Some factors affecting the production, by cultured baby-hamster kidney cells, of BHK glycoprotein I which cross-reacts immunologically with Tamm-Horsfall glycoprotein

Variation of High Mannose Chains of Tamm-Horsfall Glycoprotein Confers Differential Binding to Type 1-fimbriated Escherichia coli

Tamm-Horsfall glycoprotein (THP), the most abundant protein in mammalian urine, has been implicated in defending the urinary tract against infections by type 1-fimbriated Escherichia coli. Recent experimental evidence indicates that the defensive capability of THP relies on its single high mannose chain, which binds to E. coli FimH lectin and competes with mannosylated uroplakin receptors on the bladder surface. Here we describe several major differences, on both structural and functional levels, between human THP (hTHP) and pig THP (pTHP). pTHP contains a much higher proportion (47%) of Man5GlcNAc2 than does hTHP (8%). FimH-expressing E. coli adhere to monomeric pTHP at an approximately 3-fold higher level than to monomeric hTHP. This suggests that the shorter high mannose chain (Man5GlcNAc2) is a much better binder for FimH than the longer chains (Man6-7GlcNAc2) and that pTHP is a more potent urinary defense factor than hTHP. In addition, unlike hTHP whose polyantennary glycans are exclusively capped by sialic acid and sulfate groups, those of pTHP are also terminated by Galalpha1,3Gal epitope. This is consistent with the fact that the outer medulla of pig kidney expresses the alpha1,3-galactosyltransferase, which is completely absent in human kidney. Finally, pTHP is more resistant to leukocyte elastase hydrolysis than hTHP, thus explaining why pTHP is much less prone to urinary degradation than hTHP. These results demonstrate for the first time that the species variations of the glycomoiety of THP can lead to the differential binding of THP to type 1-fimbriated E. coli and that the differences in high mannose processing may reflect species-specific adaptation of urinary defenses against E. coli infections.

Salt-precipitation method does not isolate to homogeneity Tamm-Horsfall glycoprotein from urine of proteinuric patients and pregnant women

OBJECTIVE

Assessment of the degree of purification of Tamm-Horsfall glycoprotein from anomalous urine.

DESIGN AND METHODS

Two methods have been compared: the method of Tamm & Horsfall (T&H method) consisting in the precipitation of THP by the addition to urine of NaCl up to 0.58 mol/L and the filtration of urine through a diatomaceous earth filter (DEF method) in which THP is selectively trapped because of its gelation/aggregation tendency. The purity of THP preparations has been evaluated by SDS-PAGE analysis and Western blotting developed with anti immunoglobulin G (IgG) antibodies and antichorionic gonadotropin antibodies.

RESULTS

All THPs isolated by T&H method from proteinuric patients were contaminated by IgG and one of the five preparations from pregnant women even by chorionic gonadotropin. A smaller or no contamination was found in THPs isolated by DEF method.

CONCLUSIONS

Although albumin is the most abundant protein in the anomalous urine, it never appears in THP preparations. The consistent contamination with IgG of THP prepared by salt precipitation-method might be related to the formation of a stable complex between the two proteins.

Mechanism of release of urinary Tamm-Horsfall glycoprotein from the kidney GPI-anchored counterpart

Human Tamm-Horsfall glycoprotein (THP) is synthesised in the thick ascending limb of Henle and convoluted distal tubules, inserted into luminal cell-surface by the glycosyl-phosphatidylinositol (GPI)-anchor and excreted in urine at a rate of 50-100 mg per day. Up to date there is no indication on the way in which THP is excreted into the urinary fluid. In this study, we examined by Western blotting THP from human kidney in comparison to urinary THP. As expected for a GPI-anchored protein, THP was recovered from the kidney lysate in a Triton X-100 insoluble form, which moved in a sucrose gradient to a zone of low density. The apparent molecular weight of kidney THP appeared greater than that of urinary THP, but no difference in the electrophoretic mobility was observed when the former was subjected to GPI-specific phospholipase-C treatment, strongly suggesting that a proteolytic cleavage at the juxtamembrane-ectodomain of kidney THP is responsible for the urinary excretion.

Binding of human neutrophils to cell-surface anchored Tamm-Horsfall glycoprotein in tubulointerstitial nephritis

BACKGROUND

Human Tamm-Horsfall glycoprotein (T-H) is a glycosylphosphatidylinositol-anchored protein exposed at the surface of distal nephron cells, and urinary T-H is the released soluble counterpart. The latter has been implicated in tubulointerstitial nephritis, and the proinflammatory potential has been related to its ability to bind in vitro human neutrophils (PMNs). We have examined the conditions required for the binding of neutrophils to cell-surface anchored T-H and the consequent effects.

