Subject: Alzheimer’s prevention role discovered for prions
Date: June 29, 2007 at 6:38 pm PST
Alzheimer’s prevention role discovered for prions
30 June 2007
A role for prion proteins, the much debated agents of mad cow disease and
vCJD, has been identified. It appears that the normal prions produced by the
body help to prevent the plaques that build up in the brain to cause
Alzheimer’s disease. The possible function for the mysterious proteins was
discovered by a team of scientists led by Medical Research Council funded
scientist Professor Nigel Hooper of the University of Leeds.
Alzheimer’s and diseases like variant Creutzfeldt-Jakob Disease follow
similar patterns of disease progression and in some forms of prion disease
share genetic features. These parallels prompted Professor Hooper’s team to
look for a link between the different conditions. They found an apparent
role for normal prion proteins in preventing Alzheimer’s disease.
‘‘Our experiments have shown that the normal prion proteins found in brain
cells reduce the formation of beta-amyloid, a protein that binds with others
to build plaques in the brain that are found in Alzheimer’s disease,’’
explains Professor Hooper.
He continues: ‘‘In vCJD, the normal version of prion protein, PrPc, found
naturally in the brain is corrupted by infectious prions to cause disease.
The normal function of PrPc has been unclear.’’
Using cells grown in the lab, the team looked at the effect of high and low
levels of normal prion protein on the successful formation of beta amyloid,
the source of Alzheimer’s plaques. They found that beta amyloid did not form
in cells with higher than usual levels of PrPc. In comparison, when the
level of PrPc was low or absent, beta amyloid formation was found to go back
up again.
Mice genetically engineered to lack PrPc were also studied. Again, this
revealed that in its absence, the harmful beta-amyloid proteins were able to
form.
It appears that PrPc, the normal prion protein, exerts its beneficial effect
by stopping an enzyme called beta-secretase from cutting up amyloid protein
into the smaller beta-amyloid fragments needed to build plaques.
Further evidence for the protective role of normal prion proteins is
provided by mutated versions that are linked to genetic forms of prion
disease because beta-amyloid fragments are able to form when the normal
prion protein is corrupted by genetic mutation.
Professor Hooper concludes:
‘‘Until now, the normal function of prion proteins has remained unclear, but
our findings clearly identify a role for normal prion proteins in regulating
the production of beta-amyloid and in doing so preventing formation of
Alzheimer’s plaques. Whether this function is lost as a result of the normal
ageing process, or if some people are more susceptible to it than others we
don’t know yet.’’
‘‘The next step for our research will be to look in more detail at how the
prion protein controls beta amyloid, knowledge that could be used to design
anti-Alzheimer’s drugs. Theoretically, if we can find a way of mimicking the
prion’s function we should be able to halt the progress of Alzheimer’s.
However, there’s still a lot of work to be done in looking at levels of
prions in the human system and how these may alter as we age.”
Original research paper: ‘Cellular prion protein regulates ß- secretase
cleavage of the Alzheimer’s amyloid precursor protein’ is published in the
Proceedings of the National Academy of Sciences USA.
Press contact
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http://www.mrc.ac.uk/consumption/gro.../mrc003835.pdf
Published online before print June 15, 2007
Proc. Natl. Acad. Sci. USA, 10.1073/pnas.0609621104
Neuroscience
Cellular prion protein regulates -secretase cleavage of the Alzheimer's
amyloid precursor protein
www.pnas.org/cgi/doi/10.1073/pnas.0609621104
http://www.pnas.org/cgi/content/abst...9621104v1?etoc
Subject: Inactivation of amyloid-enhancing factor (AEF): study on
experimental murine AA amyloidosis
Date: June 24, 2007 at 1:11 pm PST
Masatoshi Omoto · Tadaaki Yokota · Dan Cui
Yoshinobu Hoshii · Hiroo Kawano · Toshikazu Gondo
Tokuhiro Ishihara · Takashi Kanda
Inactivation of amyloid-enhancing factor (AEF): study on experimental
murine AA amyloidosis
Abstract It is known that amyloid-enhancing factor (AEF)
shortens the preamyloid phase in experimentally induced
AA amyloidosis in mice. Because it is reported that AEF
serves as both a nidus and a template for amyloid formation,
AA amyloidosis may have transmissibility by a prionlike
mechanism. It has been shown that amyloid fi brils also
have AEF activity, and amyloid fi brils with AEF activity
were named fi bril-amyloid enhancing factor (F-AEF). In
this study, we investigated methods to inactivate the AEF
activity. AEF was extracted from the thyroid gland obtained
at autopsy of a patient with AA amyloidosis. Before
injection into mice, AEF was treated with several methods
for inactivation. Of all the tested treatments, 1 N NaOH,
0.1 N NaOH, and autoclaving consistently demonstrated
complete inactivation of AEF. Heat treatment led to incomplete
inactivation, but 0.01 N NaOH, 0.001 N NaOH,
pepsin, trypsin, pronase, and proteinase K treatment had
no effect on AEF activity. By analysis with transmission
electron microscopy, the AEF preparation contains amyloid
fi brils, and a change of ultrastructure was shown after
1 N NaOH, 0.1 N NaOH, and autoclaving treatment. Furthermore,
immunoblotting of AEF with antihuman AA
antibody revealed that the protein band was scarcely found
after autoclaving, 1 N NaOH, and 0.1 N NaOH treatment.
