Discovery of a potent inhibitor of chaperone-mediated autophagy that targets the HSC70-LAMP2A interaction in non-small cell lung cancer cells

Small molecule disruption of RARα/NCoR1 interaction inhibits chaperone-mediated autophagy in cancer

Chaperone-mediated autophagy (CMA), a type of selective degradation of cytosolic proteins in lysosomes, is commonly upregulated in cancer cells, contributing to their survival and growth. The lack of a specific target for CMA inhibition has limited CMA blockage to genetic manipulations or global lysosomal function inhibition. Here, using genetic modulation, transcriptional analysis, and functional studies, we demonstrate a regulatory role for the interaction of the retinoic acid receptor alpha (RARα) and its corepressor, the nuclear receptor corepressor 1 (NCoR1), on CMA in non-small cell lung cancer (NSCLC). By targeting the disruption of the NCoR1/RARα complex with a structure-based screening strategy, we identified compound CIM7, a potent and selective CMA inhibitor that has no effect on macroautophagy. CIM7 preferentially inhibits CMA in NSCLC cells over normal cells, reduces tumor growth in NSCLC cells, and demonstrates efficacy in an in vivo xenograft mouse model with no observed toxicity in blood or major tissues. These findings reveal a druggable mechanism for selective CMA inhibition and a first-in-class CMA inhibitor as a potential therapeutic strategy for NSCLC.

HSC70 Promotes Breast Cancer Progression via PTEN Autophagic Degradation and PI3K/AKT/mTOR Activation

Heat shock cognate protein 70 (HSC70) functions as a molecular chaperone and plays a crucial role in the regulation of intracellular protein modifications that are involved in tumor autophagy. However, its expression and mechanism in breast cancer have not been studied. The expression of HSC70 was verified by TCGA database and breast cancer patient tissue. We established breast cancer cell models and mouse models using knockdown HSC70. The expression and mechanism of HSC70 in breast cancer were investigated by immunocoprecipitation, protein stability, RNA stability, flow cytometry and biogenic analysis. In this study, we found that HSC70 is highly expressed in breast cancer and that high HSC70 expression positive correlated with poor prognosis using TCGA database and patient tissue verification. Subsequent experimental verification demonstrated that HSC70 drives cell cycle progression and promotes proliferation in breast cancer. Further studies revealed that HSC70 significantly promoted the phosphorylation of PI3K, AKT and mTOR but did not affect the total protein levels. Additionally, the AKT agonist SC79 reversed the effects of HSC70 knockdown on proliferation and cell cycle progression of breast cancer cells. Mechanistically, HSC70 reduces the protein stability of PTEN but does not change its mRNA level, suggesting that HSC70 binds to PTEN and promotes its autophagic degradation. More importantly, in vivo experiments demonstrated that HSC70 knockdown results in slower tumor proliferation and growth. In conclusion, HSC70 can bind to PTEN and promote its autophagic degradation, thereby activating the PI3K/AKT/mTOR signaling pathway to promote cell cycle progression and proliferation in breast cancer. These findings suggest that HSC70 may be a feasible target for breast cancer treatment.

Natural products and cancer: From drug discovery to prevention and therapy

LINKED ARTICLES

This article is part of a themed issue Natural Products and Cancer: From Drug Discovery to Prevention and Therapy. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v182.10/issuetoc.

Progress on the functions and mechanisms of natural products in anti-glioma therapy

