Chaperone-mediated autophagy substrate proteins in cancer

The role of chaperone-mediated autophagy in drug resistance

In the search for alternatives to overcome the challenge imposed by drug resistance development in cancer treatment, the modulation of autophagy has emerged as a promising alternative that has achieved good results in clinical trials. Nevertheless, most of these studies have overlooked a novel and selective type of autophagy: chaperone-mediated autophagy (CMA). Following its discovery, research into CMA's contribution to tumor progression has accelerated rapidly. Therefore, we now understand that stress conditions are the primary signal responsible for modulating CMA in cancer cells. In turn, the degradation of proteins by CMA can offer important advantages for tumorigenesis, since tumor suppressor proteins are CMA targets. Such mutual interaction between the tumor microenvironment and CMA also plays a crucial part in establishing therapy resistance, making this discussion the focus of the present review. Thus, we highlight how suppression of LAMP2A can enhance the sensitivity of cancer cells to several drugs, just as downregulation of CMA activity can lead to resistance in certain cases. Given this panorama, it is important to identify selective modulators of CMA to enhance the therapeutic response.

Moringa oleifera and Autophagy: Evidence from In Vitro Studies on Chaperone-Mediated Autophagy in HepG2 Cancer Cells

Hepatocellular carcinoma (HCC) is the most prevalent primary liver cancer in Sub-Saharan African countries, including South Africa (SA). Given the limitations in current HCC therapeutics, there is an increasing need for alternative adjuvant therapeutic options. As such, several cell survival mechanisms, such as autophagy, have been identified as potential adjuvant therapeutic targets in HCC treatment. Of the three most established autophagic pathways, the upregulation of chaperone-mediated autophagy (CMA) has been extensively described in various cancer cells, including HCC cells. CMA promotes tumor growth and chemotherapeutic drug resistance, thus contributing to HCC tumorigenesis. Therefore, the modulation of CMA serves as a promising adjuvant target for current HCC therapeutic strategies. Phytochemical extracts found in the medicinal plant, Moringa oleifera (MO), have been shown to induce apoptosis in numerous cancer cells, including HCC. MO leaves have the greatest abundance of phytochemicals displaying anticancer potential. However, the potential interaction between the pro-apoptotic effects of MO aqueous leaf extract and the survival-promoting role of CMA in an in vitro model of HCC remains unclear. This review aims to summarize the latest findings on the role of CMA, and MO in the progression of HCC.

The Complex Role of Chaperone-Mediated Autophagy in Cancer Diseases

Chaperone-mediated autophagy (CMA) is a process that rapidly degrades proteins labeled with KFERQ-like motifs within cells via lysosomes to terminate their cellular functioning. Meanwhile, CMA plays an essential role in various biological processes correlated with cell proliferation and apoptosis. Previous studies have shown that CMA was initially found to be procancer in cancer cells, while some theories suggest that it may have an inhibitory effect on the progression of cancer in untransformed cells. Therefore, the complex relationship between CMA and cancer has aroused great interest in the application of CMA activity regulation in cancer therapy. Here, we describe the basic information related to CMA and introduce the physiological functions of CMA, the dual role of CMA in different cancer contexts, and its related research progress. Further study on the mechanism of CMA in tumor development may provide novel insights for tumor therapy targeting CMA. This review aims to summarize and discuss the complex mechanisms of CMA in cancer and related potential strategies for cancer therapy.

The roles of molecular chaperones in regulating cell metabolism

Fluctuations in nutrient and biomass availability, often as a result of disease, impart metabolic challenges that must be overcome in order to sustain cell survival and promote proliferation. Cells adapt to these environmental changes and stresses by adjusting their metabolic networks through a series of regulatory mechanisms. Our understanding of these rewiring events has largely been focused on those genetic transformations that alter protein expression and the biochemical mechanisms that change protein behavior, such as post-translational modifications and metabolite-based allosteric modulators. Mounting evidence suggests that a class of proteome surveillance proteins called molecular chaperones also can influence metabolic processes. Here, we summarize several ways the Hsp90 and Hsp70 chaperone families act on human metabolic enzymes and their supramolecular assemblies to change enzymatic activities and metabolite flux. We further highlight how these chaperones can assist in the translocation and degradation of metabolic enzymes. Collectively, these studies provide a new view for how metabolic processes are regulated to meet cellular demand and inspire new avenues for therapeutic intervention.

