Autophagy最新文献

Macroautophagy/autophagy is a highly conserved catabolic process in eukaryotes and plays pivotal roles in regulating male fertility and sexual reproduction. In metazoans, mutations in core ATG (autophagy related) proteins frequently result in severe defects in sperm formation and maturation, resulting in male sterility. In contrast, autophagy has traditionally been considered dispensable for reproduction in Arabidopsis thaliana, as most atg mutants can complete fertilization and produce viable progeny without apparent reproductive defects. We recently systematically re-assessed the role of autophagy in Arabidopsis male gametophyte development and fertility using atg5 and atg7 mutants, and the double mutant. These mutants exhibited partial defects in pollen germination, pollen tube growth and seed production compared to the wild type (WT). Furthermore, our findings reveal that autophagy is essential for modulating actin dynamic organization during sperm cell formation within pollen grains and for supporting pollen tube elongation. This is achieved through the selective degradation of actin depolymerizing factors ADF7 and PFN2/Profilin2. NBR1 is identified as a key receptor mediating this process. This study provides valuable insights into the evolutionary conservation and functional divergence of autophagy in modulating male fertility, highlighting distinctions between plant and mammalian systems.

Melanosomes play a pivotal role in skin color and photoprotection. In contrast to the well-elucidated pathway of melanosome biogenesis, the process of melanosome degradation, referred to as melanophagy, is largely unexplored. Previously, we discovered that 3,4,5-trimethoxycinnamate thymol ester (TCTE) effectively inhibits skin pigmentation by activating melanophagy. In this study, we discovered a new regulatory signaling cascade that controls melanophagy in TCTE-treated melanocytes. ITCH (itchy E3 ubiquitin protein ligase) facilitates ubiquitination of the melanosome membrane protein MLANA (melan-A) during TCTE-induced melanophagy. This ubiquitinated MLANA is then recognized by an autophagy receptor protein, OPTN (optineurin). Additionally, a phospho-kinase antibody array revealed that TCTE activates PTK2 (protein tyrosine kinase 2), which phosphorylates ITCH, enhancing the ubiquitination of MLANA. Furthermore, inhibition of either PTK2 or ITCH disrupts the ubiquitination of MLANA and the MLANA-OPTN interaction in TCTE-treated cells. Taken together, our findings highlight the critical role of the PTK2-ITCH-MLANA-OPTN cascade in orchestrating melanophagy progression.Abbreviations: α-MSH: alpha-melanocyte-stimulating hormone; dichlone: 2,3-dichloro-1,4-naphthoquinone; ITCH: itchy E3 ubiquitin protein ligase; MITF: melanocyte inducing transcription factor; MLANA: melan-A; NBR1: NBR1 autophagy cargo receptor; OPTN: optineurin; PINK1: PTEN induced kinase 1; PTK2: protein tyrosine kinase 2; SQSTM1/p62: sequestosome 1; TCTE: 3,4,5-trimethoxycinnamate thymol ester; TPC2: two pore segment channel 2; VDAC1: voltage dependent anion channel 1.

Intrinsically disordered regions (IDRs) are crucial to homeostatic and organellar remodeling pathways. In reticulophagy/ER-phagy, long cytosolic IDR-containing receptors (e.g. RETREG1/FAM134B) house the LC3-interacting region (LIR) motif to recruit the phagophore. The precise functions of the IDR beyond engaging the autophagic machinery are unclear. Here, we comment on the role of the RETREG1-IDR based on our recent computer modeling and molecular dynamics (MD) simulations. Extensive analysis of the RETREG1-IDR indicates a continuum of conformations between expanded and compact structures, displaying a Janus-like feature. Using an adapted MARTINI model, we find that the IDR ensemble properties vary widely depending on the membrane anchor. IDRs alone are sufficient to promote and sense membrane curvature and can act as entropic tethers. When anchored to the Reticulon homology domain (RHD), they adopt compact collapsed conformations, acting as effector scaffolds that amplify RHD membrane remodeling properties, enhancing receptor-clustering and accelerating spontaneous budding. These findings expand the operational scope of IDRs within reticulophagy, offering fresh insights into a mechanistic understanding of membrane remodeling.