Glioma, the most prevalent primary tumor of the central nervous system (CNS), is also the most lethal primary malignant tumor. Currently, there are limited chemotherapeutics available for glioma treatment, necessitating further research to identify and develop new chemotherapeutic agents. A significant approach to discovering anti-glioma drugs involves isolating antitumor active ingredients from natural products (NPs) and optimizing their structures. Additionally, targeted drug delivery systems (TDDSs) are employed to enhance drug solubility and stability and overcome the blood-brain barrier (BBB). TDDSs can penetrate deep into the brain, increase drug concentration and retention time in the CNS, and improve the targeting efficiency of NPs, thereby reducing adverse effects and enhancing anti-glioma efficacy. This paper reviews the research progress of anti-glioma activities of NPs, including alkaloids, polyphenols, flavonoids, terpenoids, saponins, quinones, and their synthetic derivatives over the past decade. The review also summarizes anti-glioma mechanisms, such as suppression of related protein expression, regulation of reactive oxygen species (ROS) levels, control of apoptosis signaling pathways, reduction of matrix metalloproteinases (MMPs) expression, blocking of vascular endothelial growth factor (VEGF), and reversal of immunosuppression. Furthermore, the functions and advantages of NP-based TDDSs in anti-glioma therapy are examined. The key information presented in this review will be valuable for the research and development of NP-based anti-glioma drugs and related TDDSs.

Targeting chaperone-mediated autophagy in neurodegenerative diseases: mechanisms and therapeutic potential

The pathological hallmarks of various neurodegenerative diseases including Parkinson's disease and Alzheimer's disease prominently feature the accumulation of misfolded proteins and neuroinflammation. Chaperone-mediated autophagy (CMA) has emerged as a distinct autophagic process that coordinates the lysosomal degradation of specific proteins bearing the pentapeptide motif Lys-Phe-Glu-Arg-Gln (KFERQ), a recognition target for the cytosolic chaperone HSC70. Beyond its role in protein quality control, recent research underscores the intimate interplay between CMA and immune regulation in neurodegeneration. In this review, we illuminate the molecular mechanisms and regulatory pathways governing CMA. We further discuss the potential roles of CMA in maintaining neuronal proteostasis and modulating neuroinflammation mediated by glial cells. Finally, we summarize the recent advancements in CMA modulators, emphasizing the significance of activating CMA for the therapeutic intervention in neurodegenerative diseases.

Chaperone-Mediated Autophagy Reactivation Protects Against Severe Acute Pancreatitis-Associated Liver Injury Through Upregulating Keap1/Nrf2 Signaling Pathway and Inhibiting NLRP3 Inflammasome Activation

Acute liver injury (ALI) is a vital factor in the early progression of severe acute pancreatitis (SAP). It exacerbates systemic inflammation, impairs the liver's capacity to clear inflammatory mediators and cytokines, and contributes to systemic organ dysfunction syndrome (SODS). However, the mechanisms driving SAP-associated liver injury (SAP-ALI) are poorly understood, and effective therapeutic options remain limited. Chaperone-mediated autophagy (CMA), a selective form of autophagy, plays an essential role in reducing inflammation and oxidative stress by clearing damaged or dysfunctional proteins. This study examines the role of CMA in SAP-ALI and evaluates its therapeutic potential. In a sodium taurocholate-induced SAP-ALI rat model, CMA dysfunction was observed, characterized by reduced LAMP2A expression and the accumulation of CMA substrate proteins in pancreatic and hepatic tissues. The activator AR7 successfully restored CMA function, enhanced anti-inflammatory and antioxidant responses, and mitigated pancreatic and liver damage in SAP rat. In contrast, the CMA inhibitor PPD exacerbated liver injury, underscoring CMA's protective role in SAP-ALI. Mechanistic analyses demonstrated that CMA reactivation activated the Keap1/Nrf2 signaling pathway, leading to increased expression of antioxidant-related genes and suppression of NLRP3 inflammasome activation. Specifically, the protective effects of AR7-induced CMA activation were significantly reversed by the Nrf2 inhibitor ML385, which inhibited Nrf2 signaling and its associated protein levels. These findings show AR7-induced CMA reactivation as a promising therapeutic strategy for SAP-ALI, primarily through its enhancement of Keap1/Nrf2-regulated antioxidant pathways and inhibition of NLRP3 inflammasome activation.