Chloroquine induces transitory attenuation of proliferation of human lung cancer cells through regulation of mutant P53 and YAP

BACKGROUND

Non-small cell lung carcinoma (NSCLC) is the most common cause of cancer-associated deaths worldwide. Though recent development in targeted therapy has improved NSCLC prognosis, yet there is an unmet need to identify novel causative factors and appropriate therapeutic regimen against NSCLCs.

METHODS AND RESULTS

In this study, we identify key molecular factors de-regulated in NSCLCs. Analyze their expression by real-time PCR and immunoblot; map their localization by immuno-fluorescence microscopy. We further propose an FDA approved drug, chloroquine (CQ) that affects the function of the molecular factors and hence can be repurposed as a therapeutic strategy against NSCLCs. Available NSCLC mutation data reflects a high probabilistic chance of patients harboring a p53 mutation, especially a gain of function (GOF)-R273H mutation. The GOF-P53 mutation enables the P53 protein to potentially interact with non-canonical protein partners facilitating oncogenesis. In this context, analysis of existing transcriptomic data from R273H-P53 expressing cells shows a concomitant up-regulation of Yes-associated protein (YAP) transcriptional targets and its protein partner TEAD1 in NSCLCs, suggesting a possible link between R273H-P53 and YAP. We therefore explored the inter-dependence of R273H-P53 and YAP in NSCLC cells. They were found to co-operatively regulate NSCLC proliferation. Genetic or pharmacological inhibition of YAP and GOF-P53 resulted in sensitization of NSCLC cells. Further analysis of pathways controlled by GOF-P53 and YAP showed that they positively regulate the cellular homeostatic process- autophagy to mediate survival. We hence postulated that a modulation of autophagy might be a potent strategy to curb proliferation. In accordance to above, autophagy inhibition, especially with the FDA-approved drug- chloroquine (CQ) resulted in cytoplasmic accumulation and reduced transcriptional activity of GOF-P53 and YAP, leading to growth arrest of NSCLC cells.

CONCLUSION

Our study highlights the importance of GOF-P53 and YAP in NSCLC proliferation and proposes autophagy inhibition as an efficient strategy to attenuate NSCLC tumorigenesis.

Impaired degradation of YAP1 and IL6ST by chaperone-mediated autophagy promotes proliferation and migration of normal and hepatocellular carcinoma cells

Impaired degradation of the transcriptional coactivator YAP1 and IL6ST (interleukin 6 cytokine family signal transducer), two proteins deregulated in liver cancer, has been shown to promote tumor growth. Here, we demonstrate that YAP1 and IL6ST are novel substrates of chaperone-mediated autophagy (CMA) in human hepatocellular carcinoma (HCC) and hepatocyte cell lines. Knockdown of the lysosomal CMA receptor LAMP2A increases protein levels of YAP1 and IL6ST, without changes in mRNA expression. Additionally, both proteins show KFERQ-dependent binding to the CMA chaperone HSPA8 and accumulate into isolated lysosomes after stimulation of CMA by prolonged starvation. We further show that LAMP2A downregulation promotes the proliferation and migration in HCC cells and a human hepatocyte cell line, and that it does so in a YAP1- and IL6ST-dependent manner. Finally, LAMP2A expression is downregulated, and YAP1 and IL6ST expression is upregulated, in human HCC biopsies. Taken together, our work reveals a novel mechanism that controls the turnover of two cancer-relevant proteins and suggests a tumor suppressor function of CMA in the liver, advocating for the exploitation of CMA activity for diagnostic and therapeutic purposes.Abbreviations: ACTB: actin beta; ATG5: autophagy related 5; ATG7: autophagy related 7; CMA: chaperone-mediated autophagy; eMI: endosomal microautophagy; HCC: hepatocellular carcinoma; HSPA8: heat shock protein family A (Hsp70) member 8; IL6ST: interleukin 6 cytokine family signal transducer; JAK: Janus kinase; LAMP1: lysosomal associated membrane protein 1; LAMP2A: lysosomal associated membrane protein 2A; MAPK8: mitogen-activated protein kinase 8; P6: pyridine 6; SQSTM1: sequestosome 1; TUBA: tubulin alpha; VDAC1: voltage dependent anion channel 1; VP: verteporfin; YAP1: Yes1 associated transcriptional regulator.

