Project description:MiT/TFE transcriptional activity controls lysosomal biogenesis and is negatively regulated by the nutrient sensor mTORC1. Some tumors bypass this regulatory circuit via genetic alterations that drive MiT/TFE expression and activity; however, the mechanisms by which cells with intact or constitutive mTORC1 signaling maintain lysosomal catabolism remain to be elucidated. Using the murine epidermis as a model system, we find that epidermal Tsc1 deletion results in a wavy hair phenotype due to increased EGFR degradation. Unexpectedly, constitutive mTORC1 activation increases lysosomal content via up-regulated expression and activity of MiT/TFEs, while genetic or prolonged pharmacologic mTORC1 inactivation has the reverse effect. This paradoxical up-regulation of lysosomal biogenesis by mTORC1 is mediated by feedback inhibition of AKT, and a resulting suppression of AKT-induced MiT/TFE proteasomal degradation. These data suggest that oncogenic feedback loops work to restrain or maintain cellular lysosomal content during chronically inhibited or constitutively active mTORC1 signaling respectively, and reveal a mechanism by which mTORC1 regulates upstream receptor tyrosine kinase signaling.
Project description:Comprehensive proteogenomic analysis of Microphthalmia Transcription Factor (MiT) family translocation renal cell carcinoma (tRCC) tumor and normal adjacent tissues was performed to elucidate the molecular landscape of these tumors.
Project description:Translocation renal cell carcinoma (tRCC) is a poorly-characterized subtype of kidney cancer driven by MiT/TFE gene fusions. Here, we define the landmarks of tRCC through an integrative analysis of 152 patients with tRCC identified across multiple genomic, clinical trial, and retrospective cohorts. Most tRCCs harbor few somatic alterations apart from MiT/TFE fusions and homozygous deletions at chromosome 9p21.3 (19.2% of cases). Transcriptionally, tRCCs display a heightened NRF2-driven antioxidant response that is associated with resistance to many targeted therapies. Consistently, we find that outcomes for patients with tRCC treated with vascular endothelial growth factor receptor inhibitors (VEGFR-TKI) are worse than those treated with immune checkpoint inhibition (ICI). Multiparametric immunofluorescence confirmed the presence of CD8+ tumor-infiltrating T cells compatible with a clinical benefit from ICI and revealed an exhaustion immunophenotype distinct from that of clear cell RCC. Our findings comprehensively define the clinical and molecular features of tRCC and may inspire new therapeutic hypotheses.
Project description:The activation of cellular quality control pathways to maintain metabolic homeostasis and mitigate diverse cellular stresses is emerging as a critical growth and survival mechanism in many cancers. Autophagy, a highly conserved cellular self-degradative process, is a key player in the initiation and maintenance of pancreatic ductal adenocarcinoma (PDA). However, the regulatory circuits that activate autophagy, and how they enable reprogramming of PDA cell metabolism are unknown. We now show that autophagy regulation in PDA occurs as part of a broader program that coordinates activation of lysosome biogenesis, function and nutrient scavenging, through constitutive activation of the MiT/TFE family of bHLH transcription factors. In PDA cells, the MiT/TFE proteins - MITF, TFE3 and TFEB - override a regulatory mechanism that controls their nuclear translocation, resulting in their constitutive activation. By orchestrating the expression of a coherent network of genes that induce high levels of lysosomal catabolic function, the MiT/TFE factors are required for proliferation and tumorigenicity of PDA cells. Importantly, unbiased global metabolite profiling reveals that MiT/TFE-dependent autophagy-lysosomal activation is specifically required to maintain intracellular AA pools in PDA. This AA flux is part of a program that is essential for metabolic homeostasis and bioenergetics of PDA but not for their non-transformed counterparts. These results identify the MiT/TFE transcription factors as master regulators of the autophagy-lysosomal system in PDA and demonstrate a central role of the autophagosome-lysosome compartment in maintaining tumor cell metabolism through alternative amino acid acquisition and utilization. Examination of mRNA levels in pancreatic ductal adenocarcinoma (PDA) cell line 8988T after treatment with siRNA for control or TFE3
Project description:The activation of cellular quality control pathways to maintain metabolic homeostasis and mitigate diverse cellular stresses is emerging as a critical growth and survival mechanism in many cancers. Autophagy, a highly conserved cellular self-degradative process, is a key player in the initiation and maintenance of pancreatic ductal adenocarcinoma (PDA). However, the regulatory circuits that activate autophagy, and how they enable reprogramming of PDA cell metabolism are unknown. We now show that autophagy regulation in PDA occurs as part of a broader program that coordinates activation of lysosome biogenesis, function and nutrient scavenging, through constitutive activation of the MiT/TFE family of bHLH transcription factors. In PDA cells, the MiT/TFE proteins - MITF, TFE3 and TFEB - override a regulatory mechanism that controls their nuclear translocation, resulting in their constitutive activation. By orchestrating the expression of a coherent network of genes that induce high levels of lysosomal catabolic function, the MiT/TFE factors are required for proliferation and tumorigenicity of PDA cells. Importantly, unbiased global metabolite profiling reveals that MiT/TFE-dependent autophagy-lysosomal activation is specifically required to maintain intracellular AA pools in PDA. This AA flux is part of a program that is essential for metabolic homeostasis and bioenergetics of PDA but not for their non-transformed counterparts. These results identify the MiT/TFE transcription factors as master regulators of the autophagy-lysosomal system in PDA and demonstrate a central role of the autophagosome-lysosome compartment in maintaining tumor cell metabolism through alternative amino acid acquisition and utilization.