Research Advances in Chaperone-Mediated Autophagy (CMA) and CMA-Based Protein Degraders

Molecular mechanisms of chaperone-mediated autophagy (CMA) constitute essential regulatory elements in cellular homeostasis, encompassing protein quality control, metabolic regulation, cellular signaling cascades, and immunological functions. Perturbations in CMA functionality have been causally associated with various pathological conditions, including neurodegenerative pathologies and neoplastic diseases. Recent advances in targeted protein degradation (TPD) methodologies have demonstrated that engineered degraders incorporating KFERQ-like motifs can facilitate lysosomal translocation and subsequent proteolysis of noncanonical substrates, offering novel therapeutic interventions for both oncological and neurodegenerative disorders. This comprehensive review elucidates the molecular mechanisms, physiological significance, and pathological implications of CMA pathways. Additionally, it provides a critical analysis of contemporary developments in CMA-based degrader technologies, with particular emphasis on their structural determinants, mechanistic principles, and therapeutic applications. The discourse extends to current technical limitations in CMA investigation and identifies key obstacles that must be addressed to advance the development of CMA-targeting therapeutic agents.

PGC-1α regulation by FBXW7 through a novel mechanism linking chaperone-mediated autophagy and the ubiquitin-proteasome system

Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) is a key regulator of mitochondrial biogenesis and antioxidative defenses, and it may play a critical role in Parkinson's disease (PD). F-box/WD repeat domain-containing protein (FBXW7), an E3 protein ligase, promotes the degradation of substrate proteins through the ubiquitin-proteasome system (UPS) and leads to the clearance of PGC-1α. Here, we elucidate a novel post-translational mechanism for regulating PGC-1α levels in neurons. We show that enhancing chaperone-mediated autophagy (CMA) activity promotes the CMA-mediated degradation of FBXW7 and consequently increases PGC-1α. We confirm the relevance of this pathway in vivo by showing decreased FBXW7 and increased PGC-1α as a result of boosting CMA selectively in dopaminergic (DA) neurons by overexpressing lysosomal-associated membrane protein 2A (LAMP2A) in TH-Cre-LAMP2-loxp conditional mice. We further demonstrate that these mice are protected against MPTP-induced oxidative stress and neurodegeneration. These results highlight a novel regulatory pathway for PGC-1α in DA neurons and suggest targeted increasing of CMA or decreasing FBXW7 in DA neurons as potential neuroprotective strategies in PD.

2,2',4,4'-Tetrabromodiphenyl ether exposure disrupts blood-testis barrier integrity through CMA-mediated ferroptosis

2,2',4,4'-Tetrabromodiphenyl ether (PBDE-47), being the most prevalent congener of polybrominated diphenyl ethers (PBDEs), has been found to accumulate greatly in the environment and induce spermatogenesis dysfunction. However, the specific underlying factors and mechanisms have not been elucidated. Herein, male Sprague-Dawley (SD) rats were exposed to corn oil, 10 mg/kg body weight (bw) PBDE-47 or 20 mg/kg bw PBDE-47 by gavage for 30 days. PBDE-47 exposure led to blood-testis barrier (BTB) integrity disruption and aberrant spermatogenesis. Given that Sertoli cells are the main toxicant target, to explore the potential mechanism involved, we performed RNA sequencing (RNA-seq) in Sertoli cells, and the differentially expressed genes were shown to be enriched in ferroptosis and lysosomal pathways. We subsequently demonstrated that ferroptosis was obviously increased in testes and Sertoli cells upon exposure to PBDE-47, and the junctional function of Sertoli cells was restored after treatment with the ferroptosis inhibitor ferrostatin-1. Since glutathione peroxidase 4 (GPX4) was dramatically reduced in PBDE-47-exposed testes and Sertoli cells and considering the RNA-sequencing results, we examined the activity of chaperone-mediated autophagy (CMA) and verified that the expression of LAMP2a and HSC70 was upregulated significantly after PBDE-47 exposure. Notably, Lamp2a knockdown not only inhibited ferroptosis by suppressing GPX4 degradation but also restored the impaired junctional function induced by PBDE-47. These collective findings strongly indicate that PBDE-47 induces Sertoli cell ferroptosis through CMA-mediated GPX4 degradation, resulting in decreased BTB-associated protein expression and eventually leading to BTB integrity disruption and spermatogenesis dysfunction.

