Variations in promoter activity reveal a differential expression and physiology of glutamate transporters by glia in the developing and mature CNS.

Glutamate transporters regulate excitatory neurotransmission and prevent glutamate-mediated excitotoxicity in the CNS. To better study the cellular and temporal dynamics of the expression of these transporters, we generated bacterial artificial chromosome promoter Discosoma red [glutamate-aspartate transporter (GLAST)] and green fluorescent protein [glutamate transporter-1 (GLT-1)] reporter transgenic mice. Analysis of these mice revealed a differential activation of the transporter promoters not previously appreciated.

Beta-lactam antibiotics offer neuroprotection by increasing glutamate transporter expression.

Glutamate is the principal excitatory neurotransmitter in the nervous system. Inactivation of synaptic glutamate is handled by the glutamate transporter GLT1 (also known as EAAT2; refs 1, 2), the physiologically dominant astroglial protein. In spite of its critical importance in normal and abnormal synaptic activity, no practical pharmaceutical can positively modulate this protein.

Altered expression of the glutamate transporter EAAT2b in neurological disease.

Functional studies suggest that up to 95% of all glutamate transport is handled by the glutamate transporter EAAT2. Amino and C-terminal antibodies demonstrate that under normal conditions EAAT2 is specific to astrocytes. A truncated splice variant of EAAT2, known as EAAT2b, also has been identified in astrocytes and some neurons.

Climbing fiber activation of EAAT4 transporters and kainate receptors in cerebellar Purkinje cells.

Cerebellar Purkinje cells (PCs) express two glutamate transporters, EAAC1 (EAAT3) and EAAT4; however, their relative contribution to the uptake of glutamate at synapses is not known. We found that glutamate transporter currents recorded at climbing fiber (CF)-PC synapses are absent in mice lacking EAAT4 but unchanged in mice lacking EAAC1, indicating that EAAT4 is preferentially involved in clearing glutamate from CF synapses. However, comparison of CF synaptic currents between wild-type and transporter knock-out mice revealed that ionotropic glutamate receptors are responsible for >40% of the current previously attributed to transporters, indicating that PCs remove <10% of the glutamate released by the CF.

Cyclooxygenase 2 inhibition protects motor neurons and prolongs survival in a transgenic mouse model of ALS.

The pathogenesis of cell death in amyotrophic lateral sclerosis (ALS) may involve glutamate-mediated excitotoxicity, oxidative damage, and apoptosis. We used a transgenic mouse model of ALS to determine the effect of inhibition of cyclooxygenase-2 in treating the disease. Cyclooxygenase-2, present in spinal neurons and astrocytes, catalyzes the synthesis of prostaglandin E2.