Putative function of ADAM9, ADAM10,
and ADAM17 as APP a-secretase
Masashi Asai,
a,b
Chinatsu Hattori,
a
Be
aata Szab
oo,
a
Noboru Sasagawa,
a
Kei Maruyama,
c
Sei-ichi Tanuma,
b
and Shoichi Ishiura
a,
*
a
Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan
b
Department of Biochemistry, Faculty of Pharmaceutical Sciences, Tokyo University of Science, 12 Funagawara-machi,
Ichigaya, Shinjuku-ku, Tokyo 162-0826, Japan
c
Department of Pharmacology, Saitama Medical School, 38 Moro-hongo, Moroyama-cho, Iruma-gun, Saitama 350-0495, Japan
Received 11 December 2002
Abstract
The putative a-secretase cleaves the amyloid precursor protein (APP) of AlzheimerÕs disease in the middle of the amyloid b
peptide (Ab) domain. It is generally thought that the a-secretase pathway mitigates Ab formation in the normal brain. Several
studies have suggested that ADAM9, ADAM10, and ADAM17 are candidate a-secretases belonging to the ADAM (a disintegrin
and metalloprotease) family, which are membrane-anchored cell surface proteins. In this comparative study of ADAM9, ADAM10,
and ADAM17, we examined the physiological role of ADAMs by expressing these ADAMs in COS-7 cells, and both ‘‘constitutive’’
and ‘‘regulated’’ a-secretase activities of these ADAMs were determined. We tried to suppress the expression of these ADAMs in
human glioblastoma A172 cells, which contain large amounts of endogenous a-secretase, by lipofection of the double-stranded
RNA (dsRNA) encoding each of these ADAMs. The results indicate that ADAM9, ADAM10, and ADAM17 catalyze a-secretory
cleavage and therefore act as a-secretases in A172 cells. This is the first report that to suggest the endogenous a-secretase is
composed of several ADAM enzymes.
Ó 2002 Elsevier Science (USA). All rights reserved.
Keywords: a-Secretase; ADAM9; ADAM10; ADAM17; AlzheimerÕs disease; APP; A172 cells; RNAi
AlzheimerÕs disease (AD), the most prevalent neuro-
degenerative disease, is characterized by progressive
dementia and cognitive disorders. Amyloid senile pla-
ques are observed in the AD cerebral vasculature at the
histopathological level [1,2]. Amyloid b peptide (Ab), a
major component of senile plaques [3], is generated from
its precursor protein, termed amyloid precursor protein
(APP), by enzymatic digestion involving b-andc-sec-
retase activities [4]. In the normal brain, the non-amy-
loidogenic secretory pathway involving a-secretase
activity is predominant over the amyloidogenic pathway
[2]. The b-secretase was identified as a membrane-bound
aspartic protease named BACE1 (beta-site APP cleaving
enzyme 1) by enzymology and genetics experiments [5–
8]. The c-secretase was considered to be a complex,
containing presenilin as a major component [9–11].
Several lines of evidence suggest that the a-secretase
activity is modulated by metal ions and metalloprotease
inhibitors, and metalloprotease/disintegrin, ADAM9,
ADAM10, or ADAM17, have been proposed as the
a-secretase [12–14].
ADAM is a multi-functional gene family, some of
which have been shown to play a role in diverse biological
processes such as fertilization, myogenesis, neurogenesis,
and the activation of growth factors/immune regulators
[15,16]. The ADAM family has common characteristic
domains, and some ADAMs have a consensus zinc-
binding motif, HEXXH, in the catalytic domain. There-
fore, it is thought that ADAMs are potentially active
metalloproteases and their protease activity has actually
been demonstrated by several groups [12–14,17–28]. For
Biochemical and Biophysical Research Communications 301 (2003) 231–235
www.elsevier.com/locate/ybbrc
BBRC
*
Corresponding author. Fax: +81-3-5454-6739.
E-mail address: cishiura@mail.ecc.u-tokyo.ac.jp (S. Ishiura).
0006-291X/02/$ - see front matter Ó 2002 Elsevier Science (USA). All rights reserved.
doi:10.1016/S0006-291X(02)02999-6