Kinetics of a novel isoform of phosphate activated glutaminase (PAG) in SH-SY5Y neuroblastoma cells.

We have recently found that the neuroblastoma cell line SH-SY5Y expresses a novel form of phosphate activated glutaminase (PAG) which deamidates glutamine to glutamate and ammonia at high rates. Glutamate production is enhanced during the exponential phase of growth, and decreases when cell proliferation stops. Neuroblastoma PAG exists in a soluble and membrane associated form, and both the phosphate and the glutamine kinetics, as well as the effects of ammonia and glutamate are different from those of the known forms of PAG.

Novel form of phosphate activated glutaminase in cultured astrocytes and human neuroblastoma cells, PAG in brain pathology and localization in the mitochondria.

A novel form of phosphate activated glutaminase (PAG), catalyzing the synthesis of glutamate from glutamine, has been detected in cultured astrocytes and SH-SY5Y neuroblastoma cells. This enzyme form is different from that of the kidney and liver isozymes. In these cells we found high enzyme activity, but no or very weak immunoreactivity against the kidney type of PAG, and no immunoreactivity against the liver type.

Increased expression of phosphate-activated glutaminase in hippocampal neurons in human mesial temporal lobe epilepsy.

Patients with mesial temporal lobe epilepsy (MTLE) have increased basal concentrations of extracellular glutamate in the epileptogenic versus the non-epileptogenic hippocampus. Such elevated glutamate levels have been proposed to underlie the initiation and maintenance of recurrent seizures, and a key question is what causes the elevation of glutamate in MTLE. Here, we explore the possibility that neurons in the hippocampal formation contain higher levels of the glutamate synthesizing enzyme phosphate-activated glutaminase (PAG) in patients with MTLE versus patients with other forms of temporal lobe epilepsy (non-MTLE).

Brain mitochondria contain aquaporin water channels: evidence for the expression of a short AQP9 isoform in the inner mitochondrial membrane.

Aquaporins are a family of water channels found in animals, plants, and microorganisms. A subfamily of aquaporins, the aquaglyceroporins, are permeable for water as well as certain solutes such as glycerol, lactate, and urea. Here we show that the brain contains two isoforms of AQP9--an aquaglyceroporin with a particularly broad substrate specificity--and that the more prevalent of these isoforms is expressed in brain mitochondria.

Mitochondrial localization of the Parkinson's disease related protein DJ-1: implications for pathogenesis.

Both homozygous (L166P, M26I, deletion) and heterozygous mutations (D149A, A104T) in the DJ-1 gene have been identified in Parkinson's disease (PD) patients. The biochemical function and subcellular localization of DJ-1 protein have not been clarified. To date the localization of DJ-1 protein has largely been described in studies over-expressing tagged DJ-1 protein in vitro.