Proteolytic processing of amyloid beta protein precursor (APP) by thrombin.

Area of Science:

• Neuroscience
• Biochemistry
• Molecular Biology

Background:

• Alzheimer's disease is characterized by beta-amyloid deposits.
• Amyloid precursor protein (APP) processing typically avoids beta-amyloid generation.
• Identifying proteases altering APP processing is crucial for understanding Alzheimer's disease.

Purpose of the Study:

• To investigate the role of thrombin, a serine protease, in APP processing.
• To determine if thrombin can generate intermediates containing the beta/A4 peptide.

Main Methods:

• In vitro cleavage of mouse recombinant APP695 by thrombin.
• Immunoblot analysis to characterize cleavage fragments.
• Amino acid sequencing to identify cleavage sites.

Main Results:

• Thrombin cleaved recombinant APP695, producing a 28 kDa fragment.
• The 28 kDa fragment originated from the carboxy-terminal side of APP695.
• Cleavage occurred at Arg 510-Ile 511, yielding a fragment containing the entire beta/A4 peptide.

Conclusions:

• The 28 kDa fragment generated by thrombin is a potential intermediate in beta/A4 peptide formation.
• Thrombin may play a role in the altered processing of APP, contributing to Alzheimer's disease pathology.