Project description:Lysosomal-autophagic degradation of Endoplasmic Reticulum via autophagy (ER-phagy) is emerging as critical regulator of ER homeostasis and function. However, the molecular mechanisms governing ER-phagy are still unknown. Working in chondrocytes, we found that ER-phagy and lysosome biogenesis are co-activated by FGF signaling during hypertrophic differentiation, a mandatory step for bone formation. FGF induced ER-phagy trough IRS1-dependent inhibition of the insulin signaling and activation of MiT/TFE transcription factors, master regulators of lysosome biogenesis. MiT/TFE promoted ER-phagy through the induction of the ER-phagy receptor FAM134B. Notably, the activation of ER-phagy promotes chondrocytes differentiation and secretion of factors required for cartilage replacement by bone. Consistently, medaka fish knock-down for FAM134B have impaired ossification of cranial bones. Thus, ER-phagy is a transcriptionally regulated process that participates to cell differentiation during development.
Project description:Lysosomal degradation of the endoplasmic reticulum (ER) via autophagy (ER-phagy) is emerging as a critical regulator of ER homeostasis and function1. The selective incorporation of ER fragments into nascent autophagosomes is facilitated by ER resident proteins, ER-phagy receptors, that bind the autophagosomal LC3 protein via the cytosolic LC3 interacting domain (LIR) (REF). However, the molecular mechanisms that regulate ER-phagy in response to cellular needs are still largely unknown. We found that the MiT/TFE transcription factors - master regulators of lysosomal biogenesis and autophagy2- control ER-phagy by inducing the expression of the ER-phagy receptor FAM134B. This pathway is robustly activated in chondrocytes by FGF signaling, a critical regulator of chondrocyte differentiation3. FGF triggers TFEB/TFE3-mediated ER-phagy through JNK-dependent proteasomal degradation of the insulin receptor substrate 1 (IRS-1) protein and inhibition of the insulin signaling. FAM134B knock-down impairs cartilage growth and mineralization in medaka fish, suggesting a physiological role for this process during skeletal growth. Notably, we showed that the TFEB/TFE3-FAM134B axis promotes ER-phagy activation upon prolonged starvation. Thus, this study identifies MiT/TFE-factors as key transcriptional activators of ER-phagy in response to both metabolic and developmental cues.
Project description:Translocation renal cell carcinoma (tRCC) is a rare, aggressive kidney cancer primarily occurring in children. They are genetically defined by translocations involving MiT/TFE gene family members, TFE3. We utilized human kidney organoids, or tubuloids, to engineer a tRCC model by expressing of one of the most common MiT/TFE fusions, SFPQ-TFE3. Lentiviral transductions were performed as previously described with lentiviruses encoding either pLKO.1-UbC-luciferase-blast (TubCtrl), pLKO.1-UbC-TFE3-blast (TubTFE3), or pLKO.1-UbC-SFPQ-TFE3-blast (TubFus). Two days post transduction, 5 µg/ml blasticidin was added to the culture medium to select for successfully transduced cells. To study the genome-wide binding sites of the fusion, we conducted CUT&RUN sequencing. CUT&RUN experiments were performed using a modified protocol for low cell numbers using the following antibodies: anti-TFE3 (ab93808, Abcam, 1:2000). Libraries were sequenced using an Illumina NextSeq2000 (2x100bp).
Project description:To understand the role of MiT in Drosophila, we set out to identify critical gene targets by looking at changes in the WT transcriptome induced by either gain or loss of MiT function. Mutant hindgut and malpighian tubules provided loss-of function tissue and nub-Gal4-driven expression of MiT in the wing epithelium was used for gain-of-function. In the wing disc experiment, 543 genes were upregulated by exogenous MiT, and 359 genes were downregulated (>1.4 fold; P value < 0.01). In the larval HG+MT, 897 genes were downregulated and 898 were upregulated (>1.4 fold; P value < 0.01) after MiT. Among these genes, 85 were both upregulated in wing discs and downregulated in mutant HG+MT, and are the common genes that regulated by MiT in both tissues.