A small-molecule drug inhibits autophagy gene expression through the central regulator TFEB

Tumors and their microenvironments: Learning from pediatric brain pathologies

Early clues to tumors and their microenvironments come from embryonic development. Here we review the literature and consider whether the embryonic brain and its pathologies can serve as a better model. Among embryonic organs, the brain is the most heterogenous and complex, with multiple lineages leading to wide spectrum of cell states and types. Its dysregulation promotes neurodevelopmental brain pathologies and pediatric tumors. Embryonic brain pathologies point to the crucial importance of spatial heterogeneity over time, akin to the tumor microenvironment. Tumors dedifferentiate through genetic mutations and epigenetic modulations; embryonic brains differentiate through epigenetic modulations. Our innovative review proposes learning developmental brain pathologies to target tumor evolution-and vice versa. We describe ways through which tumor pharmacology can learn from embryonic brains and their pathologies, and how learning tumor, and its microenvironment, can benefit targeting neurodevelopmental pathologies. Examples include pediatric low-grade versus high-grade brain tumors as in rhabdomyosarcomas and gliomas.

Lysosomes in the immunometabolic reprogramming of immune cells in atherosclerosis

Lysosomes have a central role in the disposal of extracellular and intracellular cargo and also function as metabolic sensors and signalling platforms in the immunometabolic reprogramming of macrophages and other immune cells in atherosclerosis. Lysosomes can rapidly sense the presence of nutrients within immune cells, thereby switching from catabolism of extracellular material to the recycling of intracellular cargo. Such a fine-tuned degradative response supports the generation of metabolic building blocks through effectors such as mTORC1 or TFEB. By coupling nutrients to downstream signalling and metabolism, lysosomes serve as a crucial hub for cellular function in innate and adaptive immune cells. Lysosomal dysfunction is now recognized to be a hallmark of atherogenesis. Perturbations in nutrient-sensing and signalling have profound effects on the capacity of immune cells to handle cholesterol, perform phagocytosis and efferocytosis, and limit the activation of the inflammasome and other inflammatory pathways. Strategies to improve lysosomal function hold promise as novel modulators of the immunoinflammatory response associated with atherosclerosis. In this Review, we describe the crosstalk between lysosomal biology and immune cell function and polarization, with a particular focus on cellular immunometabolic reprogramming in the context of atherosclerosis.

TFEB promotes Ginkgetin-induced ferroptosis via TRIM25 mediated GPX4 lysosomal degradation in EGFR wide-type lung adenocarcinoma

Rationale: TFEB activation is associated with prolonged survival in LUAD patients, suggesting potential benefits of TFEB agonists in LUAD treatment. In this study, we identify ginkgetin (GK), derived from Ginkgo folium, as a natural TFEB agonist, which has demonstrated promising anticancer effects in our previous research. TFEB activation has been shown to promote GPX4 degradation, inducing ferroptosis; however, the specific E3 ligases, deubiquitinating enzymes (DUBs), and types of polyubiquitination chains involved remain unclear. The unique mechanisms associated with natural compounds like GK may help elucidate the underlying biological processes. Here, we describe a novel biological event involved in the lysosomal degradation of GPX4 induced by TFEB activation through the utilization of GK. Methods: TFEB activation was induced with GK, and TFEB knockout cells were generated using CRISPR-Cas9. The activity of TFEB and its relationship with ferroptosis were assessed by immunoprecipitation, labile iron pool and lysosomal activity assays. The types of polyubiquitination chains, E3 ligases, and DUBs involved in GPX4 degradation were analyzed using LC-MS, immunoprecipitation, and immunofluorescence. These findings were further validated in an orthotopic xenograft SCID mouse model. Results: GK binds to and activates TFEB, leading to TFEB-mediated lysosomal activation and GPX4 degradation, which induces ferroptosis in LUAD cells. These effects were impaired in TFEB knockout cells. Mechanistically, K48-linked polyubiquitination of GPX4 was required for GK induced GPX4 lysosomal translocation. TFEB knockout reduced both K48-linked ubiquitination and lysosomal translocation of GPX4. Additionally, GK promotes the binding of TFEB and TRIM25. TRIM25 and USP5 were found to competitively bind to GPX4, with TFEB activation favoring TRIM25 binding to GPX4 and reducing the interaction of USP5 and GPX4. These findings were confirmed in a xenograft SCID mouse model using TFEB knockout LUAD cells. Conclusion: This study identifies, for the first time, GK as a promising TFEB agonist for LUAD treatment. TFEB activation promotes TRIM25-mediated K48-linked polyubiquitination and lysosomal degradation of GPX4, driving ferroptosis. This ferroptosis-driven mechanism offers a novel strategy to enhance ferroptosis-based anti-LUAD therapies.

