| TFEB is a basic helix–loop–helix leucine zipper transcription factor of the MiT/TFE family that functions as a master regulator of lysosomal biogenesis, autophagy, and lysosome-dependent metabolic adaptation by binding E‑box–type CLEAR motifs in promoters of lysosomal and autophagy genes as homodimers or heterodimers with TFE3 or MITF. The protein comprises an N‑terminal bHLH‑Zip DNA‑binding and dimerization module and a C‑terminal transactivation region that recruits co‑activators, and its activity is controlled primarily through phosphorylation-dependent cytoplasmic retention versus nuclear import. Under nutrient‑replete conditions, TFEB is phosphorylated on key serines by mTORC1 at the lysosomal surface and by additional kinases, including GSK3β and ERK, creating docking sites for 14‑3‑3 proteins and confining TFEB to the cytosol or lysosomal membrane, which keeps CLEAR-driven transcription low. Starvation or lysosomal stress reduces mTORC1 activity and promotes calcineurin-dependent dephosphorylation of TFEB, leading to release from 14‑3‑3, nuclear translocation, and robust occupancy of CLEAR elements such as 5′‑GTCACGTGAC‑3′ in promoters of lysosomal hydrolases, membrane proteins, and autophagy factors, with coordinated upregulation of both lysosomal and autophagosome genes. This transcriptional switch expands lysosomal mass, increases autophagic flux, and adjusts lysosome positioning via induction of genes such as PIP4P1, thereby enhancing degradative capacity and recycling of amino acids, lipids, and other metabolites during nutrient limitation. TFEB also interacts with ACSS2 under glucose deprivation, providing local acetyl‑CoA for histone acetylation at TFEB target loci and strengthening expression of lysosome and autophagy genes, linking TFEB‑dependent catabolic gene activation to chromatin remodeling at its own binding sites. In innate immune responses to bacterial infection, lipopolysaccharide stimulation induces IRG1-dependent production of itaconate, which directly alkylates a conserved cysteine within TFEB, reduces mTOR‑mediated phosphorylation, promotes nuclear accumulation, and activates a TFEB program of lysosomal biogenesis in macrophages; genetic or biochemical disruption of this itaconate–TFEB axis impairs bacterial clearance, whereas preserving TFEB alkylation enhances antibacterial capacity. |
