Defense Date

2005

Document Type

Thesis

Degree Name

Master of Science

Department

Anatomy & Neurobiology

First Advisor

Dr. Thomas M. Reeves

Abstract

The ankyrins comprise a family of proteins serving as components of the membrane cytoskeleton, and participate in a diverse set of associations with multiple binding partners including the cytoplasmic domains of transporters, ion channels, some classes of receptors, and cell adhesion proteins. Moreover, evidence is accumulating that ankyrin participates in defining functionally distinct subcellular regions. The complex functional and structural roles of ankyrins indicate they are likely to play essential roles in the pathology of traumatic axonal injury. The current study examined changes in ankyrin-G expression following a moderate central fluid percussion injury administered to adult rats. At 1d, 3d, and 7d postinjury (or following a sham control injury), protein levels of ankyrin-G in the corpus callosum and cerebral cortex were assessed using Western Blot analysis. Three immunopositive bands were identified in both brain regions as 220,212, and 75 kD forms of ankyrin-G. Time-dependent changes in ankyrin-G were observed in the corpus callosum. At 1d injury-induced elevations were observed in the callosal 220 kD (+147% relative to sham levels) and in the 212 kD (+73%) forms of ankyrin-G, but in both cases the expression decreased to control levels by 3d and 7d. In contrast, the 75 kD form showed moderate increases at 1d postinjury, but was significantly below control levels at 3d (-54%) and at 7d (-41%). Ankyrin-G expression in the cerebral cortex was only slightly affected by the injury, with a significant decrease in the `220 kD form occurring between 1d and 3d. These data suggest that the 220 and 212 kD changes probably represent postinjury proteolytic fragments derived from intact ankyrin-G isoforms of 480 andor 270 kD, while the 75 kD effects are likely breakdown products of intact 190 kD ankyrin-G. These results were discussed as they relate to prior findings of differential vulnerabilities of callosal myelinated and unmyelinated axons to injury. In this context, the 220,212 kD changes may reflect pathology within myelinated axons, and alterations to the 75 kD form may reflect more persistent pathology affecting unmyelinated callosal fibers.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

June 2008

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