Role Of Chaperone-mediated Autophagy Research Articles

Transcriptional genes of lysosome-associated membrane protein 2A in sciatic nerve injuries by bioinformatics.

Recent studies have shown that autophagy is activated in response to nerve damage and occurs simultaneously with the initial stages of Schwann cell-mediated demyelination. Although several studies have reported that macroautophagy is involved in the peripheral nerve, the role of chaperone-mediated autophagy (CMA) has not yet been investigated in peripheral nerve injury. The present study investigates the role of CMA in the sciatic nerve. Using a mouse model of sciatic nerve injury, the authors employed immunofluorescence analysis to observe the expression of LAMP2A, a critical marker for CMA. RNA sequencing was performed to observe the transcriptional profile of Lamp2a in Schwann cells. Bioinformatics analysis was carried out to observe the hub genes associated with Lamp2a . Expression of Lamp2a , a key gene in CMA, increased following sciatic nerve injury, based on an immunofluorescence assay. To identify differentially expressed genes using Lamp2a , RNA sequence analysis was conducted using rat Schwann cells overexpressing Lamp2a . The nine hub genes ( Snrpf, Polr1d, Snip1, Aqr, Polr2h, Ssbp1, Mterf3, Adcy6 , and Sbds ) were identified using the CytoHubba plugin of Cytoscape. Functional analysis revealed that Lamp2a overexpression affected the transcription levels of genes associated with mitotic spindle organization and mRNA splicing via the spliceosome. In addition, Polr1d and Snrpf1 were downregulated throughout postnatal development but elevated following sciatic nerve injury, according to a bioinformatics study. CMA may be an integral pathway in sciatic nerve injury via mRNA splicing.

The Role of Chaperone-Mediated Autophagy in Tissue Homeostasis and Disease Pathogenesis.

Chaperone-mediated autophagy (CMA) is a selective proteolytic pathway in the lysosomes. Proteins are recognized one by one through the detection of a KFERQ motif or, at least, a KFERQ-like motif, by a heat shock cognate protein 70 (Hsc70), a molecular chaperone. CMA substrates are recognized and delivered to a lysosomal CMA receptor, lysosome-associated membrane protein 2A (LAMP-2A), the only limiting component of this pathway, and transported to the lysosomal lumen with the help of another resident chaperone HSp90. Since approximately 75% of proteins are reported to have canonical, phosphorylation-generated, or acetylation-generated KFERQ motifs, CMA maintains intracellular protein homeostasis and regulates specific functions in the cells in different tissues. CMA also regulates physiologic functions in different organs, and is then implicated in disease pathogenesis related to aging, cancer, and the central nervous and immune systems. In this minireview, we have summarized the most important findings on the role of CMA in tissue homeostasis and disease pathogenesis, updating the recent advances for this Special Issue.

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.

LAMP2A overexpression in colorectal cancer promotes cell growth and glycolysis via chaperone‑mediated autophagy.

Lysosome-associated membrane protein type 2A (LAMP2A) is a key protein in the chaperone-mediated autophagy (CMA) pathway and has been demonstrated to be involved in the pathogenesis of a number of tumors. However, the role of CMA in colorectal cancer cell proliferation, metastasis and cell survival during oxidative stress and oxaliplatin resistance remains to be elucidated. In the present study, elevated expression of LAMP2A was observed in colon cancer tissues. Then, CMA activity was increased in SW480 and HT29 colorectal cancer cells with a LAMP2A overexpression vector and CMA activity was decreased using a LAMP2A short interfering RNA vector. MTT and colony formation assays showed that the colorectal cancer cell proliferation ability and cell viability following treatment with H2O2 or oxaliplatin were decreased significantly after LAMP2A knockdown and increased significantly after LAMP2A overexpression. Wound healing assays and Transwell invasion assays demonstrated that downregulation of LAMP2A expression inhibited the cell migration and invasion abilities of colorectal cancer and that upregulation of LAMP2A expression promoted cell migration and invasion. Extracellular acidification rate (ECAR) assay and lactate determination assay showed that glycolysis in colorectal cancer cells was significantly downregulated after LAMP2A knockdown and significantly upregulated after LAMP2A overexpression. Inhibition of glycolysis by 2-DG markedly attenuated LAMP2A-induced chemoresistance in colorectal cancer cells. Collectively, these data indicated that CMA can promote colorectal cancer cell proliferation, metastasis and cell survival during oxidative stress and oxaliplatin resistance and that the mechanism is related to the glycolytic pathway, which may provide a new therapeutic target for colorectal cancer patients.

