Occludin Is a Direct Target of Thyroid Transcription Factor-1 (TTF-1/NKX2–1)

Runkle, E. Aaron; Rice, Stephen L.; Qi, Ji; Masser, Dustin R.; Antonetti, David A.; Winslow, Monte M.; Mu, David

doi:10.1074/jbc.m112.367987

Cited by 42 publications

(54 citation statements)

References 57 publications

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“…Whole-cell lysates were immunoprecipitated using 1 g of rabbit anti-HNF4␣ (H171) (Santa Cruz Biotechnology, Inc.) or IgG. Real-time qPCR was used to amplify the region near the HNF4␣ binding site in the promoter of the CLDN1 gene (26,27). Reactions were performed in triplicate in three independent experiments, and the means were normalized to 1% of the chromatin input.…”

Section: Methodsmentioning

confidence: 99%

Hepatitis C Virus Entry Is Impaired by Claudin-1 Downregulation in Diacylglycerol Acyltransferase-1-Deficient Cells

Sung

Murayama

Kang

et al. 2014

J Virol

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Diacylglycerol acyltransferase-1 (DGAT1) is involved in the assembly of hepatitis C virus (HCV) by facilitating the trafficking of the HCV core protein to the lipid droplet. Here, we abrogated DGAT1 expression in Huh-7.5 cells by using either the transcription activator-like effector nuclease (TALEN) or lentivirus vector short hairpin RNA (shRNA) and achieved complete long-term silencing of DGAT1. HCV entry was severely impaired in DGAT1-silenced Huh-7.5 cell lines, which showed markedly diminished claudin-1 (CLDN1) expression. In DGAT1-silenced cell lines, the forced expression of CLDN1 restored HCV entry, implying that the downregulation of CLDN1 is a critical factor underlying defective HCV entry. The expression of the gene coding for hepatocyte nuclear factor 4␣ (HNF4␣) and other hepatocyte-specific genes was also reduced in DGAT1-silenced cell lines. After DGAT1 gene rescue, CLDN1 expression was preserved, and HCV entry was restored. Strikingly, after DGAT1 silencing, CLDN1 expression and HCV entry were also restored by low-dose palmitic acid treatment, indicating that the downregulation of CLDN1 was associated with altered fatty acid homeostasis in the absence of DGAT1. Our findings provide novel insight into the role of DGAT1 in the life cycle of HCV. IMPORTANCEIn this study, we report the novel effect of complete silencing of DGAT1 on the entry of HCV. DGAT1 was recently reported as a host factor of HCV, involved in the assembly of HCV by facilitating the trafficking of the HCV core protein to lipid droplets. We achieved complete and long-term silencing of DGAT1 by either TALEN or repeated transduction of lentivirus shRNA. We found that HCV entry was severely impaired in DGAT1-silenced cell lines. The impairment of HCV entry was caused by CLDN1 downregulation, and the expression of HNF4␣ and other hepatocyte-specific genes was also downregulated in DGAT1-silenced cell lines. Our results suggest new roles of DGAT1 in human liver-derived cells: maintaining intracellular lipid homeostasis and affecting HCV entry by modulating CLDN1 expression. H epatitis C virus (HCV) infection poses a major threat to human health, with a prevalence of more than 160 million people worldwide (1). In addition to a combination regimen of pegylated interferon alpha (IFN-␣) and ribavirin, drugs acting directly on HCV have now been developed, although these direct-acting antivirals may prompt the emergence of resistant strains (2, 3). Our increasing understanding of the HCV-host interactions is allowing novel therapeutic approaches to be developed that modulate host factors that are required for viral entry, replication, and egress; these factors may have a higher genetic barrier to viral resistance (4).Diacylglycerol acyltransferase-1 (DGAT1) is one of two known DGAT enzymes catalyzing the final step in triglyceride biosynthesis (5, 6). The expression of DGAT1 and its physiologic role differ in humans and mice. In mice, DGAT1 is expressed in many organs, including the skeletal muscle, heart, and intestines, but it is bar...

