Autophagy最新文献

{"title":"Pneumolysin-dependent and independent non-canonical autophagy processes mediate host defense against pneumococcal infection.","authors":"Bartosz J Michno, Niedharsan Pooranachandran, Tonisha C Smith, Erin Faught, Sandra Lipowská, Andrew K Fenton, Annemarie H Meijer, Tomasz K Prajsnar","doi":"10.1080/15548627.2025.2559728","DOIUrl":"https://doi.org/10.1080/15548627.2025.2559728","url":null,"abstract":"<p><p><i>Streptococcus pneumoniae</i> is an opportunistic pathogen responsible for life-threatening diseases including pneumonia and meningitis. The host defense against pneumococci relies heavily on macrophages, which can effectively internalize and degrade bacteria. Recent studies have implicated both canonical and non-canonical autophagy-related processes in bacterial clearance, but the precise pathways mediating defense against <i>S. pneumoniae</i> remain unknown. Here, we utilize a well-established zebrafish larval infection model to investigate the role of autophagy in host defense against pneumococci <i>in vivo</i>. Using a transgenic macroautophagy/autophagy reporter line, we found the autophagy marker Map1lc3/Lc3 being recruited to pneumococci-containing vesicles upon bacterial internalization by zebrafish macrophages. The genetic inhibition of core autophagy gene <i>atg5</i> led to loss of the Lc3 associations and their impaired acidification, significantly delaying bacterial clearance. This Lc3 recruitment is partially mediated by LC3-associated phagocytosis (LAP), as knockdown of <i>cyba</i> and <i>rubcn</i> moderately reduced Lc3 association with phagosomes and diminished pneumococcal degradation. Interestingly, we observed no involvement of xenophagy components in <i>S. pneumoniae</i>-infected macrophages, suggesting the activation of another non-canonical autophagy pathway, distinct from LAP, targeting pneumococci-containing phagosomes. Instead, we found that the pneumococcal pore-forming toxin pneumolysin induces ROS-independent CASM pathways, one of which is abolished by knockdown of <i>tecpr1a</i> indicating the involvement of sphingomyelin-Tecpr1-induced LC3 lipidation (STIL). Collectively, our observations shed new light on the host immune response against <i>S. pneumoniae</i>, demonstrating that several distinct non-canonical autophagy pathways mediate bacterial degradation by macrophages and providing potential targets for the development of novel therapies to combat pneumococcal infections.<b>Abbreviations</b>: ATG: autophagy related; BMDM: bone marrow-derived macrophage; CASM: conjugation of ATG8 to single membranes; CFU: colony-forming units; Cyba: cytochrome b-245, alpha polypeptide; DPI: diphenyleneiodonium, GFP: green fluorescent protein; hpf: hours post-fertilization; hpi: hours post-infection; LAP: LC3-associated phagocytosis; Map1lc3/Lc3: microtubule-associated protein 1 light chain 3; MEF: mouse embryonic fibroblast; NADPH: nicotinamide adenine dinucleotide phosphate; Optn: optineurin; PINCA: pore-forming toxin-induced non-canonical autophagy; Ply: pneumolysin; ROS: reactive oxygen species; SLR: sequestosome-like receptors; Sqstm1: sequestosome 1; STIL: sphingomyelin-TECPR1-induced LC3 lipidation; Tecpr1: tectonin beta-propeller repeat containing 1.</p>","PeriodicalId":93893,"journal":{"name":"Autophagy","volume":" ","pages":"1-20"},"PeriodicalIF":14.3,"publicationDate":"2025-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145132865","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"ATG8ylation-orchestrated vacuolar membrane remodeling facilitates plant alkaline stress tolerance.","authors":"Jianxiong Wu, Jun Luo, Chunya Nie, Xuanang Zheng, Caiji Gao, Jun Zhou","doi":"10.1080/15548627.2025.2562885","DOIUrl":"10.1080/15548627.2025.2562885","url":null,"abstract":"<p><p>While ATG8ylation, the C-terminal lipidation of mammalian and plant Atg8 (ATG8)-family proteins, is a well-established driver of autophagosome formation, emerging evidence reveals its non-canonical role in modifying single-membrane organelles under diverse environmental stresses. In a recent study, we found that disruption of the vacuolar