Changes in the nuclear proteomic profiling of human glioblastoma cells after glutaminase overexpression

Abstract

Human glutaminase (GA) enzymes are the products of two genes, GLS and GLS2. GA isozymes play markedly different roles in tumour biology: GLS isoforms (KGA and GAC) are related to cell growth and proliferation, whereas GLS2 isoforms (GAB and LGA) are associated with low proliferation rates and are characteristics for resting or quiescent cells. Furthermore, the GAB isoform has been recently involved in transcriptional regulation. Due to the proposed roles of GAB isoform in cellular differentiation and transcriptional modulation, the aim of the present study is to profile differentially expressed nuclear proteins in order to discover putative biomarkers associated with GAB overexpression in glioma cells. Nuclear cell proteins were incubated with strong anion exchange (Q10) and weak cation exchange (CM10) ProteinChip arrays and analyzed using surface-enhanced laser desorption/ionization time-of- flight mass spectrometry (SELDI-TOF/MS) proteomics technology. T98G-GAB nuclear protein expression profiles were compared with those of T98G-WT and empty vector transfected T98G-pcDNA3 with the ProteinChip Data Manager Client 4.0 software. Eighteen proteins were found to be differentially expressed between control cells and GAB-transfected T98G cells. Nine proteins with m/z between 5.5-29.7 were identified to be highly expressed in T98G-GAB (P≤ 0.01), while the expression of two proteins with m/z values of 7.8 and 8.5 were higher in control cells (P≤ 0.01). Our study shows the potential of proteomics profiling to get a deep insight into the role of nuclear GAB in brain tumors in order to assess its suitability as a novel anti-cancer therapeutic target. References Pérez-Gómez C, et al. Co-expression of glutaminase K and L isoenzymes in human tumour cells. Biochem. J. 2005; 386, 535-42. Szeliga M, et al. Transfection with liver-type glutaminase (LGA) cDNA alteres gene expression and reduces viability, migration and proliferation of T98G glioma cells. Glia 2009; 57, 1014-23.