Downregulation of Lysosome-Associated Membrane Protein-2A Contributes to the Pathogenesis of COPD.

Macroautophagy plays an important role in the pathogenesis of chronic obstructive pulmonary disease (COPD), but the role of chaperone-mediated autophagy (CMA) has not been investigated. We investigated if and how CMA is involved in the pathogenesis of COPD. We measured the level of lysosome-associated membrane protein-2A (LAMP-2A), which is a critical component of CMA that functions as a receptor for cytosolic substrate proteins, in total lung tissues and primary human bronchial epithelial cells (HBECs) from healthy never smokers, smokers, and COPD patients. We assessed the effects of LAMP-2A knock-down on cigarette smoke extract (CSE)-induced aging, cell cycle arrest, and apoptosis in BEAS-2B cells and the expression levels of apoptosis hallmarks in primary HBECs and lung tissue sections. We found that the protein levels of LAMP-2A in lung homogenates and primary HBECs from smokers and COPD patients were lower than those from never smokers. In addition, its level in primary HBECs was negatively correlated with years of smoking. CSE caused degradation of LAMP-2A protein via the lysosomal pathway by activating macroautophagy. Knock-down of LAMP-2A markedly enhanced CSE-induced expression of senescence markers such as p16, p21, p27, and p53. G2/M cell cycle arrest, up-regulation of cyclin B1, and apoptosis in BEAS-2B cells. Apoptosis was increased in CSE-treated primary HBECs and in lung tissues from smokers and COPD patients. Cigarette smoke-induced down-regulation of LAMP-2A is involved in acceleration of aging and apoptosis of lung epithelial cells, which might at least partially contribute to COPD pathogenesis.

Chaperone-Mediated Autophagy Regulates Hypoxic Pathology in Cardiomyocytes.

Tight regulation of protein degradation pathways is essential for maintaining cardiac homeostasis. The goal of this work was to define the role of chaperone-mediated autophagy (CMA), in cardiomyocytes. CMA acts as a selective degradation pathway of proteins using a cytosolic and lysosomal co-chaperone, HSPA8/HSC70, and the CMA-specific LAMP2A (lysosomal-associated membrane protein 2A) receptor. LAMP2A protein levels are known to be necessary for CMA function. While CMA was shown to exert protection against neurodegenerative disorders and cancer, the role of CMA during cardiac pathology was not known. It was hypothesized that enhancing CMA could mitigate hypoxic pathology in cardiomyocytes. Thus, a genetic gain- and loss-of-CMA-function approach was employed using a Lamp2a-overexpressing adenovirus and a Lamp2a-silencing siRNA, respectively, in primary cardiomyocytes treated with CoCl2 (a hypoxia-mimetic agent) or vehicle control. The experiments performed clearly showed that Lamp2a-overexpression leads to CMA activation that is sufficient to attenuate hypoxia-induced cardiomyocyte death and toxicity.

New unexpected role for Wolfram Syndrome protein WFS1: a novel therapeutic target for Alzheimer's disease?

New unexpected role for Wolfram Syndrome protein WFS1: a novel therapeutic target for Alzheimer's disease?

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.

Abstract 395: Characterizing the role of chaperone-mediated autophagy in prostate cancer treatment resistance

