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The activation of mostly quiescent haematopoietic stem cells (HSCs) is a prerequisite for life-long production of blood cells 1 . This process requires major molecular adaptations to allow HSCs to meet the regulatory and metabolic requirements for cell division 2 – 4 . The mechanisms that govern cellular reprograming upon stem-cell activation, and the subsequent return of stem cells to quiescence, have not been fully characterized. Here we show that chaperone-mediated autophagy (CMA) 5 , a selective form of lysosomal protein degradation, is involved in sustaining HSC function in adult mice. CMA is required for protein quality control in stem cells and for the upregulation of fatty acid metabolism upon HSC activation. We find that CMA activity in HSCs decreases with age and show that genetic or pharmacological activation of CMA can restore the functionality of old mouse and human HSCs. Together, our findings provide mechanistic insights into a role for CMA in sustaining quality control, appropriate energetics and overall long-term HSC function. Our work suggests that CMA may be a promising therapeutic target for enhancing HSC function in conditions such as ageing or stem-cell transplantation. Haematopoietic stem cells show progressive functional decline with age that can be reversed by stimulation of chaperone-mediated autophagy in old mice and aged humans.

Chaperone-mediated autophagy (CMA) is a lysosomedependent selective degradation pathway implicated in the pathogenesis of cancer and neurodegenerative diseases. However, the mechanisms that regulate CMA are not fully understood. Here, using unbiased drug screening approaches, we discover Metformin, a drug that is commonly the first medication prescribed for type 2 diabetes, can induce CMA. We delineate the mechanism of CMA induction by Metformin to be via activation of TAK1-IKKα/β signaling that leads to phosphorylation of Ser85 of the key mediator of CMA, Hsc70, and its activation. Notably, we find that amyloid-beta precursor protein (APP) is a CMA substrate and that it binds to Hsc70 in an IKKα/β-dependent manner. The inhibition of CMA-mediated degradation of APP enhances its cytotoxicity. Importantly, we find that in the APP/ PS1 mouse model of Alzheimer's disease (AD), activation of CMA by Hsc70 overexpression or Metformin potently reduces the accumulated brain Aβ plaque levels and reverses the molecular and behavioral AD phenotypes. Our study elucidates a novel mechanism of CMA regulation via Metformin-TAK1-IKKα/β-Hsc70 signaling and suggests Metformin as a new activator of CMA for diseases, such as AD, where such therapeutic intervention could be beneficial.

INTRODUCTION Tauopathy is characterized by the pathology of tau deposits in the brain. Transmembrane protein 59 (TMEM59) is correlated with Alzheimer's disease (AD), the most common type of tauopathy. However, whether and how TMEM59 regulates tau pathology remains unknown. METHODS We analyzed TMEM59 levels in the brains of AD patients and the tauP301S transgenic (PS19) mice, evaluated behaviors and tauopathy‐related pathologies in PS19 mice with TMEM59 haploinsufficiency, and studied the regulation of TMEM59 on chaperone‐mediated autophagy (CMA) using biochemical analysis. RESULTS TMEM59 levels increased in the brains of AD patients and PS19 mice at pathological stages. TMEM59 haploinsufficiency attenuated cognitive deficits and disease‐related pathologies in PS19 mice. TMEM59 deficiency promoted lysosome‐associated membrane protein type 2A levels and CMA activity, whereas TMEM59 overexpression had the opposite effects. DISCUSSION Our study identifies an important role of TMEM59 in regulating CMA and reveals the potential of targeting TMEM59 for tauopathy intervention. Highlights Transmembrane protein 59 (TMEM59) levels increase in the brains of Alzheimer's disease patients and the tauP301S transgenic (PS19) tauopathy model mice at pathological stages. TMEM59 haploinsufficiency attenuates cognitive deficits, neurodegeneration, synapse dysfunction, gliosis, neuroinflammation, and tau pathology in PS19 mice. TMEM59 interacts with lysosome‐associated membrane protein type 2A and heat‐shock cognate 71 kDa and regulates chaperone‐mediated autophagy. TMEM59 may serve as a therapeutic target for tauopathy.

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 (CMA) is a selective type of autophagy whereby a specific subset of intracellular proteins is targeted to the lysosome for degradation. The present study investigated the mechanisms underlying the response and resistance to 5-fluorouracil (5-FU) in colorectal cancer (CRC) cell lines. In engineered 5-FU-resistant CRC cell lines, a significant elevation of lysosome-associated membrane protein 2A (LAMP2A), which is the key molecule in the CMA pathway, was identified. High expression of LAMP2A was found to be responsible for 5-FU resistance and to enhance PLD2 expression through the activation of NF-κB pathway. Accordingly, loss or gain of function of LAMP2A in 5-FU-resistant CRC cells rendered them sensitive or resistant to 5-FU, respectively. Taken together, the results of the present study suggested that chemoresistance in patients with CRC may be mediated by enhancing CMA. Thus, CMA is a promising predictor of chemosensitivity to 5-FU treatment and anti-CMA therapy may be a novel therapeutic option for patients with CRC.