proton gradient by alkaline stress rapidly triggers the translocation of ATG8 to the vacuolar membrane in plants. ATG8ylation facilitates membrane invagination through a mechanism independent of both ESCRT and the cytoskeleton. Concurrently, ATG8 recruits ATG2 to endoplasmic reticulum (ER)-vacuolar membrane contact sites, a process that may contribute to damaged membrane repair. Together, these processes enable plants to rapidly recover from vacuolar pH imbalance and adapt to alkaline conditions. Our findings advance the understanding of ATG8ylation in vacuolar membrane homeostasis and damage response, highlighting its conserved role in organellar stability and stress adaptation.<b>Abbreviations:</b> ATG, autophagy related; ER, endoplasmic reticulum; ESCRT, endosomal sorting complexes required for transport; PM, plasma membrane; ROS, reactive oxygen species; TGN, trans-Golgi network; V-ATPase, vacuolar-type H+-translocating ATPase.</p>","PeriodicalId":93893,"journal":{"name":"Autophagy","volume":" ","pages":"1-3"},"PeriodicalIF":14.3,"publicationDate":"2025-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145076918","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Aggregate fragmentation: the ticket to aggrephagy.","authors":"Mario Mauthe, Harm Kampinga, Fulvio Reggiori","doi":"10.1080/15548627.2025.2562893","DOIUrl":"10.1080/15548627.2025.2562893","url":null,"abstract":"<p><p>Our recent study identifies a previously unrecognized requirement for protein aggregate fragmentation as a prerequisite for autophagic clearance of amorphous aggregates, a process that has been termed aggrephagy. We show that aggregate fragmentation depends on two distinct but cooperative components: the DNAJB6 (DnaJ heat shock protein family (Hsp40) member B6)-HSPA/HSP70 (heat shock protein family A (Hsp70))-HSPH1/HSP110 chaperone module and the 19S regulatory particles (RPs) of the proteasome. These factors act together to not only to fragment protein aggregates but also to compact them, enabling clustering of selective autophagy receptors (SARs) and subsequent local phagophore formation. Our results show that this fragmentase activity plays a role in the aggrephagic clearance of different aggregate species, including disease-related HTT (huntingtin) aggregates.<b>Abbreviations:</b> CLPB-caseinolytic peptidase B protein homolog; DNAJB6-DnaJ heat shock protein family (Hsp40) member B6; dualPIM-dual-particles induced by multimerization; ER-endoplasmic reticulum; HSPA/HSP70-heat shock protein family A (Hsp70); HTT-polyQ119-huntingtin with an expanded polyglutamine stretch of 119 units; RP-regulatory particle; SAR-selective autophagy receptor.</p>","PeriodicalId":93893,"journal":{"name":"Autophagy","volume":" ","pages":"1-3"},"PeriodicalIF":14.3,"publicationDate":"2025-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145076940","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evolutionary diversification of the autophagy initiation complex: reduced Atg101 dependency and changes in Atg9 binding to Atg13.","authors":"Zefeng Lai, Yutaro Hama, Masahide Oku, Sidi Zhang, Yasuyoshi Sakai, Hayashi Yamamoto, Noboru Mizushima","doi":"10.1080/15548627.2025.2559683","DOIUrl":"10.1080/15548627.2025.2559683","url":null,"abstract":"<p><p>Macroautophagy/autophagy is an evolutionarily conserved process through which cells degrade cytoplasmic substances via autophagosomes. During the initiation of autophagosome formation, the ULK/Atg1 complex serves as a scaffold that recruits and regulates downstream ATG/Atg proteins and ATG9/Atg9-containing vesicles. Despite the essential role of the ULK/Atg1 complex, its components have changed during evolution; the ULK complex in mammals consists of ULK1 (or ULK2), RB1CC1, ATG13, and ATG101, whereas the Atg1 complex in the yeast <i>Saccharomyces cerevisiae</i> lacks Atg101 but instead has Atg29 and Atg31 along with Atg17. In this study, we investigated how such changes have evolved. A BLAST analysis across the major eukaryotic clades revealed that <i>ATG101</i>, which is essential for autophagy in mammals, was lost in some Holomycota lineages after acquisition