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J Biol Chem. 2013 Jan 25;288(4):2521-31. doi: 10.1074/jbc.M112.370924. Epub 2012 Dec 3.

The role of γ-secretase activating protein (GSAP) and imatinib in the regulation of γ-secretase activity and amyloid-β generation.

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1
Department of Therapeutic Area Neurodegenerative Diseases, Merck Serono S.A., Chemin des Mines 9, 1202 Geneva, Switzerland. ishruthssn@gmail.com

Abstract

γ-Secretase is a large enzyme complex comprising presenilin, nicastrin, presenilin enhancer 2, and anterior pharynx-defective 1 that mediates the intramembrane proteolysis of a large number of proteins including amyloid precursor protein and Notch. Recently, a novel γ-secretase activating protein (GSAP) was identified that interacts with γ-secretase and the C-terminal fragment of amyloid precursor protein to selectively increase amyloid-β production. In this study we have further characterized the role of endogenous and exogenous GSAP in the regulation of γ-secretase activity and amyloid-β production in vitro. Knockdown of GSAP expression in N2a cells decreased amyloid-β levels. In contrast, overexpression of GSAP in HEK cells expressing amyloid precursor protein or in N2a cells had no overt effect on amyloid-β generation. Likewise, purified recombinant GSAP had no effect on amyloid-β generation in two distinct in vitro γ-secretase assays. In subsequent cellular studies with imatinib, a kinase inhibitor that reportedly prevents the interaction of GSAP with the C-terminal fragment of amyloid precursor protein, a concentration-dependent decrease in amyloid-β levels was observed. However, no interaction between GSAP and the C-terminal fragment of amyloid precursor protein was evident in co-immunoprecipitation studies. In addition, subchronic administration of imatinib to rats had no effect on brain amyloid-β levels. In summary, these findings suggest the roles of GSAP and imatinib in the regulation of γ-secretase activity and amyloid-β generation are uncertain.

PMID:
23209290
PMCID:
PMC3554920
DOI:
10.1074/jbc.M112.370924
[Indexed for MEDLINE]
Free PMC Article
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