C-terminal Fragment of Presenilin Is the Molecular Target of a Dipeptidic γ-Secretase-specific Inhibitor DAPT (N-[N-(3,5-Difluorophenacetyl)-L-alanyl]-S-phenylglycine t-Butyl Ester)

• Published in: The Journal of biological chemistry Vol. 281; no. 21; p. 14670
• Main Authors: Yuichi Morohashi, Toshiyuki Kan, Yusuke Tominari, Haruhiko Fuwa, Yumiko Okamura, Naoto Watanabe, Chihiro Sato, Hideaki Natsugari, Tohru Fukuyama, Takeshi Iwatsubo, Taisuke Tomita
• Format: Journal Article
• Language: English
• Published: American Society for Biochemistry and Molecular Biology 26.05.2006
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M513012200

γ-Secretase is a multimeric membrane protein complex composed of presenilin (PS), nicastrin, Aph-1 and, Pen-2 that is responsible for the intramembrane proteolysis of various type I transmembrane proteins, including amyloid β-precursor protein and Notch. The direct labeling of PS polypeptides by transition-state analogue γ-secretase inhibitors suggested that PS represents the catalytic center of γ-secretase. Here we show that one of the major γ-secretase inhibitors of dipeptidic type, N -[ N -(3,5-difluorophenacetyl)- l -alanyl]- S -phenylglycine t -butyl ester (DAPT), targets the C-terminal fragment of PS, especially the transmembrane domain 7 or more C-terminal region, by designing and synthesizing DAP-BpB ( N -[ N -(3,5-difluorophenacetyl)- l -alanyl]-( S )-phenylglycine-4-(4-(8-biotinamido)octylamino)benzoyl)benzyl)methylamide), a photoactivable DAPT derivative. We also found that DAP-BpB selectively binds to the high molecular weight γ-secretase complex in an activity-dependent manner. Photolabeling of PS by DAP-BpB is completely blocked by DAPT or its structural relatives ( e.g. Compound E) as well as by arylsulfonamides. In contrast, transition-state analogue inhibitor L-685,458 or α-helical peptidic inhibitor attenuated the photolabeling of PS1 only at higher concentrations. These data illustrate the DAPT binding site as a novel functional domain within the PS C-terminal fragment that is distinct from the catalytic site or the substrate binding site.