Novel processing of beta-amyloid precursor protein catalyzed by membrane type 1 matrix metalloproteinase releases a fragment lacking the inhibitor domain against gelatinase A
Abstract
In various mammalian cell lines, beta-amyloid precursor protein (APP) is proteolytically processed to release its NH(2)-terminal extracellular domain as a soluble APP (sAPP) that contains the inhibitor domain against gelatinase A. To investigate roles of sAPP in the regulation of gelatinase A activity, we examined the correlation between the activation of progelatinase A and processing of APP. We found that stimulation of HT1080 fibrosarcoma cells with concanavalin A led to an activation of endogenous progelatinase A and to a novel processing of APP, which releases a COOH-terminally truncated form of sAPP (sAPPtrc) into the culture medium. Reverse zymographic analysis showed that sAPPtrc lacked an inhibitory activity against gelatinase A. Analyses of production of sAPPtrc in the presence of various metalloproteinase inhibitors showed that membrane type 1 matrix metalloproteinase (MT1-MMP), an activator of progelatinase A, is most likely responsible for the production of sAPPtrc. When the concanavalin A-stimulated HT1080 cells were cultured in the condition that inhibited MT1-MMP activity, sAPP and APP were associated with the extracellular matrix deposited by the cells, whereas these gelatinase A inhibitors in the matrix were d...Continue Reading
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