ABSTRACT
The link between Val232Met variant of phospholipase D3 (PLD3) and late-onset Alzheimer's disease (AD) is still obscure. While it may not affect directly the amyloid precursor protein function, PLD3 could be regulating multiple cellular compartments. Here, we investigated the function of wild-type human PLD3 (PLD3WT) and the Val232Met variant (PLD3VM) in the presence of ß-amyloid (Aß) in a Drosophila melanogaster model of AD. We expressed PLD3WT in CNS of the Aß-model flies and monitored its effect on the ER stress, cell apoptosis and recovery the Aß-induced cognitive impairment. The expression reduced ER stress and neuronal apoptosis, which resulted in normalized antioxidative phospholipids levels and brain protection. A specific O-glycosylation at pT271 in PLD3 is essential for its normal trafficking and cellular localization. The V232â¯M substitution impairs this O-glycosylation, leading to enlarged lysosomes and plausibly aberrant protein recycling. PLD3VM was less neuroprotective, and while, PLD3WT expression enhances the lysosomal functions, V232â¯M attenuated PLD3's trafficking to the lysosomes. Thus, the V232â¯M mutation may affect AD pathogenesis. Further understanding of the mechanistic role of PLD3 in AD could lead to developing novel therapeutic agents.
Subject(s)
Alzheimer Disease/genetics , Alzheimer Disease/metabolism , Neuroprotection/physiology , Phospholipase D/genetics , Phospholipase D/metabolism , Animals , Animals, Genetically Modified , Drosophila melanogaster , Genetic Predisposition to Disease , Glycosylation , Humans , Mutation , Neurons/metabolism , Neurons/pathology , Protein TransportABSTRACT
Obesity-induced insulin resistance and diabetes are significantly associated with infiltrates of inflammatory cells in adipose tissue. Previous studies recognized the involvement of autophagy in the regulation of metabolism in multiple tissues, including ß-cells, hepatocytes, myocytes, and adipocytes. However, despite the importance of macrophages in obesity-induced insulin resistance, the role of macrophage autophagy in regulating insulin sensitivity is seldom addressed. In the present study, we show that macrophage autophagy is important for the regulation of systemic insulin sensitivity. We found that macrophage autophagy is downregulated by both acute and chronic inflammatory stimuli, and blockade of autophagy significantly increased accumulation of reactive oxygen species (ROS) in macrophages. Macrophage-specific Atg7 knockout mice displayed a shift in the proportion to pro-inflammatory M1 macrophages and impairment of insulin sensitivity and glucose homeostasis under high-fat diet conditions. Furthermore, inhibition of ROS in macrophages with antioxidant recovered adipocyte insulin sensitivity. Our results provide evidence of the underlying mechanism of how macrophage autophagy regulates inflammation and insulin sensitivity. We anticipate our findings will serve as a basis for development of therapeutics for inflammatory diseases, including diabetes.