Autophagy modulation in cancer therapy: Challenges coexist with opportunities

Autophagy, a crucial intracellular degradation process facilitated by lysosomes, plays a pivotal role in maintaining cellular homeostasis. The elucidation of autophagy key genes and signaling pathways has significantly advanced our understanding of this process and has led to the exploration of autophagy as a promising therapeutic approach. This review comprehensively assesses the latest developments in small molecule modulators targeting autophagy. Moreover, the review delves into the most recent strategies for drug discovery, specifically focusing on selective agents that exploit autophagosomes and lysosomes for targeted protein degradation. Additionally, this article highlights the prevailing challenges and outlines potential future advancements in the field. By amalgamating the cutting-edge knowledge in the field, we aim to offer valuable insights and references for the anti-cancer drug development of autophagy-targeted therapies, thus contributing to the advancement of novel therapeutic interventions.

Natural product pharmacology: the British Journal of Pharmacology perspective

Natural products (NPs) have long been used as a rich source of bioactive compounds for drug development. Recent technological advancements have revitalised natural products research as evidenced by increased publications in this field. In this editorial review, we highlight key points from the 2020 British Journal of Pharmacology (BJP) practical guide, which outlines standards for natural products research reports, and provide papers published in BJP between years 2020 to 2023 that demonstrate adherence to these guidelines. Looking ahead, we discuss the potential of chemical proteomics approaches to elucidate natural products mechanisms of action and identify therapeutic targets for future research. By fostering innovation, we aim to advance natural products research and contribute to the development of novel therapeutics that will have a significant impact on healthcare.

The role of Rhizoma Paridis saponins on anti-cancer: The potential mechanism and molecular targets

Cancer is a disease characterized by uncontrolled cell proliferation, leading to excessive growth and invasion that can spread to other parts of the body. Traditional Chinese medicine has made new advancements in the treatment of cancer, providing new perspectives and directions for cancer treatment. Rhizoma Paridis is a widely used Chinese herbal medicine with documented anti-cancer effects dating back to ancient times. Modern research has shown that Rhizoma Paridis saponins (RPS) have various pharmacological activities. RPS can inhibit cancer in multiple ways, such as suppressing tumor growth, inducing cell cycle arrest, promoting cell apoptosis, enhancing cell autophagy, inducing ferroptosis, reducing inflammation, inhibiting angiogenesis, as well as inhibiting metastasis and invasion, and these findings demonstrate the potent anti-cancer activity of RPS. Polyphyllin I, polyphyllin II, polyphyllin VI, and polyphyllin VII have been widely reported as the main active ingredients with anti-cancer properties. Polyphyllin D, polyphyllin E, and polyphyllin G have also been confirmed to possess strong anti-cancer activity in recent years. Therefore, this review dives deep into the molecular mechanisms underlying the anti-cancer effects of RPS to serve as a valuable reference for future scientific research and their potential applications in cancer treatment.

Identification and validation of autophagy-related genes influenced by paris polyphylla in tongue cancer using network pharmacology

BACKGROUND

Tongue squamous cell carcinoma (TSCC) represents the most prevalent form of head and neck squamous cell carcinomas, comprising approximately one-third of all oral cancers. Paris polyphylla(PP) exhibit promising anti-tumor properties, yet their underlying mechanisms remain elusive. This study offers novel insights into the molecular mechanisms underlying TSCC treatment with PP and establishes a theoretical basis for their clinical application.

METHODS

Employing transcriptomics and network pharmacology methodologies, we identified autophagy-related key genes associated with the effects of PP. These genes were subjected to KEGG and GO enrichment analyses to determine their related functions. In vitro, CAL-27 cells were treated with 10, 30, and 60 μg/ml of PP for 24 h to assess tumor cell proliferation, apoptosis, and autophagy-related markers.