Our results suggest that, similar to Creutzfeldt–Jakob
M. Omoto (*) · T. Kanda
Department of Neurology and Clinical Neuroscience, Yamaguchi
University School of Medicine, 1-1-1 Minamikogushi, Ube City,
Yamaguchi 755-8505, Japan
Tel. +81-836-22-2719; Fax +81-836-22-2364
e-mail:
omoto-path@umin.ac.jp
T. Yokota
Department of Pathology, Kokura Memorial Hospital, Yamaguchi,
Japan
D. Cui · Y. Hoshii · H. Kawano · T. Ishihara
Department of Radiopathological and Science, Yamaguchi
University School of Medicine, Fukuoka, Japan
T. Gondo
Department of Surgical Pathology, Yamaguchi University Hospital,
Yamaguchi, Japan
disease (CJD), amyloidosis may require chemical or autoclaving
decontamination.
Key words Amyloid-enhancing factor · Amyloidosis ·
Creutzfeldt–Jakob disease · Prion · Transmission electron
snip...
Discussion
Secondary amyloidosis occurs in individuals with longstanding
infl ammatory diseases. Since the incidence of
chronic infl ammatory diseases such as tuberculosis and leprosy
has decreased in recent years, rheumatoid arthritis
(RA) is now the most common disease involving secondary
AA amyloidosis, especially in elderly patients with a long
history of RA. Autopsy studies indicate that the incidence
of secondary amyloidosis in RA patients may be between
20% and 25%.21 Generally, treating the underlying disease
is the conventional approach in AA amyloidosis, because
no specifi c treatment exists. It is not yet certain whether
preventing amyloid proteins from aggregating will be therapeutically
beneficial.
An essential factor for the development of AA amyloidosis
is a continual high plasma concentration of SAA.
However, it is still unclear why only a subset of such individuals
develops AA amyloidosis. Therefore, in addition to
high concentrations of an amyloidogenic protein, other
factors are thought to be necessary in the pathogenesis of
AA amyloidosis. AEF is thought to be one of the essential
factors for the development of amyloidosis, although the
mechanism responsible for the formation of amyloid fi brils
is still unclear. Many studies have identifi ed that AEF activity
is a large macromolecular complex, and all tissue extracts
studied to date appear to contain glycoprotein with
an approximate size of 10–15 kD.4,22–24
Most strains of mice are susceptible to developing AA
amyloid deposition following chronic administration of
infl ammatory stimuli such as casein or azocasein.25 The
prolonged preamyloid phase in experimentally induced AA
amyloidosis can be dramatically shortened by intravenous
or intraperitoneal administration of AEF with the infl am-
matory stimuli.2–4 All mice that were exposed to AEF and
injected with silver nitrate developed amyloidosis by day
7.16 Amyloid fi brils extracted from different types of amyloidosis
from a wide variety of species display biologically
similar AEF activity to that in experimental animals. In fact,
Niewold et al.26 showed that intravenous and intraperitoneal
injection of hamster AA amyloid fi brils, bovine AA
amyloid fi brils, and human light chain-derived (A?) amyloid
fi brils markedly accelerated hamster amyloidosis.
