Peptides 31 (2010) 1866–1872
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Peptides
journal homepage: www.elsevier.com/locate/peptides
Development of retro-inverso peptides as anti-aggregation drugs for -amyloid
in Alzheimer’s disease
Balpreet Matharu
a
, Omar El-Agnaf
b
, Amna Razvi
a
, Brian M. Austen
a,∗
a
Neurodegeneration Unit, Basic Medical Sciences, St George’s, University of London, Cranmer Terrace, London SW17 0RE, UK
b
Department of Biochemistry, Faculty of Medicine and Health Sciences, United Arab Emirates University, P.O. Box 17666 Al-Ain, United Arab Emirates
article info
Article history:
Received 13 April 2010
Received in revised form 29 June 2010
Accepted 29 June 2010
Available online 13 July 2010
Keywords:
-Amyloid
Alzheimer’s disease
Aggregation
abstract
Alzheimer’s disease (AD) is a devastating degenerative disorder of the brain for which there is no cure
or effective treatment. There is much evidence to suggest that -amyloid protein (A) aggregation in
the brain leading to deposits is an important step in the development of AD. Recently, two peptides,
RGKLVFFGR (OR1) and RGKLVFFGR–NH
2
(OR2) containing the sequence KLVFF, which is the central region
(residues 16–20) of A, have been found to be potent inhibitors of A aggregate formation. Here we report
that retro-inversion of these sequences increases efficacy of the peptides in the inhibition of aggregation
and toxicity of -amyloid. We describe the synthesis and inhibitory properties of these retro-inverso
peptides.
© 2010 Elsevier Inc. All rights reserved.
1. Introduction
There is considerable accumulated evidence that the deposition
of -amyloid protein (A) in the brain is a cause of the cogni-
tive decline seen in Alzheimer’s disease (AD). The aggregation of
monomeric A into larger oligomeric and fibrillar forms is seen as
an important step in the development of pathology and cognitive
loss. It seems increasingly likely that early, soluble oligomers are
actually the toxic species responsible for neurodegeneration and
neuronal cell death [18]. The soluble oligomeric A is now known to
block synaptic plasticity required for memory formation, particu-
larly in the hippocampus, where neuronal loss is seen as the disease
progresses [18]. These findings have lead to the hypothesis that
small molecules which can block, slow down or reverse A aggre-
gation, particularly in its early stages, might provide an attractive
therapeutic approach for targeting the underlying disease progres-
sion of AD. It has been shown in vitro that synthetic A peptide
readily aggregates from solution into fibrils with a crossed -sheet
conformation. Coincident with the conversion of monomeric A
to the fibrillar forms is a transition from random coil to -sheet
Abbreviations: A, amyloid peptide; AD, Alzheimer’s disease; ELISA, enzyme-
linked immunosorbent assay; MTT, methylthiazoletetrazolium; PBS, phosphate
buffered saline; Tris, Tris(hydroxymethyl)amino-methane; LDH, lactate dehydro-
genase; BSA, bovine serum albumin; TMB, 3,3,5,5-tetramethylbenzidine; BBB,
blood–brain barrier.
∗
Corresponding author. Tel.: +44 2087255651; fax: +44 2087255651.
E-mail addresses: Balpreet@doctors.org.uk (B. Matharu),
sgk200@sgul.ac.uk (B.M. Austen).
structure [16].A is amphiphilic, with a hydrophilic N-terminus
and hydrophobic C-terminus; the length of the latter affects the
rate of aggregate formation [4]. The short hydrophobic stretch at
residues 16–20 (the sequence KLVFF) in the central portion of A
appears to be critical for its aggregation [17]. The fact that A is a
natively unfolded peptide, which has little or no ordered structure
under normal physiological conditions, makes the rational design
of compounds that can stabilize the native, non-toxic conformation
of A a challenging task. However, researchers have been success-
fully able to design small modified synthetic peptides based on
the hydrophobic central region (residues 16–20) of A that can
prevent its aggregation. Recently, we have designed peptide-based
inhibitors (named OR inhibitors) of A aggregation and toxicity [2].
Our findings have led us to hypothesize that, the OR peptides rep-
resent the starting point for designing peptide inhibitors that are
suitable for chronic therapy and might be used as new drugs for
the treatment of AD. Here we describe retro-inversion of the bind-
ing sequence, as this has been discovered in other systems to lead
to peptides which are stabile to peptidases in cells, and in which
relative orientations of the amino acid side chains are the same as
those in the original sequence [8]. A preliminary report of these
retro-inverso inhibitors has been published [1].
2. Methods
2.1. Peptide synthesis, purification and characterization
A40 and 42, were synthesized and purified by HPLC as
described [4]. Monomeric A40 and A42 [5] were prepared
0196-9781/$ – see front matter © 2010 Elsevier Inc. All rights reserved.
doi:10.1016/j.peptides.2010.06.033