25356333
Familial juvenile hyperuricemic nephropathy: detection of mutations in the uromodulin gene in five Japanese families.
BACKGROUND
Familial juvenile hyperuricemic nephropathy (FJHN) is an autosomal-dominant disease characterized by hyperuricemia of underexcretion type, gout, and chronic renal failure. We previously reported linkage on chromosome 16p12 in a large Japanese family designated as family 1 in the present study. Recent reports on the discovery of mutations of the uromodulin (UMOD) gene in families with FJHN encouraged us to screen UMOD mutations in Japanese families with FJHN, including family 1.


METHODS
Six unrelated Japanese families with FJHN were examined for mutations of the UMOD gene by direct sequencing. To confirm the results of the mutation screening, parametric linkage analyses were performed using markers in 16p12 region and around other candidate genes of FJHN.


RESULTS
Five separate heterozygous mutations (Cys52Trp, Cys135Ser, Cys195Phe, Trp202Ser, and Pro236Leu) were found in five families, including family 1. All mutations were co-segregated with the disease phenotype in all families, except for family 1, in which an individual in the youngest generation was found as a phenocopy by the genetic testing. Revised multipoint linkage analysis showed that the UMOD gene was located in the interval showing logarithm of odds (LOD) score above 6.0. One family carrying no mutation in the UMOD gene showed no linkage to the medullary cystic kidney disease type 1 (MCKD1) locus, the genes of hepatocyte nuclear factor-1beta (HNF-1beta), or urate transporters URAT1 and hUAT.


CONCLUSION
Our results gave an evidence for the mutation of the UMOD gene in the majority of Japanese families with FJHN. Genetic heterogeneity of FJHN was also confirmed. Genetic testing is necessary for definite diagnosis in some cases especially in the young generation.
23797938
Autosomal dominant transmission of gouty arthritis with renal disease in a large Japanese family.
Six generations of a Japanese family had gouty arthritis and progressive nephropathy. Data on nine of 51 women (18%) and 15 of 66 men (23%) with either asymptomatic hyperuricaemia, gouty arthritis, or renal insufficiency were obtained. Renal function in four men and one woman with hyperuricaemia or gouty arthritis was also examined. Urinary excretion of uric acid was decreased in all subjects examined, including the young. Erythrocyte phosphoribosylpyrophosphate synthetase and hypoxanthine-guanine phosphoribosyltransferase activities determined in 10 patients were normal. Some patients had been treated with allopurinol to reduce serum uric acid concentrations, but the treatment did not prevent progression of renal impairment. Transmission of the disease in this large family is considered to be autosomal dominant. The data suggest that the disease in this family is the same entity as that described by other workers--that is, familial urate nephropathy. As far as is known this is the largest family with this disease so far reported.
5637932
Familial juvenile hyperuricemic nephropathy and autosomal dominant medullary cystic kidney disease type 2: two facets of the same disease?
Familial juvenile hyperuricemic nephropathy (FJHN) is an autosomal dominant disorder heralded by hyperuricemia during childhood; it is characterized by chronic interstitial nephritis, with marked thickening of tubular basement membranes, and leads to progressive renal failure during adulthood. A gene for FJHN in two Czech families was recently mapped to chromosome 16p11.2, close to the MCKD2 locus, which is responsible for a variant of autosomal dominant medullary cystic kidney disease observed in an Italian family. In a large Belgian family with FJHN, a tight linkage between the disorder and the marker D16S3060, located within the MCKD2 locus on chromosome 16p12 (maximal two-point logarithmic odds score of 3.74 at a recombination fraction of theta = 0), was observed in this study. The candidate region was further narrowed to a 1.3-Mb interval between D16S501 and D16S3036. Together with the striking clinical and pathologic resemblance between previously reported medullary cystic kidney disease type 2 and FJHN occurring in the Belgian family (including the presence of medullary cysts), this study suggests that these two disorders are facets of the same disease.
33804000
Genetic mapping studies of familial juvenile hyperuricemic nephropathy on chromosome 16p11-p13.
