Biology subjects

Chung, H.-J.

Publications and source records attributed to Chung, H.-J..

4 recordsLinked to original sources

bioRxiv2024

The human genetic variant rs6190 unveils Foxc1 and Arid5a as novel pro-metabolic targets of the glucocorticoid receptor in muscle.

The genetic determinants of the glucocorticoid receptor (GR) metabolic action remain largely unelucidated. This is a compelling gap in knowledge for the GR single nucleotide polymorphism (SNP) rs6190 (p.R23K), which has been associated in humans with enhanced metabolic health but whose mechanism of action remains completely unknown. We generated transgenic knock-in mice genocopying this polymorphism to elucidate how the mutant GR impacts metabolism. Compared to non-mutant littermates, mutant mice showed increased insulin sensitivity on regular chow and high-fat diet, blunting the diet-induced adverse effects on adiposity and exercise intolerance. Overlay of RNA-seq and ChIP-seq profiling in skeletal muscle revealed increased transactivation of Foxc1 and Arid5A genes by the mutant GR. Using myotropic adeno-associated viruses for in vivo overexpression or knockdown in muscle, we found that Foxc1 was required and sufficient for normal expression levels of insulin response pathway genes Insr and Irs1, promoting muscle insulin sensitivity. In parallel, Arid5a was required and sufficient to transcriptionally repress the lipid uptake genes C 36 and Fabp4, reducing muscle triacylglycerol accumulation. Moreover, the Foxc1 and Arid5a programs in muscle were divergently changed by glucocorticoid regimens with opposite metabolic outcomes in muscle. Finally, we found a direct human relevance for our mechanism of SNP action in the UK Biobank and All of Us datasets, where the rs6190 SNP correlated with pro-metabolic changes in BMI, lean mass, strength and glucose control according to zygosity. Collectively, our study leveraged a human nuclear receptor coding variant to unveil novel epigenetic regulators of muscle metabolism. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=150 HEIGHT=200 SRC="FIGDIR/small/586997v2_ufig1.gif" ALT="Figure 1"> View larger version (50K): org.highwire.dtl.DTLVardef@1af900borg.highwire.dtl.DTLVardef@119dcaforg.highwire.dtl.DTLVardef@e78baeorg.highwire.dtl.DTLVardef@1835427_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2021

Phodopus roborovskii SH101 as a systemic infection model of SARS-CoV-2

Severe acute respiratory syndrome CoV-2 (SARS-CoV-2) is currently causing a worldwide threat with its unusually high transmission rates and rapid evolution into diverse strains. Unlike typical respiratory viruses, SARS-CoV-2 frequently causes systemic infection by breaking the boundaries of the respiratory systems. The development of animal models recapitulating the clinical manifestations of COVID-19 is of utmost importance not only for the development of vaccines and antivirals but also for understanding the pathogenesis. However, there has not been developed an animal model for systemic infection of SARS-CoV-2 representing most aspects of the clinical manifestations of COVID-19 with systemic symptoms. Here we report that a hamster strain of Phodopus roborovskii SH101, a laboratory inbred hamster strain of P. roborovskii, displayed most symptoms of systemic infection upon SARS-CoV-2 infection as in the case of the human counterpart, unlike current COVID-19 animal models. P. roborovskii SH101 post-infection of SARS-CoV-2 represented most clinical symptoms of COVID-19 such as snuffling, dyspnea, cough, labored breathing, hunched posture, progressive weight loss, and ruffled fur, in addition to high fever following shaking chills. Histological examinations also revealed a serious right-predominated pneumonia as well as slight organ damages in the brain and liver, manifesting systemic COVID-19 cases. Considering the merit of a small animal as well as its clinical manifestations of SARS-CoV-2 infection in human, this hamster model seems to provide an ideal tool to investigate COVID-19. Author summaryAlthough the current animal models supported SARS-CoV-2 replication and displayed varying degrees of illness after SARS-CoV-2 infection, the infections of SARS-CoV-2 were mainly limited to the respiratory systems of these animals, including hACE2 transgenic mice, hamsters, ferrets, fruit bats, guinea pigs, African green monkey, Rhesus macaques, and Cynomolgus macaques. While these animal models can be a modest model for the respiratory infection, there is a clear limit for use them in the study of COVID-19 that also displays multiple systemic symptoms. Therefore, the development of an animal model recapitulating COVID-19-specific symptoms such as the right-predominated pneumonia would be the utmost need to overcome the imminent threat posed by COVID-19. We identified a very interesting hamster strain, Phodopus roborovskii SH101, which mimics almost all aspects of the clinical manifestations of COVID-19 upon SARS-CoV-2 infection. Unlike the current animal models, SARS-CoV-2-infected P. roborovskii SH101 not only displayed the symptoms of respiratory infection but also clinical manifestations specific to human COVID-19 such as high fever following shaking chills, serious right-predominated pneumonia, and minor organ damages in the brain and liver.

