TAMM-HORSFALL GLYCOPROTEIN (THG) IS A BINDER FOR SURFACE-MEMBRANE PROTEINS ON BLOOD-CELLS AND GLOMERULAR MESANGIAL CELLS

A macromolecule with a molecular weight of 90-100 kDa was purified fro m normal human pregnancy urine. The molecule was proved to be the Tamm -Horsfall glycoprotein (THG) by Western blot analysis. The macromolecu le contains carbohydrate as detected by an enzyme immunoassay. Functio nally, the glycoprotein can adhere to and stimulate the thymidine inco rporation of human mononuclear cells (MNC) in modest degree via its me mbranotropic property. In addition to MNC, the protein can also bind t o the surface of human polymorphonuclear neutrophils (PMN), red blood cells (RBC) and rat glomerular mesangial cells (RMC). Western blot ana lysis of various cell lysates with/without proteinase K pretreatment b efore cell lysis revealed that a 60 kDa and a molecule larger that 94 kDa on the surface of PMN, a 60 kDa protein on MNC and a 32 kDa protei n on RBC are the binding molecules for THG. In contrast, many proteins on the surface of RMC could be bound by THG, Immunoprecipitation of m embranous iodinated MNC lysates also confirmed that the 60 kDa molecul e on MNC is the binding protein for THG. A number of monosaccharide in cluding N-acetylneuraminic acid, N-acetyl-galactosamine, N-acetyl-gluc osamine and alpha-methyl-D-mannoside could not inhibit the mitogenic e ffect of THG on human mononuclear cells. These results suggest that TH G is capable of reacting with surface membrane proteins on different c ells, but not through the specific carbohydrate-containing lectin-like receptors on the cell surface.