Novel ?-Secretase Enzyme Modulators Directly Target
Amelie Ebke‡§1, Thomas Luebbers¶, Akio Fukumori‡§, Keiro Shirotani?, Christian Haass‡§2, Karlheinz Baumann¶3,
and Harald Steiner‡§4
RocheLimited,CH-4070 Basel, Switzerland
Background: ?-Secretase modulators (GSMs) hold great potential as anti-Alzheimer disease drugs, but their molecular
target(s) are not established.
Results: The catalytic subunit of ?-secretase, presenilin, was identified as a direct target of novel GSMs.
Conclusion: Enzyme-targeting GSMs establish allosteric modulation as a mechanism of GSM action.
?-Secretase is essential for the generation of the neurotoxic
42-amino acid amyloid ?-peptide (A?42). The aggregation-
prone hydrophobic peptide, which is deposited in Alzheimer
disease (AD) patient brain, is generated from a C-terminal frag-
ment of the ?-amyloid precursor protein by an intramembrane
cleavage of ?-secretase. Because A?42is widely believed to trig-
inhibitors of the enzyme, ?-secretase modulators (GSMs) selec-
tively lower A?42without interfering with the physiological
function of ?-secretase. The molecular target(s) of GSMs and
hence the mechanism of GSM action are not established. Here
we demonstrate by using a biotinylated photocross-linkable
derivative of highly potent novel second generation GSMs that
?-secretase is a direct target of GSMs. The GSM photoprobe
specifically bound to the N-terminal fragment of presenilin, the
catalytic subunit of ?-secretase, but not to other ?-secretase
subunits. Binding was differentially competed by GSMs of
diverse structural classes, indicating the existence of overlap-
ping/multiple GSM binding sites or allosteric alteration of the
photoprobe binding site. The ?-amyloid precursor protein
C-terminal fragment previously implicated as the GSM binding
site was not targeted by the compound. The identification of
presenilin as the molecular target of GSMs directly establishes
action and may contribute to the development of therapeuti-
cally active GSMs for the treatment of AD.
is caused by an accumulation of the aggregation-prone amy-
loid-? peptide (A?) in the brain of affected patients (1). A? is a
small 37–43-amino acid secreted peptide that is generated
from the ?-amyloid precursor protein (APP) by the sequential
action of two membrane-bound proteases, ?- and ?-secretase
(1). The latter enzyme is an intramembrane-cleaving protease
composed of presenilin (PS) 1 or 2 as the catalytic subunit,
A? from the membrane by a stepwise cleavage of the APP
C-terminal fragment (CTF) that ?-secretase generates via
ulation of A? generation are promising therapeutic strategies
to treat AD, ?- and ?-secretase are key AD drug targets, and
Apart from APP, a number of other ?-secretase substrates
have been identified (3). Among these, Notch1 represents a
substrate of major importance for the regulation of cell differ-
entiation during embryonic development as well as in adult-
hood (6). Cleavage of Notch1 by ?-secretase gives rise to the
as an essential transcriptional regulator (6). Unfortunately,
direct inhibition of A? generation by ?-secretase inhibitors
(GSIs) is problematic due to the inhibition of the Notch signal-
ing pathway (5), and a large clinical phase 3 trial has also
recently been halted due to the appearance of severe side
In contrast to GSIs, ?-secretase modulators (GSMs) may
offer safer alternatives for AD therapy. Such drugs typically
schaft(SFB596)(toH. S.andC. H.),theBundesministeriumfürBildungund
Forschung(KNDD)(toC. H.andH. S.),andtheCenterforIntegratedProtein
Science Munich (CIPSM).
supplemental Materials and Methods, Table 1, and Figs. 1–4.
1Supported by the Elitenetzwerk Bayern.
2Supported by a research professorship from the LMUexcellent program.
3To whom correspondence may be addressed. Tel.: 41-61-688-8397; Fax:
41-61-688-4484; E-mail: firstname.lastname@example.org.
4To whom correspondence may be addressed. Tel.: 49-89-2180-75480; Fax:
49-89-2180-75415; E-mail: email@example.com.
5The abbreviations used are: AD, Alzheimer disease; A?, amyloid ?-peptide;
AICD, APP intracellular domain; APP, ?-amyloid precursor protein; Bicine,
NSAID, non-steroidal anti-inflammatory drug; NTF, N-terminal fragment;
PS, presenilin; DAPT, N-[(3,5-difluorophenyl)acetyl]-L-alanyl-2-phenyl]gly-
THE JOURNAL OF BIOLOGICAL CHEMISTRY VOL. 286, NO. 43, pp. 37181–37186, October 28, 2011
© 2011 by The American Society for Biochemistry and Molecular Biology, Inc. Printed in the U.S.A.
by guest on October 18, 2015
Karlheinz Baumann and Harald Steiner
2011, 286:37181-37186. J. Biol. Chem.
Fukumori, Keiro Shirotani, Christian Haass,
Amelie Ebke, Thomas Luebbers, Akio
Directly Target Presenilin Protein
-Secretase Enzyme Modulators
doi: 10.1074/jbc.C111.276972 originally published online September 6, 2011
Find articles, minireviews, Reflections and Classics on similar topics on the
10.1074/jbc.C111.276972 Access the most updated version of this article at doi:
. JBC Affinity Sites
When a correction for this article is posted •
When this article is cited•
to choose from all of JBC's e-mail alerts Click here
This article cites 27 references, 8 of which can be accessed free at
by guest on October 18, 2015