Role of chaperone-mediated autophagy in the pathophysiology including pulmonary disorders

Selective protein degradation through chaperone‑mediated autophagy: Implications for cellular homeostasis and disease (Review)

Cells rely on autophagy for the degradation and recycling of damaged proteins and organelles. Chaperone-mediated autophagy (CMA) is a selective process targeting proteins for degradation through the coordinated function of molecular chaperones and the lysosome‑associated membrane protein‑2A receptor (LAMP2A), pivotal in various cellular processes from signal transduction to the modulation of cellular responses under stress. In the present review, the intricate regulatory mechanisms of CMA were elucidated through multiple signaling pathways such as retinoic acid receptor (RAR)α, AMP‑activated protein kinase (AMPK), p38‑TEEB‑NLRP3, calcium signaling‑NFAT and PI3K/AKT, thereby expanding the current understanding of CMA regulation. A comprehensive exploration of CMA's versatile roles in cellular physiology were further provided, including its involvement in maintaining protein homeostasis, regulating ferroptosis, modulating metabolic diversity and influencing cell cycle and proliferation. Additionally, the impact of CMA on disease progression and therapeutic outcomes were highlighted, encompassing neurodegenerative disorders, cancer and various organ‑specific diseases. Therapeutic strategies targeting CMA, such as drug development and gene therapy were also proposed, providing valuable directions for future clinical research. By integrating recent research findings, the present review aimed to enhance the current understanding of cellular homeostasis processes and emphasize the potential of targeting CMA in therapeutic strategies for diseases marked by CMA dysfunction.

The Antipsychotic Drug Aripiprazole Suppresses Colorectal Cancer by Targeting LAMP2a to Induce RNH1/miR-99a/mTOR-Mediated Autophagy and Apoptosis

The mammalian target of rapamycin (mTOR) is a critical signaling hub for sustaining cancer survival. Targeting mTOR and inducing autophagic cell death downstream of it represent promising therapeutic strategies for cancer prevention. A US Food and Drug Administration-approved drug library containing 616 small molecules is used to screen anticancer drugs against colorectal cancer (CRC) cells that rely on mTOR. This led to the identification of an antipsychotic drug aripiprazole, which significantly induced mTOR inhibition and autophagic apoptosis in CRC, in vitro and in vivo. The use of drug affinity response target stability identified lysosome-associated membrane protein 2A (LAMP2a) as a direct target of aripiprazole. LAMP2a-deficient CRC cells are refractory to aripiprazole. High LAMP2a expression is associated with poor survival of patients with CRC and negatively correlated with expression of ribonuclease inhibitor 1 (RNH1), which is later confirmed as a novel substrate of LAMP2a. Mechanistically, aripiprazole bound to the Lys401-His404 of LAMP2a and repressed its activity, subsequently inactivating RNH1/miR-99a/mTOR signaling and inducing autophagy-mediated apoptosis, thereby suppressing tumorigenesis. Liposome-mediated delivery of aripiprazole in combination with fluorouracil elicited superior therapeutic benefits in CRC, as compared to single treatments, thereby highlighting that aripiprazole may be repurposed as a novel therapeutic agent for CRC treatment.

An updated outlook on autophagy mechanism and how it supports acute myeloid leukemia maintenance

The gradual acquisition of genetic and epigenetic disturbances bestows malignant traits upon hematopoietic stem cells, subverting them into a founder and reservoir cell for de novo acute myeloid leukemia (AML) known as leukemic stem cells (LSC). Beyond its molecular heterogeneity, AML is also characterized by rewiring biological processes to support its onset and maintenance. LSC were observed to inherently and actively trigger mitochondrial turnover through selective autophagic removal such that impairing the process led to cell differentiation at the expense of its stemness. This review provides a current take on autophagy regulation mechanisms according to the current molecular characterization of the process; describes autophagy as a drug resistance mechanism, and a pivotal mechanism whereby LSC harmonize their strong reliance on mitochondrial respiration to obtain energy, and their necessity for lower internal oxidative stress to avoid exhaustion. Therefore, targeting autophagy presents a promising strategy to promote long-term remissions in AML.