Abstract Androgen deprivation therapy (ADT) and androgen receptor pathway inhibition (ARPI) remains the standard of care for advanced prostate cancer (PCa). As part of its canonical activities, the androgen receptor (AR) plays an important role in PCa metabolism. AR inhibition with ARPI subjects PCa cells to acute metabolic stress caused by reduced biosynthesis and energy production. The upregulation of ARPI-induced stress response mechanisms is essential adaptive mechanism for cell proliferation and survival. This process requires PCa cells undergoing rapid phenotypic changes to adapt to their environment and circumvent lethal outcomes. By profiling the proteomic pathway alterations associated with the ARPI stress response in LNCaP cells, we noted a significant upregulation of chaperone mediated autophagy (CMA), a stress response mechanism yet to be defined in PCa. CMA, a selective protein degradation pathway, specifically targets protein substrates via a CMA recognition motif and is an essential survival mechanism in cancer cells during energy depleted metabolic stress. Within in-vitro and in-vivo PCa models, ARPI induced CMA is reflected through the increased activity of CMA lysosomes and specifically by the increased expression of the CMA marker, lysosomal associated membrane protein 2a (L2A). L2A knockdown using shRNA not only elicited a strong anti-proliferative effect in PCa cells, but also compromised PCa metabolism with decreases in ATP levels and mTORC1 signaling. Proteomic analysis by mass spectrometry further identified that CMA promotes chromatin silencing, and the suppression of pathways associated with transcription. Conversely, L2A overexpression not only promoted PCa cell proliferation during Enza treatment, but upregulated of hallmark target genes of AR-indifferent PCa growth. The upregulation of CMA facilitated proteome remodeling during ARPI, leading to increased mTORC1 signaling and biosynthesis. In summary, our data illustrates the importance of CMA in mediating the ARPI stress response in PCa, providing novel insights into the mechanisms of ARPI treatment resistance. Citation Format: Nicholas Nikesitch, Eliana Beraldi, Fan Zhang, Hans Adomat, Robert Bell, Ladan Fazli, Christopher Wells, Nicholas Pinette, Yuzhuo Wang, Martin Gleave. Characterizing the role of chaperone-mediated autophagy in prostate cancer treatment resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 395.

Misfolded GBA/β-glucocerebrosidase impairs ER-quality control by chaperone-mediated autophagy in Parkinson disease

Inhibition of chaperone-mediated autophagy (CMA), a selective type of lysosomal degradation for intracellular proteins, may contribute to pathogenesis in neurodegenerative diseases including Parkinson disease (PD). Pathogenic variants of PD-related proteins that reside in the cytosol, including SNCA/alpha-synuclein, LRRK2 (leucine rich repeat kinase 2), UCHL1 (ubiquitin Cterminal hydrolase 1) and VPS35 (VPS35 retromer complex component), exert inhibitory effects on CMA. Decreased CMA activity has also been reported in sporadic PD patients, consistent with an association between CMA inhibition and PD. We have now reported the first example of CMA dysfunction caused by a non-cytosolic PD-related protein, GBA/β-glucocerebrosidase, the most common genetic risk factor for PD, which uncovers a new role for CMA in endoplasmic reticulum (ER) quality control.

Chaperone-Mediated Autophagy Ablation in Pericytes Reveals New Glioblastoma Prognostic Markers and Efficient Treatment Against Tumor Progression.

Background: The lack of knowledge of the progression mechanisms of glioblastoma (GB), the most aggressive brain tumor, contributes to the absence of successful therapeutic strategies. Our team has recently demonstrated a crucial new role for chaperone-mediated autophagy (CMA) in pericytes (PC)-acquired immunosuppressive function, which prevents anti-tumor immune responses and facilitates GB progression. The possible impact that GB-induced CMA in PC has on other functions that might be useful for future GB prognosis/treatment, has not been explored yet. Thus, we proposed to analyze the contribution of CMA to other GB-induced changes in PC biology and determine if CMA ablation in PC is a key target mechanism for GB treatment. Methods: Studies of RNA-seq and secretome analysis were done in GB-conditioned PC with and without CMA (from knockout mice for LAMP-2A) and compared to control PC. Different therapeutic strategies in a GB mouse model were compared. Results: We found several gene expression pathways enriched in LAMP2A-KO PC and affected by GB-induced CMA in PC that correlate with our previous findings. Phagosome formation, cellular senescence, focal adhesion and the effector function to promote anti-tumor immune responses were the most affected pathways, revealing a transcriptomic profiling of specific target functions useful for future therapies. In addition, several molecules associated with tumor mechanisms and related to tumor immune responses such as gelsolin, periostin, osteopontin, lumican and vitamin D, were identified in the PC secretome dependent on GB-induced CMA. The CMA ablation in PC with GB cells showed an expected immunogenic phenotype able to phagocyte GB cells and a key strategy to develop future therapeutic strategies against GB tumor progression. A novel intravenous therapy using exofucosylated CMA-deficient PC was efficient to make PC reach the tumor niche and facilitate tumor elimination. Conclusion: Our results corroborate previous findings on the impaired immunogenic function of PC with GB-induced CMA, driving to other altered PC functions and the identifications of new target markers related to the tumor immune responses and useful for GB prognosis/therapy. Our work demonstrates CMA ablation in PC as a key target mechanism to develop a successful therapy against GB progression.

