Axon initial segment (AIS) disruption has been described in a number of pathological environments where neuroinflammation is a contributing factor; however, whether this disruption is reversible in unknown. To address the principle of AIS structural recovery, we employed an acute neuroinflammatory model. Acute neuroinflammation induced disruption of AIS structural and functional domains and, importantly, upon resolution of neuroinflammatory conditions, was reversed.
Consistent with other studies, we observed a close interaction of microglia with AISs, and utilized this acute neuroinflammatory model to investigate the relationship between reactive microglia and AIS integrity. Gene expression analysis of microglial transcription profiles identified reactive oxygen species (ROS)-producing enzymes as candidates in AIS pathogenesis. Experiments employing mice lacking the major ROS-producing enzyme NOX2, identified ROS as mediators of AIS disruption. Furthermore, we established calcium-dependent protease calpain as a disruptor of AIS protein clustering in inflammation-induced disruption.
Since we observed an intimate interaction between microglia and the AIS, we conducted studies designed to identify a candidate in microglia that regulates microglial-AIS contact. During chronic inflammatory conditions, microglia enhance contact with AISs often completely surrounding the domain. Concomitant with this morphological change, neurofascin (Nfasc) expression increased in microglia. Nfasc is a cell adhesion molecule with cell-specific isoforms known to mediate glial-neuronal interactions, but until now, was not reported to be expressed by microglia. Here, I characterize the unique Nfasc isoform expressed by microglia and present evidence that suggests that microglial Nfasc may mediate microglial-AIS contact, a potentially pivotal interaction in the induction of AIS disruption by pro-inflammatory factors.
| Identifer | oai:union.ndltd.org:vcu.edu/oai:scholarscompass.vcu.edu:etd-6468 |
| Date | 01 January 2018 |
| Creators | Benusa, Savannah D |
| Publisher | VCU Scholars Compass |
| Source Sets | Virginia Commonwealth University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
| Rights | © The Author |
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