METHODS

A HeLa cell-line derivative permanently transformed with human T-H cDNA and expressing T-H at the cell surface was used throughout the study. The adhesion of PMNs to cells expressing T-H was analyzed by immunofluorescence microscopy before and after the opsonization of cells with anti-T-H antibodies. The oxidative burst induced by adhesion of PMNs to the cells was determined by the activation of myeloperoxidase. Quantitative and qualitative changes in the release of T-H under the adhesion of activated PMNs were determined by dot-blot and Western blot analysis.

RESULTS

No binding of neutrophils to cell-surface-anchored T-H was observed. On the contrary, the opsonization of cells with anti-T-H antibodies resulted in a dramatic adhesion of neutrophils. Such an adhesion induced the oxidative burst of PMNs and a large increment in the release of T-H, as well as the release of the slightly faster migrating T-H form, which is normally retained intracellularly.

CONCLUSIONS

These results support the notion that, after the autoimmune response, the adhesion of neutrophils to cell-surface T-H contributes to the pathogenesis of tubulointerstitial nephritis, favoring a further accumulation of T-H in the interstitium and inducing the loss of cell integrity via reactive oxygen metabolites generated by activated neutrophils.

Biochemical and quantitative analysis of Tamm Horsfall protein in rats

The involvement of Tamm Horsfall protein (THP) in nephrolithiasis is currently under investigation in several laboratories. Although rat is a commonly used species as an in vivo model for such studies, there is only limited information available about the biochemical properties and excretion profile of THP in normal rats. In order to characterize rat THP, we purified and analyzed normal male rat THP, and compared it with normal human male urinary THP by gel electrophoresis. Both THPs migrated at approximately 90 KDa, and stained similarly for protein (Coomassie blue) as well as carbohydrates (periodic acid Schiff reagent). Compositional analysis revealed that rat THP was largely similar to human THP in amino acid and carbohydrate contents but showed differences in the individual sugar components from other mammals. There was considerable variation in the day-to-day urinary excretion of THP in normal rats, with values ranging from 552.96 micrograms to 2865.60 micrograms and a mean value of 1679.54 micrograms per 24 h. It was concluded from this study that rat THP did not contain any unusual biochemical components and was primarily similar to human THP in composition and mean urinary concentration.

Intracellular transport, cell-surface exposure and release of recombinant Tamm-Horsfall glycoprotein

Human Tamm-Horsfall glycoprotein (T-H), first described as the major urinary glycoprotein, is a glycosylphosphatidyl-inositol (GPI)-anchored membrane protein which mainly resides at the luminal face of cells of the thick ascending limb of Henle's loop (TAL) and early distal convoluted tubules of nephron. Since no human renal cell-line producing T-H is available, T-H cDNA was transfected in HeLa cells and a cell line was selected in which 95% of the cells stably expressed T-H, in order to elucidate the biosynthesis, mechanisms regulating the transport of T-H along the exocytic pathway, exposure at the cell surface and release in soluble form. Treatment of cells with an exogenous reducing agent results in a drastic delay in the conversion from precursor to mature T-H. Since the accumulating T-H-precursor carries glycans not yet processed by Golgi-mannosidases, we propose that the formation of a correct set of intrachain disulphide bonds is required for T-H exit out the endoplasmic reticulum. Even the treatment of cells with an inhibitor of GPI-anchor biosynthesis results in an intracellular accumulation of T-H precursor, loss of T-H localization into Golgi apparatus and reduced surface exposure. These results indicate that the GPI-anchor addition is necessary for T-H delivery to the cell-surface. The release rate of new synthesized T-H shows an initial lag time very likely depending on the time required for T-H surface exposure. A portion of released T-H appears to contain ethanolamine, a component of GPI anchor, indicating that, at least in HeLa cells, a GPI-specific phospholipase contributes to the T-H release. Exposure of cells to monensin and brefeldin A results in a loss of accumulation of T-H in the Golgi perinuclear region and a reduced delivery to the cell surface. Under monensin treatment an intermediate T-H form non-exposed at the cell surface is released in the medium, indicating that a soluble T-H may be produced inside the cell under conditions that alter the Golgi apparatus. If such an event occurs in polarized kidney cells, a T-H release from the basolateral face may be postulated, inasmuch as the GPI-anchor is an apical sorting signal. Since T-H is a powerful autoantigen, the accumulation of soluble T-H in the interstitium of TAL may cause the formation of immunocomplexes.