Loss of chaperone-mediated autophagy is associated with low vertebral cancellous bone mass

Chaperone-mediated autophagy (CMA) is a protein degradation pathway that eliminates soluble cytoplasmic proteins that are damaged, incorrectly folded, or targeted for selective proteome remodeling. However, the role of CMA in skeletal homeostasis under physiological and pathophysiological conditions is unknown. To address the role of CMA for skeletal homeostasis, we deleted an essential component of the CMA process, namely Lamp2a, from the mouse genome. CRISPR-Cas9-based genome editing led to the deletion of both Lamp2a and Lamp2c, another Lamp2 isoform, producing Lamp2AC global knockout (L2ACgKO) mice. At 5 weeks of age female L2ACgKO mice had lower vertebral cancellous bone mass compared to wild-type (WT) controls, whereas there was no difference between genotypes in male mice at this age. The low bone mass of L2ACgKO mice was associated with elevated RANKL expression and the osteoclast marker genes Trap and Cathepsin K. At 18 weeks of age, both male and female L2ACgKO mice had lower vertebral cancellous bone mass compared to WT controls. The low bone mass of L2ACgKO mice was associated with increased osteoclastogenesis and decreased mineral deposition in cultured cells. Consistent with these findings, specific knockdown of Lamp2a in an osteoblastic cell line increased RANKL expression and decreased mineral deposition. Moreover, similar to what has been observed in other cell types, macroautophagy and proteasomal degradation were upregulated in CMA-deficient osteoblasts in culture. Thus, an increase in other protein degradation pathways may partially compensate for the loss of CMA in osteoblasts. Taken together, our results suggest that CMA plays a role in vertebral cancellous bone mass accrual in young adult mice and that this may be due to an inhibitory role of CMA on osteoclastogenesis or a positive role of CMA in osteoblast formation or function.

Inactivation of EGLN3 hydroxylase facilitates Erk3 degradation via autophagy and impedes lung cancer growth

EGLN3 is critically important for growth of various cancers including lung cancer. However, virtually nothing is known about the role and mechanism for EGLN3 hydroxylase activity in cancers. EGLN3 catalyzes the hydroxylation of extracellular signal-regulated kinase 3 (Erk3), a potent driver of cancers. The role and mechanism for EGLN3-induced stabilization of Erk3 remain to be defined. Here, we show that Erk3 interacts with heat shock cognate protein of 70 kDa (HSC70) and lysosome-associated membrane protein type 2 A (LAMP2A), two core components of chaperone-mediated autophagy (CMA). As a consequence, Erk3 is degraded by the CMA-lysosome pathway. EGLN3-catalyzed hydroxylation antagonizes CMA-dependent destruction of Erk3. Mechanistically, hydroxylation blunts the interaction of Erk3 with LAMP2A, thereby blocking lysosomal decay of Erk3. EGLN3 inactivation inhibits macrophage migration, efferocytosis, and M2 polarization. Studies using EGLN3 catalytically inactive knock-in mice indicate that inactivation of EGLN3 hydroxylase in host cells ameliorates LLC cancer growth through reprogramming the tumor microenvironment (TME). Adoptive transfer of macrophages with inactivated EGLN3 restrains tumor growth by mounting anti-tumor immunity and restricting angiogenesis. Administration of EGLN3 hydroxylase pharmacologic inhibitor to mice bearing LLC carcinoma impedes cancer growth by targeting the TME. LLC cells harboring inactivated EGLN3 exhibit reduced tumor burden via mitigating immunosuppressive milieu and inducing cancer senescence. This study provides novel insights into the role of CMA in regulating Erk3 stability and the mechanism behind EGLN3-enhanced stability of Erk3. This work demonstrates that inactivation of EGLN3 in malignant and stromal cells suppresses tumor by orchestrating reciprocal interplays between cancer cells and the TME. This work sheds new light on the role and mechanism for EGLN3 catalytic activity in regulating cancer growth. Manipulating EGLN3 activity holds promise for cancer treatment.

New Insights into the Mechanisms of Chaperon-Mediated Autophagy and Implications for Kidney Diseases.