Familial juvenile hyperuricemic nephropathy (FJHN), which is inherited as an autosomal dominant disorder, is characterized by hyperuricemia, a low fractional renal excretion of urate, and chronic renal failure that is associated with interstitial fibrosis. Studies in 4 families (3 European and 1 Japanese) have mapped the gene causing autosomal dominant FJHN to chromosome 16p11-p13. To refine this location we have pursued linkage studies in 7 European families with autosomal dominant FJHN and used 11 chromosome 16p11-p13 polymorphic loci whose order has been established as 16pter-D16S3069-D16S3060-D16S3041-D16S3036-D16S3046-[D16S403,D16S417]-D16S420-D16S3113-D16S401-D16S3133-16cen. Cosegregation between these polymorphic loci and FJHN was observed in 5 of the families, and linkage was established between FJHN and 6 loci (peak LOD score, 5.32 with D16S417, at 0% recombination), with the most likely location of FJHN being within a 22-centimorgan interval flanked centromerically by D16S401 and telomerically by D16S3069. Furthermore, FJHN in 2 families was found not to be linked to chromosome 16p11-p13, thereby demonstrating genetic heterogeneity. Thus, 5 additional families with FJHN showing linkage to chromosome 16p11-p13 loci have been identified, and genetic heterogeneity has been demonstrated in more than 25% of FJHN families. These results will facilitate the characterization of this gene regulating urate metabolism.
24239272
Familial juvenile hyperuricaemic nephropathy (FJHN): linkage analysis in 15 families, physical and transcriptional characterisation of the FJHN critical region on chromosome 16p11.2 and the analysis of seven candidate genes
Familial juvenile hyperuricaemic nephropathy (FJHN) is an autosomal dominant renal disease characterised by juvenile onset of hyperuricaemia, gouty arthritis, and progressive renal failure at an early age. Recent studies in four kindreds showed linkage of a gene for FJHN to the same genomic interval on chromosome 16p11.2, where the gene for the phenotypically similar medullary cystic disease type 2 (MCKD2) has been localised. In this study we performed linkage analysis in additional 15 FJHN families. Linkage of FJHN to 16p11.2 was confirmed in six families, which suggests that, in a large proportion of FJHN kindreds, the disease is likely to be caused by a gene or genes located outside of 16p11.2. Haplotype analysis of the new and previously analysed families provided two non-overlapping critical regions on 16p11.2–FJHN1, delimited by markers D16S499-D16S3036 and FJHN2, delimited by markers D16S412-D16S3116. Considering MCKD2 to be a distinct molecular entity, the analysis suggests that as many as three kidney disease genes may be located in close proximity on 16p11.2. From genomic databases we compiled integrated physical and transcription maps of whole critical genomic region in which 45 known genes and 129 predicted loci have been localised. We selected, analysed and found no pathogenic mutations in seven candidate genes. The linkage and haplotype analysis reported here demonstrates the genetic heterogeneity of FJHN. The report of integrated physical and mostly in-silico predicted transcription maps of the FJHN critical region provides a basis for precise experimental annotation of the current transcript map, which is essential for final identification of the FJHN gene(s).
41517319
Letter: Gouty arthritis and polycystic kidney disease.
Excerpt To the editor: The incidence of acute gouty arthritis as a complication of chronic nongouty renal disease is less than 1% (1, 2). Of a total of 11 unrelated patients with adult polycystic d...
40539567
Familial occurrence of hyperuricemia, gout, and medullary cystic disease.
We observed hyperuricemia, acute gouty arthritis, and renal medullary cystic disease in three members of a family over two generations. Two of these individuals were women who developed gout by age 20 years. Two teenage sons of one of these patients had severe hyperuricemia, which appeared due to underexcretion of uric acid. To our knowledge the occurrence of hyperuricemia, gout, and renal medullary cystic disease has not been reported previously.
19097880
Hyperuricemia, gout, and autosomal dominant polycystic kidney disease.