KEY FINDINGS

Molecular docking of MAPK3 and PSEN1 with PP revealed stable hydrogen bond interactions, indicating the therapeutic potential of these saponins in TSCC through the autophagy pathway. In vitro experiments demonstrated significant inhibition of proliferative activity in tongue squamous carcinoma CAL-27 cells and promotion of tumor cell apoptosis by PP. Western blot analysis confirmed alterations in the expression of autophagy markers P62, LC3B, and Beclin1 following treatment, suggesting activation of the autophagy pathway.

CONCLUSIONS

Our results suggest that PP inhibits tumor cells through the autophagy pathway, in which MAPK3 and PSEN1 play a role as potential functional molecules.

Recent advances in identifying protein targets of bioactive natural products

Background

Natural products exhibit structural complexity, diversity, and historical therapeutic significance, boasting attractive functions and biological activities that have significantly influenced drug discovery endeavors. The identification of target proteins of active natural compounds is crucial for advancing novel drug innovation. Currently, methods for identifying targets of natural products can be categorized into labeling and label-free approaches based on whether the natural bioactive constituents are modified into active probes. In addition, there is a new avenue for rapidly exploring the targets of natural products based on their innate functions.

Aim

This review aimed to summarize recent advancements in both labeling and label-free approaches to the identification of targets for natural products, as well as the novel target identification method based on the natural functions of natural products.

Methods

We systematically collected relevant articles published in recent years from PubMed, Web of Science, and ScienceDirect, focusing on methods employed for identifying protein targets of bioactive natural products. Furthermore, we systematically summarized the principles, procedures, and successful cases, as well as the advantages and limitations of each method.

Results

Labeling methods allow for the direct labeling of target proteins and the exclusion of indirectly targeted proteins. However, these methods are not suitable for studying post-modified compounds with abolished activity, chemically challenging synthesis, or trace amounts of natural active compounds. Label-free methods can be employed to identify targets of any natural active compounds, including trace amounts and multicomponent mixtures, but their reliability is not as high as labeling methods. The structural complementarity between natural products and their innate receptors significantly increase the opportunities for finding more promising structural analogues of the natural products, and natural products may interact with several structural analogues of receptors in humans.

Conclusion

Each approach presents benefits and drawbacks. In practice, a combination of methods is employed to identify targets of natural products. And natural products' innate functions-based approach is a rapid and selective strategy for target identification. This review provides valuable references for future research in this field, offering insights into techniques and methodologies.

SNARE proteins: Core engines of membrane fusion in cancer

Vesicles are loaded with a variety of cargoes, including membrane proteins, secreted proteins, signaling molecules, and various enzymes, etc. Not surprisingly, vesicle transport is essential for proper cellular life activities including growth, division, movement and cellular communication. Soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) mediate membrane fusion of vesicles with their target compartments that is fundamental for cargo delivery. Recent studies have shown that multiple SNARE family members are aberrantly expressed in human cancers and actively contribute to malignant proliferation, invasion, metastasis, immune evasion and treatment resistance. Here, the localization and function of SNARE proteins in eukaryotic cells are firstly mapped. Then we summarize the expression and regulation of SNAREs in cancer, and describe their contribution to cancer progression and mechanisms, and finally we propose engineering botulinum toxin as a strategy to target SNAREs for cancer treatment.

