Golgi membrane protein 1 (GOLM1) also known as Golgi phosphoprotein 2 or Golgi membrane protein GP73 is a protein that in humans is encoded by the GOLM1gene. Two alternatively spliced transcript variants encoding the same protein have been described for this gene.
The Golgi complex plays a key role in the sorting and modification of proteins exported from the endoplasmic reticulum. The protein encoded by this gene is a type II Golgi transmembrane protein. It processes protein synthesized in the rough endoplasmic reticulum and assists in the transport of protein cargo through the Golgi apparatus. The expression of this encoded protein has been observed to be upregulated in response to viral infection.
Blood levels of GP73 are higher in patients with liver cancer than in healthy individuals. In addition, levels were not significantly higher in patients with diseases other than liver disease. The current blood test used to screen for early tumors in people at high risk for liver cancer involves the alpha-fetoprotein (AFP). Patients who are at risk for non-metastatic, or primary, liver cancer typically have chronic liver disease such as cirrhosis. Such cases of cirrhosis are usually due to infection caused by infectious hepatitis (usually hepatitis B or hepatitis C, though there are other strains), or because of degenerative fatty liver disease (which can be especially severe in those with alcoholism). However, the AFP test is not usually sensitive enough to detect liver cancer in time and it often generates false positives. So far, the blood samples of more than 1,000 patients with various stages of liver and non-liver disease have been tested for the presence of GP73 in several studies. Several medical diagnostic companies are in the process of developing automated serum tests for the protein that could be performed in routine hospital laboratories.
Kladney RD, Cui X, Bulla GA, et al. (2002). "Expression of GP73, a resident Golgi membrane protein, in viral and nonviral liver disease.". Hepatology35 (6): 1431–40. doi:10.1053/jhep.2002.32525. PMID12029628.
Bauer K, Zemlin M, Hummel M, et al. (2002). "Diversification of Ig heavy chain genes in human preterm neonates prematurely exposed to environmental antigens.". J. Immunol.169 (3): 1349–56. doi:10.4049/jimmunol.169.3.1349. PMID12133958.
Kladney RD, Tollefson AE, Wold WS, Fimmel CJ (2002). "Upregulation of the Golgi protein GP73 by adenovirus infection requires the E1A CtBP interaction domain.". Virology301 (2): 236–46. doi:10.1006/viro.2002.1523. PMID12359426.
Zhang H, Li XJ, Martin DB, Aebersold R (2003). "Identification and quantification of N-linked glycoproteins using hydrazide chemistry, stable isotope labeling and mass spectrometry.". Nat. Biotechnol.21 (6): 660–6. doi:10.1038/nbt827. PMID12754519.
Otsuki T, Ota T, Nishikawa T, et al. (2007). "Signal sequence and keyword trap in silico for selection of full-length human cDNAs encoding secretion or membrane proteins from oligo-capped cDNA libraries.". DNA Res.12 (2): 117–26. doi:10.1093/dnares/12.2.117. PMID16303743.
Ramachandran P, Boontheung P, Xie Y, et al. (2006). "Identification of N-linked glycoproteins in human saliva by glycoprotein capture and mass spectrometry.". J. Proteome Res.5 (6): 1493–503. doi:10.1021/pr050492k. PMID16740002.
Bachert C, Fimmel C, Linstedt AD (2007). "Endosomal trafficking and proprotein convertase cleavage of cis Golgi protein GP73 produces marker for hepatocellular carcinoma.". Traffic8 (10): 1415–23. doi:10.1111/j.1600-0854.2007.00621.x. PMID17662025.
Gu Y, Chen W, Zhao Y, Chen L, Peng T (2009). "Quantitative analysis of elevated serum Golgi protein-73 expression in patients with liver diseases.". Ann Clin Biochem.46 (1): 38–43. doi:10.1258/acb.2008.008088. PMID19008260.