@article{buttram_engler_grossfield_urazaev_lieberman_2002, title={Glutamine uptake and metabolism to N-acetylaspartylglutamate (NAAG) by crayfish axons and glia}, volume={133}, ISSN={["1096-4959"]}, DOI={10.1016/S1096-4959(02)00124-0}, abstractNote={We have proposed that N-acetylaspartylglutamate (NAAG) or its hydrolytic product glutamate, is a chemical signaling agent between axons and periaxonal glia at non-synaptic sites in crayfish nerves, and that glutamine is a probable precursor for replenishing the releasable pool of NAAG. We report here, that crayfish central nerve fibers synthesize NAAG from exogenous glutamine. Cellular accumulation of radiolabel during in vitro incubation of desheathed cephalothoracic nerve bundles with [3H]glutamine was 74% Na(+)-independent. The Na(+)-independent transport was temperature-sensitive, linear with time for at least 4 h, saturable between 2.5 and 10 mM L-glutamine, and blocked by neutral amino acids and analogs that inhibit mammalian glutamine transport. Radiolabeled glutamine was taken up and metabolized by both axons and glia to glutamate and NAAG, and a significant fraction of these products effluxed from the cells. Both the metabolism and release of radiolabeled glutamine was influenced by extracellular Na(+). The uptake and conversion of glutamine to glutamate and NAAG by axons provides a possible mechanism for recycling and formation of the axon-to-glia signaling agent(s).}, number={2}, journal={COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY B-BIOCHEMISTRY & MOLECULAR BIOLOGY}, author={Buttram, JG and Engler, JA and Grossfield, RM and Urazaev, AK and Lieberman, EM}, year={2002}, month={Oct}, pages={209–220} }
 @article{buttram_engler_grossfeld_urazaev_lieberman_2002, title={Glutamine uptake and metabolism to N-acetylaspartylglutamate (NAAG) by crayfish axons and glia.}, volume={133B}, number={2}, journal={Comparative Biochemistry and Physiology. B, Biochemistry & Molecular Biology}, author={Buttram, J. G. and Engler, J. A. and Grossfeld, R. M. and Urazaev, A. K. and Lieberman, E. M.}, year={2002}, pages={209–220} }
 @article{engler_gottesman_harkins_urazaev_lieberman_grossfeld_2002, title={Properties of glutaminase of crayfish CNS: Implications for axon-glia signaling}, volume={114}, ISSN={["0306-4522"]}, DOI={10.1016/S0306-4522(02)00357-3}, abstractNote={Glutaminase of crayfish axons is believed to participate in recycling of axon-glia signaling agent(s). We measured the activity and properties of glutaminase in crude homogenates of crayfish CNS, using ion exchange chromatography to separate radiolabeled product from substrate. Crayfish glutaminase activity is cytoplasmic and/or weakly bound to membranes and dependent on time, tissue protein, and glutamine concentration. It resembles the kidney-type phosphate-activated glutaminase of mammals in being stimulated by inorganic phosphate and alkaline pH and inhibited by the product glutamate and by the glutamine analog 6-diazo-5-oxo-L-norleucine. During incubation of crayfish CNS fibers in Na(+)-free saline containing radiolabeled glutamine, there is an increased formation of radiolabeled glutamate in axoplasm that is temporally associated with an increase in axonal pH from about 7.1 to about 8.0. Both the formation of glutamate and the change in pH are reduced by 6-diazo-5-oxo-L-norleucine. Our results suggest that crayfish glutaminase activity is regulated by cellular changes in pH and glutamate concentration. Such changes could impact availability of the axon-glia signaling agents glutamate and N-acetylaspartylglutamate.}, number={3}, journal={NEUROSCIENCE}, author={Engler, JA and Gottesman, JM and Harkins, JC and Urazaev, AK and Lieberman, EM and Grossfeld, RM}, year={2002}, pages={699–705} }