Cleavage of Hsp70.1 causes lysosomal cell death under stress conditions

Autophagy mediates the degradation of intracellular macromolecules and organelles within lysosomes. There are three types of autophagy: macroautophagy, microautophagy, and chaperone-mediated autophagy. Heat shock protein 70.1 (Hsp70.1) exhibits dual functions as a chaperone protein and a lysosomal membrane stabilizer. Since chaperone-mediated autophagy participates in the recycling of ∼30% cytosolic proteins, its disorder causes cell susceptibility to stress conditions. Cargo proteins destined for degradation such as amyloid precursor protein and tau protein are trafficked by Hsp70.1 from the cytosol into lysosomes. Hsp70.1 is composed of an N-terminal nucleotide-binding domain (NBD) and a C-terminal domain that binds to cargo proteins, termed the substrate-binding domain (SBD). The NBD and SBD are connected by the interdomain linker LL1, which modulates the allosteric structure of Hsp70.1 in response to ADP/ATP binding. After the passage of the Hsp70.1-cargo complex through the lysosomal limiting membrane, high-affinity binding of the positive-charged SBD with negative-charged bis(monoacylglycero)phosphate (BMP) at the internal vesicular membranes activates acid sphingomyelinase to generate ceramide for stabilizing lysosomal membranes. As the integrity of the lysosomal limiting membrane is critical to ensure cargo protein degradation within the acidic lumen, the disintegration of the lysosomal limiting membrane is lethal to cells. After the intake of high-fat diets, however, β-oxidation of fatty acids in the mitochondria generates reactive oxygen species, which enhance the oxidation of membrane linoleic acids to produce 4-hydroxy-2-nonenal (4-HNE). In addition, 4-HNE is produced during the heating of linoleic acid-rich vegetable oils and incorporated into the body via deep-fried foods. This endogenous and exogenous 4-HNE synergically causes an increase in its serum and organ levels to induce carbonylation of Hsp70.1 at Arg469, which facilitates its conformational change and access of activated μ-calpain to LL1. Therefore, the cleavage of Hsp70.1 occurs prior to its influx into the lysosomal lumen, which leads to lysosomal membrane permeabilization/rupture. The resultant leakage of cathepsins is responsible for lysosomal cell death, which would be one of the causative factors of lifestyle-related diseases.

Investigating autophagy and intricate cellular mechanisms in hepatocellular carcinoma: Emphasis on cell death mechanism crosstalk

Hepatocellular carcinoma (HCC) stands as a formidable global health challenge due to its prevalence, marked by high mortality and morbidity rates. This cancer type exhibits a multifaceted etiology, prominently linked to viral infections, non-alcoholic fatty liver disease, and genomic mutations. The inherent heterogeneity of HCC, coupled with its proclivity for developing drug resistance, presents formidable obstacles to effective therapeutic interventions. Autophagy, a fundamental catabolic process, plays a pivotal role in maintaining cellular homeostasis, responding to stressors such as nutrient deprivation. In the context of HCC, tumor cells exploit autophagy, either augmenting or impeding its activity, thereby influencing tumorigenesis. This comprehensive review underscores the dualistic role of autophagy in HCC, acting as both a pro-survival and pro-death mechanism, impacting the trajectory of tumorigenesis. The anti-carcinogenic potential of autophagy is evident in its ability to enhance apoptosis and ferroptosis in HCC cells. Pertinently, dysregulated autophagy fosters drug resistance in the carcinogenic context. Both genomic and epigenetic factors can regulate autophagy in HCC progression. Recognizing the paramount importance of autophagy in HCC progression, this review introduces pharmacological compounds capable of modulating autophagy-either inducing or inhibiting it, as promising avenues in HCC therapy.

Chaperone-mediated autophagy: Molecular mechanisms, biological functions, and diseases

Chaperone-mediated autophagy (CMA) is a lysosomal degradation pathway that eliminates substrate proteins through heat-shock cognate protein 70 recognition and lysosome-associated membrane protein type 2A-assisted translocation. It is distinct from macroautophagy and microautophagy. In recent years, the regulatory mechanisms of CMA have been gradually enriched, including the newly discovered NRF2 and p38-TFEB signaling, as positive and negative regulatory pathways of CMA, respectively. Normal CMA activity is involved in the regulation of metabolism, aging, immunity, cell cycle, and other physiological processes, while CMA dysfunction may be involved in the occurrence of neurodegenerative disorders, tumors, intestinal disorders, atherosclerosis, and so on, which provides potential targets for the treatment and prediction of related diseases. This article describes the general process of CMA and its role in physiological activities and summarizes the connection between CMA and macroautophagy. In addition, human diseases that concern the dysfunction or protective role of CMA are discussed. Our review deepens the understanding of the mechanisms and physiological functions of CMA and provides a summary of past CMA research and a vision of future directions.