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  • Title: Rac1 changes the substrate specificity of gamma-secretase between amyloid precursor protein and Notch1.
    Author: Boo JH, Sohn JH, Kim JE, Song H, Mook-Jung I.
    Journal: Biochem Biophys Res Commun; 2008 Aug 08; 372(4):913-7. PubMed ID: 18538664.
    Abstract:
    Beta amyloid peptide is generated from amyloid precursor protein (APP) by proteolytic cleavage of beta- and gamma-secretases, and plays a critical role in the pathogenesis of Alzheimer's disease. Since gamma-secretase cleaves several proteins including APP and Notch in a number of cell types, it is important to understand the conditions determining gamma-secretase substrate specificity. In the present study, inhibition of Rac1 attenuated gamma-secretase activity for APP, resulting in decreased production of the APP intracellular domain but accumulated C-terminal fragments (APP-CTF). In contrast, Rac1 inhibitor, NSC23766 increased production of the Notch1 intracellular domain but slightly decreased the ectodomain-shed form of Notch1 (NotchDeltaE). To elucidate the mechanism underlying these observations, we performed co-immunoprecipitation experiments to analyze the interaction between Rac1 and presenilin1 (PS1), a component of the gamma-secretase complex. Inhibition of Rac1 enhanced its interaction with PS1. Under the same condition, PS1 interacted more strongly with NotchDeltaE than with APP-CTF. Our results suggested that PS1 determines the preferred substrate for gamma-secretase between APP and Notch1, depending on the activation status of Rac1.
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