of <i>ATG29</i> and <i>ATG31</i> by their common ancestor. Additionally, the acquisition of a cap structure in Atg13 preceded the loss of <i>ATG101</i>. However, some Holomycota species have both <i>ATG101</i> and <i>ATG29-ATG31</i>, including <i>Aspergillus oryzae</i> and <i>Komagataella phaffii</i>. Yeast two-hybrid assays showed that ATG101 is required for ATG13-ATG9 interaction in mammals but dispensable in <i>A. oryzae</i>, probably because of a shift in the <i>Ao</i>Atg9-binding site in <i>Ao</i>Atg13. We found an additive effect between <i>atg101</i> and <i>atg31</i> deletions in starvation-induced autophagy in <i>K. phaffii</i>. Furthermore, both <i>Kp</i>Atg101 and <i>Kp</i>Atg31 are involved in Atg1 complex assembly in <i>K. phaffii</i>. These findings suggest that the reduced importance of Atg101 in the Atg13-Atg9 interaction and Atg1 complex assembly enabled the eventual loss of <i>ATG101</i> in some Holomycota species, including <i>S. cerevisiae</i>.</p>","PeriodicalId":93893,"journal":{"name":"Autophagy","volume":" ","pages":"1-18"},"PeriodicalIF":14.3,"publicationDate":"2025-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145034787","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Microautophagy: definition, classification, and the complexity of the underlying mechanisms.","authors":"Yasuyoshi Sakai, Christian Behrends, Ana Maria Cuervo, Jayanta Debnath, Masanori Izumi, Andreas Jenny, Maurizio Molinari, Shuhei Nakamura, Masahide Oku, Marisa S Otegui, Laura Santambrogio, Han-Ming Shen, Tomohiko Taguchi, Michael Thumm, Takashi Ushimaru, Zhiping Xie, Fulvio Reggiori","doi":"10.1080/15548627.2025.2559687","DOIUrl":"10.1080/15548627.2025.2559687","url":null,"abstract":"<p><p>Recently, rapid progress in the field of microautophagy (MI-autophagy) revealed the existence of multiple subtypes that differ in both intracellular membrane dynamics and molecular mechanisms. As a result, a single umbrella term \"microautophagy\" has become too vague, even creating some confusion among researchers both within and outside the field. We herein describe different subtypes of MI-autophagic processes and propose a systematic approach for naming them more accurately.<b>Abbreviation:</b> ATG, autophagy related; e-MI, endosomal microautophagy; ER, endoplasmic reticulum; ESCRT, endosomal sorting complex required for transport; EV, extracellular vesicle; HSPA8/HSC70, heat shock protein family A (Hsp70) member 8; ILVs, intralumenal vesicles; l-MI, lysosomal microautophagy; MAP1LC3/LC3, microtubule associated protein 1 light chain 3; MCOLN1, mucolipin TRP cation channel 1; microautophagy, MI-autophagy; MVBs, multivesicular bodies; SQSTM1, sequestosome 1; v-MI, vacuolar microautophagy.</p>","PeriodicalId":93893,"journal":{"name":"Autophagy","volume":" ","pages":"1-7"},"PeriodicalIF":14.3,"publicationDate":"2025-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145031418","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"SCAMP5 regulates AP-4-dependent sorting and trafficking of ATG9A for presynaptic autophagy via PI4KB/PI4KIIIβ recruitment and PtdInsP4 production at the TGN.","authors":"Seung Hyun Ryu, Jungmihn Lee, Unghwi Lee, Kitae Kim, Go-Eun Jun, Jeongmin Oh, Sang-Eun Lee, Sunghoe Chang","doi":"10.1080/15548627.2025.2559689","DOIUrl":"10.1080/15548627.2025.2559689","url":null,"abstract":"<p><p>Neuronal autophagosome formation at distant presynaptic sites relies on ATG9A trafficking, a process mediated by AP-4 at the trans-Golgi network (TGN), but the molecular mechanisms governing its sorting for presynaptic delivery have remained elusive. Here, we uncover an unexpected role for SCAMP5, a key regulator of synaptic vesicle dynamics, in orchestrating presynaptic macroautophagy/autophagy through its actions at the TGN. SCAMP5 depletion severely impairs autophagosome formation at presynaptic boutons. Mechanistically, we identify SCAMP5 as a novel binding partner of PI4KB/PI4KIIIβ (phosphatidylinositol 4-kinase beta), where it controls PI4KB recruitment to the TGN and subsequent phosphatidylinositol-4-phosphate (PtdIns4P) production. As PtdIns4P is essential for AP-4 recruitment, SCAMP5 depletion disrupts AP-4-mediated ATG9A trafficking to presynaptic sites, thereby compromising presynaptic autophagy and subsequent protein turnover. Our findings establish that SCAMP5 coordinates ATG9A-dependent presynaptic autophagy through PI4KB recruitment and PtdIns4P production at the TGN, revealing a novel pathway critical for maintaining presynaptic protein homeostasis.