The relationship between hyperuricemia, gout, and autosomal dominant polycystic kidney disease (ADPKD) is not widely recognized. In an attempt to further clarify this relationship, the authors have studied 17 patients with ADPKD, 9 controls, 9 patients with proven gout and chronic renal failure, 11 patients with gout and normal renal function, and 11 patients with chronic renal failure. The mean serum uric acid concentration was higher in patients with ADPKD as a group than in controls (8.0 +/- 1.7 mg/dl vs. 6.4 +/- 1.6 mg/dl, p less than .02). Clinical gout was identified in 24% of patients with ADPKD; none of the patients with chronic renal failure of other etiologies had gout. Fractional excretion of uric acid and the activity of the enzyme hypoxanthine guanine phosphoribosyl transferase (HGPRT) were not different among the groups studied. From this study the authors conclude that ADPKD should be included among those diseases associated with hyperuricemia and gout. A partial deficiency in HGPRT or abnormal renal handling of uric acid do not appear to be responsible for the increased incidence of gout in patients with ADPKD.
36953401
Chromosome 1 localization of a gene for autosomal dominant medullary cystic kidney disease.
There is a group of inherited cystic nephropathies that are characterized by juvenile onset recessive inheritance (familial juvenile nephronophthisis, FJN) or by adult onset dominant inheritance (medullary cystic disease, MCD) and share similar clinico-pathological presentation to the extent that they are usually grouped together under the term FJN/MCD complex. The main symptoms consist of renal cyst formation in the medulla or the corticomedullary junction and salt wasting. Although earlier reports had suggested that one single gene may be responsible for this pathology, recent reports have shown that the FJN complex itself comprises a genetically heterogeneous group. Here we are presenting two large Cypriot families that segregate autosomal dominant medullary cystic kidney disease (ADMCKD) with hyperuricemia and gout and with very late age of onset (mean 62.2 and 51.5 years). We performed DNA linkage mapping using highly polymorphic microsatellite markers and found linkage to marker locus D1S1595 at 1q21 with a two-point lod score of 6.45 at Theta = 0.00. Analysis of haplotypes and of critical recombinants enabled confinement of the disease locus within an approximately 8 cM region between marker loci D1S498 and D1S2125. FISH mapping with a large P1 clone confirmed the physical localization within 1q21. The two families share the same disease haplotype, thus suggesting their relationship through a common ancestor and the possible existence of a single ADMCKD-causing mutation within these families. To our knowledge this is the first genetic locus identified to cause FJN/MCD pathology of the dominant adult type.
39275496
Towards the identification of (a) gene(s) for autosomal dominant medullary cystic kidney disease.
Medullary cystic kidney disease (MCKD) belongs with nephronophthisis (NPH) in a group of inherited tubulo-interstitial nephritis, which has been referred to as the NPH-MCKD complex. Although MCKD and NPH share morphological features, they differ in several respects. The most common variant is recessive juvenile NPH, with onset in childhood and leading to end-stage renal disease (ESRD) within the 2nd decade of life; the most frequent extrarenal involvement is tapeto-retinal degeneration. MCKD is a dominant condition recognized in later life and leading to ESRD at the age of 50 years; hyperuricemia and gout can be associated features. The first sign of MCKD is polyuria; later, the clinical findings relate to renal insufficiency. Originally, NPH and MCKD were considered separate entities. Subsequently, it has been suggested that the two diseases were a single disorder due to the clinico-pathological identity. This unifying conception was later refuted due to the identification of MCKD dominant families. Recently, considerable insight has been gained into the genetics of the NPH-MCKD complex. The majority of juvenile NPH cases are due to deletion of the NPHP1 gene on chromosome 2q13. Genes for infantile and adolescent NPH have been localized respectively to chromosome 9q22-q31 and 3q22. A new locus, NPHP4, has been recently identified on chromosome 1p36. Two genes predisposing to dominant MCKD, MCKD1 and MCKD2, have been localized to chromosome 1q21 and 16p12. Independent confirmation of the locations of MCKD1 and MCKD2 in other MCKD families, with or without hyperuricemia and gout, has been reported. The gene for familial juvenile hyperuricemic nephropathy (FJHN), a phenotype that is very similar to MCKD, was recently mapped to 16p12, in a region overlapping with the MCKD2 locus, raising the question as to whether MCKD2 and FJHN are allelic variants of the same disease entity. The ultimate proof of the allelism between MCKD2 and FJHN will be provided by the identification of the responsible gene(s). Identification and characterization of the MCKD and FJHN genes will help to clarify the pathogenesis and classification of hereditary tubulo-interstitial nephritides.
