Sensitive Diagnostic System Based on Conventional PCR for Detection of African Swine Fever Virus in Food Waste.

African swine fever virus (ASFV), a highly contagious virus, can cause diseases with high mortality rates in pigs, making it a pathogen of social and economic significance. ASFV has been reported to show potential long-term survival in living livestock, such as pigs, but also in leftover cooking meat and undercooked pork meat. Hence, it is possible that there could be direct reinfection or secondary infection through feed produced from household food waste and treatment facilities. Many polymerase chain reaction (PCR)-based molecular diagnostic techniques to detect ASFV in clinical swine samples have been reported. However, those with applicability for food waste samples, which contain relatively low viral copy numbers and may contain various unknown inhibitors of PCR, are still lacking. In this study, we developed a conventional PCR-based diagnostic system that can detect ASFV with high sensitivity from food waste sample types. The technique shows a 10-100 times higher limit of detection compared to that of previously reported methods based on conventional PCR and quantitative real-time PCR. It is also capable of amplifying a sequence that is approximately 751 nucleotides, which is advantageous for similarity analysis and genotyping. Moreover, a ASFV-modified positive material different from ASFV that could synthesize 1400 nucleotide amplicons was developed to identify false-positive cases and thus enhance diagnostic accuracy. The method developed herein may be applicable for future ASFV monitoring, identification, and genotyping in food waste samples. Supplementary Information: The online version contains supplementary material available at 10.1007/s12088-022-01007-y.

Factors influencing caregiver burden by dementia severity based on an online database from Seoul dementia management project in Korea.

BACKGROUNDS: As the prevalence of dementia rises, caregiver burden also increases in South Korea, especially for informal family caregivers. This study aimed to analyze factors affecting caregiver burden by the severity of dementia based on data of patients in Seoul. METHODS: A total of 12,292 individuals aged ≥65 years enrolled in the Seoul Dementia Management Project from 2010 to 2016 in an online database were selected. Caregiver's burden was assessed using the Korea version of Zarit Burden Interview. Multiple regression analyses were performed to determine factors associated with primary caregiver's burden after stratifying the severity of dementia. RESULTS: Most patients showed moderate levels of cognitive impairment (49.4%), behavior problems (82.6%), and ADL dependency (73.6%). After stratifying the severity of dementia, caregivers caring for patients with mild symptoms of dementia were experienced with higher caregiver burden if patients were under a lower score of IADL. Significant factors for caregiver burden among caregivers supporting patients with moderate symptoms of dementia include caregivers' residence with patients, subjective health status, and co-work with secondary caregivers. Lastly, caregivers for patients with severe dementia symptoms experienced a higher caregiver burden from limited cognitive function, problematic behavior, and caregivers' negative health status. CONCLUSION: In terms of sample size, this study had far more patients than any other domestic or international study. It was meaningful in that it analyzed characteristics of patients with dementia and caregivers affecting the burden of caregivers in Korea. Intensive social supports with multiple coping strategies focusing on different levels of patients' clinical symptoms and caregivers' needs should be planned to relieve the caregiver burden.

27-Hydroxycholesterol induces macrophage gene expression via LXR-dependent and -independent mechanisms.

27-Hydroxycholesterol (27OHChol) exhibits agonistic activity for liver X receptors (LXRs). To determine roles of the LXR agonistic activity in macrophage gene expression, we investigated the effects of LXR inhibition on the 27OHChol-induced genes. Treatment of human THP-1 cells with GSK 2033, a potent cell-active LXR antagonist, results in complete inhibition in the transcription of LXR target genes (such as LXRα and ABCA1) induced by 27OHChol or a synthetic LXR ligand TO 901317. Whereas expression of CCL2 and CCL4 remains unaffected by GSK 2033, TNF-α expression is further induced and 27OHChol-induced CCL3 and CXCL8 genes are suppressed at both the transcriptional and protein translation levels in the presence of GSK 2033. This LXR antagonist downregulates transcript levels and surface expression of CD163 and CD206 and suppresses the transcription of CD14, CD80, and CD86 genes without downregulating their surface levels. GSK 2033 alone had no effect on the basal expression levels of the aforementioned genes. Collectively, these results indicate that LXR inhibition leads to differential regulation of 27-hydroxycholesterolinduced genes in macrophages. We propose that 27OHChol induces gene expression and modulates macrophage functions via LXR-dependent and -independent mechanisms.

Hearing loss through apoptosis of the spiral ganglion neurons in apolipoprotein E knockout mice fed with a western diet.

