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Necroptosis and ferroptosis are two distinct necrotic cell death modalities with no known common molecular mechanisms. Necroptosis is activated by ligands of death receptors such as tumor necrosis factor-α (TNF-α) under caspase-deficient conditions, whereas ferroptosis is mediated by the accumulation of lipid peroxides upon the depletion/or inhibition of glutathione peroxidase 4 (GPX4). The molecular mechanism that mediates the execution of ferroptosis remains unclear. In this study, we identified 2-amino-5-chloro-N,3-dimethylbenzamide (CDDO), a compound known to inhibit heat shock protein 90 (HSP90), as an inhibitor of necroptosis that could also inhibit ferroptosis. We found that HSP90 defined a common regulatory nodal between necroptosis and ferroptosis. We showed that inhibition of HSP90 by CDDO blocked necroptosis by inhibiting the activation of RIPK1 kinase. Furthermore, we showed that the activation of ferroptosis by erastin increased the levels of lysosome-associated membrane protein 2a to promote chaperone-mediated autophagy (CMA), which, in turn, promoted the degradation of GPX4. Importantly, inhibition of CMA stabilized GPX4 and reduced ferroptosis. Our results suggest that activation of CMA is involved in the execution of ferroptosis.

Mutations in lysosomal-associated membrane protein 2 (LAMP-2) gene are associated with Danon disease, which often leads to cardiomyopathy/heart failure through poorly defined mechanisms. Here, we identify the LAMP-2 isoform B (LAMP-2B) as required for autophagosome–lysosome fusion in human cardiomyocytes (CMs). Remarkably, LAMP-2B functions independently of syntaxin 17 (STX17), a protein that is essential for autophagosome–lysosome fusion in non-CMs. Instead, LAMP-2B interacts with autophagy related 14 (ATG14) and vesicle-associated membrane protein 8 (VAMP8) through its C-terminal coiled coil domain (CCD) to promote autophagic fusion. CMs derived from induced pluripotent stem cells (hiPSC-CMs) from Danon patients exhibit decreased colocalization between ATG14 and VAMP8, profound defects in autophagic fusion, as well as mitochondrial and contractile abnormalities. This phenotype was recapitulated by LAMP-2B knockout in non-Danon hiPSC-CMs. Finally, gene correction of LAMP-2 mutation rescues the Danon phenotype. These findings reveal a STX17-independent autophagic fusion mechanism in human CMs, providing an explanation for cardiomyopathy in Danon patients and a foundation for targeting defective LAMP-2B–mediated autophagy to treat this patient population.

Endoplasmic reticulum (ER) and lysosomes coordinate a network of key cellular processes including unfolded protein response (UPR) and autophagy in response to stress. How ER stress is signaled to lysosomes remains elusive. Here we find that ER disturbance activates chaperone-mediated autophagy (CMA). ER stressors lead to a PERK-dependent activation and recruitment of MKK4 to lysosomes, activating p38 MAPK at lysosomes. Lysosomal p38 MAPK directly phosphorylates the CMA receptor LAMP2A at T211 and T213, which causes its membrane accumulation and active conformational change, activating CMA. Loss of ER stress-induced CMA activation sensitizes cells to ER stress-induced death. Neurotoxins associated with Parkinson’s disease fully engages ER-p38 MAPK–CMA pathway in the mouse brain and uncoupling it results in a greater loss of SNc dopaminergic neurons. This work identifies the coupling of ER and CMA as a critical regulatory axis fundamental for physiological and pathological stress response. The endoplasmic reticulum (ER) and lysosome are central to cellular stress responses, but it is unclear how ER stress is signaled to lysosomes. Here the authors show that ER stress activates chaperone-mediated autophagy (CMA) via direct phosphorylation of the CMA receptor LAMP2A by the lysosomal p38 MAPK.