25359743
UROMODULIN mutations cause familial juvenile hyperuricemic nephropathy.
Gout, which is commonly associated with hyperuricemia, affects 0.2% of the population. Hyperuricemia has a heterogeneous etiology that may be due to either over production and/or reduced renal clearance, of urate. In order to identify the mechanisms underlying reduced excretion of urate, we undertook positional cloning studies of familial juvenile hyperuricaemic nephropathy (FJHN), which is an autosomal dominant disorder characterized by hyperuricaemia, a low fractional renal excretion of urate, and chronic renal failure that is associated with interstitial fibrosis. The FJHN locus has been previously localized to a 22 centiMorgan interval flanked centromerically by D16S401 and telomerically by D16S3069, on chromosome 16p11-p13. This interval contains over 120 genes and we selected 13 renal expressed sequences to search for mutations in 5 unrelated FJHN families that contained 21 affected and 24 unaffected members. This revealed 5 heterozygous missense mutations (Cys77Tyr, Cys126Arg, Asn128Ser, Cys255Tyr and Cys300Gly) that altered evolutionary conserved residues in the gene encoding UROMODULIN. UROMODULIN, which is an 85 Kda glycoprotein, has roles in renal stone formation, the modulation of immune responses, and urothelial cytoprotection. The results of our studies, which have identified the gene causing FJHN, now indicate a further, novel role for UROMODULIN in urate metabolism.
37555962
Familial Juvenile Gouty Nephropathy: Exclusion of 16p12 from the Candidate Locus
Background/Aims: Familial juvenile gouty nephropathy (FJGN, MIM 162000) is an autosomal-dominant renal disease characterized by underexcretion-type hyperuricemia, gouty arthritis, and progressive renal disease at younger ages. We analyzed the localization of the responsible gene for FJGN concerning the chromosomal region of 16p12 using parametric linkage analysis in our FJGN. Methods: The affected members of this family were accompanied with polyuria due to nephrogenic diabetes insipidus and without hypertension. Fifteen samples were collected from 9 affected and 6 nonaffected members of the family. By using microsatellite markers mainly focused on the short arm of chromosome 16, two point and multipoint linkage analyses were carried out. Results: All of the 2-point logarithm of odds (LOD) scores were typically negative and all of the multipoint LOD scores were less than –3.0 in our FJGN family. Conclusion: The results suggested that the localization of the responsible gene to 16p12 can be excluded in our FJGN family. This finding means that the responsible gene for FJGN is not common.
27568812
Functional reconstitution, membrane targeting, genomic structure, and chromosomal localization of a human urate transporter.
Elevated serum levels of uric acid have been associated with an increased risk for gout, hypertension, cardiovascular disease, and renal failure. The molecular mechanisms for the diminished excretion of urate in these disorders, however, remain poorly understood. Human galectin 9, which is highly homologous to the rat urate transporter rUAT, has been reported to be a secreted or cytosolic protein. We provide data that galectin 9 is hUAT, the first identified human urate transporter. hUAT is a highly selective urate ion channel when inserted in lipid bilayers. When expressed in renal epithelial cells it is an integral plasma membrane protein with at least two transmembrane domains. The gene for hUAT consists of 11 exons and is mapped to chromosome 17; a highly homologous gene, hUAT2, maps to a nearby region of chromosome 17 and is also likely to be a urate transporter. hUAT is expressed in a wide variety of tissues and is present in at least three isoforms; hUAT2 is less widely expressed at severalfold lower levels than hUAT. Further knowledge about the functions of hUAT, its isoforms, and hUAT2, as well as mutational analysis of hUAT1 and hUAT2 in individuals or families with hyperuricemia, should significantly improve our understanding of the molecular mechanisms of urate homeostasis.