The autophagy paradox: A new hypothesis in neurodegenerative disorders

A recent study showed that while autophagy is usually tied to protein and organelle turnover, it can also play dual roles in neurodegenerative diseases. Traditionally, autophagy was seen as protective since it removes damaged proteins and organelles. but new data suggests autophagy can sometimes promote neuron death. and This review tackles autophagy's seemingly contradictory effects in neurodegeneration, or the "autophagy paradox. " It offers a framework for understanding autophagy in neurodegenerative research and the cellular processes involved. In short, our data uncovers a harmful autophagy role in certain situations, conflicting the view that it's always beneficial. We describe the distinct, disease-specific autophagy pathways functioning in various neurodegenerative diseases. Part two concerns potential therapeutic implications of manipulating autophagy and current strategies targeting the autophagic system, suggesting interesting areas for future research into tailored modulators. This could eventually enable activating or controlling specific autophagy pathways and aid in developing more effective treatments. Researchers believe more molecular-level research is needed so patient-tailored autophagy-modulating therapeutics can be developed given this dilemma. Moreover, research must translate faster into effective neurodegenerative disease treatment options. This article aims to provide a wholly new perspective on autophagy's classically described role in these severe diseases, challenging current dogma and opening new therapeutic avenue options.

Strategy for treating MAFLD: Electroacupuncture alleviates hepatic steatosis and fibrosis by enhancing AMPK mediated glycolipid metabolism and autophagy in T2DM rats

BACKGROUND

Recent studies have highlighted type 2 diabetes (T2DM) as a significant risk factor for the development of metabolic dysfunction-associated fatty liver disease (MAFLD). This investigation aimed to assess electroacupuncture's (EA) impact on liver morphology and function in T2DM rats, furnishing experimental substantiation for its potential to stall MAFLD progression in T2DM.

METHODS

T2DM rats were induced by a high-fat diet and a single intraperitoneal injection of streptozotocin, and then randomly assigned to five groups: the T2DM group, the electroacupuncture group, the metformin group, combination group of electroacupuncture and metformin, combination group of electroacupuncture and Compound C. The control group received a standard diet alongside intraperitoneal citric acid - sodium citrate solution injections. After a 6-week intervention, the effects of each group on fasting blood glucose, lipids, liver function, morphology, lipid droplet infiltration, and fibrosis were evaluated. Techniques including Western blotting, qPCR, immunohistochemistry, and immunofluorescence were employed to gauge the expression of key molecules in AMPK-associated glycolipid metabolism, insulin signaling, autophagy, and fibrosis pathways. Additionally, transmission electron microscopy facilitated the observation of liver autophagy, lipid droplets, and fibrosis.

RESULTS

Our studies indicated that hyperglycemia, hyperlipidemia and IR promoted lipid accumulation, pathological and functional damage, and resulting in hepatic steatosis and fibrosis. Meanwhile, EA enhanced the activation of AMPK, which in turn improved glycolipid metabolism and autophagy through promoting the expression of PPARα/CPT1A and AMPK/mTOR pathway, inhibiting the expression of SREBP1c, PGC-1α/PCK2 and TGFβ1/Smad2/3 signaling pathway, ultimately exerting its effect on ameliorating hepatic steatosis and fibrosis in T2DM rats. The above effects of EA were consistent with metformin. The combination of EA and metformin had significant advantages in increasing hepatic AMPK expression, improving liver morphology, lipid droplet infiltration, fibrosis, and reducing serum ALT levels. In addition, the ameliorating effects of EA on the progression of MAFLD in T2DM rats were partly disrupted by Compound C, an inhibitor of AMPK.

CONCLUSIONS

EA upregulated hepatic AMPK expression, curtailing gluconeogenesis and lipogenesis while boosting fatty acid oxidation and autophagy levels. Consequently, it mitigated blood glucose, lipids, and insulin resistance in T2DM rats, thus impeding liver steatosis and fibrosis progression and retarding MAFLD advancement.

Altered autophagic flux in GNE mutant cells of Indian origin: Potential drug target for GNE myopathy

Autophagy phenomenon in the cell maintains proteostasis balance by eliminating damaged organelles and protein aggregates. Imbalance in autophagic flux may cause accumulation of protein aggregates in various neurodegenerative disorders. Regulation of autophagy by either calcium or chaperone play a key role in the removal of protein aggregates from the cell. The neuromuscular rare genetic disorder, GNE Myopathy, is characterized by accumulation of rimmed vacuoles having protein aggregates of β-amyloid and tau that may result from altered autophagic flux. In the present study, the autophagic flux was deciphered in HEK cell-based model for GNE Myopathy harbouring GNE mutations of Indian origin. The refolding activity of HSP70 chaperone was found to be reduced in GNE mutant cells compared to wild type controls. The autophagic markers LC3II/I ratio was altered with increased number of autophagosome formation in GNE mutant cells compared to wild type cells. The cytosolic calcium levels were also increased in GNE mutant cells of Indian origin. Interestingly, treatment of GNE mutant cells with HSP70 activator, BGP-15, restored the expression and refolding activity of HSP70 along with autophagosome formation. Treatment with calcium chelator, BAPTA-AM restored the cytoplasmic calcium levels and autophagosome formation but not LC3II/I ratio significantly. Our study provides insights towards GNE mutation specific response for autophagy regulation and opens up a therapeutic advancement area in calcium signalling and HSP70 function for GNE related Myopathy.