Effects of genetic ablation and pharmacological inhibition of HuR on gene expression, iron metabolism, and hormone levels

BACKGROUND

HuR/ELAV1, a ubiquitous RNA-binding protein, belongs to the RNA-binding protein family and is crucial for stabilizing and regulating the translation of various mRNA targets, influencing gene expression. Elevated HuR levels are associated with multiple disorders, including cancer and neurodegenerative diseases. Despite the identification of small molecule inhibitors targeting HuR, their detailed characterization remains limited. Recently, Eltrombopag, an FDA-approved drug for immune thrombocytopenic purpura and chemotherapy-induced thrombocytopenia, emerged as a potential HuR inhibitor. However, the specific molecular pathways influenced by both HuR and Eltrombopag are not fully understood.

RESULTS

Our study demonstrates that Eltrombopag operates via HuR inhibition, affecting gene expression regulation at the posttranscriptional level. We show that both HuR knockout and Eltrombopag treatment modulate iron metabolism by decreasing ferritin heavy chain (FTH1) and light chain (FTL) synthesis while increasing the expression of iron-regulatory protein 2 (IRP2), a key regulator of ferritin translation. Additionally, HuR inhibition reduces the levels of glycoprotein hormones, alpha polypeptide (CGA), a marker associated with hormone-induced tumors, suggesting a potential use of Eltrombopag in treatment of cancers overexpressing CGA. We observed that the main of control is manifested at the level of translation inhibition, with proteasome-mediated regulation also playing an important role.

CONCLUSIONS

These findings uncover novel posttranscriptional mechanisms governed by HuR and its inhibitor, elucidating pathways relevant to HuR-mediated regulation and molecular therapies aimed at targeting this protein.

Ubiquitination of TFEB increased intestinal permeability to aggravate metabolic dysfunction-associated steatohepatitis

BACKGROUND AND AIMS

Increased intestinal permeability exacerbates the development of metabolic dysfunction-associated steatohepatitis (MASH), but the underlying mechanisms remain unclear. Autophagy is important for maintaining normal intestinal permeability. Here, we investigated the impact of intestinal transcription factor EB (TFEB), a key regulator of autophagy, on intestinal permeability and MASH progression.

APPROACH AND RESULTS

TFEB expression was analyzed in the proximal colon of 45 individuals with metabolic dysfunction-associated steatotic liver disease and 23 healthy controls. We used immunoprecipitation-mass spectrometry to identify TFEB-interacting proteins. Intestine-specific Tfeb knockout mice were generated by mating Tfebfl/fl mice with Villin- Cre mice. The mice were fed a high-fat, high-sucrose diet, and assessments were performed to evaluate intestinal permeability and MASH progression. Intestinal TFEB levels were reduced in patients with MASH and negatively correlated with intestinal permeability and hepatic toxicity. Intestine-specific TFEB deficiency increased intestinal permeability and worsened MASH severity, whereas moderate TFEB overexpression conferred protective effects. Mechanistically, the E3 ligase TRIP12 promotes the ubiquitination and degradation of nuclear TFEB, thereby inhibiting autophagic flux to aggravate intestinal barrier impairment and subsequently promote MASH progression. Importantly, a peptide PT1 designed to block the TRIP12-TFEB interaction reduced MASH progression.

CONCLUSIONS

The ubiquitination of TFEB plays a pivotal role in increasing intestinal permeability and promoting the progression of MASH by inhibiting autophagy. Intestinal TFEB may represent a novel therapeutic target for the treatment of MASH.