Abstract Context Papillary thyroid carcinoma (PTC) is the most common endocrine malignancy. Chaperone-mediated autophagy (CMA), 1 type of autophagy, is thought to promote or suppress cancer development in different cancer types. However, the effect of CMA on PTC development and the underlying mechanisms remain unknown. Objective To determine whether CMA plays implied critical roles in the development of PTC. Design We investigated the association between CMA and PTC development in PTC tissues and normal thyroid tissues by detecting the key protein of CMA, lysosome-associated membrane protein type 2A (LAMP2A), using quantitative polymerase chain reaction (PCR) and immunohistochemistry, which were further validated in the TGCA dataset. The effect of CMA on PTC development was studied by cell proliferation, migration, and apoptosis assays. The underlying mechanisms of peroxisome proliferator-activated receptor γ (PPARγ)-stromal cell-derived factor 1 (SDF1)/ C-X-C motif chemokine receptor 4 (CXCR4) signaling were clarified by western blotting, quantitative PCR, and rescue experiments. Knockdown and tamoxifen were used to analyze the effect of estrogen receptor (ER) α on CMA. Results Our study confirmed that CMA, indicated by LAMP2A expression, was significantly increased in PTC tumor tissues and cell lines, and was associated with tumor size and lymph node metastasis of patients. Higher CMA in PTC promoted tumor cell proliferation and migration, thereby promoting tumor growth and metastasis. These effects of CMA on PTC were exerted by decreasing PPARγ protein expression to enhance SDF1 and CXCR4 expression. Furthermore, CMA was found positively regulated by ERα signaling in PTC. Conclusion Our investigation identified CMA regulated by ERα promoting PTC tumor progression that enhanced tumor cell proliferation and migration by targeting PPARγ-SDF1/CXCR4 signaling, representing a potential target for treatment of PTC.

Parkinson’s Disease (PD) is characterized by selective loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc). PANoptosis, a programmed inflammatory cell death integrating pyroptosis, apoptosis, and necroptosis, contributes to DA neuron degeneration in PD. The E3 ubiquitin ligase Parkin and the inflammasome sensor NOD-like receptor protein 3 (NLRP3) are known to play critical regulatory roles in DA neuron degeneration. However, whether Parkin modulated NLRP3 via chaperone-mediated autophagy (CMA) to inhibit PANoptosis remained unclear. To verify the above hypothesis, SN4741 cells and C57BL/6 mice were treated with rotenone to establish PD models. PANoptosis activation and DA neurons degeneration were observed in PD models, and these pathological manifestations were mitigated by the NLRP3 inhibitor MCC950. Besides, Parkin interacted with NLRP3, ubiquitinated its K353 residue, and then promoted NLRP3 degradation via CMA. Parkin overexpression or CMA activation alleviated DA neuron damage and PANoptosis, while K353R mutation abolished these effects. It was revealed that Parkin mediated CMA-dependent degradation of NLRP3 (targeting K353) to suppress PANoptosis and protect DA neurons in PD. CMA activators or NLRP3 inhibitors may serve as disease-modifying therapies for PD.

Chaperone‐mediated autophagy (CMA) represents a critical lysosomal degradation pathway in the context of intervertebral disc degeneration (IVDD) associated with senescence. This study revealed a novel mechanism of CMA regulation involving targeted degradation of acyl‐CoA synthetase long‐chain family member 4 (ACSL4), which can delay nucleus pulposus cell (NPC) senescence and inhibit IVDD progression. Mechanistic investigations demonstrated that the acetyltransferase KAT2B can facilitate the acetylation of ACSL4 at lysine residues K500, K571, and K692. This post‐translational modification served as a molecular switch, significantly enhancing the affinity between ACSL4 and the CMA recognition chaperone HSPA8, thereby promoting the efficient targeting and degradation of ACSL4 via the CMA pathway. Besides, engineered exosomes are harnessed to deliver the key CMA receptor LAMP2A in an in vivo model, effectively delaying cellular senescence and significantly attenuating IVDD progression. Overall, these findings establish the crucial protective role of CMA in preventing IVDD through the degradation of ACSL4, providing novel insights for developing therapeutic strategies targeting CMA activation to alleviate disc degeneration and associated chronic pain. Intervertebral disc degeneration is triggered by ACSL4 accumulation‐mediated ferroptosis of nucleus pulposus cells due to CMA dysfunction. KAT2B promotes ACSL4 degradation via CMA through acetylation. AAV‐mediated LAMP2A delivery or engineered exosomes rescue nucleus pulposus cell senescence and disc degeneration. This study identifies CMA‐regulated ferroptosis suppression as a key mechanism in disc degeneration and proposes LAMP2A‐targeted therapy for clinical translation.

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.

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.