Effect of Tau Hyperphosphorylation on Cellular Pathology
Item
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Title
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Effect of Tau Hyperphosphorylation on Cellular Pathology
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Identifier
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d_2009_2013:8f328bf9bec1:11494
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identifier
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12003
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Creator
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Corbo, Christopher P.,
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Contributor
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Alejandra del C. Alonso
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Date
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2012
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Language
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English
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Publisher
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City University of New York.
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Subject
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Cellular biology | Neurosciences | actin | Alzheimer's disease | importin | microtubules | neurodegeneration | tau
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Abstract
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Hyperphosphorylation of the microtubule associated protein tau is shown to be involved in several dementias that classify as tauopathies. In these diseases, tau is known to bind to itself rather than associate with microtubules. When CHO cells express wild type tau, the microtubule network is healthy and shows normal microtubule movement and tau associated with the microtubules. When expressing pathological human tau (PH-tau, pseudophosphorylated at T212, T231, S262),however, PH-tau is present throughout the cytoplasm, rather than associated with microtubules. The cells exhibit excessive membrane blebbing in order to remove PH-tau. This blebbing leads to a shrinkage of PH-tau expressing cells. Internally the presence of excessive cytoplasmic vacuoles and aggregated PH-tau in the form of filaments are found. The exposure of wild type expressing cells to okadaic acid shows the same pathologies. Additionally, all three sites used in the PH-tau construct are phosphorylated when wild type tau is exposed to okadaic acid.;Tau interacts with actin as well as with microtubules. PH-tau seems to cause a major breakdown in the F-actin structure within the cells. These cells appear to be either totally void of F-actin or have F-actin forming punctate spots within the cells. This actin breakdown is also occurs in wild type tau expressing cells treated with okadaic acid. The CUNY CSI Computer Science Department is working in collaboration to develop ImageJ plugins to quantify the amount of F-actin and the length of individual F-actin filaments. This work demonstrates that when PH-tau is expressed, the level of tau is inversely proportional to the level of F-actin in the cells. Interestingly, the level of total actin does not change between wild type tau and PH-tau expressing cells, suggesting that this lack of F-actin does not change expression, but rather interferes with its polymerization.;When CHO cells are transfected with PH-tau, this protein can be found in the nucleus of the cells. We found a nuclear localization signal that allows the chaperon protein importin to bind to tau. To see if this site was responsible for the translocation of tau into the nucleus, we eliminated importin's binding site through site directed mutagenesis of the full-length tau gene. The elimination of the importin binding site inhibited tau from being able to translocate into the nucleus but did not stop any of the pathologies seen previously.
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Type
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dissertation
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Source
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2009_2013.csv
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degree
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Ph.D.
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Program
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Biology