TFEB Phase Separation Mediates the Amelioration Effect of Intermittent Fasting on Inflammatory Colitis

Intermittent fasting (IF) has been shown to ameliorate inflammation including DSS-induced colitis. It is well known that autophagy can limit inflammation and TFEB is a master transcriptional factor that regulates the processes of autophagy. However, whether TFEB is involved in the regulation of IF-mediated amelioration of inflammation and its mechanism remained unclear. In this study, we found that IF ameliorated DSS-induced colitis and induced TFEB. Nutrition deprivation induced TFEB puncta formation, which processes the characteristics of liquid-liquid phase separation (LLPS) showed by fluorescence recovery after photobleaching (FRAP) assay and 1,6-hexanediol treatment. We found the 24-33 amino acids of Coiled-Coil (CC) domain located in N terminus is essential for TFEB phase separation. Deletion of 24-33 amino acids within the CC domain inhibited TFEB-mediated target gene expression. In addition, we found transcription co-activators, EP300 and MED1, co-localized with TFEB condensate to formed a transcriptional hub that promotes the efficient expression of target genes. More importantly, TFEB inhibitor with ability to suppress TFEB puncta formation abolished the IF-mediated amelioration of DSS colitis. Together, these findings revealed a critical role of TFEB phase separation in the regulation of its transcriptional activity and anti-inflammatory functions induced by IF.

Sesamin alleviates lipid accumulation induced by elaidic acid in L02 cells through TFEB regulated autophagy

Introduction

Non-alcoholic fatty liver disease (NAFLD) is a common chronic disease seriously threatening human health, with limited treatment means, however. Sesamin, a common lignan in sesame seed oil, exhibits anti-inflammatory, antioxidant, and anticancer properties. Our previous studies have shown an ameliorative effect of sesamin on lipid accumulation in human hepatocellular carcinoma (HePG2) induced by oleic acid, with its protective effects unclear in the case of 9-trans-C18:1 elaidic acid (9-trans-C18,1).

Methods

L02 cells, an important tool in scientific researches due to its high proliferation ability, preserved hepatocyte function, and specificity in response to exogenous factors, were incubated with 9-trans-C18:1 to establish an in vitro model of NAFLD in our study. The lipid accumulation in cells and the morphology of mitochondria and autolysosomes were observed by Oil Red O staining and transmission electron microscopy. The effects of sesamin on oxidative stress, apoptosis, mitochondrial function, autophagy as well as related protein levels in L02 cells were also investigated in the presence of 9-trans-C18:1.

Results

The results showed that sesamin significantly accelerated the autophagy flux of L02 cells induced by 9-trans-C18:1 as well as elevated protein levels of transcription factor EB (TFEB) and its downstream target lysosome-associated membrane protein 1(LAMP1), along with up-regulated levels of TFEB and LAMP1 in the nucleus indicated by Immunofluorescence. In addition, PTEN-induced putative kinase 1 and Parkin mediated mitophagy was activated by sesamin. The direct inhibitor Eltrombopag and indirect inhibitor MHY1485 of TFEB reversed the protective effect of sesamin, suggesting the involvement of autophagy in the lipid-lowering process of sesamin.

Discussion

This work suggests that sesamin regulates autophagy through TFEB to alleviate lipid accumulation in L02 cells induced by 9-trans-C18:1, providing a potential target for the prevention and treatment of NAFLD.

Transcription factor EB reprograms branched-chain amino acid metabolism and promotes pancreatic cancer progression via transcriptional regulation of BCAT1

Pancreatic cancer cells have a much higher metabolic demand than that of normal cells. However, the abundant interstitium and lack of blood supply determine the lack of nutrients in the tumour microenvironment. Although pancreatic cancer has been reported to supply extra metabolic demand for proliferation through autophagy and other means, the specific regulatory mechanisms have not yet been elucidated. In this study, we focused on transcription factor EB (TFEB), a key factor in the regulation of autophagy, to explore its effect on the phenotype and role in the unique amino acid utilisation pattern of pancreatic cancer cells (PCCs). The results showed that TFEB, which is generally highly expressed in pancreatic cancer, promoted the proliferation and metastasis of PCCs. TFEB knockdown inhibited the proliferation and metastasis of PCCs by blocking the catabolism of branched-chain amino acids (BCAAs). Concerning the mechanism, we found that TFEB regulates the catabolism of BCAAs by regulating BCAT1, a key enzyme in BCAA metabolism. BCAA deprivation alone did not effectively inhibit PCC proliferation. However, BCAA deprivation combined with eltrombopag, a drug targeting TFEB, can play a two-pronged role in exogenous supply deprivation and endogenous utilisation blockade to inhibit the proliferation of pancreatic cancer to the greatest extent, providing a new therapeutic direction, such as targeted metabolic reprogramming of pancreatic cancer.