<b>Abbreviations:</b> AP-4: adaptor protein 4; ATG9A: autophagy related 9A; PI4KB/PI4KIIIβ: phosphatidylinositol 4-kinase beta; PtdIns4P: phosphatidylinositol-4-phosphate; SCAMP5: secretory carrier membrane protein 5; TGN: trans-Golgi network.</p>","PeriodicalId":93893,"journal":{"name":"Autophagy","volume":" ","pages":"1-20"},"PeriodicalIF":14.3,"publicationDate":"2025-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145076906","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Non-coding RNAs regulate autophagy in kidney disease: friend or foe?","authors":"Yankun Li, Tongtong Ma, Xinhua Liang, Tingting Jin, Xingqi Zhao, Junmin Huang, Junfeng Hao, Huafeng Liu, Peng Wang","doi":"10.1080/15548627.2025.2551683","DOIUrl":"10.1080/15548627.2025.2551683","url":null,"abstract":"<p><p>Macroautophagy/autophagy is a conserved cellular process that degrades misfolded proteins and damaged organelles to regulate cell survival and division. Normal levels of autophagy are observed in healthy kidney cells. In contrast, excessive or insufficient autophagy is observed during kidney disease progression. However, canonical treatments that regulate autophagy using chemical reagents may induce unexpected side effects in other organs. This necessitates the development of therapeutic approaches with fewer adverse effects. Non-coding RNAs, which are highly tissue-specific, regulate autophagy and accurately modulate the expression of related genes. This review presents evidence of the effects of non-coding RNAs on the progression of kidney diseases and their responses to treatment <i>in vitro</i>, <i>in vivo</i>, and in clinical trials. Our analyses and interpretations of key findings elucidate the pathogenesis of kidney diseases and explore potential new therapeutic approaches.<b>Abbreviations:</b> 3' UTR: 3' untranslated region; 3-MA: 3-methyladenine; ADPKD: autosomal dominant polycystic kidney disease; AKI: acute kidney injury; ccRCC: clear cell RCC; ATG: autophagy related gene; ceRNA: competing endogenous RNA; circRNA: circular RNA; CKD: chronic kidney disease; DKD: diabetic kidney disease; HG: high glucose; IRI: ischemia-reperfusion injury; lncRNA: long non-coding RNA; LPS: lipopolysaccharide; miRNA: microRNA; MTOR: mechanistic target of rapamycin kinase; ncRNA: non-coding RNA; PI3K: phosphoinositide 3-kinase; RCC: renal cell carcinoma; ROS: reactive oxygen species; RTEC: renal tubular epithelial cells; ULK1: unc-51 like autophagy activating kinase 1; UUO: unilateral ureteral obstruction; VHL: von Hippel-Lindau tumor suppressor.</p>","PeriodicalId":93893,"journal":{"name":"Autophagy","volume":" ","pages":"1-24"},"PeriodicalIF":14.3,"publicationDate":"2025-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144982306","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"KDM4A-induced tumor senescence enhances the efficacy of immunotherapy by inhibiting AGT-PHB1 axis-mediated mitophagy in colorectal cancer.","authors":"Tanxing Cai, Zhenxing Liang, Zhiping Chen, Yang Li, Wei Xiao, Wenfeng Liang, Hao Xie, Huashan Liu, Ziwei Zeng, Xin Yang, Shuanglin Luo, Xiaobin Zheng, Keli Zhong, Liang Huang, Li Xiong, Liang Kang","doi":"10.1080/15548627.2025.2551680","DOIUrl":"https://doi.org/10.1080/15548627.2025.2551680","url":null,"abstract":"<p><p>Immune checkpoint inhibitors (ICIs) can re-active the immune response and induce a complete response in mismatch repair-deficient and microsatellite instability-high (dMMR/MSI-H) colorectal cancer (CRC). However, most CRCs exhibit proficient mismatch repair and microsatellite stable (pMMR/MSS) phenotypes with limited immunotherapy response because of sparse intratumoral CD8⁺ T-lymphocyte infiltration. Cellular senescence has been reported to involve