Mechanisms of calpain mediated proteolysis of voltage gated sodium channel α-subunits following in vitro dynamic stretch injury
Article first published online: 12 APR 2012
© 2012 The Authors. Journal of Neurochemistry © 2012 International Society for Neurochemistry
Journal of Neurochemistry
Volume 121, Issue 5, pages 793–805, June 2012
How to Cite
von Reyn, C. R., Mott, R. E., Siman, R., Smith, D. H. and Meaney, D. F. (2012), Mechanisms of calpain mediated proteolysis of voltage gated sodium channel α-subunits following in vitro dynamic stretch injury. Journal of Neurochemistry, 121: 793–805. doi: 10.1111/j.1471-4159.2012.07735.x
- Issue published online: 1 MAY 2012
- Article first published online: 12 APR 2012
- Accepted manuscript online: 19 MAR 2012 05:08AM EST
- Received December 21, 2011; revised manuscript received March 1, 2012; accepted March 2, 2012.
- NMDA receptor;
- sodium channel;
- traumatic brain injury
J. Neurochem. (2012) 121, 793–805.
Although enhanced calpain activity is well documented after traumatic brain injury (TBI), the pathways targeting specific substrate proteolysis are less defined. Our past work demonstrated that calpain cleaves voltage gated sodium channel (NaCh) α-subunits in an in vitro TBI model. In this study, we investigated the pathways leading to NaCh cleavage utilizing our previously characterized in vitro TBI model, and determined the location of calpain activation within neuronal regions following stretch injury to micropatterned cultures. Calpain specific breakdown products of α-spectrin appeared within axonal, dendritic, and somatic regions 6 h after injury, concurrent with the appearance of NaCh α-subunit proteolysis in both whole cell or enriched axonal preparations. Direct pharmacological activation of either NMDA receptors (NMDArs) or NaChs resulted in NaCh proteolysis. Likewise, a chronic (6 h) dual inhibition of NMDArs/NaChs but not L-type voltage gated calcium channels significantly reduced NaCh proteolysis 6 h after mechanical injury. Interestingly, an early, transient (30 min) inhibition of NMDArs alone significantly reduced NaCh proteolysis. Although a chronic inhibition of calpain significantly reduced proteolysis, a transient inhibition of calpain immediately after injury failed to significantly attenuate NaCh proteolysis. These data suggest that both NMDArs and NaChs are key contributors to calpain activation after mechanical injury, and that a larger temporal window of sustained calpain activation needs consideration in developing effective treatments for TBI.