6552399
Uromodulin: a unique 85-kilodalton immunosuppressive glycoprotein isolated from urine of pregnant women.
Crude fractions of urine from pregnant women are immunosuppressive in vitro. An 85-kilodalton immunosuppressive glycoprotein purified to homogeneity from such urine inhibited in vitro assays of human T-cell and monocyte activity at concentrations of 10(-9) to 10(-11) molar. This material was nontoxic and blocked early events required for normal T-cell proliferation in vitro. On the basis of its tissue source and its in vitro activity, the name "uromodulin" is proposed for this glycoprotein.
25589628
Uromodulin (Tamm-Horsfall glycoprotein/uromucoid) is a phosphatidylinositol-linked membrane protein.
Uromodulin, originally identified as an immunosuppressive glycoprotein in the urine of pregnant women, has been previously shown to be identical to human Tamm-Horsfall glycoprotein (THP). THP is synthesized by the kidney and localizes to the renal thick ascending limb and early distal tubule. It is released into the urine in large quantities and thus represents a potential candidate for a protein secreted in a polarized fashion from the apical plasma membrane of epithelial cells in vivo. After introduction of the full-length cDNA encoding uromodulin/THP into HeLa, Caco-2, and Madin-Darby canine kidney cells by transfection, however, the expressed glycoprotein was almost exclusively cell-associated, as determined by immunoprecipitation after radioactive labeling of the cells. By immunofluorescence, THP was localized to the plasma membranes of transfected cells. In transfected cell extracts, THP also remained primarily in the detergent phase in a Triton X-114 partitioning assay, indicating that it has a hydrophobic character, in contrast to its behavior after isolation from human urine. Triton X-114 detergent-associated THP was redistributed to the aqueous phase after treatment of cell extracts with phosphatidylinositol-specific phospholipase C. Treatment of intact transfected HeLa cells with phosphatidylinositol-specific phospholipase C also resulted in the release of THP into the medium, suggesting that it is a glycosylphosphatidylinositol (GPI)-linked membrane protein. Similar to other known GPI-linked proteins, uromodulin/THP contains a stretch of 16 hydrophobic amino acids at its extreme carboxyl terminus which could function as a GPI addition signal and was shown to label with [3H]ethanolamine. The results indicate that THP is a member of this class of lipid-linked membrane proteins and is released into the urine after the loss of its hydrophobic anchor, probably by the action of a phospholipase or protease.
22696174
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.
21204324
Pathologic localization of Tamm-Horsfall protein in interstitial deposits in renal disease.
Interstitial periodic acid-Schiff positive deposits of amorphous or fibrillar material were observed in 32% of kidneys with a variety of tubulointerstitial diseases, including medullary cystic disease (60%), chronic pyelonephritis (20%), and hydronephrosis (33%). Immunofluorescent staining for Tamm-Horsfall protein showed interstitial localization of this protein which was identical in distribution, shape, size, and fine detail with the periodic acid-Schiff positive deposits. The deposits appeared to originate from disrupted tubules and were sometimes surrounded by inflammatory infiltrate. The intrarenal localization of Tamm-Horsfall protein outside of distal tubules in pathologic states indicates that this protein may have a role in the pathogenesis of renal disease.
44560184
Tamm-Horsfall protein. Abnormal localization in renal disease.
Interstitial deposits of periodic acid-Schiff positive fibrillar material have been detected in a variety of diseases associated with tubulointerstitial pathology. This material has been shown to be Tamm-Horsfall protein by immunofluorescent, immunochemical, and electron microscopic studies. Prospective evaluation of 133 kidneys revealed deposits in 11 per cent. These deposits included medullary cystic disease (50 per cent), obstructive uropathy and vesicoureteral reflux (21 per cent), and tubulointerstitial disease (29 per cent). Tamm-Horsfall protein was also detected in Bowman's space in four cases of obstructive uropathy. It is proposed that these deposits result from severe tubular damage with release of Tamm-Horsfall protein from its normal intracellular and intralumenal locations into the renal interstitium. We speculate that the intersitial deposition of this sequestered protein may result in a continued inflammatory response and progressive renal damage.