Mechanoelectrical transduction, ion movement and water stasis in uromodulin

Mechanical movement of a column of the urinary glycoprotein uromodulin modulates an applied voltage. This change is a property of the glycoprotein and its interaction with the walls of the container and is related to its capacitance. The voltage modulation is not accompanied by changes in rotationally restricted water as has been reported for hyaluronic acid. Diffusion experiments with tritiated water also support the hypothesis that uromodulin acts as a water barrier, but allows ion movement.

Rapid isolation of Tamm-Horsfall glycoprotein (uromodulin) from human urine

An isolation method for Tamm-Horsfall protein is described which is based on the observation that a diatomaceous earth filter is able to retain most of the glycoprotein present in urine and that the glycoprotein is easily desorbed from the filter by deionized water. This behaviour depends on the tendency of Tamm-Horsfall glycoprotein at normal urinary concentrations to form a gel in a solution containing mono- and divalent ions. By means of two-step filtration, the glycoprotein was purified to homogeneity. The yield was of about 20 mg/l of urine, and the time required for the isolation was approximately 5-6 h. This procedure should be particularly useful for preparing large amounts of Tamm-Horsfall glycoprotein oligosaccharides in order to investigate their potential use as immunosuppressive agents both in vitro and in vivo.

Characterization of N-acetyl-beta-D-galactosaminyltransferase from guinea-pig kidney involved in the biosynthesis of Sda antigen associated with Tamm-Horsfall glycoprotein

This study reports the catalytic activity of N-acetyl-beta-D-galactosaminyltransferase from guinea-pig kidney towards such non-glycoprotein acceptors as small oligosaccharides and glycolipids, having a carbohydrate structure similar to that of the Sda antigen associated with human Tamm-Horsfall glycoprotein. 3'-O-Sialyllactose, but not 6'-O-sialyllactose or lactose, was an effective acceptor of the glycosyltransferase. On the basis of enzymic and chemical treatment of the tetrasaccharide obtained by the transfer of [14C]GalNAc to 3'-O-sialyllactose, we propose that the glycosyltransferase attaches beta-D-GalNAc to O-4 of the galactose residue that is substituted at O-3 by sialic acid. The GM3 ganglioside, in which the identical carbohydrate moiety of 3'-O-sialyllactose is bound to a ceramide residue, did not serve as an acceptor of the kidney-N-acetyl-beta-D-galactosaminyltransferase and did not behave as a competitive inhibitor of the Tamm-Horsfall glycoprotein in the transferase assay. These results indicate that the hydrophobic moiety in the ganglioside hinders the action of N-acetylgalactosaminyltransferase. Study of the transferase activity towards a heterogeneous glycopeptide species prepared from a Sd(a-) Tamm-Horsfall glycoprotein indicated that guinea-pig kidney enzyme preferentially transferred [14C]GalNAc to the oligosaccharides having a tetraantennary branching-structure.

Immunochemistry of urinary calcium oxalate crystal growth inhibitor (CGI)

Calcium oxalate crystal growth inhibitor (CGI) was isolated from human urine in monomeric form (14,000 daltons). Antibody was elicited and purified to monospecificity by affinity chromatography. Tamm-Horsfall protein was isolated from human urine and an antibody to Tamm-Horsfall protein compared to anti-CGI. The anti-CGI reacted with its antigen on immunodiffusion, by ELISA and by Western Blotting of polyacrylamide gel electrophoresis-separated antigen. Immunofluorescent localization of CGI was found in distal renal tubules. This was precisely the localization of Tamm-Horsfall protein. Isolated Tamm-Horsfall protein was found to bind CGI which could only be partially removed with EDTA. While anti-CGI is suitable to assay CGI in human urine by ELISA techniques, it will also detect CGI that is complexed to THP. While the CGI found in human urine possesses 90% of the urinary macromolecular crystal growth inhibitor activity, THP is without effect on crystal growth, in spite of bound CGI. The balance between free CGI and that bound to Tamm-Horsfall protein may be important in the overall balance of urinary macromolecules that affect calcium oxalate nephrolithiasis.