immune cell infiltration through a senescence-associated secretory phenotype (SASP). However, the relationship between CRC cellular senescence and CD8⁺ T-lymphocyte infiltration remains unclear. Through integrated analysis of clinical cohorts and transcriptomic data across mismatch repair (MMR) subtypes, we identified cellular senescence as a hallmark of dMMR tumors, accompanied by elevated expression of KDM4A (lysine demethylase 4A). Clinically, KDM4A^high CDKN2A/p16^high expression correlated with improved CRC patient prognosis. Mechanistically, KDM4A upregulated AGT (angiotensinogen) expression through H3K9me3 demethylation and promoted CRC cellular senescence. Meanwhile, KDM4A-driven senescence suppressed tumor growth and enhanced intratumoral CD8⁺ T-lymphocyte infiltration via enhancing SASP-associated secretion. Furthermore, AGT disrupted PHB1 (prohibitin 1)-mediated basal mitophagy, triggering cytoplasmic mitochondrial DNA (mtDNA) accumulation that activated CGAS-STING1 signaling and enhanced SASP secretion. Crucially, KDM4A overexpression potentiated anti-PDCD1/PD1 efficacy in MSI-H CRC and reversed therapy resistance in MSS CRC. Conclusively, we established a KDM4A-AGT-PHB1 (KAP) grade system that robustly predicts immunotherapy responsiveness in pMMR CRC patients.<b>Abbreviation</b>: AGT: angiotensinogen; BafA: bafilomycin A₁; CCCP: carbonyl cyanide 3-chlorophenylhydrazone; CRC: colorectal cancer; CDKN1A/p21: cyclin dependent kinase inhibitor 1A; CDKN2A/p16: cyclin dependent kinase inhibitor 2A; CHX: cycloheximide; Co-IP: co-immunoprecipitation; dMMR: deficient mismatch repair; EdU: 5-ethynyl-2'-deoxyuridine; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; IL6: interleukin 6; IL8: interleukin 8; IHC: immunohistochemical; KDM4A: lysine demethylase 4A; mtDNA: mitochondrial DNA; MS: mass spectrometry; NFKB/NF-κB: nuclear factor kappa B; PHB1: prohibitin 1; PHB2: prohibitin 2; PINK1: PTEN induced kinase 1; pMMR: proficient mismatch repair; PRKN/parkin: parkin RBR E3 ubiquitin protein ligase; SASP: senescence-associated secretory phenotype; SA-GLB1/β-gal: senescence-associated galactosidase beta 1; TIMM23: translocase of inner mitochondrial membrane 23; TOMM20: translocase of outer mitochondrial membrane 20; TRIM21: tripartite motif containing 21; TUBB/beta-tubulin: tubulin beta class I.</p>","PeriodicalId":93893,"journal":{"name":"Autophagy","volume":" ","pages":"1-22"},"PeriodicalIF":14.3,"publicationDate":"2025-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145024824","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"PPA2 activates MTFP1-DNM1L fission signaling to govern mitochondrial proliferation and mitophagy.","authors":"Soumya Ranjan Mishra, Priyadarshini Mishra, Kewal Kumar Mahapatra, Bishnu Prasad Behera, Gajanan Kendre, Moureq Rashed Alotaibi, Vijay Pandey, Birija Sankar Patro, Daniel J Klionsky, Sujit Kumar Bhutia","doi":"10.1080/15548627.2025.2552900","DOIUrl":"10.1080/15548627.2025.2552900","url":null,"abstract":"<p><p>The inorganic pyrophosphatase PPA2, a matrix-localized protein, maintains mitochondrial function. Here, we identified the role of PPA2 in activating mitochondrial fission signaling. We found that PPA2 overexpression promotes mitochondrial fission by upregulating the mitochondrial translocation of phosphorylated DNM1L S616. Moreover, PPA2 interacts with MTFP1, a mitochondrial inner membrane protein, to induce fission signaling; cells knocked down for MTFP1 and overexpressing PPA2 failed to induce DNM1L activation and subsequent mitochondrial fission. Furthermore, in physiological conditions, PPA2 directed mitochondrial fission at the midzone through MFF-DNM1L, leading to mitochondrial proliferation. Interestingly, during mitochondrial stress following CCCP treatment, PPA2 triggers peripheral fission through FIS1 and DNM1L to segregate parts of damaged mitochondria, which is essential for mitophagy. In addition, PPA2 utilized the C-terminal LC3-interacting region (LIR) of MTFP1 for mitophagy-mediated clearance of damaged mitochondria. In conclusion, PPA2 activates mitochondrial fission signaling through MTFP1-DNM1L and is essential in defining the site of mitochondrial fission, leading to mitochondrial proliferation or mitophagy for maintaining mitochondrial homeostasis.