Hyper-activation of N-methyl-D-aspartate receptors (NRs) is associated with excitotoxic cell death during secondary injury following traumatic brain injury (TBI). The efficiency of the NR is dependent on the location of receptors in membrane raft microdomains that provide a platform for coupling of NRs and effector proteins. In many neurodegenerative diseases, activation of the autophagy pathway has been suggested to contribute to glutamate excitotoxicity, but whether increased autophagy signaling contributes to pathology after TBI has not been defined. In these studies, I investigate whether membrane rafts mediate NR signaling and autophagy in cortices of adult male rats subjected to moderate TBI and in sham-operated controls. These studies demonstrate that membrane rafts of the normal rat cortex contain a novel multi-protein signaling complex that links the NR2B glutamate receptor and the autophagic protein Beclin 1. TBI caused a rapid disruption of this complex in which NR2B and pCaMKII were recruited to membrane microdomains. Alteration in NR2B-Beclin 1 association in membrane rafts resulted in activation of autophagy as demonstrated by increased expression of key autophagic proteins Beclin 1, ATG 5 and ATG 7, and significant increases in autophagic vacuoles in neurons of traumatized brains. Administration of the NR2B antagonist RO 25-6981 significantly blocked TBI-induced redistribution of NR2B signaling intermediates and Beclin 1 and delayed the increase in autophagy protein expression in traumatized cortices. Thus, stimulation of autophagy by NR2B signaling may be regulated by redistribution of Beclin 1 in membrane rafts after TBI.
| Identifer | oai:union.ndltd.org:UMIAMI/oai:scholarlyrepository.miami.edu:oa_dissertations-1203 |
| Date | 08 April 2009 |
| Creators | Bigford, Gregory E. |
| Publisher | Scholarly Repository |
| Source Sets | University of Miami |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Open Access Dissertations |
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