bims-nocaut 2026-07-05 papers

J Cell Sci. 2026 Jul 01. pii: jcs264806. [Epub ahead of print]139(13):

Disentangling the response to lysosomal damage.

Hemmo Meyer, Akiko Kuma, Shuhei Nakamura.

The limiting membrane of lysosomes is prone to damage that can have deleterious consequences for cellular homeostasis. Cells respond to this damage with an array of molecular countermeasures, ranging from membrane repair mechanisms to elimination of terminally damaged lysosomes by selective macroautophagy. The various elements of this response therefore need to be carefully assessed in the context of the specific pathological or experimental conditions being studied. Emerging evidence has revealed further complexity within the lysosomal damage response, such as processes that contribute to initial membrane resealing as well as lysosome regeneration required to restore the lysosomal system. These mechanisms involve unusual ubiquitylation, non-canonical ATG8 lipidation, or modifications that govern lysosome tubulation or microlysophagy pathways. Therefore, caution is advised when using previously established lysosome damage reporters that might confound interpretation of the underlying events and outcomes. This Opinion article seeks to shed light on the emerging regulatory mechanisms of lysosomal regeneration and evaluate the appropriateness of various reporters and assays for studying the lysosomal damage response.

Keywords: ATG8; ESCRT; Lysosomes; Membrane permeabilization; Microautophagy; Ubiquitin

DOI: https://doi.org/10.1242/jcs.264806

Autophagy. 2026 Jun 30.

Mechanistic studies of autophagic cargo recruitment and membrane shaping through in vitro reconstitution.

Wenxin Zhang, Thomas Litschel, Anne Schreiber, Rocco D'Antuono, Sharon A Tooze.

Macroautophagy/autophagy, a conserved intracellular catabolic pathway, removes deleterious cytosolic material to maintain homeostasis and survival. Upon autophagy induction, a unique double-membraned structure, the phagophore, forms and engulfs cytosolic material, the cargo, as it closes to become an autophagosome. Mammalian Atg8-family proteins (ATG8s) are ubiquitin-like proteins which are essential for engulfment of the cargo and membrane closure. ATG8s are recruited to the phagophore by ATG12-ATG5-ATG16L1, an E3-like ligase which is recruited by PtdIns3P-binding WIPI proteins. Covalent lipidation of the ATG8s to phosphatidylethanolamine by the E3 ligase occurs specifically on the phagophore membrane allowing recruitment of cytosolic cargo and cargo receptors, such as SQSTM1/p62. While ATG8-cargo receptor interactions are well established, how the ATG8s bind cargo and cargo receptors on the inner membrane of the phagophore has not been studied. To recapitulate these events, we use giant unilamellar vesicles (GUVs) and encapsulate protein machinery and cargo, generating a membrane platform to which ATG8 proteins can be recruited. Inside the GUVs we reconstituted WIPI2B-directed and cargo-directed ATG8 lipidation revealing distinct roles of WIPI2B and SQSTM1 in initiating ATG8 conjugation. We show that SQSTM1 and SQSTM1 droplets are recruited to the GUV inner membrane through interaction with membrane bound ATG8s. Through the development of a bead-based membrane deformation assay, we show redistribution and local enrichment of membrane-bound ATG8s occurs upon binding to SQSTM1 droplets. Our work demonstrates fundamental molecular mechanisms into phagophore-ATG8-cargo interactions providing novel model systems to investigate ATG8-cargo interactions on the inner phagophore membrane.Abbreviations:ATG: autophagy related; cDICE: continuous droplet interface crossing encapsulation; DOPE: 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine; GABARAP: GABA type A receptor-associated protein; GUV: giant unilamellar vesicle; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; LIR: LC3-interacting region; LUV: large unilamellar vesicle; NBD: 7-nitrobenz-2-oxa-1,3-diazol-4-yl; PE: phosphatidylethanolamine; PtdIns: phosphatidylinositol; PtdIns3P: phosphatidylinositol-3-phosphate; PolyUb: K63-linked polyubiquitin; POPC: 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine; POPE: 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine; Rh-PE: 18:1 Liss Rhod PE; SQSTM1/p62: sequestosome 1; WIPI2B: WD repeat domain, phosphoinositide interacting 2B.

Keywords: ATG8 lipidation; giant unilamellar vesicles; in vitro reconstitution; liquid-liquid phase separation; membrane expansion

DOI: https://doi.org/10.1080/15548627.2026.2697432

Autophagy. 2026 Jun 28. 1-17

RAPSN/rapsyn aggregation-induced HSPA/HSP70-BAG3 aggrephagy maintains CHRN integrity in myasthenia gravis.

Yujia Liu, Guofang Xia, Huaiying Shi, Simeng Zhu, Hailong Li, Yifan Shi, Wanling Ouyang, Congfeng Xu, Ailian Du.