microbiology↗

bioRxiv2018

A nonsense mutant of the hepatitis B virus large S protein antagonizes multiple tumor suppressor pathways through c-Jun activation domain-binding protein1

Hepatitis B virus (HBV) is a major cause of hepatocellular carcinoma (HCC). Previous studies have identified recurrent nonsense mutations in the HBV large S (LHBs) gene from the liver from HBV core antigen-positive HCC patients. These nonsense mutants have been shown to be oncogenic in mouse xenograft models using a mouse embryonic fibroblast cell line. Here, we expressed in a liver cell line Huh-7 a carboxy terminally truncated protein from a nonsense mutant of the LHBs gene, sW182* (stop codon at tryptophane-182). Although the sW182* protein appeared not to be very stable in the cultured liver cells, we confirmed that the protein can be highly expressed and retained for a prolonged period of time in the hepatocytes in the mouse liver, indicating its stable nature in the physiological condition.\n\nIn the Huh-7 cells, the sW182* mutant downregulated tumor suppressors p53 and Smad4. This downregulation was reversed by a proteasome inhibitor MG132, implying the involvement of proteasome-based protein degradation in the observed regulation of the tumor suppressors. On the other hand, we found that c-Jun activation domain-binding protein 1 (Jab1) physically interacts with the sW182*, but not wild-type LHBs. RNA interference (RNAi) of Jab1 restored the levels of the downregulated p53 and Smad4. The sW182* mutant inhibited the promoter activity of downstream target genes of the tumor suppressors. Consistently, Jab1 RNAi reversed the inhibition.\n\nThese results suggest that the LHBs nonsense mutant antagonizes the tumor suppressor pathways through Jab1 in the liver contributing to HCC development.

molecular biology↗

bioRxiv2018

Oligomeric α-synuclein-specific degradation by HtrA2/Omi to bestow a neuroprotective function

Although the malfunction of HtrA2/Omi leads to Parkinsons disease (PD), the underlying mechanism has remained unknown. Here, we showed that HtrA2/Omi specifically removed oligomeric -Syn but not monomeric -Syn to protect oligomeric -Syn-induced neurodegeneration. Experiments using mnd2 mice indicated that HtrA2/Omi degraded oligomeric -Syn specifically without affecting monomers. Transgenic Drosophila melanogaster experiments of the co-expression -Syn and HtrA2/Omi and expression of genes individually also confirmed that pan-neuronal expression of HtrA2/Omi completely rescued Parkinsonism in the -Syn-induced PD Drosophila model by specifically removing oligomeric -Syn. HtrA2/Omi maintained the health and integrity of the brain and extended the life span of transgenic flies. Because HtrA2/Omi specifically degraded oligomeric -Syn, co-expression of HtrA2/Omi and -Syn in Drosophila eye maintained a healthy retina, while the expression of -Syn induced retinal degeneration. This work showed that the bacterial function of HtrA to degrade toxic misfolded proteins is evolutionarily conserved in mammalian brains as HtrA2/Omi.

neuroscience↗