Study on the Carbohydrate Side Chain Composition and Its Effects on Protein Binding Capacities and Immune Responses of Tamm-Horsfall Glycoprotein (THP) Purified from Urine of Normal Individuals and Patients Receiving Renal Allograft Transplantation

• Main Authors: Tsai-Hung Wu, 吳采虹
• Other Authors: Chia-Li Yu
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/43372415395449108763

博士 === 國立陽明大學 === 臨床醫學研究所 === 96 === Background: Urinary Tamm-Horsfall glycoprotein (THP) is a pleotropic binding ligand of various proteins and a potent stimulator for immunocompetent cells. It is still unclear whether protein core or glycomoieties play an essential role in stimulating immune functions. In addition, whether the sugar side chains are modified in pathological state such as in allograft transplantation is also unknown. Methods: THP molecules were purified from urine of normal individuals (N-THG) and allograft renal transplant patients (R-THP). The various THP molecules were treated with carbohydrate-, protein-, and glycoprotein-degrading enzymes and then tested for the effects on their biological/immunological activities. Results: N-THP molecule contained high amount of Sia��(2,3)Gal/GalNAc, moderate amount of β(1,4)GlcNAc oligomers/GlcNAc/branched mannose, and low amount of mannose residues, but no Sia��(2,6)Gal/GalNAc, in the side chains. It could bind very efficiently to human tumor necrosis factor (TNF)-��, immunoglobulin G (IgG), complement (C1q) and bovine serum albumin (BSA), moderate-efficiently to human interleukin - 8 (IL-8), and less efficiently to human IL-6 and interferon (IFN)-��. These purified molecules were further enzyme-digested with neuraminidase (Nase), β-galactosidase (Gase), protein-specific V8 protease (V8), proteinase K (PaseK), carboxypeptidase Y (Case), or O-sialoglycoprotein endo- peptidase (Oase). N-THP molecules digested by V8, Oase, and PaseK, significantly ameliorated in their protein-binding, mononuclear cell proliferating-, and polymorphonuclear neutrophil (PMN) phagocytosis-enhancing capacities. Compared to N-THP, R-THP contained lesser amounts of Sia��(2,3)Gal/GalNAc, mannose residues, and ��(1,4)GlcNAc, but not GlcNAc/branched mannose. The binding capacity of R-THG to C1q and TNF-���nwas also decreased. In addition, R-THG exhibited less mononuclear cell-stimulating and PMN phagocytosis-enhancing activities than N-THG. The defective mononuclear cell-stimulation by R-THP was due to impaired NF-�羠 p52 translocation from the cytoplasm to the nucleus. The cell-stimulating effects of N- and R-THP could be abolished by treatment with ��-galactosidase and neuraminidase. It is quite interesting that a potent apoptosis-inducing activity of R-THP on mononuclear cells and PMN was observed. Conclusions: These results suggest that the intact protein core structure, but not carbohydrate side chains, is essential for pleotropic biological/immunological activities of normal THP molecule. On the other hand, in patients undergoing allograft renal transplantation, THP is not only modified in carbohydrate compositions but also capable of inducing mononuclear cells and PMN apoptosis, leading to an impaired immune status in vivo. Taken together, protein core of THP molecule is more important than sugar side chains in normal physiologic condition. Carbohydrate side chain alterations may occur in various pathologic states including renal allograft transplantation.