Substrate sequence influences ?-secretase modulator activity, role of the transmembrane domain of the amyloid precursor protein.

ABSTRACT: A subset of non-steroidal anti-inflammatory drugs modulates the ? cleavage site in the amyloid precursor protein (APP) to selectively reduce production of A?42. It is unclear precisely how these ?-secretase modulators (GSMs) act to preferentially spare A?40 production as well as Notch processing and signaling. In an effort to determine the substrate requirements in NSAID/GSM activity, we determined the effects of sulindac sulfide and flurbiprofen on ?-cleavage of artificial constructs containing several ?-secretase substrates. Using FLAG-tagged constructs that expressed extracellularly truncated APP, Notch-1, or CD44, we found that these substrates have different sensitivities to sulindac sulfide. ?-Secretase cleavage of APP was altered by sulindac sulfide, but CD44 and Notch-1 were either insensitive or only minimally altered by this compound. Using chimeric APP constructs, we observed that the transmembrane domain (TMD) of APP played a pivotal role in determining drug sensitivity. Substituting the APP TMD with that of APLP2 retained the sensitivity to ?-cleavage modulation, but replacing TMDs from Notch-1 or ErbB4 rendered the resultant molecules insensitive to drug treatment. Specifically, the GXXXG motif within APP appeared to be critical to GSM activity. Consequently, the modulatory effects on ?-cleavage appears to be substrate-dependent. We hypothesize that the substrate present in the ?-secretase complex influences the conformation of the complex so that the binding site of GSMs is either stabilized or less favorable to influence the cleavage of the respective substrates.

SUBMITTER: Sagi SA 

PROVIDER: S-EPMC3220583 | biostudies-literature | 2011 Nov

REPOSITORIES: biostudies-literature