Increasing evidence points to a causative role for amyloid-beta peptide (Abeta) in the pathogenesis of Alzheimer's disease (AD). Thus, mechanisms through which Abeta affects cellular properties have come under intensive study. Higher concentrations of Abeta(1-40/42), present later in the course of AD, form aggregates and fibrils which nonspecifically damage membranes of virtually any cell. Earlier in AD, when lower levels of Abeta are present, specific interactions of Abeta with particular cells, as well as sensitive subcellular loci, could also mediate cellular toxicity. We have identified a novel endoplasmic reticulum-associated Abeta binding protein termed ERAB which has properties of a b-hydroxyacyl-Coenzyme A dehydrogenase/short-chain alcohol dehydrogenase. Recombinant human ERAB binds Abeta(1-40/42) specifically, though it does not interact with beta-amyloid precursor protein (betaAPP) or forms of Abeta containing C-terminal amino acids from the precursor. ERAB, constitutively produced by neuroblastoma cells, was co-immunoprecipitated with Abeta; following exposure of cultures to exogenous Abeta, ERAB was rapidly redistributed to the inner aspect of the plasma membrane. Toxicity of Abeta to neuroblastoma cells was prevented by liposome-mediated introduction of blocking anti-ERAB F(ab')2 into the cells, and was enhanced by overexpression of ERAB in COS cells. We propose that ERAB is a critical intracellular target potentiating Abeta-mediated cellular perturbation and, ultimately, cytotoxicity. We hypothesized that Abeta influences ERAB by effecting ERAB translocation to the plasma/nuclear membrane, where induction of cell stress, marked by generation of toxic aldehydes and events triggering apoptosis, occurs.
Our first aim i s to determine the contribution of ERAB enzymatic activity and ERAB binding to Abeta on cytotoxicity by analyzing ERAB-Abeta-induced generation of toxic aldehydes and apoptosis.
Our second aim i s to analyze the contribution of ERAB to Abeta-induced cell stress using transgenic mice; we hypothesize that mice with targeted overexpression of ERAB will display exaggerated cytotoxicity in an Abeta-rich environment, and that this will be further exacerbated by ischemic stress. The long-term goal of this wok is to determine if ERAB is an important cellular cofactor for Abeta cytotoxicity, in order to assess whether inhibition of ERAB might be a novel neuroprotective strategy for future drug development.
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