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The Nucleocytoplasmic Shuttling of Thyroid Hormone Receptor [alpha] in Neuronal and Non-Neuronal Cell Lines
Powers, Jeremy Michael
Powers, Jeremy Michael
Abstract
Thyroid hormone receptor-alpha (TRalpha) functions in the nucleus as a transcription factor. Prior studies in non-neuronal cells have established that TRalpha shuttles rapidly between the nucleus and the cytoplasm; however, the physiological significance of shuttling remains unknown. TRalpha plays an essential role in the growth, development and function of the nervous system, thus neuronal cells provide an important model system for studying TRalpha shuttling. To better understand the properties of TRalpha shuttling in neuronal and non-neuronal cell lines, we compared the intracellular localization of full-length TRalpha, individual TRalpha domains, and domain combinations. The four functional domains of TRalpha are the transactivation (A/B) domain which contains a novel nuclear localization sequence (NLS), the DNA-binding domain (DBD), the hinge domain (HD) which contains a classical bipartite NLS, and the ligand-binding domain (LBD). Expression vectors for green fluorescent protein (GFP) tagged individual and combination domains and GFP-tagged full-length TRalpha were transiently transfected into non-neuronal and neuronal cell lines. Fusion protein distribution patterns were visualized by fluorescence microscopy and scored for a nuclear, cytoplasmic or whole cell distribution. We found that the A/B and HD have NLS activity in both non-neuronal and neuronal cell lines but that the HD is likely to contain a stronger signal for import. The most distinct cell-type specific difference in localization was a shift to the cytoplasm with these domains in neuronal cells. In all cell lines, the DBD was found to shift the A/B domain to the nucleus but shift the HD to the cytoplasm. The LBD of TRalpha showed strong export activity, as it completely reversed the nuclear localization of the HD alone in all cell lines. Our findings suggest that there are differences in TRalpha localization between non-neuronal and neuronal cell lines, possibly providing an example of transcription factor regulation by compartmentalization.
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Thesis is part of Honors ETD pilot project, 2008-2013. Migrated from Dspace in 2016.
Date
2009-05-17
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Keywords
Thyroid hormones, Nuclear receptors, Nucleocytoplasmic shuttling, Gene regulation
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Department
Neuroscience