Hyperactivation of the AXL-ICD/SIRT2 axis by Amyloid-β impairs astrocytic autophagic flux and exacerbates neuroinflammation
Autophagy dysfunction and neuroinflammation are central to Alzheimer’s disease (AD), yet how extracellular amyloid-β (Aβ) couples to impaired autophagic flux and heightened neuroinflammation remains unknown. Here, we identify the TAM receptor AXL as a molecular transducer that couples Aβ sensing to the regulation of autophagy and neuroinflammation in astrocytes. Aβ induces γ-secretase-dependent cleavage of AXL, generating a nuclear intracellular domain (AXL-ICD) that forms phase-separated condensates and activates autophagy gene transcription through SIRT2-mediated recruitment of the RUVBL1/2-INO80 chromatin-remodeling complex. This axis is activated in astrocytes of postmortem AD brains. Concurrently, AXL-ICD binds to the SIRT2 catalytic domain and suppresses its deacetylase activity, increasing α-tubulin acetylation and altering microtubule dynamics. While moderate AXL-ICD levels promote autophagic flux, excessive elevation paradoxically triggers microtubule hyperstabilization, thereby impairing autophagosome-lysosome fusion and causing pathological accumulation of autophagosomes and H2O2. The inhibitory peptide AxSBiP disrupts the AXL-ICD/SIRT2 interaction, restores autophagic flux, reduces plaque burden, and normalizes Aβ-induced H2O2 production and astrogliosis in APP/PS1 mice. We propose the AXL-ICD/SIRT2 axis as an effective therapeutic target to reduce Aβ burden and neuroinflammation in AD.