Impaired glutamate uptake and EAAT2 downregulation in an enterovirus chronically infected human glial cell line

Abstract

Rapid and efficient uptake of glutamate via the high-affinity glutamate transporter EAAT2 is important for limiting glutamate-mediated excitotoxicity involved in neuronal death. Furthermore, there is evidence of altered glutamate uptake and catabolism in motor neuron diseases. Such a defect has been reported in amyotrophic lateral sclerosis, the major motor neuron disease, and was associated with impairment in EAAT2 processing. We recently reported the presence of enterovirus genome specifically in the anterior horn of amyotrophic lateral sclerosis cases, suggesting the involvement of a chronic/persistent enterovirus infection in amyotrophic lateral sclerosis. To investigate a putative link between enterovirus infection and the glutamate-mediated excitotoxicity observed in amyotrophic lateral sclerosis, we developed an in vitro model consisting of a human glial cell line infected with ECHOvirus 6, one of the enteroviruses with sequences closely related to those detected in patients with amyotrophic lateral sclerosis. In these glial cells, an ECHOvirus 6 chronic infection was established, resulting in altered extracellular glutamate uptake. This correlated with an aberrant splicing of the EAAT2 pre-messenger ribonucleic acid and a significant loss of EAAT2 protein expression, similar to that observed in patients with amyotrophic lateral sclerosis. These results provide convincing evidence that an enterovirus chronic/persistent infection may alter glial glutamate uptake and catabolism. As enteroviruses are extremely common human pathogens, they may act as a trigger in the development of certain motor neuron diseases, such as amyotrophic lateral sclerosis.

Association of Human Herpesvirus-6B with Mesial Temporal Lobe Epilepsy

“…cDNA was amplified using primers specific for EAAT-2 [36]. PCR for EAAT-2 was run for 35 cycles using the following conditions: 95 °C for 45 s, 55 °C for 1 min, and 72 °C for 1 min.…”

Cumulative Mutations in the Genome of Echovirus 6During Establishment of a Chronic Infection in Precursors of Glial Cells

“…In vitro, the virus can establish a chronic infection in the human pre-astrocytes cell line, the Dev cells. Although the morphological aspect of infected Dev cells does not change, this chronic infection provokes some modifications in cell biology: a down regulation of the expression of a cellular receptor-transporter of glutamate (EAAT2) leading to a decrease of glutamate uptake [25]. This was attributed to an abnormal splicing of the pre-messenger RNA.…”

Neurochemical Aspects of Excitotoxicity

“…The specificity of glutamate splice variants in neurodegenerative diseases remains unknown because aberrant splicing of glutamate transporters was also reported in other neurological disorders including hypoxia , traumatic brain injury , epilepsy (Hoogland et al, 2004), Alzheimer disease (Maragakis et al, 2004), Huntington disease (Hoogland et al, 2004), AIDS dementia complex , multiple sclerosis (Vallejo-Illarramendi et al, 2006), olivopontocerebellar atrophy (Dirson et al, 2002), schizophrenia (Lauriat et al, 2006), and glaucoma . Altered glutamate transport and aberrant splicing of EAAT2 expression was also reported in glial cells from ALS patients infected with enterovirus (Legay et al, 2003). It still remains unknown whether changes in expression and distribution of splice variants of EAAT2 are the cause or consequence of EAAT2 activity.…”