Microtubule and F -actin interaction in the cytoskeletal system of non-mammalian erythrocytes and thrombocytes.
Item
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Title
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Microtubule and F -actin interaction in the cytoskeletal system of non-mammalian erythrocytes and thrombocytes.
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Identifier
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AAI3144110
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identifier
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3144110
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Creator
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Lee, Kyeng Gea.
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Contributor
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Adviser: William D. Cohen
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Date
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2004
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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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Biology, Cell
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Abstract
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Interaction between microtubules and actin filaments may be crucial for common cell processes such as cytokinesis and for the specific functions of differentiated cells. Microtubules and actin filaments are known to have different mechanical properties, and proper distribution of these elements can provide cells with distinctive characteristics. This work focuses on functional and structural interaction of microtubules and actin filaments in nucleated erythrocytes and thrombocytes. The cytoskeleton of the nucleated erythrocytes contains a peripheral or marginal band of microtubules responsible for cell shape maintenance. Confocal fluorescence microscopy shows that the marginal band colocalizes with a band of F-actin in non-mammalian vertebrate erythrocytes. Functionally, the F-actin band is implicated in maintaining the ellipsoidal shape of the marginal band as revealed by studies using proteases. Also, hyperstabilization of the F-actin band protects against low temperature-induced disassembly of marginal band microtubules, showing that microtubule stability in the marginal band is dependent on the F-actin band. Studies using pointed erythrocytes, induced by temperature cycling, show that hyperstabilization of the F-actin band reduces the number of pointed cells generated. Since these cells contain pointed or fractured marginal bands, this indicates that increased stabilization of the F-actin band increases stability of the marginal band. In contrast, thrombocytes exhibit a different form of microtubule and F-actin interaction. In unactivated thrombocytes, which are flattened, ovoid cells, marginal band microtubules colocalize with a band of F-actin in a pattern similar to that of erythrocytes, except that the F-actin band is thinner and localized only at the periphery. Unlike erythrocytes, thrombocytes undergo drastic shape changes when activated by various stimuli. In activated thrombocytes with altered shape, typical F-actin-microtubule colocalization in the marginal band is lost, and F-actin has an outward distribution while microtubules remain central, possibly remodeling the nucleus. Functionally, marginal band microtubules in unactivated thrombocytes are found to be cold labile and their disappearance alters cell shape. Pre-exposure of unactivated thrombocytes to F-actin disassembly-promoting agents blocks normal activation-induced shape change. These findings indicate that thrombocyte microtubules are responsible for maintaining unactivated cell shape, while F-actin is the major driving force for post-activational cell shape changes.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
