ABSTRACT
The pathogenic event common to all forms of Alzheimer's disease is the abnormal accumulation of the amyloid beta-peptide (Abeta). Here we provide strong evidence that intracellular cholesterol compartmentation modulates the generation of Abeta. Using genetic, biochemical and metabolic approaches, we found that cholesteryl-ester levels are directly correlated with Abeta production. Acyl-coenzyme A:cholesterol acyltransferase (ACAT), the enzyme that catalyses the formation of cholesteryl esters, modulates the generation of Abeta through the tight control of the equilibrium between free cholesterol and cholesteryl esters. We also show that pharmacological inhibitors of ACAT, developed for the treatment of atherosclerosis, are potent modulators of Abeta generation, indicating their potential for use in the treatment of Alzheimer's disease.
Subject(s)
Amyloid beta-Peptides/metabolism , Cholesterol/metabolism , Sterol O-Acyltransferase/metabolism , Amyloid Precursor Protein Secretases , Amyloid beta-Peptides/biosynthesis , Amyloid beta-Protein Precursor/genetics , Amyloid beta-Protein Precursor/metabolism , Animals , Aspartic Acid Endopeptidases , Biomarkers , Cell Fractionation , Cell Line , Cholesterol/genetics , Endopeptidases/metabolism , Enzyme Inhibitors/pharmacology , Humans , Intracellular Membranes/chemistry , Membrane Glycoproteins/metabolism , Membrane Proteins/metabolism , Mice , Mice, Transgenic , Neurons/metabolism , Presenilin-1 , Pyridines/pharmacology , Sterol O-Acyltransferase/antagonists & inhibitorsABSTRACT
We studied a novel function of the presenilins (PS1 and PS2) in governing capacitative calcium entry (CCE), a refilling mechanism for depleted intracellular calcium stores. Abrogation of functional PS1, by either knocking out PS1 or expressing inactive PS1, markedly potentiated CCE, suggesting a role for PS1 in the modulation of CCE. In contrast, familial Alzheimer's disease (FAD)-linked mutant PS1 or PS2 significantly attenuated CCE and store depletion-activated currents. While inhibition of CCE selectively increased the amyloidogenic amyloid beta peptide (Abeta42), increased accumulation of the peptide had no effect on CCE. Thus, reduced CCE is most likely an early cellular event leading to increased Abeta42 generation associated with FAD mutant presenilins. Our data indicate that the CCE pathway is a novel therapeutic target for Alzheimer's disease.
Subject(s)
Alzheimer Disease/physiopathology , Calcium Channels/metabolism , Calcium/metabolism , Membrane Proteins/metabolism , Amyloid beta-Peptides/metabolism , Amyloid beta-Protein Precursor/metabolism , Animals , Calcium Channel Blockers/pharmacology , Calcium Channels/drug effects , Calcium Channels, L-Type/drug effects , Calcium Channels, L-Type/metabolism , Calcium Channels, N-Type/drug effects , Calcium Channels, N-Type/metabolism , Cells, Cultured , Cytochalasin D/pharmacology , Humans , Imidazoles/pharmacology , Ion Transport/drug effects , Ion Transport/genetics , Membrane Proteins/genetics , Membrane Proteins/pharmacology , Mice , Mice, Transgenic , Mutagenesis, Site-Directed , Neurons/cytology , Neurons/metabolism , Patch-Clamp Techniques , Peptide Fragments/metabolism , Presenilin-1 , Presenilin-2 , TransfectionABSTRACT
Perturbed Ca(2+) homeostasis is a common molecular consequence of familial Alzheimer's disease-linked presenilin mutations. We report here the molecular interaction of the large hydrophilic loop region of presenilin 2 (PS2) with sorcin, a penta-EF-hand Ca(2+)-binding protein that serves as a modulator of the ryanodine receptor intracellular Ca(2+) channel. The association of endogenous sorcin and PS2 was demonstrated in cultured cells and human brain tissues. Membrane-associated sorcin and a subset of the functional PS2 complexes were co-localized to a novel subcellular fraction that is distinctively positive for calcineurin B. Sorcin was found to interact with PS2 endoproteolytic fragments but not full-length PS2, and the sorcin/PS2 interaction was greatly enhanced by treatment with the Ca(2+) ionophore A23187. Our findings reveal a molecular link between PS2 and intracellular Ca(2+) channels (i.e. ryanodine receptor) and substantiate normal and/or pathological roles of PS2 in intracellular Ca(2+) homeostasis.
