Network of brain protein level changes in glutaminase deficient fetal mice

Glutaminase is a multifunctional enzyme encoded by gene Gls involved in energy metabolism, ammonia trafficking and regeneration of neurotransmitter glutamate. To address the proteomic basis for the neurophenotypes of glutaminase-deficient mice, brain proteins from late gestation wild type, Gls+/- and Gls-/- male mice were subjected to two-dimensional gel electrophoresis, with subsequent identification by mass spectrometry using nano-LC-ESI-MS/MS. Protein spots that showed differential genotypic variation were quantified by immunoblotting. Differentially expressed proteins unambiguously identified by MS/MS included neurocalcin delta, retinol binding protein-1, reticulocalbin-3, cytoskeleton proteins fascin and tropomyosin alpha-4-chain, dihydropyrimidinase-related protein-5, apolipoprotein IV and proteins from protein metabolism proteasome subunits alpha type 2, type 7, heterogeneous nuclear ribonucleoprotein C1/C2 and H, voltage-gated anion-selective channel proteins 1 and 2, ATP synthase subunit β and transitional endoplasmic reticulum ATPase. An interaction network determined by Ingenuity Pathway Analysis revealed a link between glutaminase and calcium, Akt and retinol signaling, cytoskeletal elements, ATPases, ion channels, protein synthesis and the proteasome system, intermediary, nucleic acid and lipid metabolism, huntingtin, guidance cues, transforming growth factor beta-1 and hepatocyte nuclear factor 4-alpha. The network identified involves (a) cellular assembly and organization and (b) cell signaling and cell cycle, suggesting that Gls is crucial for neuronal maturation.