Joey Dominguez
September 3, 2012
Fall 2012
R40, DNA, α1-antichymotrypsin
sDNA Aptamer Selection against α1-antichymotrypsin for the Prevention and Degradation of Senile Plaques and Neurofibrillary Tangles
Tauopathies are neurodegenerative
diseases characterized by the formation of tau protein aggregates, or
neurofibrillary tangles, within nervous cells.
In some tauopathies, as with Alzheimer’s disease, aggregates of protein
fragments, or senile plaques, form between neurons. Though no single protein triggers the formation of tangles and
plaques, alpha1‑antichymotrypsin (ACT) both inhibits amyloid beta’s degradation,
directly leading to the formation of senile plaques, and exists as a secondary
component of these plaques. (Abraham, et.
al 2000; Abraham, et. al. 1988) In addition, elevated levels of ACT have been
shown to induce tau hyperphosphorylation characteristic of Alzheimer’s disease,
arguably the most famous tauopathy. (J. Padmanabhan, et al., 2006) Because of ACT’s clear role in the
development of tauopathies, several studies have identified it as a potential
target for an inhibitory therapeutic mechanism. (Porcellini, et. al, 2008; Padmanabhan, et. al., 2006)
Due to ACT’s ability to bind DNA, ACT
is a prime candidate for the development of an aptamer. Aptamers, nucleic acid oligomers, bind with
high specificity to target molecules, serving as tools for labeling particular
molecules, delivering chemicals to a target molecule, and, ideally, inhibiting
the activity of the target molecule.
Since overexpression of ACT has been linked to major characteristics of
tauopathies, the development of an inhibitory aptamer for ACT could antagonize
the onset and progression of several tauopathies. Aptamers are selected from a pool of
randomized oligomers through the SELEX process which gradually reduces the
variability of the pool until only those aptamers which bind most strongly with
the target molecule under a set of predetermined temperature, pH, and salt
concentration conditions remain. An ssDNA
SELEX process includes binding and selection under predetermined environmental
conditions, asymmetric PCR amplification, and purification. The resulting pool can then be used for
additional rounds of selection.
Specific Aim 1: Aptamer Selection for an Inhibitory Therapy
against ACT
Normally, ACT binds to
serine proteases, serving to protect the respiratory tract from proteolytic enzymes;
its accumulation within the cerebrospinal fluid and nervous system lead to the
formation of tangles and plaques. (Kalsheker, 1996) Inhibiting ACT activity could both prevent the
accumulation of amyloid beta and the hyperphosphorylation of tau, impeding if
not completely halting the formation of both the tangles and plaques.
The selection of an inhibitory aptamer against
ACT could lead to the development of a therapeutic tool which could then be
widely applied to several tauopathies.
Specific Aim 2: Selection and Modification of an Aptamer for ACT Degradation
The
major factor leading to the development of the tangles and plaques is not ACT’s
presence in the nervous system, but rather its accumulation. Even if an inhibitory aptamer against ACT could
not be developed, an ubiquitinated aptamer could bind to excessive ACT and, by
tagging the ACT for degradation, relieve the stresses caused by the
overexpression. In addition, the
ubiquitin tag could serve to reduce the senile plaques since ACT serves as a
component.
ACT can be obtained from Abcam for 1 mg at
$492, costing roughly $2.00 per round of selection. It has a molecular weight of 45 kD. The catalogue number for ACT is ab80517. Abcam can be contacted at 888-772-2226.
Reference
Abraham, Carmela R., et al.
“a1-Antichymotrypsin Inhibits Aß Degradation in Vitro and in Vivo.” Annals
of the New York Academy of Sciences 920 (2000): 245-48. Wiley Online
Library. Web. 03 Sept. 2012.
Abraham, Carmela R., Dennis J. Selkoe,
and Huntington Potter. “Immunochemical identification of the serine protease
inhibitor a1-antichymotrypsin in the brain amyloid deposits of Alzheimer’s
disease.” Cell 52.4 (1988): 487-501. ScienceDirect. Web. 03 Sept.
2012.
Kalsheker, Noor A.
“a1-antichymotrypsin.” The International Journal of Biochemistry & Cell
Biology 28.9 (1996): 961-64. ScienceDirect. Web. 03 Sept. 2012.
Padmanabhan, Jaya, et al.
“Alpha1-antichymotrypsin, an inflammatory protein overexpressed in Alzheimer’s
disease brain, induces tau phosphorylation in neurons.” Brain 129.11
(2006): 3020-34. ingentaconnect. Web. 03 Sept. 2012.
Porcellin, E., et al. “Elevated plasma
levels of alpha-1-anti-chymotrypsin in age-related cognitive decline and
Alzheimer’s disease: a potential therapeutic target.” Curr Pharm Des
14.26 (2008): 2659-64. Abstract. PubMed. Web. 03 Sept. 2012.
1 comment:
Dear Joey,
Here are some suggestions:
1. please include the telephone number for abcam in the budget section
2. include molecular weight in the budget section
,..ordering target now!
We'll talk some more soon!
Gwen
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