Autophagy and regulation of aquaporins in the kidneys

Aquaporins (AQPs) are water channel proteins that facilitate the transport of water molecules across cell membranes. To date, seven AQPs have been found to be expressed in mammal kidneys. The cellular localization and regulation of the transport properties of AQPs in the kidney have been widely investigated. Autophagy is known as a highly conserved lysosomal pathway, which degrades cytoplasmic components. Through basal autophagy, kidney cells maintain their functions and structure. As a part of the adaptive responses of the kidney, autophagy may be altered in response to stress conditions. Recent studies revealed that autophagic degradation of AQP2 in the kidney collecting ducts leads to impaired urine concentration in animal models with polyuria. Therefore, the modulation of autophagy could be a therapeutic approach to treat water balance disorders. However, as autophagy is either protective or deleterious, it is crucial to establish an optimal condition and therapeutic window where autophagy induction or inhibition could yield beneficial effects. Further studies are needed to understand both the regulation of autophagy and the interaction between AQPs and autophagy in the kidneys in renal diseases, including nephrogenic diabetes insipidus.

The role of heat shock proteins in the pathogenesis of heart failure (Review)

The influence of heat shock proteins (HSPs) on protein quality control systems in cardiomyocytes is currently under investigation. The effect of HSPs on the regulated cell death of cardiomyocytes (CMCs) is of great importance, since they play a major role in the implementation of compensatory and adaptive mechanisms in the event of cardiac damage. HSPs mediate a number of mechanisms that activate the apoptotic cascade, playing both pro‑ and anti‑apoptotic roles depending on their location in the cell. Another type of cell death, autophagy, can in some cases lead to cell death, while in other situations it acts as a cell survival mechanism. The present review considered the characteristics of the expression of HSPs of different molecular weights in CMCs in myocardial damage caused by heart failure, as well as their role in the realization of certain types of regulated cell death.

Autophagy, a critical element in the aging male reproductive disorders and prostate cancer: a therapeutic point of view

Autophagy is a highly conserved, lysosome-dependent biological mechanism involved in the degradation and recycling of cellular components. There is growing evidence that autophagy is related to male reproductive biology, particularly spermatogenic and endocrinologic processes closely associated with male sexual and reproductive health. In recent decades, problems such as decreasing sperm count, erectile dysfunction, and infertility have worsened. In addition, reproductive health is closely related to overall health and comorbidity in aging men. In this review, we will outline the role of autophagy as a new player in aging male reproductive dysfunction and prostate cancer. We first provide an overview of the mechanisms of autophagy and its role in regulating male reproductive cells. We then focus on the link between autophagy and aging-related diseases. This is followed by a discussion of therapeutic strategies targeting autophagy before we end with limitations of current studies and suggestions for future developments in the field.

Autophagy/Mitophagy in Airway Diseases: Impact of Oxidative Stress on Epithelial Cells

Autophagy is the key process by which the cell degrades parts of itself within the lysosomes. It maintains cell survival and homeostasis by removing molecules (particularly proteins), subcellular organelles, damaged cytoplasmic macromolecules, and by recycling the degradation products. The selective removal or degradation of mitochondria is a particular type of autophagy called mitophagy. Various forms of cellular stress (oxidative stress (OS), hypoxia, pathogen infections) affect autophagy by inducing free radicals and reactive oxygen species (ROS) formation to promote the antioxidant response. Dysfunctional mechanisms of autophagy have been found in different respiratory diseases such as chronic obstructive lung disease (COPD) and asthma, involving epithelial cells. Several existing clinically approved drugs may modulate autophagy to varying extents. However, these drugs are nonspecific and not currently utilized to manipulate autophagy in airway diseases. In this review, we provide an overview of different autophagic pathways with particular attention on the dysfunctional mechanisms of autophagy in the epithelial cells during asthma and COPD. Our aim is to further deepen and disclose the research in this direction to stimulate the develop of new and selective drugs to regulate autophagy for asthma and COPD treatment.