The early stages of age-related macular degeneration (AMD) are characterized by the accumulation of basal laminar deposits (BLamDs). The mechanism for BLamDs accumulating between the retinal pigment epithelium (RPE) and its basal lamina remains elusive. Here we examined the role in AMD of lysosome-associated membrane protein-2 (LAMP2), a glycoprotein that plays a critical role in lysosomal biogenesis and maturation of autophagosomes/phagosomes. LAMP2 was preferentially expressed by RPE cells, and its expression declined with age. Deletion of the Lamp2 gene in mice resulted in age-dependent autofluorescence abnormalities of the fundus, thickening of Bruch’s membrane, and the formation of BLamDs, resembling histopathological changes occurring in AMD. Moreover, LAMP2-deficient mice developed molecular signatures similar to those found in human AMD—namely, the accumulation of APOE, APOA1, clusterin, and vitronectin—adjacent to BLamDs. In contrast, collagen 4, laminin, and fibronectin, which are extracellular matrix proteins constituting RPE basal lamina and Bruch’s membrane were reduced in Lamp2 knockout (KO) mice. Mechanistically, retarded phagocytic degradation of photoreceptor outer segments compromised lysosomal degradation and increased exocytosis in LAMP2-deficient RPE cells. The accumulation of BLamDs observed in LAMP2-deficient mice was eventually followed by loss of the RPE and photoreceptors. Finally, we observed loss of LAMP2 expression along with ultramicroscopic features of abnormal phagocytosis and exocytosis in eyes from AMD patients but not from control individuals. Taken together, these results indicate an important role for LAMP2 in RPE function in health and disease, suggesting that LAMP2 reduction may contribute to the formation of BLamDs in AMD.

Danon disease is a rare, X-linked, monogenic cardiomyopathy caused by mutations in the lysosomal-associated membrane 2 gene ( ), which encodes the LAMP2 protein. In male patients, the predominant phenotype is progressive cardiac hypertrophy, cardiac dysfunction, and early death. There are no directed therapies for the disease. In this phase 1 study, we evaluated the safety and efficacy of a single infusion of RP-A501, a recombinant adeno-associated virus serotype 9 containing the transgene , which encodes an isoform of LAMP2. The primary outcomes were the safety and toxic effects of RP-A501, myocardial LAMP2 transduction and protein expression, stabilization of or reduction in heart-failure symptoms, and stabilization of or improvement in cardiac structure and function. Key secondary outcomes were sustained reduction in or stabilization of symptoms, immunologic response to RP-A501, end-stage heart failure, and overall survival. Exploratory outcomes included improvement in serologic markers of cardiac disease, patient-reported outcomes, and quality-of-life assessments. RP-A501 infusion was administered to seven male patients with Danon disease: five who were 15 years of age or older and two who were between 11 and 14 years of age. All the patients received a transient immunomodulatory regimen of prednisone, tacrolimus or sirolimus, and rituximab. Phase 1 data over 24 to 54 months, including interim data from a long-term follow-up study, are reported here. One patient had complement-mediated thrombotic microangiopathy (grade 4) with thrombocytopenia and acute kidney injury. Three patients had glucocorticoid-related exacerbation (grade 3) of Danon disease-related skeletal myopathy. One patient with left ventricular systolic dysfunction at baseline had progressive heart failure and underwent transplantation 5 months after infusion. In the six patients with normal left ventricular ejection fraction at baseline, we observed cardiac LAMP2 protein expression and a reduction from baseline in or stabilization of the left ventricular mass index, preservation of left ventricular ejection fraction, and reduction in or stabilization of the levels of cardiac troponin I and N-terminal pro-B-type natriuretic peptide. At 24 to 54 months, all the patients were alive, with complete resolution of side effects. A single infusion of RP-A501 appeared to be safe and was associated with cardiac LAMP2 expression and evidence of clinical improvement over a period of 24 to 54 months. (Funded by Rocket Pharmaceuticals; ClinicalTrials.gov number, NCT03882437.).

This review focuses on chaperone-mediated autophagy （CMA）, one of the proteolytic systems that contributes to degradation of intracellular proteins in lysosomes. CMA substrate proteins are selectively targeted to lysosomes and translocated into the lysosomal lumen through the coordinated action of chaperones located at both sides of the membrane and a dedicated protein translocation complex. The selectivity of CMA permits timed degradation of spe- cific proteins with regulatory purposes supporting a modulatory role for CMA in enzymatic metabolic processes and subsets of the cellular transcriptional program. In addition, CMA contributes to cellular quality control through the removal of damaged or malfunctioning proteins. Here, we describe recent advances in the understanding of the molecular dynamics, regulation and physiology of CMA, and discuss the evidence in support of the contribution of CMA dysfunction to severe human disorders such as neurodegeneration and cancer.

