Although the synthesis of a protein is dictated by its genome, it alone does not form the complete structure of the protein which is required in many cases to perform the biological functions. It is the post translational modifications that play additional role in forming a protein with optimal biological activity. In gastric mucosa, several posttranslational modifications responsible for the processing of mucus glycoproteins and immunoglobulins have been well characterized in endoplasmic reticulum and in Golgi. But the tyrosine protein sulfation involving the transfer of sulfate from 3' phosphoadenosine 5' phosphosulfate to the hydroxyl group of tyrosine in protein has gained very little attention. Alcohol induced secretion of mucus glycoprotein of gastric mucosa has been well documented, however, the basic biochemical events which trigger this process are still unknown. In the present project, attention is directed to the role of tyrosine sulfation as the signal for this secretory response. Since our preliminary study indicates that ethanol stimulates tyrosine sulfation, the proposal mainly concerns the effect of ethanol on the enzyme responsible for this modification. Two major secretory proteins will be studied: the N-glycosidic immunoglobulin which is known to use the tyrosine sulfation as a signal when its major secretory pathway is impaired and O-glycosidic mucus glycoproteins. To understand the basic biochemical events involved in the ethanol stimulation of tyrosylprotein sulfation, gastric mucosa isolated from rats of control and ethanol fed groups will be used. The differences in the activity of tyrosylprotein sulfotransferase (TPST) and the synthesis and secretion of gastric secretory proteins in these two groups will be investigated. The experiments will include characterization of the ethanol induced changes in TPST, testing the possible involvement of other factors and kinetics of the purified enzyme(s). Role of lipids in ethanol stimulation of TPST and using antibody to TPST the change in TPST level and its turnover will be investigated. In addition, cDNA encoding TPST will be isolated and used for evaluation of changes in the TPST m-RNA levels and its stability in the control and ethanol group. Tyrosylprotein sulfation dependent secretion of O-glycosidic glycoprotein, N-glycosidic immunoglobulin and other gastric secretory proteins and their processing in presence of ethanol will be studied. It is believed that the findings from this project should improve the understanding on tyrosylprotein sulfation and its relation to alcoholism.
| Kasinathan, C; Gandhi, N; Ramaprasad, P et al. (2007) Tyrosine sulfation of statherin. Int J Biol Sci 3:237-41 |
| Kasinathan, C; Ramaprasad, P; William, S et al. (1998) Stimulation of tyrosylprotein sulfotransferase activity by ethanol: role of increased enzyme level. Alcohol 15:271-6 |
| Ramaprasad, P; Kasinathan, C (1998) In vivo induction of tyrosylprotein sulfotransferase by ethanol: role of increased enzyme synthesis. Alcohol Clin Exp Res 22:1120-4 |
| Ramaprasad, P; Kasinathan, C (1998) Isolation of tyrosylprotein sulfotransferase from rat liver. Gen Pharmacol 30:555-9 |
| William, S; Ramaprasad, P; Kasinathan, C (1997) Purification of tyrosylprotein sulfotransferase from rat submandibular salivary glands. Arch Biochem Biophys 338:90-6 |