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 PTP1B inhibitor MSI-1436 ameliorates liver insulin sensitivity by modulating autophagy, ER stress and systemic inflammation in Equine metabolic syndrome affected horses

BACKGROUND

Equine metabolic syndrome (EMS) is a multifactorial pathology gathering insulin resistance, low-grade inflammation and past or chronic laminitis. Among the several molecular mechanisms underlying EMS pathogenesis, increased negative insulin signalling regulation mediated by protein tyrosine phosphatase 1 B (PTP1B) has emerged as a critical axis in the development of liver insulin resistance and general metabolic distress associated to increased ER stress, inflammation and disrupted autophagy. Thus, the use of PTP1B selective inhibitors such as MSI-1436 might be considered as a golden therapeutic tool for the proper management of EMS and associated conditions. Therefore, the present investigation aimed at verifying the clinical efficacy of MSI-1436 systemic administration on liver metabolic balance, insulin sensitivity and inflammatory status in EMS affected horses. Moreover, the impact of MSI-1436 treatment on liver autophagy machinery and associated ER stress in liver tissue has been analysed.

METHODS

Liver explants isolated from healthy and EMS horses have been treated with MSI-1436 prior to gene and protein expression analysis of main markers mediating ER stress, mitophagy and autophagy. Furthermore, EMS horses have been intravenously treated with a single dose of MSI-1436, and evaluated for their metabolic and inflammatory status.

RESULTS

Clinical application of MSI-1436 to EMS horses restored proper adiponectin levels and attenuated the typical hyperinsulinemia and hyperglycemia. Moreover, administration of MSI-1436 further reduced the circulating levels of key pro-inflammatory mediators including IL-1β, TNF-α and TGF-β and triggered the Tregs cells activation. At the molecular level, PTP1B inhibition resulted in a noticeable mitigation of liver ER stress, improvement of mitochondrial dynamics and consequently, a regulation of autophagic response. Similarly, short-term ex vivo treatment of EMS liver explants with trodusquemine (MSI-1436) substantially enhanced autophagy by upregulating the levels of HSC70 and Beclin-1 at both mRNA and protein level. Moreover, the PTP1B inhibitor potentiated mitophagy and associated expression of MFN2 and PINK1. Interestingly, inhibition of PTP1B resulted in potent attenuation of ER stress key mediators' expression namely, CHOP, ATF6, HSPA5 and XBP1.

CONCLUSION

Presented findings shed for the first time promising new insights in the development of an MSI-1436-based therapy for proper equine metabolic syndrome intervention and may additionally find potential translational application to human metabolic syndrome treatment.

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 in Neurodegenerative Diseases: Molecular Mechanisms and Pharmacological Opportunities

Chaperone-mediated autophagy (CMA) is a protein degradation mechanism through lysosomes. By targeting the KFERQ motif of the substrate, CMA is responsible for the degradation of about 30% of cytosolic proteins, including a series of proteins associated with neurodegenerative diseases (NDs). The fact that decreased activity of CMA is observed in NDs, and ND-associated mutant proteins, including alpha-synuclein and Tau, directly impair CMA activity reveals a possible vicious cycle of CMA impairment and pathogenic protein accumulation in ND development. Given the intrinsic connection between CMA dysfunction and ND, enhancement of CMA has been regarded as a strategy to counteract ND. Indeed, genetic and pharmacological approaches to modulate CMA have been shown to promote the degradation of ND-associated proteins and alleviate ND phenotypes in multiple ND models. This review summarizes the current knowledge on the mechanism of CMA with a focus on its relationship with NDs and discusses the therapeutic potential of CMA modulation for ND.

Role of Chaperone-Mediated Autophagy in Ageing Biology and Rejuvenation of Stem Cells

What lies at the basis of the mechanisms that regulate the maintenance and self-renewal of pluripotent stem cells is still an open question. The control of stemness derives from a fine regulation between transcriptional and metabolic factors. In the last years, an emerging topic has concerned the involvement of Chaperone-Mediated Autophagy (CMA) as a key mechanism in stem cell pluripotency control acting as a bridge between epigenetic, transcriptional and differentiation regulation. This review aims to clarify this new and not yet well-explored horizon discussing the recent studies regarding the CMA impact on embryonic, mesenchymal, and haematopoietic stem cells. The review will discuss how CMA influences embryonic stem cell activity promoting self-renewal or differentiation, its involvement in maintaining haematopoietic stem cell function by increasing their functionality during the normal ageing process and its effects on mesenchymal stem cells, in which modulation of CMA regulates immunosuppressive and differentiation properties. Finally, the importance of these new discoveries and their relevance for regenerative medicine applications, from transplantation to cell rejuvenation, will be addressed.