Chaperone-mediated autophagy (CMA) is a separate type of lysosomal proteolysis, characterized by its selectivity of substrate proteins and direct translocation into lysosomes. Recent studies have declared the involvement of CMA in a variety of physiologic and pathologic situations involving the kidney, and it has emerged as a potential target for the treatment of kidney diseases. The role of CMA in kidney diseases is context-dependent and appears reciprocally with macroautophagy. Among the renal resident cells, the proximal tubule exhibits a high basal level of CMA activity, and restoration of CMA alleviates the aging-related tubular alternations. The level of CMA is up-regulated under conditions of oxidative stress, such as in acute kidney injury, while it is declined in chronic kidney disease and aging-related kidney diseases, leading to the accumulation of oxidized substrates. Suppressed CMA leads to the kidney hypertrophy in diabetes mellitus, and the increase of CMA contributes to the progress and chemoresistance in renal cell carcinoma. With the progress on the understanding of the cellular functions and uncovering the clinical scenario, the application of targeting CMA in the treatment of kidney diseases is expected.

The Role of Chaperone-Mediated Autophagy in Bortezomib Resistant Multiple Myeloma.

Background: Multiple myeloma (MM) remains incurable despite high-dose chemotherapy, autologous stem cell transplants and novel agents. Even with the improved survival of MM patients treated with novel agents, including bortezomib (Bz), the therapeutic options in relapsed/refractory MM remain limited. The majority of MM patients eventually develop resistance to Bz, although the mechanisms of the resistance are poorly understood. Methods: Lysosomal associated membrane protein 2A (LAMP2A) mRNA and protein expression levels were assessed in ex vivo patient samples and a Bz-resistant MM cell line model by in real-rime PCR, western blotting and immunohistochemistry. In vitro modelling of chaperone-mediated autophagy (CMA) activity in response to ER stress were assessed by western blotting and confocal microscopy. The effects of CMA inhibition on MM cell viability and Bz sensitivity in MM cells were assessed by Annexin V/7AAD apoptosis assays using flow cytometry. Results: In this study, there is evidence that CMA, a chaperone-mediated protein degradation pathway, is upregulated in Bz-resistant MM and the inhibition of CMA sensitises resistant cells to Bz. The protein levels of LAMP2A, the rate-limiting factor of the CMA pathway, are significantly increased in MM patients resistant to Bz and within our Bz-resistant cell line model. Bz-resistant cell lines also possessed higher basal CMA activity than the Bz-sensitive parent cell line. In MM cell lines, CMA activity was upregulated in response to ER stress induced by Bz. The inhibition of CMA sensitises Bz-resistant cells to Bz and the combination of CMA inhibition and Bz in vitro had a more cytotoxic effect on myeloma cells than Bz alone. Conclusion: In summary, the upregulation of CMA is a potential mechanism of resistance to Bz and a novel target to overcome Bz-resistant MM.

The Role of Chaperone-Mediated Autophagy in Hepatitis C Virus-Induced Pathogenesis.

Lysosome incorporate and degrade proteins in a process known as autophagy. There are three types of autophagy; macroautophagy, microautophagy, and chaperone-mediated autophagy (CMA). Although autophagy is considered a nonselective degradation process, CMA is known as a selective degradation pathway. All proteins internalized in the lysosome via CMA contain a pentapeptide KFERQ-motif, also known as a CMA-targeting motif, which is necessary for selectivity. CMA directly delivers a substrate protein into the lysosome lumen using the cytosolic chaperone HSC70 and the lysosomal receptor LAMP-2A for degradation. Hepatitis C virus (HCV) NS5A protein interacts with hepatocyte-nuclear factor 1α (HNF-1α) together with HSC70 and promotes the lysosomal degradation of HNF-1α via CMA, resulting in HCV-induced pathogenesis. HCV NS5A promotes recruitment of HSC70 to the substrate protein HNF-1α. HCV NS5A plays a crucial role in HCV-induced CMA. Further investigations of HCV NS5A-interacting proteins containing CMA-targeting motifs may help to elucidate HCV-induced pathogenesis.

Chaperone-mediated autophagy sustains haematopoietic stem-cell function.

Activation of mostly quiescent hematopoietic stem cells (HSC) is a prerequisite for life-long blood production1, 2. This process requires major molecular adaptations to meet the regulatory and metabolic requirements for cell division3–8. The mechanisms governing cellular reprograming upon stem cell activation and their subsequent return to quiescence are still not fully characterized. Here, we describe a role for chaperone-mediated autophagy (CMA)9, a selective form of lysosomal protein degradation, in sustaining adult HSC function. CMA is required for stem cell protein quality control and upregulation of fatty acid metabolism upon HSC activation. We identify that CMA activity decreases with age in HSC and show that genetic or pharmacological activation of CMA can restore functionality of old HSC. Together, our findings provide mechanistic insights into a new role for CMA in sustaining quality control, appropriate energetics and overall long-term hematopoietic stem cell function. Our work supports that CMA may be a promising therapeutic target to enhance hematopoietic stem cell function in conditions such as aging or stem cell transplantation.

