A long-term objective of the proposed study is to identify and understand factors that affect the cleavability of human amyloid precursor protein (APP). The proteolytic cleavage of APP by the beta-secretase is the required first reaction leading to the generation of amyloid beta-peptide, precipitation of which in the brain tissue is widely believed to cause neurodegeneration in Alzheimer's disease. Our preliminary studies indicated that the cleavability of APP was influenced by the protein structure of APP: the removal of APP ectodomain, either by deletion mutagenesis or by protein unfolding, could release the inhibition imposed on the cleavage site by the native protein; familial Alzheimer's disease mutations affected this autoinhibitory mechanism and caused increased cleavage. Since heparin binding to APP reversed the effect of the mutation, it was hypothesized that intracellular heparan sulfates, by forming complexes with APP inside the cell, could function to inhibit the proteolytic reaction.
Specific aims of this proposal include: (i) crystallographic characterization of the juxtamembrane domain of APP, which contains the secretase cleavage site; (ii) crystallographic characterization of APP:heparin complexes; and (iii) mutagenesis studies to probe the interaction between heparin and APP, and to investigate the role of intracellular heparan sulfates in the proteolytic processing of APP. The eventual goal is to use this knowledge to help design heparin-like compounds to reinforce the autoinhibitory mechanism for controlling the synthesis of amyloid beta-peptide in aged individuals to prevent Alzheimer's disease.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
1R01GM077547-01A1
Application #
6983011
Study Section
Macromolecular Structure and Function C Study Section (MSFC)
Program Officer
Basavappa, Ravi
Project Start
2005-09-01
Project End
2010-08-31
Budget Start
2005-09-01
Budget End
2006-08-31
Support Year
1
Fiscal Year
2005
Total Cost
$286,125
Indirect Cost
Name
Yale University
Department
Pharmacology
Type
Schools of Medicine
DUNS #
043207562
City
New Haven
State
CT
Country
United States
Zip Code
06520
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Xue, Yi; Lee, Sangwon; Wang, Yongcheng et al. (2011) Crystal structure of the E2 domain of amyloid precursor protein-like protein 1 in complex with sucrose octasulfate. J Biol Chem 286:29748-57
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