Age-related hearing loss (ARHL) is a neurodegenerative disease associated with an aged population. ARHL is influenced by biological factors such as aging, sex difference, and atherosclerosis. The mechanisms of ARHL caused by atherosclerosis have not been previously determined in apolipoprotein E knockout (ApoE KO) male mice. To investigate the onset and cause of the hearing loss, ApoE KO male mice were treated with a western diet (ApoE KO-WD) for 16 weeks. The lipid profile, atherosclerotic plaques throughout the aorta, and auditory brainstem response (ABR) thresholds were measured in the ApoE KO-WD male mice. The expression of S100 calcium-binding protein B (S100B), a neuronal damage biomarker, was also observed. Reactive oxygen species (ROS) and apoptosis rates were detected in the cochlea of the ApoE KO male mice. Atherosclerotic plaques on the aorta and ABR thresholds were significantly increased in the ApoE KO-WD male mice at 24 weeks of age. ABR thresholds had a statistically significant positive correlation with the area of atherosclerotic plaques (r = 0.783, p = 0.013) in male mice at 24 weeks of age. S100B protein expression and the dihydroethidium (DHE) reaction to ROS in the cochlear spiral ganglion neurons (SGNs) were significantly increased in the ApoE KO and ApoE KO-WD male mice. Cells positive for active caspase-3 and terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling (TUNEL) in the SGNs were significantly increased in ApoE KO-WD male mice indicating an increased rate of cellular apoptosis. In conclusion, ROS in the SGNs were activated by increased S100B expression in ApoE KO-WD male mice, and this resulted in an increased apoptosis rate. Thus, hearing loss began at 16 weeks in ApoE KO-WD male mice. Our results suggest that the ApoE KO-WD male mice are a suitable animal model for studying ARHL associated with exacerbated atherosclerosis.

Silk Fibroin Promotes the Regeneration of Pancreatic ß-Cells in the C57BL/KsJ-Leprdb/db Mouse.

Diabetes mellitus is a chronic metabolic disease, and its progression leads to serious complications. Although various novel therapeutic approaches for diabetes mellitus have developed in the last three decades, its prevalence has been rising more rapidly worldwide. Silk-related materials have been used as anti-diabetic remedies in Oriental medicine and many studies have shown the effects of silk fibroin (SF) in both in vitro and in vivo models. In our previous works, we reported that hydrolyzed SF improved the survival of HIT-T15 cells under high glucose conditions and ameliorated diabetic dyslipidemia in a mouse model. However, we could not provide a precise molecular mechanism. To further evaluate the functions of hydrolyzed SF on the pancreatic ß-cell, we investigated the effects of hydrolyzed SF on the pancreatic ß-cell proliferation and regeneration in the mouse model. Hydrolyzed SF induced the expression of the proliferating cell nuclear antigen (PCNA) and reduced the apoptotic cell population in the pancreatic islets. Hydrolyzed SF treatment not only induced the expression of transcription factors involved in the pancreatic ß-cell regeneration in RT-PCR results but also increased neurogenin3 and Neuro D protein levels in the pancreas of those in the group treated with hydrolyzed SF. In line with this, hydrolyzed SF treatment generated insulin mRNA expressing small cell colonies in the pancreas. Therefore, our results suggest that the administration of hydrolyzed SF increases the pancreatic ß-cell proliferation and regeneration in C57BL/KsJ-Leprdb/db mice.

School and individual factors on game addiction: A multilevel analysis.

This study investigated the protective or risk factors of game addiction at individual and school-level using multilevel modelling. Data from Korea Children and Youth Panel Survey was used for the analyses. The findings revealed that individual-level variables, including gender, delinquency, family intimacy, stress, self-esteem and self-control, were significant predictors of game addiction. Furthermore, protective school climate contributed to decreasing the level of game addiction and risky school climates positively predicted game addiction. The effect of individual-level variables on game addiction was different depending on the type or level of school-level variables. Based on the findings, implications and suggestions for future studies were discussed.

The endosomal trafficking factors CORVET and ESCRT suppress plasma membrane residence of the renal outer medullary potassium channel (ROMK).