Chaperone-mediated autophagy selectively targets single cytoplasmic proteins for degradation. Macian and colleagues show that such autophagy is induced by engagement of the TCR to target negative regulators of T cell activation. Chaperone-mediated autophagy (CMA) targets soluble proteins for lysosomal degradation. Here we found that CMA was activated in T cells in response to engagement of the T cell antigen receptor (TCR), which induced expression of the CMA-related lysosomal receptor LAMP-2A. In activated T cells, CMA targeted the ubiquitin ligase Itch and the calcineurin inhibitor RCAN1 for degradation to maintain activation-induced responses. Consequently, deletion of the gene encoding LAMP-2A in T cells caused deficient in vivo responses to immunization or infection with Listeria monocytogenes . Impaired CMA activity also occurred in T cells with age, which negatively affected their function. Restoration of LAMP-2A in T cells from old mice resulted in enhancement of activation-induced responses. Our findings define a role for CMA in regulating T cell activation through the targeted degradation of negative regulators of T cell activation.

Background Traumatic brain injury (TBI) represents a major cause of disability and death worldwide with sustained neuroinflammation and autophagy dysfunction contributing to the cellular damage. Stimulator of interferon genes (STING)-induced type-I interferon (IFN) signalling is known to be essential in mounting the innate immune response against infections and cell injury in the periphery, but its role in the CNS remains unclear. We previously identified the type-I IFN pathway as a key mediator of neuroinflammation and neuronal cell death in TBI. However, the modulation of the type-I IFN and neuroinflammatory responses by STING and its contribution to autophagy and neuronal cell death after TBI has not been explored. Methods C57BL/6J wild-type (WT) and STING −/− mice (8–10-week-old males) were subjected to controlled cortical impact (CCI) surgery and brains analysed by QPCR, Western blot and immunohistochemical analyses at 2 h or 24 h. STING expression was also analysed by QPCR in post-mortem human brain samples. Results A significant upregulation in STING expression was identified in late trauma human brain samples that was confirmed in wild-type mice at 2 h and 24 h after CCI. This correlated with an elevated pro-inflammatory cytokine profile with increased TNF-α, IL-6, IL-1β and type-I IFN (IFN-α and IFN-β) levels. This expression was suppressed in the STING −/− mice with a smaller lesion volume in the knockout animals at 24 h post CCI. Wild-type mice also displayed increased levels of autophagy markers, LC3-II, p62 and LAMP2 after TBI; however, STING −/− mice showed reduced LAMP2 expression suggesting a role for STING in driving dysfunctional autophagy after TBI. Conclusion Our data implicates a detrimental role for STING in mediating the TBI-induced neuroinflammatory response and autophagy dysfunction, potentially identifying a new therapeutic target for reducing cellular damage in TBI.

Lysosome-associated membrane proteins (LAMPs) play a critical role in various cellular processes, including phagocytosis, lipid transport, neoangiogenesis, and tissue remodeling. Recent discussions have focused on their involvement in autophagy related to tumor progression. Emerging studies have underscored the connection between tumorigenesis and autophagy, highlighting that dysregulation of this process is associated with the resistance of tumor cells to conventional chemotherapy across numerous malignancies, including colorectal cancer (CRC). Currently, there is a notable absence of reliable prognostic biomarkers for effectively stratifying and predicting treatment responses in CRC patients. Our study examines the expression of LAMP1 and LAMP2 proteins and genes alongside key autophagy markers such as BECLIN1 and LC3B, investigating their relationships with CRC invasiveness. We present original data illustrating the association of LAMP molecules with standard autophagy markers and tumor budding. Our findings provide novel insights into the significance of these markers in CRC invasiveness, their relationship with survival rates, and their potential role as prognostic biomarkers.

Chaperone-mediated autophagy (CMA) selectively degrades a subset of cytosolic proteins in lysosomes. A potent physiological activator of CMA is nutrient deprivation, a condition in which intracellular triglyceride stores or lipid droplets (LDs) also undergo hydrolysis (lipolysis) to generate free fatty acids for energetic purposes. Here we report that the LD-associated proteins perilipin 2 (PLIN2) and perilipin 3 (PLIN3) are CMA substrates and their degradation through CMA precedes lipolysis. In vivo studies revealed that CMA degradation of PLIN2 and PLIN3 was enhanced during starvation, concurrent with elevated levels of cytosolic adipose triglyceride lipase (ATGL) and macroautophagy proteins on LDs. CMA blockage both in cultured cells and mouse liver or expression of CMA-resistant PLINs leads to reduced association of ATGL and macrolipophagy-related proteins with LDs and the subsequent decrease in lipid oxidation and accumulation of LDs. We propose a role for CMA in LD biology and in the maintenance of lipid homeostasis. Cuervo and colleagues find that perilipin proteins associated with lipid droplets are degraded by chaperone-mediated autophagy to facilitate recruitment of the lipolytic machinery to lipid droplets.