Alzheimer amyloid precursor aspartyl proteinase activity in CHAPSO homogenates of Spodoptera frugiperda cells
Presenilins are polytopic, integral proteins that control intramembranous proteolysis at the "gamma-" and "epsilon-" cleavage sites of the Alzheimer amyloid-beta precursor protein (APP) to yield amyloid-beta peptide (Abeta) and the APP intracellular domain (AICD). We have overexpressed a constitutively active, pathogenic form of PS1 (known as PS1 Delta exon 9) together with its substrate, APP-C99, in Spodoptera frugiperda (Sf9) cells. Sf9 cells have been reported to lack endogenous gamma-secretase, an unexpected finding since there exists an insect homologue of PS1. In our hands, neither intact insect cells coexpressing PS1 Delta exon 9/APP-C99 nor the aqueous homogenates of these cells displayed obvious products of the gamma- or epsilon-secretase reactions, as reported. Surprisingly, when APP-C99-expressing cells were homogenized in 3[(3-cholamidopropyl) dimethylammonio]-2-hydroxypropanesulfonic acid (CHAPSO), a detergent known to support gamma-secretase activity, subsequent incubation led to the accumulation of an AICD-like peptide (AICD-L). Aspartyl proteinase inhibitors were effective in preventing the appearance of AICD-L, but inhibitors of other classes of proteinases were ineffective. Immunoprecipitation-mass spectrometry of AICD-L revealed its identity as the minor of the two known AICDs.
|Authors||Carter, T. L.;Verdile, G.;Groth, D.;Bogush, A.;Thomas, S.;Shen, P.;Fraser, P. E.;Mathews, P.;Nixon, R. A.;Ehrlich, M. E.;Kwok, J. B.;St George-Hyslop, P.;Schofield, P.;Li, Y.;Yang, A.;Martins, R. N.;Gandy, S. :|
|Publisher Name||ALZ DIS ASSOC DIS|
|Published Date||2004-01-01 00:00:00|