Transcriptional and posttranslational regulation of GS. GS is transcriptionally regulated by β-catenin, STAT5, GATA3, FOXO, YAP, and c-Myc. GS protein stability is regulated by acetylation. GS is acetylated by histone acetyltransferase, p300/CBP, and acetylated GS is ubiquitinated by the E3 ligase, CRBN. Ubiquitinated GS is segregated by p97/VCP and then degraded by the proteasome. STAT5: signal transducer and activator of transcription 5, GATA3: GATA Binding Protein 3, YAP: yes-associated protein, FOXO: members of the class O of forkhead box transcription factors, GS: glutamine synthetase, CBP: cyclic AMP response element-binding protein, CRBN: cereblon, Ub: ubiquitin, p97/VCP: valosin-containing protein.