The AEF activity found in the amyloid fi bril preparation
was named F-AEF.6 Furthermore, intravenous injection
of amyloid-like fi brils made from synthetic peptides of
transthyretin27 or denatured silk28 accelerates murine AA
amyloidosis. By double immunogold labeling and microautoradiographic
methods, Johan et al. reported that intravenously
administered, radiolabeled, heterologous,
amyloid-like, synthetic fi brils reached the lung and spleen,
accelerated amyloidosis, and were associated with topographical
deposition of murine protein AA fi brils in the recipient
mouse.29
Drastic structural changes of amyloid protein from the
normal and soluble forms to the unique ß-sheet fi brils may
be the most important event in amyloidosis. Recently, it was
reported that AEF serves as both a nidus and a template
for amyloid formation,8 and AA amyloidosis may show
transmissibility as a prion-like mechanism.9 Johan et al. also
suggested that amyloid-like synthetic fi brils had a nidus activity,
29 and amyloid-enhancing activity may occur through
the mechanism of amyloid-like fi brils serving as seed for
fi bril formation. Moreover, by using the method of negative
staining with TEM, electron micrographs of amyloid fi brils
were observed under some conditions. O’Nuallain et al.
revealed that electron micrographs of islet amyloid polypeptide
showed aggregates initially and then grew into fi bril
formations after incubation.30 In contrast, Santhoshkumar
et al. revealed that, using TEM, amyloid ß-peptide showed
signifi cantly decreased fi bril formation and some amorphous
aggregates after incubation with aA-crystallin in
their in vitro study.31 They suggested that aA-crystallin had
the ability to inhibit amyloid fi bril formation. Similarly, in
our study, electron micrographs of F-AEF revealed some
amorphous aggregates after autoclaving, 1 N NaOH, and
0.1 N NaOH treatment and short and transformed fi brils
after heat treatment. Furthermore, immunoblotting of AEF
with antihuman AA antibody revealed that a protein band
was scarcely found after autoclaving, 1 N NaOH, and 0.1 N
NaOH treatments and that weak protein bands were found
after heat treatment. We suggested that these results indicated
the activity of F-AEF disappeared after autoclaving,
1 N NaOH, and 0.1 N NaOH treatments and that the activity
of F-AEF was decreased after heat treatment.
Prion diseases are associated with the accumulation of a
conformational isomer (PrPSc) of host-derived prion protein
(PrPC), and PrPSc forms amyloid fi brils. The exogenous abnormal
form of the prion protein is generally regarded as a
seed that promotes the association of cellular proteins.
Prions are very resistant to inactivation, and accidental
transmission has occurred through the use of inadequate
decontamination procedures.
In our experiments with mice, the activity of F-AEF was
markedly decreased after autoclaving treatment under conditions
of 132°C for 1 h and 1 N NaOH and 0.1 N NaOH
treatment for 1 h. For CJD materials, the Committee on
Health Care Issues of the American Neurological Association
recommended treatment with 1 N NaOH as a standard
sterilization procedure.18 Heat treatment led to substantial
but incomplete inactivation in this study. The Committee
on Health Care Issues of the American Neurological Association
reported that boiling was an ineffective procedure
for CJD tissues and contaminated materials.18 Tateishi et al.
showed that heat treatment with SDS was effective.17
The acceleration of amyloid deposition may be a primary
event in disease, CJD, bovine spongiform encephalopathy
(BSE), familial amyloid polyneuropathy, and AA and
human senile systemic amyloidosis.32 Walker et al. reported
Aß amyloid extracted from an Alzheimer disease brain may
have potential of prion protein.33
The property described for F-AEF is similar to that
of prion reported in CJD. Chemical or autoclaving decontamination
for CJD is necessary for most items associated
with surgery or autopsy.34 We suggest that amyloidosis may
need chemical or autoclaving decontamination similar to
CJD.
Acknowledgments We thank Mr. Jitsuo Kashitani for excellent technical
assistance. This work was supported by a grant from the Intractable
Disease Division, the Ministry of Health and Welfare, a Research
Committee for Epochal Diagnosis and Treatment of amyloidosis in
Japan, and a Research Committee for amyloidosis.
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