Non-amyloidogenic processing of APP

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DESCRIPTION (provided by applicant): Alzheimer disease (AD) is neuropathologically characterized by the presence of extracellular amyloid 2 (A2) deposits and intracellular neurofibrillary tangles. Amyloid 2 is derived from the amyloidogenic processing of the amyloid 2 precursor protein (A2PP). In the amyloidogenic pathway, A2PP is sequentially cleaved by 2-secretase (beta-site A2PP cleaving enzyme 1; BACE1) and a multi-subunit protease complex known as 3-secretase to produce a soluble ectodomain fragment (A2PPs2) and A2. In the non-amyloidogenic pathway, 1-secretase cleaves A2PP within the A2 sequence, thereby precluding the formation of A2-peptides and generating a soluble, neuroprotective, N-terminal ectodomain termed A2PPs1. A member of the ADAM (a disintegrin and metalloproteinase) family of enzymes, ADAM10 (EC 3.4.24.81), seems to be responsible for the 1-secretase-mediated ectodomain shedding of A2PP. Whilst some of the main therapeutic avenues for AD involve the development of inhibitors of amyloidogenic A2PP processing, the activation of ADAM10 and the non-amyloidogenic pathway represents a logical alternative strategy. Unfortunately, studies involving the characterization of ADAM10 activity as 1-secretase in A2PP processing and in the processing of other substrates have been obstructed by the lack of an Adam10 knock-out mouse model. Adam10-deficient mice have been generated (Hartmann, 2002), but their early lethality at day E9.5 prevents a reliable analysis of ADAM10's 1-secretase function in vivo, especially in neuronal cells. The aim of this study is to generate an inducible conditional knock-out (cKO) animal model in which investigate ADAM10 activity in neurons in vivo. We believe that an inducible cKO mouse model will be crucial to fully characterize both the full functional portfolio of ADAM10 1-secretase activity as well as its clinical relevance, which may go way beyond the study of AD. Our specific aims are: Specific Aim 1: To conditionally knock-out (cKO) the murine Adam10 gene in neurons. The early lethality of Adam10-deficient mice has prevented a reliable analysis of Adam10 function in vivo in neuronal cells. In this aim we will generate an inducible cKO mouse model in which loss of function of Adam10 will be targeted to neurons expressing the CreERT2 protein. We will use this model to characterize the consequences of Adam10 loss of function in the metabolism of A2PP and Notch, and in A2 deposition in an animal model of amyloid deposition. PUBLIC HEALTH RELEVANCE: The early lethality observed in Adam10-deficient mice generated by classical Cre recombination has prevented a reliable analysis of ADAM10's 1-secretase function in vivo, in particular in neuronal cells. The aim of this study is to generate an inducible conditional knock-out (cKO) animal model in which to investigate ADAM10's activity in neurons in vivo. We believe that an inducible cKO mouse model will be crucial to fully characterize both the full functional portfolio of ADAM10 1-secretase activity as well as its clinical relevance in Alzheimer disease, where the activation of ADAM10 and the non-amyloidogenic pathway represent a logical alternative strategy that has not been well investigated due to the lack of an Adam10 knock-out mouse model.