Cerebral FURIN deficiency impairs astrocytic lipophagy through ITGAV maturation

FURIN cleaves a subset of proproteins into functional mature fragments. Evidence suggests that FURIN is involved in brain development and the associated diseases, whereas the potential mechanisms remain incompletely understood. Here, we report that cerebral FURIN-deficient mice exhibit cognitive decline and neurodegeneration. Lipid droplets (LDs) that are preferentially accumulated in astrocytes correlate with an increase of the LD markers PLIN2 and PLIN3, and conversely a decreased level of autophagic proteins including ATG5, BECN1 and MAP1LC3/LC3 as well as LAMP1. Accordingly, silencing of Furin in astrocytic cells impairs lipophagic flux with alterations in lipid metabolites. We then demonstrate that cytosolic ITGAV (integrin alpha V) is a principal substrate of FURIN. An ITGAV mutant that prevents FURIN-mediated maturation diminishes lysosomal puncta and lipophagic processing, in which a translational mechanism contributes to the reduction of autophagic proteins. We finally show that the mature but not mutant ITGAV rescues LD accumulation in FURIN-defective cells. Collectively, these data highlight the fact that ITGAV maturation is a key event in astrocytic lipophagy regulation which is involved in neurodegeneration of FURIN-deficient mice.