Brain injury-induced proteolysis is reduced in a novel calpastatin-overexpressing transgenic mouse

Authors

  • Kathleen M. Schoch,

    1. Spinal Cord and Brain Injury Research Center and Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky, USA
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  • Catherine R. von Reyn,

    1. Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania, USA
    2. Janelia Farm Research Campus HHMI, Ashburn, Virginia, USA
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  • Jifeng Bian,

    1. Prion Research Center (PRC), Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, USA
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  • Glenn C. Telling,

    1. Prion Research Center (PRC), Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, USA
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  • David F. Meaney,

    1. Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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  • Kathryn E. Saatman

    Corresponding author
    • Spinal Cord and Brain Injury Research Center and Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky, USA
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Address correspondence and reprint requests to Kathryn E. Saatman, Spinal Cord and Brain Injury Research Center (SCoBIRC), University of Kentucky, B473 Biomedical and Biological Sciences Research Building (BBSRB), 741 South Limestone Street, Lexington, KY 40536-0509, USA. E-mail: k.saatman@uky.edu

Abstract

The calpain family of calcium-dependent proteases has been implicated in a variety of diseases and neurodegenerative pathologies. Prolonged activation of calpains results in proteolysis of numerous cellular substrates including cytoskeletal components and membrane receptors, contributing to cell demise despite coincident expression of calpastatin, the specific inhibitor of calpains. Pharmacological and gene-knockout strategies have targeted calpains to determine their contribution to neurodegenerative pathology; however, limitations associated with treatment paradigms, drug specificity, and genetic disruptions have produced inconsistent results and complicated interpretation. Specific, targeted calpain inhibition achieved by enhancing endogenous calpastatin levels offers unique advantages in studying pathological calpain activation. We have characterized a novel calpastatin-overexpressing transgenic mouse model, demonstrating a substantial increase in calpastatin expression within nervous system and peripheral tissues and associated reduction in protease activity. Experimental activation of calpains via traumatic brain injury resulted in cleavage of α-spectrin, collapsin response mediator protein-2, and voltage-gated sodium channel, critical proteins for the maintenance of neuronal structure and function. Calpastatin overexpression significantly attenuated calpain-mediated proteolysis of these selected substrates acutely following severe controlled cortical impact injury, but with no effect on acute hippocampal neurodegeneration. Augmenting calpastatin levels may be an effective method for calpain inhibition in traumatic brain injury and neurodegenerative disorders.

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