Mycobacterium tuberculosis (Mtb), the etiological agent of tuberculosis (TB), remains a significant global health challenge. Mtb is transmitted by respiratory aerosols and infects a variety of myeloid populations. Our recent study shows that the Mtb virulence lipid phthiocerol dimycocerosate (PDIM) promotes the intracellular survival of Mtb in macrophages by inhibiting NADPH oxidase, thereby impairing LC3-associated phagocytosis, and in vivo PDIM also antagonizes canonical macroautophagy/autophagy. In addition, mice defective in autophagy in myeloid cells fail to develop B-cell follicles in the lungs during chronic infection. Here, we present a summary of our recent publication, highlighting the most significant findings and discussing how they provide new insight into the role of autophagy and the diversity of lung myeloid cells in the pathogenesis of Mtb.

Synaptic damage is a crucial pathological process in traumatic brain injury. However, the mechanisms driving this process remain poorly understood. In this report, we demonstrate that the accumulation of damaged mitochondria, resulting from impaired mitphagy, plays a significant role in causing synaptic damage. Moreover, copper induced downregulation of BNIP3 is a key player in regulating mitophagy. DMSA alleviates synaptic damage and mitochondrial dysfunction by promoting urinary excretion of copper. Mechanistically, we find that copper downregulate BNIP3 by increasing the nuclear translocation of NFKB, which is triggered by TRIM25-mediated ubiquitination-dependent degradation of NFKBIA. Our study underscores the importance of copper accumulation in the regulation of BNIP3-mediated mitophagy and suggests that therapeutic targeting of the copper-TRIM25-NFKB-BNIP3 axis holds promise to attenuate synaptic damage after traumatic brain injury.

The calcium-activated phosphatase PPP3/calcineurin dephosphorylates TFEB (transcription factor EB) to trigger its nuclear translocation and the activation of macroautophagic/autophagic targets. However, the detailed molecular mechanism regulating TFEB activation remains poorly understood. Here, we highlighted the importance of SMURF1 (SMAD specific E3 ubiquitin protein ligase 1) in the activation of TFEB for lysosomal homeostasis. SMURF1 deficiency prevents the calcium-triggered ubiquitination of the catalytic subunit of PPP3/calcineurin in a manner consistent with defective autophagic degradation of damaged lysosomes. Mechanically, PPP3CB/CNA2 plays a bridging role in the recruitment of SMURF1 by LGALS3 (galectin 3) upon lysosome damage. Importantly, PPP3CB increases the dissociation of the N-terminal tail (NT) and C-terminal carbohydrate-recognition domain (CRD) of LGALS3, which may promote the formation of open conformers in a PPP3CB dephosphorylation activity-dependent manner. In addition, PPP3CB is ubiquitinated at lysine 146 by the recruited SMURF1 in response to intracellular calcium stimulation. The K63-linked ubiquitination of PPP3CB enhances the recruitment of TFEB. Moreover, TFEB directly interacts with both PPP3CB and the regulatory subunit PPP3R1 which facilitate the conformational correction of TFEB for its activation for the transcription of TFEB-targeted genes. Altogether, our results highlighted a critical mechanism for the regulation of PPP3/calcineurin activity via its ubiquitin ligase SMURF1 in response to lysosomal membrane damage, which may account for a potential target for the treatment of stress-related diseases.Abbreviation AID: autoinhibitory domain; ATG: autophagy related; CD: catalytic domain; CRD: carbohydrate-recognition domain; CsA: cyclosporin A; DMSO: dimethyl sulfoxide; ESCRT: endosomal sorting complexes required for transport; GSK3B: glycogen synthase kinase 3 beta; LAMP1: lysosomal associated membrane protein 1; LGALS3: galectin 3; LLOMe: L-leucyl-L-leucine methyl ester; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; ML-SA1: mucolipin synthetic agonist 1; MTORC1: mechanistic target of rapamycin kinase complex 1; NT: N-terminal tail; PPP3CB: protein phosphatase 3 catalytic subunit beta; PPP3R1: protein phosphatase 3 regulatory subunit B, alpha; SMURF1: SMAD specific E3 ubiquitin protein ligase 1; SQSTM1/p62: sequestosome 1; TFEB: transcription factor EB; VCP/p97: valosin containing protein; YWHA/14-3-3: tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein.