The Multifaceted Roles of Autophagy in Infectious, Obstructive, and Malignant Airway Diseases

Autophagy is a highly conserved dynamic process by which cells deliver their contents to lysosomes for degradation, thus ensuring cell homeostasis. In response to environmental stress, the induction of autophagy is crucial for cell survival. The dysregulation of this degradative process has been implicated in a wide range of pathologies, including lung diseases, representing a relevant potential target with significant clinical outcomes. During lung disease progression and infections, autophagy may exert both protective and harmful effects on cells. In this review, we will explore the implications of autophagy and its selective forms in several lung infections, such as SARS-CoV-2, Respiratory Syncytial Virus (RSV) and Mycobacterium tuberculosis (Mtb) infections, and different lung diseases such as Cystic Fibrosis (CF), Chronic Obstructive Pulmonary Disease (COPD), and Malignant Mesothelioma (MM).

Chaperone-Mediated Autophagy and Its Implications for Neurodegeneration and Cancer

Proteostasis, also known as protein homeostasis, is critical for cell survival. Autophagy is a cellular process that degrades and recycles damaged or long-lived proteins, misfolded proteins, and damaged or abnormal organelles in order to preserve homeostasis. Among the three forms of autophagy, chaperone-mediated autophagy (CMA) is distinct from macroautophagy and microautophagy; it does not require the formation of vacuoles and only degrades selected individual proteins. CMA helps to maintain cellular homeostasis by regulating protein quality, bioenergetics, and substrate-associated cellular processes at the right moment. This pathway's dysfunction has been linked to several diseases and disorders. Neurodegenerative diseases and cancer have received the most attention. In various neurodegenerative disorders, especially in their later stages, CMA activity declines. CMA has been shown to act as a tumor suppressor in cancer by destroying specific tumor promoters. Once a tumor has grown, it also helps tumor survival and the metastatic cascade. The presence of changes in CMA in these diseases disorders raises the idea of targeting CMA to restore cellular homeostasis as a potential therapeutic method. Manipulation of CMA activity may be effective therapeutic strategies for treating these diseases. Therefore, in this paper; we introduce the basic processes, regulatory mechanisms, and physiological functions of CMA; evidences supporting the role of impaired CMA function in neurodegeneration and cancer; and the potential of how targeting CMA could be a promising therapeutic method for the two diseases.

HSc70 interactome reveal major role of macroautophagy and minor role of chaperone mediated autophagy in K-Ras G12V cell proliferation and survival

