title: Serine 204 phosphorylation and O-β-GlcNAC interplay of IGFBP-6 as therapeutic indicator to regulate IGF-II functions in viral mediated hepatocellular carcinoma.
abstract: Hepatocellular carcinoma is mainly associated with viral hepatitis B and C. Activation of cell growth stimulator IGF-II gene is observed in tumor formation especially in viral associated hepatocellular carcinoma. Elevated IGF-II levels are indicator of increased risk for cholangiocellular and hepatocellular carcinomas through over saturation of IGF-II binding capacities with IGF receptors leading to cellular dedifferentiation. In HCV, core protein is believed to trans-activate host IGF-II receptor through PKC pathway and the inhibition of tumor cell growth can be achieved by blocking IGF-II pathway either at transcriptional level or increasing its binding with IGFBPs (Insulin like growth factor proteins) at C-terminal, so that it is not available in free form. IGFBP-6 is a specific inhibitor of IGF-II actions. Affinity of IGFBPs with IGFs is controlled by post-translational modifications. Phosphorylation of IGFBPs inhibits IGFs action on target cells while O-glycosylation prevents binding of IGFBP-6 to glycosaminoglycans and cell membranes and resulting in a 10-fold higher affinity for IGF-II. O-glycosylation and phosphorylation operate the functional expression of cellular proteins, this switching on and off the protein expression is difficult to monitor in vivo. By using neural network based prediction methods, we propose that alternate O-β-GlcNAc modification and phosphorylation on Ser 204 control the binding of IGFBP-6 with IGF-II. This information may be used for developing new therapies by regulating IGFBP-6 assembly with IGF-II to minimize the risk of viral associated hepatocellular carcinoma. We can conclude that during HCV/HBV infection, O-β-GlcNAc of IGFBP-6 at Ser 204 diminish their binding with IGF-II, increase IGF-II cellular expression and promote cancer progression which can lead to hepatocellular carcinoma. Furthermore, this site can be used for developing new therapies to control the IGF-II actions during viral infection to minimize the risk of hepatocellular carcinoma.
authors.affiliation: Applied and Functional Genomics Lab, Centre of Excellence in Molecular Biology, University of the Punjab, Lahore, Pakistan.
authors.forename: Waqar
authors.initials: W
authors.lastname: Ahmad
authors.forename: Khadija
authors.initials: K
authors.lastname: Shabbiri
authors.forename: Bushra
authors.initials: B
authors.lastname: Ijaz
authors.forename: Sultan
authors.initials: S
authors.lastname: Asad
authors.forename: Noreen
authors.initials: N
authors.lastname: Nazar
authors.forename: Shazia
authors.initials: S
authors.lastname: Nazar
authors.forename: Kiran
authors.initials: K
authors.lastname: Fouzia
authors.forename: Humera
authors.initials: H
authors.lastname: Kausar
authors.forename: Sana
authors.initials: S
authors.lastname: Gull
authors.forename: Muhammad T
authors.initials: MT
authors.lastname: Sarwar
authors.forename: Imaran
authors.initials: I
authors.lastname: Shahid
authors.forename: Sajida
authors.initials: S
authors.lastname: Hassan
mesh_terms: D000117:Acetylglucosamine / Q000378:metabolism*; D000595:Amino Acid Sequence; D006528:Carcinoma, Hepatocellular / Q000821:virology*; D006031:Glycosylation; D016174:Hepacivirus / Q000472:pathogenicity; D006509:Hepatitis B / Q000150:complications* / Q000821:virology; D006515:Hepatitis B virus / Q000472:pathogenicity; D006526:Hepatitis C / Q000150:complications* / Q000821:virology; D006801:Humans; D018976:Insulin-Like Growth Factor Binding Protein 6 / Q000378:metabolism*; D007335:Insulin-Like Growth Factor II / Q000378:metabolism*; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011485:Protein Binding; D016415:Sequence Alignment; D012694:Serine / Q000378:metabolism*
chemical_list: D018976:Insulin-Like Growth Factor Binding Protein 6; D012694:Serine; D007335:Insulin-Like Growth Factor II; D000117:Acetylglucosamine