Lysophagy protects against ANXA11 amyloid fibril toxicity and propagation in FTLD

BACKGROUND: Accumulation of Annexin A11 (ANXA11) aggregates is a distinct pathological hallmark of amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). While genetic studies have linked ANXA11 mutations (e.g., D40G) to disease, the precise molecular events converting aggregation into neurotoxicity and intercellular propagation remain elusive. We hypothesize that lysosomal integrity serves as a critical checkpoint in ANXA11 proteinopathy and that its failure drives disease progression. METHODS: To model the human pathology of ANXA11, we generated pre-formed fibrils (PFFs) of wild-type and FTLD/ALS-linked D40G mutant ANXA11. Human iPSC-derived neurons, 3D cerebral organoids, and bulk RNA-sequencing were employed to investigate neurotoxicity. High-resolution imaging, lentiviral knockdown, and biochemical assays were performed to delineate the lysosomal damage response and the subsequent "prion-like" spreading of aggregates. RESULTS: The internalized ANXA11 fibrils accumulated in lysosomes, triggering lysosomal membrane permeabilization (LMP). The D40G mutation exacerbated this toxicity, leading to severe LMP, mitochondrial depolarization, and specific transcriptional downregulation of the dynactin subunit ACTR10. Mechanistically, we identified a protective signaling axis involving p38 MAPK, MK2, and HSP27 that senses ANXA11-induced lysosomal damage and initiates lysophagy. Notably, in human cerebral organoids, failure of this lysophagic clearance facilitated the cytoplasmic escape of ANXA11, thereby accelerating its seeding activity and propagation to neighboring cells. Pharmacological or genetic modulation of this pathway significantly altered neuronal survival. CONCLUSIONS: Our study established lysosomal rupture as a primary driver of ANXA11-associated neurodegeneration and validated the p38/MK2/HSP27 axis as a crucial defense mechanism in human neural tissue. These findings provide a novel mechanistic link between lysosomal quality control and ANXA11 propagation, highlighting that enhancing lysophagic flux represents a promising translational strategy to halt the progression of FTLD and ALS.