Constitutively active K-Ras oncogene mutation at G12V changes the proteome of cells and activates macroautophagy for cell advantage. Inhibition of macroautophagy impairs K-Ras mediated tumor progression to a limited extent with increase of spontaneous tumors due to poorly understood mechanisms. Here, we show that inhibition of macroautophagy in K-Ras G12V mouse embryonic fibroblasts (MEFs) hyper activates chaperon mediated autophagy (CMA). Quantitative identification of CMA substrates through co-immunoprecipitation of CMA component heat shock cognate 70 (Hsc70) demonstrates a shift of proteins from macroautophagy to CMA mediated degradation. However, macroautophagy impairment show significant inhibition on proliferation and CMA hyper activation provides a basal support to macroautophagy-inhibited MEFs for survival. On the other hand, K-Ras G12V MEFs impaired of CMA reduces number of Hsc70 clients but activated macroautophagy significantly compensated CMA loss. Nonetheless, co-inhibition of CMA and macroautophagy had a synergistic detrimental effect on both proliferation and survival of MEFs expressing K-Ras G12V mutant. Our results point to K-Ras G12V MEFs dependency on macroautophagy and CMA partly compensates its loss for survival but not hyper-proliferation; implicating that targeting both macroautophagy and CMA as a promising therapeutic target in G12V mutation associated K-Ras cancers. SIGNIFICANCE: The present study provides a framework of Hsc70 interacting proteins, which differentially interact with Hsc70 in response to autophagy alterations. The role of proteins accumulation and induced proteo-toxicity could be underlying factor in macroautophagy and CMA co-inhibited K-Ras G12V MEFs phenotype. Our study provides rational for adaptive mechanisms in K-Ras tumors inhibited with different autophagy pathways and also supports targeting both macroautophagy and CMA simultaneously as therapeutic target. At the same time current study will help in characterizing the underlying cellular processes that may play a role in escaping tutor suppressor role CMA and macroautophagy in cancers harboring K-Ras G12V mutation that may be further utilized to identify molecular targets for K-Ras-driven cancers.

Clusterin overexpression in mice exacerbates diabetic phenotypes but suppresses tumor progression in a mouse melanoma model

Clusterin (CLU) is an ATP-independent small heat shock protein-like chaperone, which functions both intra- and extra-cellularly. Consequently, it has been functionally involved in several physiological (including aging), as well as in pathological conditions and most age-related diseases, e.g., cancer, neurodegeneration, and metabolic syndrome. To address CLU function at an in vivo model we established CLU transgenic (Tg) mice bearing ubiquitous or pancreas-targeted CLU overexpression (OE). Our downstream analyses in established Tg lines showed that ubiquitous or pancreas-targeted CLU OE in mice affected antioxidant, proteostatic and metabolic pathways. Targeted OE of CLU in the pancreas, which also resulted in CLU upregulation in the liver likely via systemic effects, increased basal glucose levels in the circulation and exacerbated diabetic phenotypes. Furthermore, by establishing a syngeneic melanoma mouse tumor model we found that ubiquitous CLU OE suppressed melanoma cells growth, indicating a likely tumor suppressor function in early phases of tumorigenesis. Our observations provide in vivo evidence corroborating the notion that CLU is a potential modulator of metabolic and/or proteostatic pathways playing an important role in diabetes and tumorigenesis.

The Multifaceted Role of CMA in Glioma: Enemy or Ally?

Chaperone-mediated autophagy (CMA) is a catabolic pathway fundamental for cell homeostasis, by which specific damaged or non-essential proteins are degraded. CMA activity has three main levels of regulation. The first regulatory level is based on the targetability of specific proteins possessing a KFERQ-like domain, which can be recognized by specific chaperones and delivered to the lysosomes. Target protein unfolding and translocation into the lysosomal lumen constitutes the second level of CMA regulation and is based on the modulation of Lamp2A multimerization. Finally, the activity of some accessory proteins represents the third regulatory level of CMA activity. CMA's role in oncology has not been fully clarified covering both pro-survival and pro-death roles in different contexts. Taking all this into account, it is possible to comprehend the actual complexity of both CMA regulation and the cellular consequences of its activity allowing it to be elected as a modulatory and not only catabolic machinery. In this review, the role covered by CMA in oncology is discussed with a focus on its relevance in glioma. Molecular correlates of CMA importance in glioma responsiveness to treatment are described to identify new early efficacy biomarkers and new therapeutic targets to overcome resistance.