Astragaloside I Promotes Lipophagy and Mitochondrial Biogenesis to Improve Hyperlipidemia by Regulating Akt/mTOR/TFEB Pathway

The simultaneous enhancement of lipophagy and mitochondrial biogenesis has emerged as a promising strategy for lipid lowering. The transcription factor EB (TFEB) exhibits a dual role, whereby it facilitates the degradation of lipid droplets (LDs) through the process of lipophagy while simultaneously stimulating mitochondrial biogenesis to support the utilization of lipophagy products. The purpose of this study was to explore the effect of astragaloside I (AS I) on hyperlipidemia and elucidate its underlying mechanism. AS I improved serum total cholesterol and triglyceride levels and reduced hepatic steatosis and lipid accumulation in db/db mice. AS I enhanced the fluorescence colocalization of LDs and autophagosomes and promoted the proteins and genes related to the autolysosome. Moreover, AS I increased the expression of mitochondrial biogenesis-related proteins and genes, indicating that AS I promoted lipophagy and mitochondrial biogenesis. Mechanistically, AS I inhibits the protein level of p-TFEB (ser211) expression and promotes TFEB nuclear translocation. The activation of TFEB by AS I was impeded upon the introduction of the mammalian target of rapamycin (mTOR) agonist MHY1485. The inhibition of p-mTOR by AS I and the activation of TFEB were no longer observed after administration of the Akt agonist SC-79, which indicated that AS I activated TFEB to promote lipophagy-dependent on the Akt/mTOR pathway and may be a potentially effective pharmaceutical and food additive for the treatment of hyperlipidemia.

Design and validation of a reporter mouse to study the dynamic regulation of TFEB and TFE3 activity through in vivo imaging techniques

TFEB and TFE3 belong to the MiT/TFE family of transcription factors that bind identical DNA responsive elements in the regulatory regions of target genes. They are involved in regulating lysosomal biogenesis, function, exocytosis, autophagy, and lipid catabolism. Precise control of TFEB and TFE3 activity is crucial for processes such as senescence, stress response, energy metabolism, and cellular catabolism. Dysregulation of these factors is implicated in various diseases, thus researchers have explored pharmacological approaches to modulate MiT/TFE activity, considering these transcription factors as potential therapeutic targets. However, the physiological complexity of their functions and the lack of suitable in vivo tools have limited the development of selective MiT/TFE modulating agents. Here, we have created a reporter-based biosensor, named CLEARoptimized, facilitating the pharmacological profiling of TFEB- and TFE3-mediated transcription. This innovative tool enables the measurement of TFEB and TFE3 activity in living cells and mice through imaging and biochemical techniques. CLEARoptimized consists of a promoter with six coordinated lysosomal expression and regulation motifs identified through an in-depth bioinformatic analysis of the promoters of 128 TFEB-target genes. The biosensor drives the expression of luciferase and tdTomato reporter genes, allowing the quantification of TFEB and TFE3 activity in cells and in animals through optical imaging and biochemical assays. The biosensor's validity was confirmed by modulating MiT/TFE activity in both cell culture and reporter mice using physiological and pharmacological stimuli. Overall, this study introduces an innovative tool for studying autophagy and lysosomal pathway modulation at various biological levels, from individual cells to the entire organism.Abbreviations: CLEAR: coordinated lysosomal expression and regulation; MAR: matrix attachment regions; MiT: microphthalmia-associated transcription factor; ROI: region of interest; TBS: tris-buffered saline; TF: transcription factor; TFE3: transcription factor binding to IGHM enhancer 3; TFEB: transcription factor EB; TH: tyrosine hydroxylase; TK: thymidine kinase; TSS: transcription start site.