<b>Abbreviations:</b> CCCP: carbonyl cyanide m-chlorophenyl hydrazone; Co-IP: co-immunoprecipitation; CQ: chloroquine; IMM: inner mitochondrial membrane; LIR: LC3-interacting region; MLS: mitochondrial localization signal; mtDNA: mitochondrial DNA; OMM: outer mitochondrial membrane; RT: room temperature.</p>","PeriodicalId":93893,"journal":{"name":"Autophagy","volume":" ","pages":"1-24"},"PeriodicalIF":14.3,"publicationDate":"2025-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144982269","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"LC3 and GABARAP independent autophagy of misfolded procollagen in mouse osteoblasts.","authors":"Elena Makareeva, Shakib Omari, Anna M Roberts-Pilgrim, Laura Gorrell, Bella Radant, Muthulakshmi Sellamani, Edward L Mertz, Basma Khoury, Kenneth Kozloff, Sergey Leikin","doi":"10.1080/15548627.2025.2551478","DOIUrl":"10.1080/15548627.2025.2551478","url":null,"abstract":"<p><p>Bone synthesis should depend on autophagy because over 10% of type I procollagen (PC1) - a heterotrimer of COL1A1 and COL1A2 chains and the precursor of the main bone matrix molecule - is misfolded and rerouted from osteoblast endoplasmic reticulum (ER) to lysosomes. However, osteoblast-specific macroautophagy knockouts in mice have produced only mild bone effects. To reconcile these observations, we compared how hypomorphic expression and a conditional knockout (cKO) of <i>Atg5</i> - encoding a protein required for autophagosome formation - affected <i>Col1a2</i>^G610C/+ versus wild-type <i>Col1a2</i>^+/+ osteoblasts <i>in vivo</i> and <i>in vitro</i>. The Gly610-to-Cys substitution (G610C) in the triple helical region of the COL1A2/proα2(I) chain increases PC1 misfolding, causing its accumulation in the ER, cell stress, and osteoblast malfunction. Because autophagy reroutes misfolded PC1 from the ER to lysosomes, disruption of PC1 autophagy should significantly increase osteoblast malfunction and bone pathology in <i>Col1a2</i>^G610C/+ mice. Nonetheless, the present study revealed only minor effects of the <i>atg5</i> cKO on osteoblast function and bone formation in the <i>Col1a2</i>^G610C/+ mice, like in <i>Col1a2</i>^+/+ controls. The cKO did not reduce the autophagy flux of misfolded G610C or wild-type PC1 in primary osteoblast cultures, even though the LC3 and GABARAP lipidation and therefore autophagosome formation were disrupted. Live-cell imaging in <i>atg5</i> cKO osteoblasts demonstrated that PC1 was efficiently delivered to lysosomes without LC3 via ER exit site (ERES) microautophagy. Taken together, these observations indicate that LC3- and GABARAP-independent ERES microautophagy is the primary pathway of misfolded procollagen degradation in osteoblasts both in culture and <i>in vivo</i>.<b>Abbreviations</b>: ATG5: autophagy related 5; ATG7: autophagy related 7; Baf: bafilomycin A₁; BFA: brefeldin A; BGLAP/Ocn/osteocalcin: bone gamma-carboxyglutamate protein; COL1A1/proα1(I): collagen type I alpha 1 chain; COL1A2/proα2(I): collagen type I alpha 2 chain; cKO: conditional knockout; ER: endoplasmic reticulum; ERES: ER exit site; G610C mutation: COL1A2 p.Gly706Cys replacing Gly in position 610 from the start of the triple helix with Cys; GABARAP: GABA type A receptor-associated protein; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MAR: mineral apposition rate; Ob: osteoblast; Oc: osteoclast; OI: osteogenesis imperfecta; PC1: procollagen type I, a heterotrimer of two COL1A1 and one COL1A2 chains, precursor of collagen type I; PDI: protein disulfide isomerase; RB1CC1/FIP200: RB1 inducible coiled-coil 1; SP7/osterix: Sp7 transcription factor; SQSTM1/p62: sequestosome 1; WT: wild type.</p>","PeriodicalId":93893,"journal":{"name":"Autophagy","volume":" ","pages":"1-16"},"PeriodicalIF":14.3,"publicationDate":"2025-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12487762/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144982319","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}