Accelerated CHRN/AChR/nicotinic acetylcholine receptor internalization induced by auto-antibodies impairs neuromuscular junction transmission and contributes to myasthenia gravis (MG), a typical autoimmune disease. Although CHRN internalization is well established in MG pathogenesis, the downstream cellular events, especially those related to autophagy, remain poorly described. Here, we report that RAPSN/rapsyn, an intracellular CHRN-binding protein essential for its clustering, accumulates as aggregates in experimental autoimmune myasthenia gravis (EAMG) mice. In CHRN antibody-treated myotubes, RAPSN dissociates from internalized CHRN and forms aggregates due to exposure of its hydrophobic domains. These aggregates in turn impair the trafficking and membrane incorporation of newly synthesized CHRN, thereby exacerbating CHRN loss. Notably, the accumulation of RAPSN aggregates facilitates formation of HSPA/HSP70-BAG3 complex, which recognizes and transports the aggregates along microtubules to form perinuclear aggresomes for subsequent lysosomal degradation. Accordingly, pharmacological inhibition or knockdown of HSPA-BAG3 complex increases RAPSN aggregation, which participates in enhanced CHRN loss and worsened muscle weakness in EAMG mice. This study identifies HSPA-BAG3 aggrephagy as a protective mechanism that clears RAPSN aggregates to maintain CHRN integrity and suggests a potential therapeutic strategy for MG.Abbreviation: 3-MA: 3-methyladenine; AAV: adeno-associated virus; CASA: chaperone-assisted selective autophagy; CHRN/nicotinic acetylcholine receptor: cholinergic receptor nicotinic; CHRN-ab: CHRN antibodies; CHX: cycloheximide; CMAP: compound muscle action potential; CQ: chloroquine; EAMG: experimental autoimmune myasthenia gravis; ER: endoplasmic reticulum; GAS: gastrocnemius; MAP1LC3A/B: microtubule associated protein 1 light chain 3 alpha/beta; MG: myasthenia gravis; NMJ: neuromuscular junction; Rapa: rapamycin; RAPSN/rapsyn: receptor associated protein of the synapse; SQSTM1: sequestosome 1; TA: tibialis anterior; αBTX-A594: α-bungarotoxin-Alexa-594.

Keywords: Aggregate; CHRN; HSPA; RAPSN; autophagy; myasthenia gravis

DOI: https://doi.org/10.1080/15548627.2026.2693778

Autophagy. 2026 Jul 03. 1-3

Receptor-cargo coupling during ER-autophagy depends on coat proteins and ER membrane properties.

Shuliang Chen, Subhrajit Banerjee, Peter Novick, William A Prinz, Susan Ferro-Novick.

Selective autophagy of the endoplasmic reticulum (reticulophagy) is driven by receptor-mediated ER remodeling. Reticulophagy receptors are essential for ER turnover. Productive cargo recognition during autophagosome-mediated reticulophagy depends on the interaction of the receptor with the COPII subunit Sfb3/Lst1 (SEC24C in mammals) as well as the phospholipid composition of the ER. We unexpectedly found that the conserved reticulophagy receptor Atg40 traffics to the vacuole/lysosome without cargo (ER membrane proteins) or Sfb3/Lst1 in neutral lipid-deficient mutant cells. Comprehensive lipidomic profiling of this lipid mutant revealed a shift in the phosphatidylethanolamine (PE)-to-phosphatidylcholine (PC) ratio, a compositional change predicted to alter biophysical properties of the ER, including membrane bendability. The discovery that membrane properties regulate receptor - cargo coupling efficiency at autophagic sites, as they do at secretory exit sites, extends current mechanistic models of reticulophagy and suggests membrane properties may also affect cargo selection on other types of selective autophagy pathways.

Keywords: Coat proteins; membrane curvature; neutral lipid; receptor–cargo coupling; reticulophagy

DOI: https://doi.org/10.1080/15548627.2026.2695313

Nat Commun. 2026 Jul 02. pii: 5789. [Epub ahead of print]17(1):

VPS13C/PARK23 initiates lipid transfer and membrane remodeling for efficient lysosomal repair.

Oluwatobi Andrew Adeosun, Christian Schröer, Elisabeth Südhoff, Fabio Bergenthal, Katharina Sommer, Emely Döffinger, Britta Fiedler, Angelika Hilderink, Ann-Katrin Lehmann, Lea Sophie Pohle, Sergei M Korneev, Florian Fröhlich, Kenji Maeda, Rainer Kurre, Michael Holtmannspötter, Bianca M Esch, Joost C M Holthuis.

Perturbations in lysosome integrity are tightly linked to neurological disorders and ageing, but the underlying pathogenic mechanisms are incompletely understood. Using an unbiased proteomic approach, we here identified the bridge-like lipid transport protein VPS13C/PARK23 as a key component of a global early response pathway to lysosome damage. VPS13C readily binds lysosomes under mechanical or osmotic tension in anticipation of membrane lesions. The latter trigger a conformational change in the protein's C-terminus, involving its ATG2C domain acting as sensor of damage-induced lipid packing defects. We show that ER-lysosome contacts formed by VPS13C provide critical binding platforms for OSBP/ORPs to enable efficient ER wrapping of damaged lysosomes. A chemical approach to assess directional ER-to-lysosome lipid transport revealed that VPS13C is essential for large-scale lipid delivery to acutely damaged lysosomes to facilitate their repair. Our findings offer new mechanistic insights into how loss-of-function mutations in VPS13C may enhance the risk of Parkinson's disease.

DOI: https://doi.org/10.1038/s41467-026-75145-y