Neuronal fatty acid-binding protein enhances autophagy and suppresses amyloid-[beta] pathology in a Drosophila model of Alzheimer's disease

Fatty acid-binding proteins (FABPs) are small cytoplasmic proteins involved in intracellular lipid transport and bind free fatty acids, cholesterol, and retinoids. FABP3, the major neuronal FABP in the adult brain, is upregulated in the CSF of patients with Alzheimer's disease (AD). However, the precise role of neuronal FABPs in AD pathogenesis remains unclear. This study investigates the contribution of fabp, the Drosophila homolog of FABP3 and FABP7, to amyloid [beta] (A[beta]) pathology using a Drosophila model. Neuronal knockdown of fabp shortened the lifespan of flies and increased age-related protein aggregates in the brain. In an AD model, fabp knockdown in neurons increased A[beta] accumulation and A[beta]-induced neurodegeneration, whereas fabp overexpression ameliorated A[beta] pathology. Notably, fabp overexpression stimulated autophagy, which was inhibited by the knockdown of Eip75B, the Drosophila homolog of the peroxisome proliferator-activated receptor (PPAR). The PPAR activator rosiglitazone restored autophagy impaired by fabp knockdown and reduced fabp knockdown-induced increased A[beta] aggregation and cell death. Furthermore, knockdown of either fabp or Eip75B in the wing imaginal disc or adult fly brain reduced the expression of Atg6 and Atg8a. Additionally, treatment of the fabp knockdown AD model flies with polyunsaturated fatty acids, such as docosahexaenoic acid or linoleic acid, partially alleviated cell death in the developing eye, restored impaired autophagy flux, reduced A[beta] aggregation, and attenuated A[beta]-induced cell death. Our results suggest that Drosophila fabp plays an important role in maintaining protein homeostasis during aging and protects neurons from A[beta]-induced cell death by enhancing autophagy through the PPAR pathway. These findings highlight the potential importance of neuronal FABP function in AD pathogenesis.