Prion disease is a fatal and infectious neurodegenerative disorder caused by the trans-conformation conversion of PRNP/PrP^C to PRNP/PrP^Sc. Accumulated PRNP/PrP^Sc-induced ER stress causes chronic unfolded protein response (UPR) activation, which is one of the fundamental steps in prion disease progression. However, the role of various ER-resident proteins in prion-induced ER stress is elusive. This study demonstrated that ARL6IP5 is compensatory upregulated in response to chronically activated UPR in the cellular prion disease model (RML-ScN2a). Furthermore, overexpression of ARL6IP5 overcomes ER stress by lowering the expression of chronically activated UPR pathway proteins. We discovered that ARL6IP5 induces reticulophagy to reduce the PRNP/PrP^Sc burden by releasing ER stress. Conversely, the knockdown of ARL6IP5 leads to inefficient macroautophagic/autophagic flux and elevated PRNP/PrP^Sc burden. Our study also uncovered that ARL6IP5-induced reticulophagy depends on Ca²⁺-mediated AMPK activation and can induce 3 MA-inhibited autophagic flux. The detailed mechanistic study revealed that ARL6IP5-induced reticulophagy involves interaction with soluble reticulophagy receptor CALCOCO1 and lysosomal marker LAMP1, leading to degradation in lysosomes. Here, we delineate the role of ARL6IP5 as a novel ER stress regulator and reticulophagy inducer that can effectively reduce the misfolded PRNP/PrP^Sc burden. Our research opens up a new avenue of selective autophagy in prion disease and represents a potential therapeutic target.Abbreviations: ARL6IP5: ADP ribosylation factor-like GTPase 6 interacting protein 5; AMPK: adenosine 5'-monophosphate (AMP)-activated protein kinase; CALCOCO1: calcium binding and coiled-coil domain 1; CQ: chloroquine; DAPI: 4'6-diamino-2-phenylindole; ER: endoplasmic reticulum; ERPHS: reticulophagy/ER-phagy sites; KD: knockdown; KD-CON: knockdown control; LAMP1: lysosomal-associated membrane protein 1; MAP1LC3/LC3, microtubule-associated protein 1 light chain 3; MTOR: mechanistic target of rapamycin kinase; MβCD: methyl beta cyclodextrin; 3 MA: 3-methyladenine; OE: overexpression; OE-CON: empty vector control; PrDs: prion diseases; PRNP/PrP^C: cellular prion protein (Kanno blood group); PRNP/PrP^Sc: infectious scrapie misfolded PRNP; Tm: tunicamycin; UPR: unfolded protein response; UPS: ubiquitin-proteasome system.

The renoprotective effects of SLC5A2/SGLT2 (solute carrier 5 (sodium/glucose cotransporter), member 2) inhibitors have recently been demonstrated in non-diabetic chronic kidney disease (CKD), even without overt albuminuria. However, the mechanism underlying this renoprotection is largely unclear. We investigated the renoprotective mechanisms of the SLC5A2 inhibitor empagliflozin with a focus on ALB (albumin) reabsorption and macroautophagy/autophagy in proximal tubules using wild-type or drug-inducible lrp2/Megalin or atg5 knockout mice with high-fat diet (HFD)-induced obesity or 5/6 nephrectomy that elevated intraglomerular pressure without overt albuminuria. Empagliflozin treatment of HFD-fed mice reduced several hallmarks of lipotoxicity in the proximal tubules, such as phospholipid accumulation in the lysosome, inflammation and fibrosis. Empagliflozin, which decreases intraglomerular pressure, not only reduced the HFD-induced increase in ALB reabsorption via LRP2 in the proximal tubules (i.e. total nephron ALB filtration), as assessed by urinary ALB excretion caused by genetic ablation of Lrp2, but also ameliorated the HFD-induced imbalance in circulating ALB-bound fatty acids. Empagliflozin alleviated the HFD-induced increase in autophagic demand and successfully prevented autophagic stagnation in the proximal tubules. Similarly, empagliflozin decreased ALB exposure and autophagic demand in 5/6 nephrectomized mice. Finally, empagliflozin reduced HFD-induced vulnerability to ischemia-reperfusion injury, whereas LRP2 blockade and atg5 ablation separately diminished this effect. Our findings indicate that empagliflozin reduces ALB exposure and prevents autophagic stagnation in the proximal tubules even without overt albuminuria. Autophagy improvement may be critical for the renoprotection mediated by SLC5A2 inhibition.