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Section: Methodsmentioning

confidence: 99%

Hepatitis C Virus Entry Is Impaired by Claudin-1 Downregulation in Diacylglycerol Acyltransferase-1-Deficient Cells

Sung

Murayama

Kang

et al. 2014

J Virol

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“…To determine whether TTF-1 transactivates the miR-29ab1 promoter, we cotransfected A549 lung adenocarcinoma cells with a reporter construct containing 539 bp of the human miR-29b-1/a gene (miR-29ab1) 5= flanking sequence subcloned upstream of a luciferase reporter and increasing amounts of an expression vector containing either wild-type (WT) TTF-1 or TTF-1 lacking its homeodomain (TTF-1⌬HD), which is known to be critical for transcriptional activation of its target gene promoters (22,35). As can be seen, increasing amounts of TTF-1 expression vector caused upregulation of miR-29ab1 promoter activity in a dosedependent manner (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The transcription start site of miR-29b1 and miR-29a was previously identified (21), and a 539-bp fragment (bp Ϫ481 to ϩ58) was cloned and inserted into the pGL3-basic vector. The human TTF-1 expression plasmid pcDNA3.1(ϩ)-wt-TTF-1 (Addgene; plasmid 49989) and a TTF-1 expression plasmid lacking the homeodomain [pcDNA3.1(ϩ)-TTF-1-HDD; Addgene plasmid 52063] were gifts from David Mu (22). pcDNA3.1 and pRL-TK (Promega) vectors were used to normalize DNA and transfection efficiency, respectively.…”

Section: Methodsmentioning

confidence: 99%

The MicroRNA 29 Family Promotes Type II Cell Differentiation in Developing Lung

Guo

Benlhabib

Mendelson

2016

Molecular and Cellular Biology

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“…The TTF-1 gene is essential to lung development (23). To date, the investigation of KGF effects on the expression of TTF-1 are limited.…”

Section: Discussionmentioning

confidence: 99%

Effect of keratinocyte growth factor on growth and transdifferentiationof primary alveolar epithelial type II cells

Liu¹,

Feng²,

Tian³

et al. 2015

Turk J Med Sci

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Background/aim: To investigate the effects of keratinocyte growth factor (KGF) on the growth and transdifferentiation of primary alveolar epithelial type II cells (AECIIs). Materials and methods:The number of primary AECIIs, their viability, and cell cycle and apoptosis were studied under KGF treatment using a hemocytometer, trypan blue exclusion, and flow cytometry, respectively. Positive expressions of surfactant protein C (SP-C), aquaporin 5 (AQP5), and thyroid transcription factor 1(TTF-1) were examined with indirect immunofluorescence; mRNA levels of SP-C, AQP5, and TTF-1 were determined by polymerase chain reaction. Results:In response to KGF treatment, cell numbers were significantly increased, more cells were blocked in the S phase, and fewer cells were apoptotic or necrotic on days 2 and 4, but there was little effect on cell viability. In addition, KGF treatment resulted in higher levels of SP-C on days 2 and 8 while lowering them on day 4, higher levels of AQP5 on day 4 while lowering them on day 8, and higher levels of TTF-1 on days 2, 6, and 8. Conclusion:KGF treatment promoted proliferation of AECIIs, inhibited cell apoptosis, promoted transdifferentiation of AECIIs, and induced alveolar epithelial type I cells to revert to AECIIs.

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Occludin Is a Direct Target of Thyroid Transcription Factor-1 (TTF-1/NKX2–1)

Cited by 42 publications

References 57 publications

Hepatitis C Virus Entry Is Impaired by Claudin-1 Downregulation in Diacylglycerol Acyltransferase-1-Deficient Cells

Hepatitis C Virus Entry Is Impaired by Claudin-1 Downregulation in Diacylglycerol Acyltransferase-1-Deficient Cells

The MicroRNA 29 Family Promotes Type II Cell Differentiation in Developing Lung

Effect of keratinocyte growth factor on growth and transdifferentiationof primary alveolar epithelial type II cells

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