GLUL (GS) belongs to the glutamine synthetase family and functions to catalyze the synthesis of glutamine from glutamate and ammonia in an ATP-dependent reaction. This protein plays a role in ammonia and glutamate detoxification, acid-base homeostasis, cell signaling, and cell proliferation. Glutamine is an abundant amino acid, and is important to the biosynthesis of several amino acids, pyrimidines, and purines. Mutations in this gene are associated with congenital glutamine deficiency, and overexpression of this gene was observed in some primary liver cancer samples. GLUL antibodies can be used in a panel with HSP70 and GPC3 antibodies to distinguish hepatocellular carcinoma (at least two out of three positive) from nonmalignant lesions. In immunohistochemistry of normal tissue, GLUL has cytoplasmic positivity in adipocytes, glial cells, macrophages and hepatocytes in multiple tissues, including the brain, thyroid, lung, liver, pancreas, intestine, bladder, breast and reproductive organs. References: Hepatology. 2007 Mar;45(3):725-34, PMID: 17326147; J Hepatol. 2009 Apr;50(4):746-54: 19231003