PS are thought to be the catalytic core of the aspartyl protease γ-secretase which is required for Aβ production linked to AD pathology. In mammals, PS1/γ-secretase cleaves notch-1 receptor in response to ligand binding followed by an ectodomain shedding cleavage event (LaVoie and Selkoe, 2003; De Strooper et al., 1999; Wong et al., 1997). Notch intracellular domain (NICD) is then liberated, translocates to the nucleus and regulates gene expression. Interestingly, recent studies suggest that notch-1 functions in embryonic and adult neurogenesis are distinct (Alexson et al., 2006).