Localization of Tamm-Horsfall-glycoprotein-like immunoreactivity in cultured baby-hamster kidney cells, shown by immunofluorescence and by light- and electron-microscopic immunoperoxidase techniques

Tamm-Horsfall glycoprotein was isolated from hamster urine, and antiserum against it was produced in rabbits. IgG was isolated from the antiserum. Immunocytochemical methods were used to localize Tamm-Horsfall-like immunoreactivity in three substrains of baby-hamster kidney (BHK) cells. Indirect immunofluorescence techniques showed that, in two substrains (BHK-21/C13/2P and BHK-21/C13/3P), a proportion of the cells fluoresced brilliantly, whereas those of the third substrain (BHK-21/ICRF) were totally negative. Related findings were obtained by the immunoperoxidase optical-microscopic technique. From the results of immunoperoxidase techniques using the electron microscope, it was concluded that the substance was present in association with the plasma membranes of the reacting cells. Our data suggest that the line of baby-hamster kidney cells, BHK-21/C13, may contain cells of renal-tubular epithelial origin, and that the proportion of these may be variable from one subculture to another.

Glycosyl transferases of baby hamster kidney cells and ricin-resistant mutants. O-glycan biosynthesis

Extracts of baby hamster kidney (BHK) cells catalyzed the incorporation of N-acetylgalactosamine from UDP-N-acetyl[14C]galactosamine into myelin basic protein and an acylated tetrapeptide, N-acetylthreonyl-triproline, based on the threonine residue 98, glycosylated in myelin basic protein. The incorporated N-acetylgalactosamine residues were shown to be in alpha linkage to the peptide moieties. Several ricin-resistant BHK cell lines contained enhanced (approximately twofold) levels of the transferase activity. Apomucins obtained from bovine submaxillary gland mucin by chemical or enzymic degradation were relatively poor acceptors. Using asialomucin as acceptor, galactosyl, transferase activities and a weak sialyl transferase activity were detected in BHK cell extracts. Galactose transfer occurred at two sites: to peptide-linked N-acetylgalactosamine residues to form the linkage, galactosyl-(beta 1 leads to 3)-N-acetylgalactosamine and to terminally linked N-acetylglucosamine residues that exist as a minor constituent in bovine submaxillary mucin O-glycans, to form a galactosyl N-acetylglucosamine linkage. This reaction was not inhibited by ovalbumin, an efficient acceptor of the beta 1 leads to 4 galactosyl transferase involved in N-glycan assembly. Incorporation of galactose and N-acetylgalactosamine into endogenous proteins of BHK cell extracts was also detected. Sialic acid, fucose and N-acetylglucosamine residues were not incorporated. The incorporated N-acetylgalactosamine residues were shown to be in alpha linkage to polypeptide, and galactose incorporation represented synthesis of the galactosyl-(beta 1 leads to 3)-N-acetylgalactosamine sequence linked to polypeptide. The major endogenous protein labelled by either sugar had a molecular weight of approximately 80 000. A BHK-cell-associated glycoprotein, analogous to the urinary Tamm-Horsfall glycoprotein of molecular weight similar to the major endogenous acceptor of glycosylation, was not glycosylated in the experiments in vitro.

Tamm-Horsfall glycoprotein in human amniotic fluid

Radioimmunoassay of material cross-reacting with urinary Tamm-Horsfall glycoprotein in human amniotic fluid was carried out. The cross-reacting material was shown to be identical with urinary Tamm-Horsfall glycoprotein by double immunodiffusion and by crossed immunoelectrophoresis. The concentrations of the substance from 16-25 weeks pregnancy were found to increase from average levels of 0.9 mg . l(-1) to 4.9 mg . 1(-1) over this period. The concentrations were considerably higher (up to 33 mg . l(-1) close to term. Measurements of the glycoprotein in amniotic fluid may be a useful index for development of renal function in the foetus.

Precipitin reaction between Sda-active human Tamm-Horsfall glycoprotein and anti-Sda-serum

Human Tamm-Horsfall glycoprotein isolated from an Sd(a+) donor, with high Sda inhibitory activity, was labelled with 14C-formaldehyde. The labelled glycoprotein was precipitated by anti-Sda sera. A good correlation was found between the precipitating and agglutinating titers of different anti-Sda sera.

The presence in serum of proteins which are immunologically cross-reactive with Tamm-Horsfall glycoprotein

Affinity chromatography, with rabbit anti-(human Tamm-Horsfall glycoprotein) IgG, was applied to the isolation from normal human serum of protein, which is immunologically cross-reactive with the urinary glycoprotein. The antigen-antibody complex was dissociated with the use of sodium thiocyanate solution, a medium which fails to dissociate urinary Tamm-Horsfall glycoprotein-antigen complex. The cross-reactive serum proteins were isolated in amounts of 19-24 mg/l of serum. They have apparent molecular weights, assessed by disc-gel electrophoresis in the presence of sodium dodecyl sulphate, of 125 000, 84 000 and 74 000 respectively, with mobilities differing from that of urinary Tamm-Horsfall glycoprotein. They have a much lower immunoreactivity towards the antibody than does the urinary glycoprotein. Tamm-Horsfall glycoprotein could not be demonstrated in normal serum by the techniques used. The implications of these findings are discussed in terms of pathology involving Tamm-Horsfall glycoprotein.

