The actin cytoskeleton is essential for a vast array of cellular processes and behaviors including migration, cell division, cell adhesion, intracellular trafficking, and maintenance of cell shape. Regulation of cytoskeletal dynamics is achieved through the actions of a diverse group actin-binding proteins. The actin-binding protein Apxl, is a member of the Shroom protein family, which also includes Apx and KIAA1202. Shroom, the most well-characterized member of this family, binds and bundles actin stress fibers and is required for apical constriction of the neuroepithelium during neural tube closure in mice and Xenopus embryos. Apxl was named for its similarity to Apical Protein Xenopus (Apx), a regulator of an amilioride-sensitive sodium channel. All Shrm family members possess at least two of three conserved domains; a N-terminal PDZ domain, a centrally located ASD1 (APX/Shroom Domain) and a C-terminal ASD2 domain. Because of its similarity to Shroom, mouse Apxl was sequenced and cloned in order to begin initial characterization of the protein. Western blot analysis has shown that mAxpl is expressed in the majority of adult tissues. Immunofluorescence analysis of frozen sections has demonstrated that Apxl is specifically expressed in multiple populations of polarized cells, such as the neuroepithelium, vascular endothelium, and the epithelium of renal tubules. The subcellular localization of Apxl was investigated and Apxl was found to reside at the plasma membrane of non-adherent cells and in the apical compartment of polarized cells, possibly through interactions with cortical actin or members of the apical junctional complex. Analysis of Apxl deletion proteins has revealed that the ASD1 domain is crucial for proper localization,while the requirement for the PDZ domain varies in different cell lines. Cytochalasin D treatment of Rat1 fibroblasts has indicated that disruption of the actin cytoskeleton perturbs Apxl localization. Additionally, Apxl directly binds actin through its ASD1 domain in F-actin cosedimentation experiments. Apxl is expressed in multiple polarized cell types where it binds cortical actin and localizes to the apical junctional complex. Although the biological function of Apxl is unknown, its expression pattern, subcellular localization, and similarity to Shroom suggest that Apxl may play a role in regulation of cellular architecture throughout development.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-12062006-154940 |
| Date | 23 January 2007 |
| Creators | Phillips, Jennifer E |
| Contributors | Beth Stronach, PhD, Kirill Kiselyov, PhD, Jeffrey Brodsky, PhD, Jeffrey Hildebrand, PhD |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu/ETD/available/etd-12062006-154940/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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