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Published on: December 14, 2015
Excitotoxin-induced changes in transglutaminase during differentiation of cerebellar granule cells
D Caccamo1, M Currò, G Cusumano
1Department of Biochemical, Physiological and Nutritional Sciences, University of Messina, Policlinico Universitario, Via Consolare Valeria, I-98125 Messina, Italy.
Abstract:
Excitotoxicity induced by NMDA receptor stimulation is able to increase the activity of many enzymes involved in neuronal cell death. Primary cultures of rat cerebellar granule cells were used to elucidate the role of transglutaminase reaction in the excitotoxic cell response, and to evaluate the role of glutamate receptors in cell survival and degeneration. Granule neurons, maintained in vitro for two weeks, were exposed to NMDA at different stages of differentiation. Following NMDA receptor activation, increases in transglutaminase activity were observed in cell cultures. The levels of enzyme activity were higher in cells at 5 days in vitro than in those at 8-9 or 13-14 days in vitro. Moreover, NMDA exposure up-regulated tTG expression in neurons as young as 5 days in vitro. These cultures also exhibited morphological changes with clear apoptotic features. Results obtained demonstrate that susceptibility of granule cells to excitotoxicity depends on the developmental stage of neurons.
Insights
NMDA receptor activation increases transglutaminase activity in developing neurons, leading to excitotoxicity. This enzyme
Area of Science:
- Neuroscience
- Cell Biology
- Biochemistry
Background:
- Excitotoxicity, triggered by NMDA receptor stimulation, is implicated in neuronal cell death.
- The role of transglutaminase (TG) enzymes in excitotoxic responses requires further elucidation.
- Glutamate receptors play a critical role in neuronal survival and degeneration pathways.
Purpose of the Study:
- To investigate the involvement of the transglutaminase reaction in the excitotoxic response of cerebellar granule cells.
- To assess the influence of glutamate receptors on neuronal cell survival and degeneration.
- To determine the developmental stage-dependent susceptibility of neurons to excitotoxicity.
Main Methods:
- Primary cultures of rat cerebellar granule cells were maintained in vitro for up to two weeks.
- Cultures were exposed to NMDA at different developmental stages (5, 8-9, and 13-14 days in vitro).
- Transglutaminase activity and transglutaminase 2 (tTG) expression levels were measured post-NMDA exposure.
Main Results:
- NMDA receptor activation led to increased transglutaminase activity in cultured cerebellar granule cells.
- Higher transglutaminase activity was observed in younger neurons (5 days in vitro) compared to older ones.
- NMDA exposure upregulated tTG expression and induced apoptotic morphological changes, particularly in 5-day-old cultures.
Conclusions:
- Transglutaminase activation is a key component of the excitotoxic cascade in cerebellar granule cells.
- Neuronal susceptibility to NMDA-induced excitotoxicity is significantly dependent on the developmental stage.
- Younger, developing neurons are more vulnerable to excitotoxicity, involving increased tTG activity and apoptosis.
