BREAKDOWN OF MEMBRANE PHOSPHOLIPIDS IN ALZHEIMER-DISEASE - INVOLVEMENT OF EXCITATORY AMINO-ACID RECEPTORS

Membrane phospholipids are not only essential membrane constituents bu t also determine many membrane functions and integrity. Normal recepto r function, signal transduction, and transport of essential substrates depend strongly on normal membrane phospholipid metabolism. Studies o f plasma membrane phospholipid composition have indicated that ethanol amine glycerophospholipids decrease, whereas serine glycerophospholipi ds increase significantly, in Alzheimer disease (AD). The release of a rachidonate from the sn-2 position of glycerophospholipids is catalyze d by phospholipases and lipases. These enzymes are coupled to EAA rece ptors. Overstimulation of these receptors may be involved in abnormal calcium homeostasis, degradation of membrane phospholipids, and the ac cumulation of free fatty acids, prostaglandins, and lipid peroxides. A ccumulation of the mentioned metabolites, as well as abnormalities in signal transduction owing to stimulation of lipases and phospholipases , may be involved in the pathogenesis of the neurodegeneration in AD.