LMB Promotes The Nuclear Translocation Of TFEB

TFEB is a member of the MiTF/TFE (microphthalmia-transcription factor E) subfamily of bHLH-LZ (basic-helix-loop-helix leucine-zipper) factors. TFEB plays a critical role in the celluar physiological processes. Early studies showed that the regulating aberration of TFEB has been known to contribute to the pathogenesis of several human diseases, such as placenta angiogenesis and renal cell carcinoma. Recent study showed that TFEB is a master gene of the control of lysosomal biogenesis and autophagy. Also, TFEB can positively regulates lipid metabolism. More and more research evidences showed that TFEB is a key regulator of celluar stress and metabolism. So the deep study of the molecular meachism of TFEB is of great importance.A number of proteins can shuttle between cytoplasm and nuclear, which we can call shuttling proteins. The import and export of a protein cargo can be facilited by protein called importin or exportin, which can recognize the nuclear localization signals (NLSs) or nuclear export signals (NESs), respectively. Leptomycin B(LMB) can bind CRM1 to inhibit the its binding with the cargo proteins. Therefore, LMB can suppress the cytoplasm accumulation of the protein containing NES. Previous study showed that TFEB contains a canonic NES between amino acids 241 and 252. Mutation of NLS in TFEB blocks its nuclear accumulation in resonse to mTORCl inhibition. However, it remains unknown whether TFEB contains an NES and its shuttling mechanism.In this study, we domenstrated that TFEB is a shuttling protein. We demonstrated that the cytoplasmic accumulation of TFEB can be blocked by treatment of leptomycin B. TFEB can totally block the cytoplasmic distribution of TFEB compared with Torinl, a n inhibitor of mTORC 1, which can facilitate the nuclear localization of TFEB with a disperse in the lysosome. The N terminal of TFEB is essential for its cytoplasmic localization. Surprisingly, LMB did not affect the activity of mTORCl or the phosphorylation of TFEB. The subcellular localization of Rags is not altered by LMB. Also, The binding of TFEB with Rags or 14-3-3 is not impaired by LMB. A potential NES was identified, LMB can facilitate the translocation of TFEB through the NES.