Chaperone Mediated Autophagy Substrates and Components in Cancer

Chaperone-mediated autophagy (CMA) represents a specific way of lysosomal protein degradation and contrary to macro and microautophagy is independent of vesicles formation. The role of CMA in different physiopathological processes has been studied for several years. In cancer, alterations of the CMA principal components, Hsc70 and Lamp2A protein and mRNA levels, have been described in malignant cells. However, changes in the expression levels of these CMA components are not always associated with changes in CMA activity and their biological significance must be carefully interpreted case by case. The objective of this review is to discuss whether altering the CMA activity, CMA substrates or CMA components is accurate to avoid cancer progression. In particular, this review will discuss about the evidences in which alterations CMA components Lamp2A and Hsc70 are associated or not with changes in CMA activity in different cancer types. This analysis will help to better understand the role of CMA activity in cancer and to elucidate whether CMA can be considered as target for therapeutics. Further, it will help to define whether the attention of the investigation should be focused on Lamp2A and Hsc70 because they can have an independent role in cancer progression beyond of their participation in altered CMA activity.

Mutant p53 as a Regulator and Target of Autophagy

One of the most notoriously altered genes in human cancer is the tumor-suppressor TP53, which is mutated with high frequency in more cancers than any other tumor suppressor gene. Beyond the loss of wild-type p53 functions, mutations in the TP53 gene often lead to the expression of full-length proteins with new malignant properties. Among the defined oncogenic functions of mutant p53 is its effect on cell metabolism and autophagy. Due to the importance of autophagy as a stress adaptive response, it is frequently dysfunctional in human cancers. However, the role of p53 is enigmatic in autophagy regulation. While the complex action of the wild-type p53 on autophagy has extensively been described in literature, in this review, we focus on the conceivable role of distinct mutant p53 proteins in regulating different autophagic pathways and further discuss the available evidence suggesting a possible autophagy stimulatory role of mutant p53. Moreover, we describe the involvement of different autophagic pathways in targeting and degrading mutant p53 proteins, exploring the potential strategies of targeting mutant p53 in cancer by autophagy.

Verteporfin disrupts multiple steps of autophagy and regulates p53 to sensitize osteosarcoma cells

Background

Osteosarcoma (OS) is a malignant tumor of the bone mostly observed in children and adolescents. The current treatment approach includes neoadjuvant and adjuvant chemotherapy; however, drug resistance often hinders therapy in OS patients. Also, the post-relapse survival of OS patients is as low as 20%. We therefore planned to understand the molecular cause for its poor prognosis and design an appropriate therapeutic strategy to combat the disease.

Methods

We analyzed OS patient dataset from Gene Expression Omnibus (GEO) and identified the differentially expressed genes and the top deregulated pathways in OS. Subsequently, drugs targeting the major de-regulated pathways were selected and the following assays were conducted- MTT assay to assess cytotoxicity of drugs in OS cells; immunoblotting and immunostaining to analyze key protein expression and localization after drug treatment; LysoTracker staining to monitor lysosomes; Acridine Orange to label acidic vesicles; and DCFDA to measure Reactive Oxygen Species (ROS).

Results

The differential gene expression analysis from OS patient dataset implicated the striking involvement of cellular processes linked to autophagy and protein processing in the development of OS. We therefore selected the FDA approved drugs, chloroquine (CQ) and verteporfin (VP) known for autophagy inhibitory and proteotoxic functions to explore against OS. Importantly, VP, but not CQ, showed an extensive dose-dependent cytotoxicity. It resulted in autophagy disruption at multiple steps extending from perturbation of early autophagic processes, inhibition of autophagic flux to induction of lysosomal instability. Interestingly, VP treated protein lysates showed a ROS-dependent high molecular weight (HMW) band when probed for P62 and P53 protein. Further, VP triggered accumulation of ubiquitinated proteins as well. Since VP had a pronounced disruptive effect on cellular protein homeostasis, we explored the possibility of simultaneous inhibition of the ubiquitin-proteasomal system (UPS) by MG-132 (MG). Addition of a proteasomal inhibitor significantly aggravated VP induced cytotoxicity. MG co-treatment also led to selective targeting of P53 to the lysosomes.

Conclusion

Herein, we propose VP and MG induce regulation of autophagy and protein homeostasis which can be exploited as an effective therapeutic strategy against osteosarcoma.

