Deposition of the amyloid beta peptide (Abeta) in the brain is critical to the pathogenesis of Alzheimer's Disease (AD). Gamma-secretase is a key enzyme responsible for generating Abeta from its precursor protein.
Gamma-secretase has attracted a lot of attention recently because:
1) it is a highly unusual protease
2) it cleaves many important membrane proteins (Notch, cadherins) and regulates subsequent signalling and
3) the enzyme is considered to be a drug target in AD research. Gamma-secretase is the high molecular weight complex composed of at least four essential, integral membrane proteins including presenilin, Nicastrin, Aph-1 and Pen-2.
It is particularly important to study the structure-function relationship of gamma-secretase from biological, enzymatical and pathological perspectives. Direct analysis of the structure is difficult because handling such hydrophobic complex in cell and membrane free conditions is extremely problematic. In this project, we plan to take advantage of the camel antibody as a tool for the structural analysis of gamma-secretase. Camel antibodies consist of only heavy chains with highly stable variable regions.
The variable region fragment (called nanobody) can be easily expressed as a recombinant protein maintaining specificity and stability. We will immunize camel against the gamma-secretase compex, generate a phage display library of nanobodies, and then screen gamma-secretase binders/inhibitors. Analyses of the obtained inhibitors will provide information about the import ant domains of the gamma-secretase complex. The inhibitors can be applied in a multitude of applications. We will focus on the structural analysis of gamma-secretase, and on cell biological studies. Since these nanobodies can be engineered with modifications that allow them to cross the blood brain barrier, a longer term goal is to use the nanobodies as therapeutics to inhibit gamma-secretase in Alzheimer's Disease.
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