Transcription factor TFEB cell-autonomously modulates Transcription factor TFEB cell-autonomously modulates susceptibility to intestinal epithelial cell injury in vivo susceptibility to intestinal epithelial cell injury in vivo

Understanding the transcription factors that modulate epithelial resistance to injury is necessary for understanding intestinal homeostasis and injury repair processes. Recently, transcription factor EB (TFEB) was implicated in expression of autophagy and host defense genes in nematodes and mammalian cells. However, the in vivo roles of TFEB in the mammalian intestinal epithelium were not known. Here, we used mice with a conditional deletion of Tfeb in the intestinal epithelium ( Tfeb Δ IEC ) to examine its importance in defense against injury. Unperturbed Tfeb Δ IEC mice exhibited grossly normal intestinal epithelia, except for a defect in Paneth cell granules. Tfeb Δ IEC mice exhibited lower levels of lipoprotein ApoA1 expression, which is downregulated in Crohn’s disease patients and causally linked to colitis susceptibility. Upon environmental epithelial injury using dextran sodium sulfate (DSS), Tfeb Δ IEC mice exhibited exaggerated colitis. Thus, our study reveals that TFEB is critical for resistance to intestinal epithelial cell injury, potentially mediated by APOA1. The intestinal epithelium is the major site of interaction between the host and colonizing microbes. It is formed by one layer of intestinal epithelial cells, which include enterocytes, mucus-secreting goblet cells, antimicrobial-secreting Paneth cells, and hormone-secreting enteroendocrine (or chromaffin) cells. A major function To discover transcription factors that are important for host defense in the intestinal epithelium, we previously followed an unbiased approach in the model organism C . elegans . We discovered that transcription factor TFEB (called HLH-30 in nematodes) is important for the induction of host defense genes in C . elegans infected with pathogenic bacteria 11 . TFEB was previously discovered as a transcription factor binding to the E µ heavy chain immunoglobulin enhancer 12 , and important for the induction of CD40 ligand in T cells 13 . More recently, TFEB was identified as a key transcriptional activator of a large set of genes during cellular stress, including autophagy and lysosomal genes, known as the Coordinated Lysosomal Expression and Regulation (CLEAR) network 14–16 . TFEB activity is regulated post-translationally. Phosphorylation of TFEB by mTORC1, ERK2, and GSK3 results in its cytosolic retention 16–18 . Dephosphorylation of TFEB can be triggered by release of lysosomal Ca 2 + and subsequent activation of protein phosphatase calcineurin, as well as by mTOR inhibition, causing its relo- calization into the nucleus 19 . In our previous studies, we discovered that C . elegans HLH-30/TFEB controls the induction of genes with antimicrobial or cytoprotective functions, and that both classes of genes are required for host defense against infection. However, whether HLH-30/TFEB is required within the intestinal epithelium for this function is not known. We also showed that TFEB is required in murine macrophages for proper induction of several cytokines and chemokines after phagocytosis of Gram + or Gram- bacterial pathogens, indicating that TFEB is a novel and evolutionarily conserved transcription factor in the host response to bacterial infection 11,20 . Based on this precedent, it is important to determine the functional importance of TFEB in barrier protection and repair in the mammalian intestinal epithelium. defense against diverse challenges, including epithelial injury, in vivo . From the present study, it is apparent that TFEB exerts an important function in intestinal epithelial cells to ensure proper Paneth cell function and protect the intestinal epithelium from injury. sequenced gene using Cuffdiff 54 corrected p-value (q-value) accession GSE98266. differentially