| 研究実績の概要 |
I have found that FLCN complex localizing on the lysosome regulates TFE3 transcriptional activity, which in turn upregulate metabolic genes. I have obtained a clue to support a new concept that FLCN-TFE3-HIF1a axis coordinate nutrient and hypoxia signaling as follows.
1) Regulation of hypoxia response pathway by aberrantly activated TFE3 transcription factor. We have reported that FLCN-TFE3 axis regulates cell proliferation and differentiation through the metabolic reprogramming. In 2020, I clarified that aberrantly activated chimeric TFE3 directly transcribed HIF1a and HIF2a and upregulated hypoxia responsive genes.
2) Essential role of HIF1a in tumorigenesis by a chimeric TFE3. I have crossed HIF1a and / or HIF2a conditional KO mice with KI mice which express oncogenic chimeric TFE3 in kidneys. HIF1a knockout significantly reduced kidney tumor development, indicating its essential role as a downstream molecule of chimeric TFE3.
3) Lipid metabolism pathway as an important downstream of TFE3-HIF1a axis. I performed RNA sequencing on chimeric TFE3 expressing kidneys which were knockout with HIF1a and / or HIF2a. GO analysis demonstrated that genes involved in lipid metabolism were significantly upregulated by the expression of chimeric TFE3 and downregulated by knockingout HIF1a.
4) Regulation of lipid metabolism by TFE3-mTORC1-HIF1a axis. I found that amino acid starvation and hypoxia stress could activate chimeric TFE3-HIF transcriptional axis, resulting in upregulation of lipid metabolism genes.
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