Protein trafficking can act as the primary regulatory mechanism for ion channels with high open probabilities, such as the renal outer medullary (ROMK) channel. ROMK, also known as Kir1.1 (KCNJ1), is the major route for potassium secretion into the pro-urine and plays an indispensable role in regulating serum potassium and urinary concentrations. However, the cellular machinery that regulates ROMK trafficking has not been fully defined. To identify regulators of the cell-surface population of ROMK, we expressed a pH-insensitive version of the channel in the budding yeast Saccharomyces cerevisiae We determined that ROMK primarily resides in the endoplasmic reticulum (ER), as it does in mammalian cells, and is subject to ER-associated degradation (ERAD). However, sufficient ROMK levels on the plasma membrane rescued growth on low-potassium medium of yeast cells lacking endogenous potassium channels. Next, we aimed to identify the biological pathways most important for ROMK regulation. Therefore, we used a synthetic genetic array to identify non-essential genes that reduce the plasma membrane pool of ROMK in potassium-sensitive yeast cells. Genes identified in this screen included several members of the endosomal complexes required for transport (ESCRT) and the class-C core vacuole/endosome tethering (CORVET) complexes. Mass spectroscopy analysis confirmed that yeast cells lacking an ESCRT component accumulate higher potassium concentrations. Moreover, silencing of ESCRT and CORVET components increased ROMK levels at the plasma membrane in HEK293 cells. Our results indicate that components of the post-endocytic pathway influence the cell-surface density of ROMK and establish that components in this pathway modulate channel activity.

Lipotoxicity induces hepatic protein inclusions through TANK binding kinase 1-mediated p62/sequestosome 1 phosphorylation.

Obesity commonly leads to hepatic steatosis, which often provokes lipotoxic injuries to hepatocytes that cause nonalcoholic steatohepatitis (NASH). NASH, in turn, is associated with the accumulation of insoluble protein aggregates that are composed of ubiquitinated proteins and ubiquitin adaptor p62/sequestosome 1 (SQSTM1). Formation of p62 inclusions in hepatocytes is the critical marker that distinguishes simple fatty liver from NASH and predicts a poor prognostic outcome for subsequent liver carcinogenesis. However, the molecular mechanism by which lipotoxicity induces protein aggregation is currently unknown. Here, we show that, upon saturated fatty acid-induced lipotoxicity, TANK binding kinase 1 (TBK1) is activated and phosphorylates p62. TBK1-mediated p62 phosphorylation is important for lipotoxicity-induced aggregation of ubiquitinated proteins and formation of large protein inclusions in hepatocytes. In addition, cyclic GMP-AMP synthase (cGAS) and stimulator of interferon genes (STING), upstream regulators of TBK1, are involved in lipotoxic activation of TBK1 and subsequent p62 phosphorylation in hepatocytes. Furthermore, TBK1 inhibition prevented formation of ubiquitin-p62 aggregates not only in cultured hepatocytes, but also in mouse models of obesity and NASH. CONCLUSION: These results suggest that lipotoxic activation of TBK1 and subsequent p62 phosphorylation are critical steps in the NASH pathology of protein inclusion accumulation in hepatocytes. This mechanism can provide an explanation for how hypernutrition and obesity promote the development of severe liver pathologies, such as steatohepatitis and liver cancer, by facilitating the formation of p62 inclusions. (Hepatology 2018).

Inhibition of Glycogen Synthase II with RNAi Prevents Liver Injury in Mouse Models of Glycogen Storage Diseases.

Glycogen storage diseases (GSDs) of the liver are devastating disorders presenting with fasting hypoglycemia as well as hepatic glycogen and lipid accumulation, which could lead to long-term liver damage. Diet control is frequently utilized to manage the potentially dangerous hypoglycemia, but there is currently no effective pharmacological treatment for preventing hepatomegaly and concurrent liver metabolic abnormalities, which could lead to fibrosis, cirrhosis, and hepatocellular adenoma or carcinoma. In this study, we demonstrate that inhibition of glycogen synthesis using an RNAi approach to silence hepatic Gys2 expression effectively prevents glycogen synthesis, glycogen accumulation, hepatomegaly, fibrosis, and nodule development in a mouse model of GSD III. Mechanistically, reduction of accumulated abnormally structured glycogen prevents proliferation of hepatocytes and activation of myofibroblasts as well as infiltration of mononuclear cells. Additionally, we show that silencing Gys2 expression reduces hepatic steatosis in a mouse model of GSD type Ia, where we hypothesize that the reduction of glycogen also reduces the production of excess glucose-6-phosphate and its subsequent diversion to lipid synthesis. Our results support therapeutic silencing of GYS2 expression to prevent glycogen and lipid accumulation, which mediate initial signals that subsequently trigger cascades of long-term liver injury in GSDs.