Through the back door: Unconventional protein secretion

Proteins are secreted from eukaryotic cells by several mechanisms besides the well-characterized classical secretory system. Proteins destined to enter the classical secretory system contain a signal peptide for translocation into the endoplasmic reticulum. However, many proteins lacking a signal peptide are secreted nonetheless. Contrary to conventional belief, these proteins are not just released as a result of membrane damage leading to cell leakage, but are actively packaged for secretion in alternative pathways. They are called unconventionally secreted proteins, and the best-characterized are from fungi and mammals. These proteins have extracellular functions including cell signaling, immune modulation, as well as moonlighting activities different from their well-described intracellular functions. Among the pathways for unconventional secretion are direct transfer across the plasma membrane, release within plasma membrane-derived microvesicles, use of elements of autophagy, or secretion from endosomal/multivesicular body-related components. We review the fungal and metazoan unconventional secretory pathways and their regulation, and propose experimental criteria to identify their mode of secretion.

Chaperone-mediated autophagy in cancer: Advances from bench to bedside

Chaperone-mediated autophagy (CMA), a selective form of autophagy, where cellular proteins with KFERQ-like motif are targeted to the lysosome for degradation, is necessary to maintain cellular homeostasis. The role of CMA in neurodegenerative diseases has been extensively studied in the past decades, with defects in the pathway being strongly associated with disease. Recently, accumulating evidence has demonstrated a consistent increase in basal CMA activity in a wide array of cancer cell lines and human tumor biopsies, suggesting a potential link between CMA and cancer. On the other hand, an anti-oncogenic role for CMA under physiological conditions in non-transformed cells is also proposed despite the pro-tumorigenic function of CMA in cancer cells. The growing number of connections between CMA and cancers has generated interest in modulating CMA activity for therapeutic purposes. Here, we describe recent advances in the understanding of the molecular regulation of CMA, and discuss the evidence in support of the contribution of CMA dysfunction to cancers.

The Lethality of [Pazopanib + HDAC Inhibitors] Is Enhanced by Neratinib

Sarcomas are a diverse set of malignancies. For soft tissue sarcomas, the kinase and chaperone inhibitor pazopanib is a standard of care therapeutic. Previously, we demonstrated that HDAC inhibitors enhanced pazopanib lethality against sarcoma and other tumor cell types in vitro and in vivo. The present studies defined mechanisms of drug-combination resistance. Exposure of sarcoma and PDX ovarian carcinoma cells to [pazopanib + entinostat] caused a prolonged activation of ERBB1 and transient/prolonged activations of ERBB2, c-KIT, and c-MET, in a cell-specific fashion. The activities of mTORC1, mTORC2, GRP78, HSP90, and HSP70 were reduced, expression of Beclin1 and ATG5 enhanced, and the ATM-AMPK-ULK1-ATG13-Beclin1/ATG5 pathway activated. Inhibition of ERBB1/2/4 using neratinib or of c-MET using crizotinib significantly enhanced [pazopanib + entinostat] lethality. For neratinib with [pazopanib + entinostat], this effect correlated with reduced phosphorylation and expression of ERBB1, ERBB2, c-KIT, and c-MET and reduced expression, regardless of mutational status, of N-RAS and K-RAS. [Pazopanib + entinostat + neratinib] reduced the phosphorylation of the Hippo pathway proteins MST1/3/4 and MOB1 whereas this treatment increased the phosphorylation of LATS1, YAP, and TAZ. The activation of ATM, ULK-1, and eIF2α was further enhanced by [pazopanib + entinostat + neratinib] as was the expression of ATG5 and Beclin1. Compared to other manipulations, knock down of eIF2α or over-expression of BCL-XL significantly reduced killing by the three-drug interaction. In vivo, pazopanib and entinostat, and also neratinib and entinostat, both combined to significantly suppress the growth of sarcoma tumors.

