Up-regulation of tissue-type transglutaminase after traumatic brain injury

Tissue-type transglutaminase (tTG, EC 2.3.2.13) has been implicated in various disease paradigms including neurodegenerative disease. In these studies, tTG induction after traumatic brain injury was studied using a rat cortical impact model. Using western blots, two forms of tTG protein expression were identified--an approximately 79-kDa primary form (tTG-L) and a less abundant approximately 70-kDa form (tTG-S). Both forms of tTG protein were elevated after injury. In ipsilateral cortex, peak induction of tTG-L protein [561% +/- 80% of control (n = 5)] was observed five days after injury, with expression remaining elevated after two weeks. Peak induction of tTG-S protein [302% +/- 81% of control (n = 5)] was observed three days after injury. Lesser tTG protein induction was observed in hippocampus. Northern blot analysis demonstrated two tTG transcripts in the ipsilateral cortex with peak induction of tTG-L mRNA three days after injury. However, tTG-S mRNA was not identified in control samples and only faintly detected in injured tissue. To facilitate analysis of low abundance transcripts in smaller tissue samples, a semiquantitative real-time PCR strategy was used. Semi-quantitative PCR analysis of tTG-L mRNA induction in ipsilateral cortex (peak after three days; 414% +/- 21% of control, n = 3) confirmed tTG-L mRNA induction determined by northern blot (410% of control).