GLS2 and rheumatoid arthritis: In addition, cell viability in FLSs-RA was significantly reduced compared to normal FLSs under glutamine deprivation, suggesting that FLSs-RA exhibits features of "glutamine intoxication," in other words, that glutamine degradation is important in the pathogenesis of RA synovitis GLSs include kidney-type glutaminase (GLS1) and liver-type glutaminase (GLS2) isoforms have been identified, which differ in kinetic properties, protein structure, and organization [21].