Targetome analysis of chaperone-mediated autophagy in cancer cells

Chaperone-mediated autophagy (CMA) is a lysosomal degradation pathway of select soluble proteins. Nearly one-third of the soluble proteins are predicted to be recognized by this pathway, yet only a minor fraction of this proteome has been identified as CMA substrates in cancer cells. Here, we undertook a quantitative multiplex mass spectrometry approach to study the proteome of isolated lysosomes in cancer cells during CMA-activated conditions. By integrating bioinformatics analyses, we identified and categorized proteins of multiple cellular pathways that were specifically targeted by CMA. Beyond verifying metabolic pathways, we show that multiple components involved in select biological processes, including cellular translation, was specifically targeted for degradation by CMA. In particular, several proteins of the translation initiation complex were identified as bona fide CMA substrates in multiple cancer cell lines of distinct origin and we show that CMA suppresses cellular translation. We further show that the identified CMA substrates display high expression in multiple primary cancers compared to their normal counterparts. Combined, these findings uncover cellular processes affected by CMA and reveal a new role for CMA in the control of translation in cancer cells.

Abbreviations: 6-AN: 6-aminonicotinamide; ACTB: actin beta; AR7: atypical retinoid 7; CHX: cycloheximide; CMA: chaperone-mediated autophagy; CQ: chloroquine; CTS: cathepsins; DDX3X: DEAD-box helicase 3 X-linked; EEF2: eukaryotic translation elongation factor 2; EIF4A1: eukaryotic translation initiation factor 4A1; EIF4H: eukaryotic translation initiation factor 4H; GEO: Gene Expression Omnibus; GO: Gene Ontology; GSEA: gene set enrichment analysis; HK2: hexokinase 2; HSPA8/HSC70: heat shock protein family A (Hsp70) member 8; LAMP: lysosomal-associated membrane protein; LDHA: lactate dehydrogenase A; NES: normalized enrichment score; NFKBIA: NFKB inhibitor alpha; PCA: principle component analysis; PQ: paraquat; S.D.: standard deviation; SUnSET: surface sensing of translation; TMT: tandem mass tags; TOMM40/TOM40: translocase of outer mitochondrial membrane 40.

ARD1 contributes to IKKβ-mediated breast cancer tumorigenesis

The expression of IκB kinase β (IKKβ) promotes the growth of breast cancer cells. Meanwhile, IKKβ mediates the phosphorylation and subsequent degradation of arrest-defective protein 1 (ARD1). However, the relationship between IKKβ and ARD1 in the occurrence of breast cancer has not been reported. In this study, we found that IKKβ not only acts directly on mammalian target of rapamycin (mTOR) activity but also indirectly acts on mTOR activity through posttranscriptional modification of ARD1, thereby effectively promoting the growth of breast cancer cells. ARD1 prevents mTOR activity and breast cancer cell growth by stabilizing tuberous sclerosis complex 2 (TSC2) to induce autophagy. Moreover, acetylation of heat shock protein 70 (Hsp70) also contributes to ARD1-mediated autophagy. Therefore, upstream IKKβ can further promote the occurrence of breast cancer by mediating the function of ARD1.

Sorting nexin 10 controls mTOR activation through regulating amino-acid metabolism in colorectal cancer

Amino-acid metabolism plays a vital role in mammalian target of rapamycin (mTOR) signaling, which is the pivot in colorectal cancer (CRC). Upregulated chaperone-mediated autophagy (CMA) activity contributes to the regulation of metabolism in cancer cells. Previously, we found that sorting nexin 10 (SNX10) is a critical regulator in CMA activation. Here we investigated the role of SNX10 in regulating amino-acid metabolism and mTOR signaling pathway activation, as well as the impact on the tumor progression of mouse CRC. Our results showed that SNX10 deficiency promoted colorectal tumorigenesis in male FVB mice and CRC cell proliferation and survival. Metabolic pathway analysis of gas chromatography–mass spectrometry (GC-MS) data revealed unique changes of amino-acid metabolism by SNX10 deficiency. In HCT116 cells, SNX10 knockout resulted in the increase of CMA and mTOR activation, which could be abolished by chloroquine treatment or reversed by SNX10 overexpression. By small RNA interference (siRNA), we found that the activation of mTOR was dependent on lysosomal-associated membrane protein type-2A (LAMP-2A), which is a limiting factor of CMA. Similar results were also found in Caco-2 and SW480 cells. Ultra-high-performance liquid chromatography–quadrupole time of flight (UHPLC-QTOF) and GC-MS-based untargeted metabolomics revealed that 10 amino-acid metabolism in SNX10-deficient cells were significantly upregulated, which could be restored by LAMP-2A siRNA. All of these amino acids were previously reported to be involved in mTOR activation. In conclusion, this work revealed that SNX10 controls mTOR activation through regulating CMA-dependent amino-acid metabolism, which provides potential target and strategy for treating CRC.

