GSAP regulates lipid homeostasis and mitochondrial function associated with Alzheimer's disease

Biochemical, pathogenic, and human genetic data confirm that GSAP (gamma-secretase activating protein), a selective gamma-secretase modulatory protein, plays important roles in Alzheimer's disease (AD) and Down's syndrome. However, the molecular mechanism(s) underlying GSAP-dependent pathogenesis remains largely elusive. Here, through unbiased proteomics and single-nuclei RNAseq, we identified that GSAP regulates multiple biological pathways, including protein phosphorylation, trafficking, lipid metabolism, and mitochondrial function. We demonstrated that GSAP physically interacts with the Fe65-APP complex to regulate APP trafficking/partitioning. GSAP is enriched in the mitochondria-associated membrane (MAM) and regulates lipid homeostasis through the amyloidogenic processing of APP. GSAP deletion generates a lipid environment unfavorable for AD pathogenesis, leading to improved mitochondrial function and the rescue of cognitive deficits in an AD mouse model. Finally, we identified a novel GSAP single-nucleotide polymorphism that regulates its brain transcript level and is associated with an increased AD risk. Together, our findings indicate that GSAP impairs mitochondrial function through its MAM localization and that lowering GSAP expression reduces pathological effects associated with AD.

Automated summary

Research has shown that GSAP plays important roles in Alzheimer's disease and Down's syndrome by regulating multiple biological pathways including protein phosphorylation, trafficking, lipid metabolism, and mitochondrial function. GSAP physically interacts with the Fe65-APP complex to regulate APP trafficking/partitioning, is enriched in the mitochondria-associated membrane, and affects lipid homeostasis through the amyloidogenic processing of APP. Deletion of GSAP can lead to an unfavorable lipid environment for AD pathogenesis, improved mitochondrial function, and rescue of cognitive deficits in an AD mouse model.