Several studies suggest that signal transduction systems are altered in the brain and peripheral tissues of patients with Alzheimer's Disease (AD). The overall goal of this research is to discover the molecular basis of the changes that are known to occur in key trigger steps in signal transduction systems in Alzheimer Disease (AD) patients and to demonstrate their pathophysiological importance. The long history of using cultured fibroblasts to elucidate fundamental mechanisms in inherited neurological disease suggests that this approach will be productive for AD research. Changes in cultured cells cannot be secondary to neurodegeneration. Cells are available from multiple AD families with different chromosomal abnormalities and from subjects with other neurodegenerative disorders. Our recent studies on a limited number of cell lines demonstrate that signal transduction systems in cultured fibroblasts from AD patients and age-matched controls are strikingly different: (1) The beta-adrenergic induction of cAMP declines about 80%. (2) The bradykinin stimulated formation of IP3, and bradykinin cell surface receptors increase by about 80%. (3) Two approaches indicate abnormal internal calcium compartments. (4)113 pS K+ channels that are sensitive to TEA are missing. (5) The mitochondrial membrane potentials are elevated. The experiments in the current proposal will test the hypothesis that the multiple abnormalities in signal transduction systems in AD fibroblasts transcend genetic differences and that an apoE4,E4 gene makeup increases the magnitude of the difference. Mechanistically, this implies that a similar series of pathophysiologically important cellular events follows from multiple gene defects. The goal of the current grant is to analyze fibroblasts from multiple AD families and from subjects with other degenerative diseases to test if these abnormalities are unique to AD or to particular AD families. These results will reveal whether the changes are diagnostically useful and will suggest whether a common molecular mechanism underlies all of the changes. Biochemical and molecular techniques will reveal whether similar underlying events lead to the AD related changes in beta-adrenergic and bradykinin receptors by examining the number and affinity of cell surface and internalized receptors, their transcription and their coupling to G proteins. Complete elucidation of the cellular pathophysiology of AD must explain these alterations in signal transduction systems in cultured cells from AD subjects.
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