Abstract
The role of calpain in voltage gated sodium channel proteolysis after an in-vitro stretch injury
Journal of neurotrauma, v 24(7), pp 1252-1252
01 Jul 2007
Abstract
The voltage gated sodium channel has been shown to play an integral role after axonal stretch injury, leading to rapid increases in axoplasmic calcium. Here we investigate the proteolysis of the voltage gated sodium channel by two proteases shown to be activated following traumatic brain injury, calpain and caspase 3.Voltage gated sodium channel proteolysis was investigated by (1) using an in-vitro stretch model of dissociated cortical cultures that mimics the mechanics of in-vivo traumatic brain injury, by (2) activating calpain or caspase 3 in adult rat brain homogenates, and by (3) increasing cytoplasmic Ca2concentration with the ionophore ionomycin or the mitochondrial membrane uncoupler FCCP. Following injury or treatment, lysates were probed for both the full length and proteolytic fragments of the sodium channel using immunoblotting. In the stretch in-jury model, proteolysis of the voltage gated sodium channel appeared six hours following a 60-80% strain (n3). Elevated Ca2to activate calpain in whole rat brain homogenates and FCCP or ionomycin treatment on dissociated cortical cultures all lead to sodium channel proteolysis that could be blocked with the calpain inhibitor MDL28170 (n4). Conversely, active caspase 3 did not lead to voltage gated sodium channel proteolysis in rat brain homogenates (n2). Many membrane bound proteins have been shown to be targets of the Ca2regulatedprotease calpain, including the NMDA receptor and voltage gated calcium channels, and this proteolysis results in changes in regulation, kinetics, and signaling pathways directed by the membrane proteins. Our data indicates that proteolysis of the voltage gated sodium channel can occur in rat brain homogenates, dissociated cortical cultures, and following stretch injury. Proteolysis can be prevented by blocking calpain activation, suggesting that the immediate increases in axoplasmic calcium after stretch injury can lead to a rapid proteolysis of the voltage gated sodium channel. Due to the integral role of the voltage gated sodium channel for neurotransmission, this suggests that calpain can play a significant role in rapidly changing functional properties of the axon (e.g., conduction velocity, speed) after injury.
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Details
- Title
- The role of calpain in voltage gated sodium channel proteolysis after an in-vitro stretch injury
- Creators
- Catherine R von Reyn - University of PennsylvaniaDavid F. Meaney - University of Pennsylvania
- Publication Details
- Journal of neurotrauma, v 24(7), pp 1252-1252
- Conference
- 25th Annual National Neurotrauma Society Symposium, 25th (Kansas City, Missouri, United States, 29 Jul 2007–01 Aug 2007)
- Publisher
- Mary Ann Liebert, Inc
- Number of pages
- 1
- Resource Type
- Abstract
- Language
- English
- Academic Unit
- School of Biomedical Engineering, Science, and Health Systems
- Other Identifier
- 991019520115304721