The Role of Chaperone-Mediated Autophagy in Cell Cycle Control and Its Implications in Cancer.

The cell cycle involves a network of proteins that modulate the sequence and timing of proliferation events. Unregulated proliferation is the most fundamental hallmark of cancer; thus, changes in cell cycle control are at the heart of malignant transformation processes. Several cellular processes can interfere with the cell cycle, including autophagy, the catabolic pathway involved in degradation of intracellular constituents in lysosomes. According to the mechanism used to deliver cargo to the lysosome, autophagy can be classified as macroautophagy (MA), microautophagy (MI), or chaperone-mediated autophagy (CMA). Distinct from other autophagy types, CMA substrates are selectively recognized by a cytosolic chaperone, one-by-one, and then addressed for degradation in lysosomes. The function of MA in cell cycle control, and its influence in cancer progression, are already well-established. However, regulation of the cell cycle by CMA, in the context of tumorigenesis, has not been fully addressed. This review aims to present and debate the molecular mechanisms by which CMA can interfere in the cell cycle, in the context of cancer. Thus, cell cycle modulators, such as MYC, hypoxia-inducible factor-1 subunit alpha (HIF-1α), and checkpoint kinase 1 (CHK1), regulated by CMA activity will be discussed. Finally, the review will focus on how CMA dysfunction may impact the cell cycle, and as consequence promote tumorigenesis.

Lipid excess affects chaperone-mediated autophagy in hypothalamus

Obesity is a major health problem worldwide. Overweight and obesity directly affect health-related quality of life and also have an important economic impact on healthcare systems. In experimental models, obesity leads to hypothalamic inflammation and loss of metabolic homeostasis. It is known that macroautophagy is decreased in the hypothalamus of obese mice but the role of chaperone-mediated autophagy is still unknown. In this study, we aimed to investigate the role of hypothalamic chaperone-mediated autophagy in response to high-fat diet and also the direct effect of palmitate on hypothalamic neurons. Mice received chow or high-fat diet for 3 days or 1 week. At the end of the experimental protocol, chaperone-mediated autophagy in hypothalamus was investigated, as well as cytokines expression. In other set of experiments, neuronal cell lines were treated with palmitic acid, a saturated fatty acid. We show that chaperone-mediated autophagy is differently regulated in response to high-fat diet intake for 3 days or 1 week. Also, when hypothalamic neurons are directly exposed to palmitate there is activation of chaperone-mediated autophagy. High-fat diet causes hypothalamic inflammation concomitantly to changes in the content of chaperone-mediated autophagy machinery. It remains to be studied the direct role of inflammation and lipids itself on the activation of chaperone-mediated autophagy in the hypothalamus in vivo and also the neuronal implications of chaperone-mediated autophagy inhibition in response to obesity.

Deficient Chaperone-Mediated Autophagy Promotes Lipid Accumulation in Macrophage

Chaperone-mediated autophagy (CMA) serves as a critical upstream regulator of lipophagy and lipid metabolism in hepatocyte. However, the role of CMA in lipid metabolism of macrophage, the typical component of atherosclerotic plaque, remains unclear. In our study, LAMP-2A (L2A, a CMA marker) was reduced in macrophages exposed to high dose of oleate, and lipophagy was impaired in advanced atherosclerosis in ApoE (−/−) mice. Primary peritoneal macrophages isolated from macrophage-specific L2A-deficient mice exhibited pronounced intracellular lipid accumulation. Lipid regulatory enzymes, including long-chain-fatty-acid-CoA ligase 1 (ACSL1) and lysosomal acid lipase (LAL), were increased and reduced in L2A-KO macrophage, respectively. Other lipid-related proteins, such as SR-A, SR-B (CD36), ABCA1, or PLIN2, were not associated with increased lipid content in L2A-KO macrophage. In conclusion, deficient CMA promotes lipid accumulation in macrophage probably by regulating enzymes involved in lipid metabolism. CMA may represent a novel therapeutic target to alleviate atherosclerosis by promoting lipid metabolism.Graphical abstract