Title:  Secretases related to Alzheimer's dementia

United States Patent:  6,313,268

Appl. No.:  294987

This invention is directed to a novel .beta.-secretase that produces the A.beta. peptide found in Alzheimer's Disease. One .beta.-secretase is a protein having a molecular weight of about 61, 81 or 88 kDa that cleaves an amyloid precursor protein (APP) substrate. Another is a protease complex having a molecular between about 180 and 200 kDa, which, in one embodiment, contains the 61, 81, and 88 kDa proteins and, in another embodiment, contains proteins having a molecular weight of about 66, 60, 33 and 29 kDa. Another .beta.-secretase has a molecular weight between about 50 and 90 kDA. The invention is also directed to methods of selecting agents that inhibit A.beta. peptide production and treating Alzheimer's disease in patients.

SUMMARY OF THE INVENTION

The invention is directed to various novel .beta.-secretases. One such .beta.-secretase contains a protein having a molecular weight of about 61, 81 or 88 kDa as determined by cleavage of an APP substrate in a non-reducing SDS-PAGE in gel activity assay. In one embodiment, the .beta.-secretase contains a protein that cleaves the APP substrate in the .beta.-secretase recognition site at the Lys-Met bond.

Another is a protease complex having a molecular weight between about 180 and 200 kiloDaltons (kDa) as determined by Sephacryl chromatography that cleaves an APP substrate. In one embodiment, the protease complex cleaves the APP substrate in the .beta.-secretase recognition site at the Lys-Met bond. In another embodiment, the protease complex contains proteins having molecular weights of about 66, 60, 33 and 29 kDa as determined by a reducing SDS-PAGE in gel protein staining assay. In another embodiment, the protease complex containis proteins having molecular weights of about 61, 81 and 88 kDa as determined by cleavage of an APP substrate in a non-reducing SDS-PAGE in gel activity assay.

Another .beta.-secretase has a molecular weight between about 50 and 90 kDA as determined by Sephacryl chromatography and cleaves an APP substrate. In one embodiment, that .beta.-secretase cleaves the APP substrate in the .beta.-secretase recognition site at the Met-Asp bond. In another embodiment, the .beta.-secretase contains 2 proteins having different electronegative charges as determined by ion exchange chromatography.

The invention is also directed to a method of selecting an agent that inhibits cleavage of the APP substrate by the .beta.-secretases described above. The invention is further directed to a method of inhibiting production of an A.beta. peptide by a cell or by an Alzheimer's disease patient using such a selected agent.

Claim 1 of 11 Claims

I claim:

1. An isolated .beta.-secretase comprising a protein having a molecular weight selected from the group consisting of about 61, 81 and 88 kiloDaltons (kDa) as determined by cleavage of an amyloid precursor protein (APP) substrate in a non-reducing sodium dodecyl sulfate polyacrylamide gel electrophoreis (SDS-PAGE) in gel activity assay.

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