Macroautophagy/autophagyis a lysosomal-regulated degradation process that participates incellular stress and then promotes cell survival or triggers celldeath. Ferroptosis was initially described as anautophagy-independent, iron-regulated, nonapoptotic cell death.However, recent studies have revealed that autophagy is positivelyassociated with sensitivity to ferroptosis. Nonetheless, themolecular mechanisms by which these two types of regulated cell death(RCD) modulate each other remain largely unclear. Here, we screened85 deubiquitinating enzymes (DUBs) and found that overexpression ofUSP13 (ubiquitin specific peptidase 13) could significantlyupregulate NFE2L2/NRF2 (NFE2 like bZIP transcription factor 2)protein levels. In addition, in 39 cases of KRAS-mutated lungadenocarcinoma (LUAD), we found that approximately 76% of USP13overexpression is positively correlated with NFE2L2 overexpression.USP13 interacts with and catalyzes the deubiquitination of thetranscription factor NFE2L2. Additionally, USP13 depletion promotesan autophagy-to-ferroptosis switch invitro andin xenograft tumor mouse models, through the activation of theNFE2L2-SQSTM1/p62 (sequestosome 1)-KEAP1 axis in KRAS mutant cellsand tumor tissues. Hence, targeting USP13 effectively switchedautophagy-to-ferroptosis, thereby inhibiting KRAS (KRASproto-oncogene, GTPase) mutant LUAD, suggesting the therapeuticpromise of combining autophagy and ferroptosis in the KRAS-mutantLUAD.Abbreviation: ACSL4: acyl-CoA synthetase long-chain family member 4; ACTB: actin beta; AL: autolysosomes; AP: autophagosomes; BCL2L1/BCL-xL: BCL2 like 1; CCK8: Cell Counting Kit-8; CQ: chloroquine; CUL3: cullin 3; DMSO: dimethyl sulfoxide; DOX: doxorubicin; DUB: deubiquitinating enzyme; Ferr-1: ferrostatin-1; GPX4: glutathione peroxidase 4; GSEA: gene set enrichment analysis; 4HNE: 4-hydroxynonenal; IKE: imidazole ketone erastin; KEAP1: kelch like ECH associated protein 1; KRAS: KRAS proto-oncogene, GTPase; LCSC: lung squamous cell carcinoma; IF: immunofluorescence; LUAD: lung adenocarcinoma; Lys05: Lys01 trihydrochloride; MAPK1/ERK2/p42: mitogen-activated protein kinase 1; MAPK3/ERK1/p44; MTOR: mechanistic target of rapamycin kinase; NFE2L2/NRF2: NFE2 like bZIP transcription factor, 2; NQO1: NAD(P)H quinone dehydrogenase 1; PG: phagophore; RCD: regulated cell death; RAPA: rapamycin; ROS: reactive oxygen species; SLC7A11/xCT: solute carrier family 7 member 11; SQSTM1/p62: sequestosome 1; TEM: transmission electron microscopy; TUBB/beta-tubulin: tubulin, beta; UPS: ubiquitin-proteasome system; USP13: ubiquitin specific peptidase 13.