Cell Calcium 40 (2006) 41–51
Up-regulation of inositol 1,4,5-trisphosphate receptor type
1 is responsible for a decreased endoplasmic-reticulum
Ca
2+
content in presenilin double knock-out cells
Nael Nadif Kasri
b,1
, Sarah L. Kocks
a,1
, Leen Verbert
a
, S´ ebastien S. H´ ebert
c
,
Geert Callewaert
a
, Jan B. Parys
a
, Ludwig Missiaen
a
, Humbert De Smedt
a,∗
a
Laboratorium voor Fysiologie, Campus Gasthuisberg O/N1, bus 802, Katholieke Universiteit Leuven, 3000 Leuven, Belgium
b
Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, NY 11724, USA
c
Center for Human Genetics,VIB4, Campus Gasthuisberg O/N1, bus 802, Katholieke Universiteit Leuven, 3000 Leuven, Belgium
Received 18 January 2006; received in revised form 12 March 2006; accepted 16 March 2006
Available online 3 May 2006
Abstract
Presenilins (PS) are proteins involved in the pathogenesis of autosomal-dominant familial cases of Alzheimer’s disease. Mutations in PS
are known to induce specific alterations in cellular Ca
2+
signaling which might be involved in the pathogenesis of neurodegenerative diseases.
Mouse embryonic fibroblasts (MEF) deficient in PS1 and PS2 (PS DKO) as well as the latter rescued with PS1 (Rescue), were used to
investigate the underlying mechanism of these alterations in Ca
2+
signaling. PS DKO cells were characterized by a decrease in the [Ca
2+
]
ER
as measured by ER-targeted aequorin luminescence and an increased level of type 1 inositol 1,4,5-trisphosphate receptor (IP
3
R1). The lower
[Ca
2+
]
ER
was associated with an increase in a Ca
2+
leak from the ER. The increased IP
3
R1 expression and the concomitant changes in ER
Ca
2+
handling were reversed in the Rescue cells. Moreover using RNA-interference mediated reduction of IP
3
R1 we could demonstrate that
the up-regulation of this isoform was responsible for the increased Ca
2+
leak and the lowered [Ca
2+
]
ER
in PS DKO cells. Finally, we show that
the decreased [Ca
2+
]
ER
in PS DKO cells was protective against apoptosis.
© 2006 Elsevier Ltd. All rights reserved.
Keywords: Presenilin; Ca
2+
leak; Inositol 1,4,5-trisphosphate receptor
1. Introduction
The majority of early-onset, autosomal-dominant familial
cases of Alzheimer’s disease (AD) is caused by mutations in
the presenilin genes (PS1 and PS2). PS1 and PS2 are highly
conserved pleiotropic proteins, localized predominantly in
the endoplasmic reticulum (ER). Presenilins form a multi-
protein complex with nicastrin, APH-1 and PEN-2 and are
responsible for -secretase activity [1]. Mutations in the PS
lead to a gain of function and thereby to an altered -secretase
mediated cleavage of -amyloid precursor protein (APP)
∗
Corresponding author. Tel.: +32 16 345725; fax: +32 16 345991.
E-mail address: Humbert.Desmedt@med.kuleuven.be (H. De Smedt).
1
Both authors contributed equally to this work.
resulting in increased production of neurotoxic amyloid -
peptide (A). A second less understood cellular effect of PS
mutations is the dysregulation of intracellular Ca
2+
signaling
pathways, which was observed in a variety of experimental
systems [2–5].
These changes in Ca
2+
signaling may be highly relevant
for the pathogenesis of AD, since Ca
2+
dysregulation can con-
tribute to several key features of AD, including increased A
production [6,7], hyperphosphorylation of tau [8], enhanced
vulnerability to cell death [5,9], and even memory-related
deficits [10].
The ER contains two main types of Ca
2+
-release channels,
the inositol 1,4,5-trisphosphate receptors (IP
3
R, ∼300 kDa)
and the ryanodine receptors (RyR, ∼565 kDa), each rep-
resented by three different isoforms with similar structural
0143-4160/$ – see front matter © 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.ceca.2006.03.005