Targeting Chaperone-Mediated Autophagy for Disease Therapy

PURPOSE OF THE REVIEW

To reason that targeting chaperone-mediated autophagy (CMA) represents a promising approach for disease therapy, we will summarize advances in researches on the relationship between CMA and diseases and discuss relevant strategies for disease therapy by targeting the CMA process.

RECENT FINDINGS

CMA is a unique kind of selective autophagy in lysosomes. Under physiological conditions, CMA participates in the maintenance of cellular homeostasis by protein quality control, bioenergetics, and timely regulated specific substrate-associated cellular processes. Under pathological conditions, CMA interplays with various disease conditions. CMA makes adaptive machinery to address stress, while disease-associated proteins alter CMA which is involved in pathogeneses of diseases. As more proteins are identified as CMA substrates and regulators, dysregulation of CMA has been implicated in an increasing number of diseases, while rectifying CMA alteration may be a benefit for these diseases.

SUMMARY

Alterations of CMA in diseases mainly including neurodegenerative diseases and many cancers raise the possibility of targeting CMA to recover cellular homeostasis as one potential strategy for therapy of relevant diseases.

Chaperone-mediated autophagy: Advances from bench to bedside

Protein homeostasis or proteostasis is critical for proper cellular function and survival. It relies on the balance between protein synthesis and degradation. Lysosomes play an important role in degrading and recycling intracellular components via autophagy. Among the three types of lysosome-based autophagy pathways, chaperone-mediated autophagy (CMA) selectively degrades cellular proteins with KFERQ-like motif by unique machinery. During the past several years, significant advances have been made in our understanding of how CMA itself is modulated and what physiological and pathological processes it may be involved in. One particularly exciting discovery is how other cellular stress organelles such as ER signal to CMA. As more proteins are identified as CMA substrates, CMA function has been associated with an increasing number of important cellular processes, organelles, and diseases, including neurodegenerative diseases. Here we will summarize the recent advances in CMA biology, highlight ER stress-induced CMA, and discuss the role of CMA in diseases.

An Intervention Target for Myocardial Fibrosis: Autophagy

Myocardial fibrosis (MF) is the result of metabolic imbalance of collagen synthesis and metabolism, which is widespread in various cardiovascular diseases. Autophagy is a lysosomal degradation pathway which is highly conserved. In recent years, research on autophagy has been increasing and the researchers have also become cumulatively aware of the specified association between autophagy and MF. This review highlights the role of autophagy in MF and the potential effects through the administration of medicine.

Molecular control of chaperone-mediated autophagy

Chaperone-mediated autophagy (CMA) is a selective form of autophagy in which cytosolic proteins bearing a pentapeptide motif biochemically related to the KFERQ sequence, are recognized by the heat shock protein family A member 8 (HSPA8) chaperone, delivered to the lysomal membrane, and directly translocated across the lysosomal membrane by a protein complex containing lysosomal associated membrane protein 2a (Lamp2a). Since its discovery over two decades ago, the importance of this pathway in cell proteostasis has been made increasingly apparent. Deregulation of this pathway has been implicated in a variety of diseases and conditions, including lysosomal storage diseases, cancer, neurodegeneration and even aging. Here, we describe the main molecular features of the pathway, its regulation, cross-talk with other degradation pathways and importance in disease.