Chemotherapy's effects on autophagy in the treatment of Hodgkin's lymphoma: a scoping review

BACKGROUND

Classical Hodgkin Lymphomas (HL) are a unique malignant growth with an excellent initial prognosis. However, 10-30% of patients will still relapse after remission. One primary cellular function that has been the focus of tumor progression is autophagy. This process can preserve cellular homeostasis under stressful conditions. Several studies have shown that autophagy may play a role in developing HL. Therefore, this review aimed to explore chemotherapy's effect on autophagy in HL, and the effects of autophagy on HL.

METHODS

A scoping review in line with the published PRISMA extension for scoping reviews (PRISMA-ScR) was conducted. A literature search was conducted on the MEDLINE database and the Cochrane Central Register of Controlled Trials (CENTRAL). All results were retrieved and screened, and the resulting articles were synthesized narratively.

RESULTS

The results showed that some cancer chemotherapy also induces autophagic flux. Although the data on HL is limited, since the mechanisms of action of these drugs are similar, we can infer a similar relationship. However, this increased autophagy activity may reflect a mechanism for increasing tumor growth or a cellular compensation to inhibit its growth. Although evidence supports both views, we argued that autophagy allowed cancer cells to resist cell death, mainly due to DNA damage caused by cytotoxic drugs.

CONCLUSION

Autophagy reflects the cell's adaptation to survive and explains why chemotherapy generally induces autophagy functions. However, further research on autophagy inhibition is needed as it presents a viable treatment strategy, especially against drug-resistant populations that may arise from HL chemotherapy regimens.

Neddylation activated TRIM25 desensitizes triple-negative breast cancer to paclitaxel via TFEB-mediated autophagy

BACKGROUND

Paclitaxel (PTX) treatment resistance is an important factor leading to poor prognosis in triple-negative breast cancer (TNBC), therefore there is an urgent need to identify new target for combination therapy. Neddylation is a post-translational process that introduces a ubiquitin-like protein called neural precursor cell expressed developmentally downregulated protein 8 (NEDD8). Previous studies have found that neddylation is activated in multiple tumors, but its relationship with PTX chemotherapy sensitivity has not been reported.

METHODS

Differences in UBC12 and NEDD8 expression levels between PTX-sensitive and PTX-insensitive TNBC tissues were validated using public databases and immunohistochemistry. The in vitro and in vivo functional experiments were used to observe the effect of neddylation inhibition combined with PTX therapy on tumor progression. Co-IP, western blot and PCR assays were used to investigate the molecular mechanisms. Molecular docking was used to simulate the protein binding of UBC12 and TRIM25. Molecular dynamics simulation was used to observe the changes in TRIM25 protein conformation.

RESULTS

We found that in TNBC that is insensitive to PTX, NEDD8 and NEDD8 conjugating enzyme UBC12 are highly expressed. Treatment with the NEDD8-activating enzyme (NAE) inhibitor mln4924 or knockdown of UBC12 significantly increased the sensitivity of the tumor to PTX, and this increase in sensitivity is related to UBC12-mediated autophagy activation. Mechanistically, UBC12 can transfer NEDD8 to E3 ubiquitin ligase tripartite motif containing 25 (TRIM25) at K117. Molecular dynamics simulations indicate that the neddylation modification of TRIM25 reduces steric hindrance in its RING domain, facilitating the binding of TRIM25 and ubiquitylated substrates. Subsequently, TRIM25 promotes the nuclear translocation of transcription factor EB (TFEB) and transcription of autophagy related genes by increasing K63-polyubiquitination of TFEB, thereby reducing tumor sensitivity to PTX.

CONCLUSIONS

Neddylation is activated in PTX-insensitive TNBC. Specifically, autophagy gene transcriptional activation mediated by the UBC12/TRIM25/TFEB axis reduces TNBC sensitivity to PTX. Neddylation suppression combination with PTX treatment shows a synergistic anti-tumor effect.

Intermittent hypoxia training enhances Aβ endocytosis by plaque associated microglia via VPS35-dependent TREM2 recycling in murine Alzheimer's disease

BACKGROUND

Beta-amyloid (Aβ) deposition in the brain parenchyma is a crucial initiating step in the amyloid cascade hypothesis of Alzheimer's disease (AD) pathology. Furthermore, dysfunction of plaque-associated microglia, also known as disease-associated microglia (DAM) has been reported to accelerate Aβ deposition and cognitive impairment. Our previous research demonstrated that intermittent hypoxia training (IHT) improved AD pathology by upregulating autophagy in DAM, thereby enhancing oligomeric Aβ (oAβ) clearance. Considering that oAβ internalization is the initial stage of oAβ clearance, this study focused on the IHT mechanism involved in upregulating Aβ uptake by DAM.