Properties of a glycopeptide isolated from human Tamm-Horsfall glycoprotein. Interaction with leucoagglutinin and anti-(human Tamm-Horsfall glycoprotein) antibodies

A sialylated glycopeptide isolated after Pronase digestion of human Tamm-Horsfall glycoprotein behaves as a powerful monovalent hapten in the precipitin reaction between human Tamm-Horsfall glycoprotein and leucoagglutinin, but fails to inhibit the interaction of the glycoprotein with rabbit anti-(human Tamm-Horsfall glycoprotein) antibodies. The glycopeptide is much less active than the intact glycoprotein as an inhibitor of lymphocyte transformation induced by leucoagglutinin.

Specific interaction of human Tamm-Horsfall gylcoprotein with leucoagglutinin, a lectin from Phaseolus vulgaris (red kidney bean)

Human Tamm-Horsfall glycoprotein inhibits lymphocyte transformation induced by leucoagglutinin and haemagglutinin from Phaseolus vulgaris (red kidney bean). The glycoprotein interacts with the two lectins, giving insoluble precipitates. The interaction with leucoagglutinin is highly specific, and the shape of the precipitin curve is that of an antigen-antibody reaction; precipitation is specifically inhibited by N-acetyl-D-galactosamine. Results are discussed, and it is suggested that inhibition of lymphocyte transformation is due to competition between human Tamm-Horsfall glycoprotein and carbohydrate receptors on lymphocytes for the two lectins. The interaction between human Tamm-Horsfall glycoprotein and Phaseolus vulgaris lectins has been used to develop a one-step procedure for the separation of the two lectins by affinity chromatography on (human Tamm-Horsfall-glycoprotein)-Sepharose.

Pathophysiology of Tamm-Horsfall protein

Tamm-Horsfall protein, a renal glycoprotein present in normal urine, is the primary constituent of urinary casts. Immunoelectron microscopy has shown that this protein is localized selectively along surface membranes of the thick ascending loop of Henle. In this surface membrane site, the unique aggregation and gel formation of Tamm-Horsfall protein in response to increasing concentrations of electrolytes within physiologic ranges may influence the permeability characteristics of this nephron segment. These aggregation characteristics also play a role in pathologic conditions and lead to the prolonged persistence of interstitial Tamm-Horsfall protein deposits in several tubulointerstitial diseases. Recent studies have demonstrated immunologic responses to this protein, including an immune complex tubulointerstitial nephritis in rats mediated by autoantibodies to Tamm-Horsfall protein.

Localization by immunofluorescence and by light- and electron-microscopic immunoperoxidase techniques of Tamm-Horsfall glycoprotein in adult hamster kidney

1. Tamm-Horsfall glycoprotein was isolated from hamster urine and antiserum against it was produced in rabbits. Immunoglobulin G was isolated from the antiserum. 2. Indirect methods of immunofluorescence staining were applied to kidney sections previously fixed by both perfusion and immersion methods. Tamm-Horsfall glycoprotein was identified associated with only the cells of the ascending limb of the loop of Henle and the distal convoluted tubule. Maculae densae were free of the glycoprotein. 3. Indirect immunoperoxidase procedures with light microscopy were applied to kidney sections. The results extended those found by immunofluorescence by showing that the glycoprotein is largely associated with the plasma membrane of the cells. Macula densa cells were shown to be free of the glycoprotein, although the luminal surface of the remaining cells in the transverse section of the nephron at that region was shown to contain it. 4. A variety of immuno-electron-microscopic techniques were applied to sections previously fixed in a number of ways. Providing periodate/lysine/paraformaldehyde was used as the fixative, the glycoprotein was often seen to be present not only on the luminal surface of the cells of the thick ascending limb of the loop of Henle and of the distal convoluted tubule, but also on the basal plasma membrane, including the infoldings. 5. It is generally accepted that the hyperosmolarity in the medulla of the kidney results from passage of Cl(-) ions with their accompanying Na(+) ions across the single cell layer of the lumen of the thick ascending limb of the loop of Henle, a region of the nephron with relatively high impermeability to water. We suggest that Tamm-Horsfall glycoprotein operates as a barrier to decrease the passage of water molecules by trapping the latter at the membrane of the cells. Our hypothesis requires the glycoprotein on the basal plasma membrane also.