Objective Hepatocyte nuclear factor 4-alpha(HNF4A)is a critical transcription factor in the liver and pancreas.Dysfunctions of HNF4A lead to maturity onset diabetes of the young 1(MODY1).Notably,MODY1 patients with HN...Objective Hepatocyte nuclear factor 4-alpha(HNF4A)is a critical transcription factor in the liver and pancreas.Dysfunctions of HNF4A lead to maturity onset diabetes of the young 1(MODY1).Notably,MODY1 patients with HNF4A pathogenic mutations exhibit decreased responses to arginine and reduced plasma triglyceride levels,but the mechanisms remain unclear.This study aims to investigate the potential target genes transcriptionally regulated by HNF4A and explore its role in these metabolic pathways.Methods A stable 293T cell line expressing the HNF1A reporter was overexpressed with HNF4A.RNA sequencing(RNA-seq)was performed to analyze transcriptional differences.Transcription factor binding site prediction was then conducted to identify HNF4A binding motifs in the promoter regions of relevant target genes.Results RNA-seq results revealed a significant upregulation of transmembrane 4 L six family member 5(TM4SF5)mRNA in HNF4A-overexpressing cells.Transcription factor binding predictions suggested the presence of five potential HNF4A binding motifs in the TM4SF5 promoter.Finally,we confirmed that the DR1 site in the-57 to-48 region of the TM4SF5 promoter is the key binding motif for HNF4A.Conclusion This study identified TM4SF5 as a target gene of HNF4A and determined the key binding motif involved in its regulation.Given the role of TM4SF5 as an arginine sensor in mTOR signaling activation and triglyceride secretion,which closely aligns with phenotypes observed in MODY1 patients,our findings provide novel insights into the possible mechanisms by which HNF4A regulates triglyceride secretion in the liver and arginine-stimulated insulin secretion in the pancreas.展开更多
G-protein coupled receptors （GPCRs） class C represent a distant group among the large family of GPCRs. This class includes the receptors for the main neurotransmitters, glutamate and gamma-aminobutyric acid （GABA）...G-protein coupled receptors （GPCRs） class C represent a distant group among the large family of GPCRs. This class includes the receptors for the main neurotransmitters, glutamate and gamma-aminobutyric acid （GABA）, and the receptors for Ca2＋, some taste and pheromone molecules, as well as some orphan receptors. Like any other GPCRs, these receptors possess a heptahelical domain （HD） involved in heterotrimeric G-protein activation, but most of them also have a large extracellular domain （VFT） responsible for agonist recognition and binding. These receptors are dimers, either homo or heterodimers. Then whereas have mGluRs is homodimers, GABAB receptor was the first heteromeric G-protein coupled receptor （GPCR） identified. Indeed, both GB1 and GB2 subunits appear necessary to get a functional GABAB receptor. We have demonstrated that the interactions be- tween VFT domain of both GB1 and GB2 were important for receptor activation. We have also shown the dynamic movement of trans-membrane of mGluRs within dimers. Then we have found that the GABAB receptor induced acti- vation of ERK1/2/CREB and protected neurons from apoptosis by trans-activating IGF-1R. We have also demon- strated that GABAB receptor activation has been modulated by the dynamic protein-protein interactions between re- ceptors and its downstream signal proteins such as FAK1 and Rap l. Finally, we have performed the HTS screening and found the first negative allosteric modulator for GABAB receptors.展开更多
文摘Objective Hepatocyte nuclear factor 4-alpha(HNF4A)is a critical transcription factor in the liver and pancreas.Dysfunctions of HNF4A lead to maturity onset diabetes of the young 1(MODY1).Notably,MODY1 patients with HNF4A pathogenic mutations exhibit decreased responses to arginine and reduced plasma triglyceride levels,but the mechanisms remain unclear.This study aims to investigate the potential target genes transcriptionally regulated by HNF4A and explore its role in these metabolic pathways.Methods A stable 293T cell line expressing the HNF1A reporter was overexpressed with HNF4A.RNA sequencing(RNA-seq)was performed to analyze transcriptional differences.Transcription factor binding site prediction was then conducted to identify HNF4A binding motifs in the promoter regions of relevant target genes.Results RNA-seq results revealed a significant upregulation of transmembrane 4 L six family member 5(TM4SF5)mRNA in HNF4A-overexpressing cells.Transcription factor binding predictions suggested the presence of five potential HNF4A binding motifs in the TM4SF5 promoter.Finally,we confirmed that the DR1 site in the-57 to-48 region of the TM4SF5 promoter is the key binding motif for HNF4A.Conclusion This study identified TM4SF5 as a target gene of HNF4A and determined the key binding motif involved in its regulation.Given the role of TM4SF5 as an arginine sensor in mTOR signaling activation and triglyceride secretion,which closely aligns with phenotypes observed in MODY1 patients,our findings provide novel insights into the possible mechanisms by which HNF4A regulates triglyceride secretion in the liver and arginine-stimulated insulin secretion in the pancreas.
文摘G-protein coupled receptors （GPCRs） class C represent a distant group among the large family of GPCRs. This class includes the receptors for the main neurotransmitters, glutamate and gamma-aminobutyric acid （GABA）, and the receptors for Ca2＋, some taste and pheromone molecules, as well as some orphan receptors. Like any other GPCRs, these receptors possess a heptahelical domain （HD） involved in heterotrimeric G-protein activation, but most of them also have a large extracellular domain （VFT） responsible for agonist recognition and binding. These receptors are dimers, either homo or heterodimers. Then whereas have mGluRs is homodimers, GABAB receptor was the first heteromeric G-protein coupled receptor （GPCR） identified. Indeed, both GB1 and GB2 subunits appear necessary to get a functional GABAB receptor. We have demonstrated that the interactions be- tween VFT domain of both GB1 and GB2 were important for receptor activation. We have also shown the dynamic movement of trans-membrane of mGluRs within dimers. Then we have found that the GABAB receptor induced acti- vation of ERK1/2/CREB and protected neurons from apoptosis by trans-activating IGF-1R. We have also demon- strated that GABAB receptor activation has been modulated by the dynamic protein-protein interactions between re- ceptors and its downstream signal proteins such as FAK1 and Rap l. Finally, we have performed the HTS screening and found the first negative allosteric modulator for GABAB receptors.