METHODS

IHT was administered to 8-month-old APP/PS1 mice or 6-month-old microglial vacuolar protein sorting 35 (VPS35) knockout mice in APP/PS1 background (MG VPS35 KO: APP/PS1) for 28 days. After the IHT, the spatial learning-memory capacity of the mice was assessed. Additionally, AD pathology was determined by estimating the nerve fiber and synapse density, Aβ plaque deposition, and Aβ load in the brain. A model of Aβ-exposed microglia was constructed and treated with IHT to explore the related mechanism. Finally, triggering receptor expressed on myeloid cells 2 (TREM2) intracellular recycling and Aβ internalization were measured using a fluorescence tracing technique.

RESULTS

Our results showed that IHT ameliorated cognitive function and Aβ pathology. In particular, IHT enhanced Aβ endocytosis by augmenting the intracellular transport function of microglial TREM2, thereby contributing to Aβ clearance. Furthermore, IHT specifically upregulated VPS35 in DAM, the primary cause for the enhanced intracellular recycling of TREM2. IHT lost ameliorative effect on Aβ pathology in MG VPS35 KO: APP/PS1 mice brain. Lastly, the IHT mechanism of VPS35 upregulation in DAM was mediated by the transcriptional regulation of VPS35 by transcription factor EB (TFEB).

CONCLUSION

IHT enhances Aβ endocytosis in DAM by upregulating VPS35-dependent TREM2 recycling, thereby facilitating oAβ clearance and mitigation of Aβ pathology. Moreover, the transcriptional regulation of VPS35 by TFEB demonstrates a close link between endocytosis and autophagy in microglia. Our study further elucidates the IHT mechanism in improving AD pathology and provides evidence supporting the potential application of IHT as a complementary therapy for AD.

The interplay between autophagy and cGAS-STING signaling and its implications for cancer

Autophagy is an intracellular process that targets various cargos for degradation, including members of the cGAS-STING signaling cascade. cGAS-STING senses cytosolic double-stranded DNA and triggers an innate immune response through type I interferons. Emerging evidence suggests that autophagy plays a crucial role in regulating and fine-tuning cGAS-STING signaling. Reciprocally, cGAS-STING pathway members can actively induce canonical as well as various non-canonical forms of autophagy, establishing a regulatory network of feedback mechanisms that alter both the cGAS-STING and the autophagic pathway. The crosstalk between autophagy and the cGAS-STING pathway impacts a wide variety of cellular processes such as protection against pathogenic infections as well as signaling in neurodegenerative disease, autoinflammatory disease and cancer. Here we provide a comprehensive overview of the mechanisms involved in autophagy and cGAS-STING signaling, with a specific focus on the interactions between the two pathways and their importance for cancer.

Inhibiting autophagy before it starts

Autophagy, an important cellular stress response mechanism, is often exploited by a variety of cancer cells to sustain rapid growth under stresses such as nutrient deprivation and hypoxia. Autophagy also plays a key role in tumor resistance to chemotherapy, radiotherapy or targeted therapy. Inhibition of autophagy is therefore a promising tumor treatment strategy. However, there is still a lack of effective autophagy inhibitors suitable for clinical use. Most drug development has focused on enzymes like the VPS34 and ULK1 kinases, or the cysteine protease ATG4B, which plays different roles in autophagy. We discovered a drug molecule Eltrombopag that inhibits the expression of autophagic lysosomal genes at the stage of transcriptional level, where the synthesis of these proteins has not really begun, by directly inhibiting the TFEB (transcription factor EB). This drug can improve the therapeutic effect of Temozolomide on glioblastoma treatment, further confirming the value of inhibiting autophagy in the treatment of cancer.Abbreviation: VPS34: vacuolar protein sorting 34; ULK1: unc-51 like autophagy activating kinase 1; TFEB: transcription factor EB; MITF: microphthalmia-associated transcription factor; TFE3: transcription factor E3; EO: Eltrombopag; ITC: isothermal titration calorimetry; bHLH-LZ: basic helix-loop-helix leucine zipper; LAMP1: lysosomal-associated membrane protein 1; CTSF: cathepsin F; HEXA: hexosaminidase subunit alpha.

From the regulatory mechanism of TFEB to its therapeutic implications

Transcription factor EB (TFEB), known as a major transcriptional regulator of the autophagy-lysosomal pathway, regulates target gene expression by binding to coordinated lysosomal expression and regulation (CLEAR) elements. TFEB are regulated by multiple links, such as transcriptional regulation, post-transcriptional regulation, translational-level regulation, post-translational modification (PTM), and nuclear competitive regulation. Targeted regulation of TFEB has been victoriously used as a treatment strategy in several disease models such as ischemic injury, lysosomal storage disorders (LSDs), cancer, metabolic disorders, neurodegenerative diseases, and inflammation. In this review, we aimed to elucidate the regulatory mechanism of TFEB and its applications in several disease models by targeting the regulation of TFEB as a treatment strategy.

Targeting autophagy with small-molecule activators for potential therapeutic purposes

Autophagy is well-known to be a lysosome-mediated catabolic process for maintaining cellular and organismal homeostasis, which has been established with many links to a variety of human diseases. Compared with the therapeutic strategy for inhibiting autophagy, activating autophagy seems to be another promising therapeutic strategy in several contexts. Hitherto, mounting efforts have been made to discover potent and selective small-molecule activators of autophagy to potentially treat human diseases. Thus, in this perspective, we focus on summarizing the complicated relationships between defective autophagy and human diseases, and further discuss the updated progress of a series of small-molecule activators targeting autophagy in human diseases. Taken together, these inspiring findings would provide a clue on discovering more small-molecule activators of autophagy as targeted candidate drugs for potential therapeutic purposes.

Tetramerization of upstream stimulating factor USF2 requires the elongated bent leucine zipper of the bHLH-LZ domain

Upstream stimulating factors (USFs), including USF1 and USF2, are key components of the transcription machinery that recruit coactivators and histone-modifying enzymes. Using the classic basic helix-loop-helix leucine zipper (bHLH-LZ) domain, USFs bind the E-box DNA and form tetramers that promote DNA looping for transcription initiation. The structural basis by which USFs tetramerize and bind DNA, however, remains unknown. Here, we report the crystal structure of the complete bHLH-LZ domain of USF2 in complex with E-box DNA. We observed that the leucine zipper (LZ) of USF2 is longer than that of other bHLH-LZ family transcription factors and that the C-terminus of USF2 forms an additional α-helix following the LZ region (denoted as LZ-Ext). We also found the elongated LZ-Ext facilitates compact tetramer formation. In addition to the classic interactions between the basic region and DNA, we show a highly conserved basic residue in the loop region, Lys271, participates in DNA interaction. Together, these findings suggest that USF2 forms a tetramer structure with a bent elongated LZ-Ext region, providing a molecular basis for its role as a key component of the transcription machinery.

Dissecting the multifaced function of transcription factor EB (TFEB) in human diseases: From molecular mechanism to pharmacological modulation

The transcription factor EB (TFEB) is a transcription factor of the MiT/TFE family that translocations from the cytoplasm to the nucleus in response to various stimuli, including lysosomal stress and nutrient starvation. By activating genes involved in lysosomal function, autophagy, and lipid metabolism, TFEB plays a crucial role in maintaining cellular homeostasis. Dysregulation of TFEB has been implicated in various diseases, including cancer, neurodegenerative diseases, metabolic diseases, cardiovascular diseases, infectious diseases, and inflammatory diseases. Therefore, modulating TFEB activity with agonists or inhibitors may have therapeutic potential. In this review, we reviewed the recently discovered regulatory mechanisms of TFEB and their impact on human diseases. Additionally, we also summarize the existing TFEB inhibitors and agonists (targeted and non-targeted) and discuss unresolved issues and future research directions in the field. In summary, this review sheds light on the crucial role of TFEB, which may pave the way for its translation from basic research to practical applications, bringing us closer to realizing the full potential of TFEB in various fields.