36219257
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.
25467367
Biosynthesis and oligosaccharide processing of human Tamm-Horsfall glycoprotein permanently expressed in HeLa cells.
Human Tamm-Horsfall glycoprotein (T-H) is produced by renal cells of ascending limb of loop of Henle and is largely excreted in urine. N-linked glycans account for close to 30% of the weight of T-H. We studied the biosynthesis of recombinant T-H permanently expressed in HeLa cells. The conversion from the precursor (84 kDa) to the mature form (97 kDa) mainly depends on the processing of glycans from the high-mannose to polyantennary type. The conversion from precursor to mature form is very slow and the glycan structure of precursor appears to be that of a glycoprotein not yet processed by Golgi alpha 1,2 mannosidase. Since T-H has a very high number of disulfide bridges (more than 50 cysteine residues/mol) one may infer that the rate limiting step for the precursor export out of ER is the formation of a correct set of disulfide bonds. Mature T-H isolated from HeLa cells retained one N-linked chain with the high-mannose structure similarly to urinary T-H. This result indicates that the occurrence of one unprocessed high-mannose chain in mature T-H is host-cell independent and very likely related to the T-H primary structure.
33707799
Protein misfolding and degradation in genetic diseases
Investigations of genetic diseases such as cystic fibrosis, α‐1‐antitrypsin deficiency, phenylketonuria, mitochondrial acyl‐CoA dehydrogenase deficiencies, and many others have shown that enhanced proteolytic degradation of mutant proteins is a common molecular pathological mechanism. Detailed studies of the fate of mutant proteins in some of these diseases have revealed that impaired or aberrant folding of mutant polypeptides typically results in prolonged interaction with molecular chaperones and degradation by intracellular proteases before the functional conformation is acquired. This appears to be the case for many missense mutations and short in‐frame deletions or insertions that represent a major fraction of the mutations detected in genetic diseases. In some diseases, or under some circumstances, the degradation system is not efficient. Instead, aberrant folding leads to accumulation of protein aggregates that damage the cell. Mechanisms by which misfolded proteins are selected for degradation have first been delineated for the endoplasmatic reticulum; this process has been termed "protein quality control." Similar mechanisms appear to be operative in all cellular compartments in which proteins fold. Within the context of genetic diseases, we review knowledge on the molecular processes underlying protein quality control in the various subcellular compartments. The important impact of such systems for variability of the expression of genetic deficiencies is emphasised. Hum Mutat 14:186–198, 1999. © 1999 Wiley‐Liss, Inc.
13471746
Tamm Horsfall protein binds to a single class of carbohydrate specific receptors on human neutrophils.
Several studies have implicated urinary Tamm Horsfall protein (THP) in the aetiology of tubulointerstitial inflammation. Previous research has demonstrated that particulate THP will initiate inflammatory activation of human polymorphonuclear leukocytes (PMN) through a trypsin sensitive mechanism. The present study describes the binding of 125I-monomeric THP to human PMN at 4 degrees C and demonstrates that radiolabeled THP binds to PMN in a saturable, reversible and time dependent manner. The addition of 400 to 600 ng 125I-THP/2 x 10(6) PMN was sufficient to achieve saturable binding. Scatchard analysis of binding data yielded linear plots suggesting a single class of receptors with a mean density of 26218/cell and a dissociation constant (KD) of 4.2 x 10(-9) M. Binding reached steady state by 15 minutes and could be rapidly displaced by the addition of an excess of unlabeled THP. The KD calculated from experimentally derived kinetic rate constants (k1 and k2) was of a similar order of magnitude (0.9 x 10(-9) M) to that generated from Scatchard plots. In addition 125I-THP bound specifically to PMN plasma membrane immobilized on nitrocellulose filters, a process which could be inhibited by unlabeled monomeric THP. Chemical modification of unlabeled THP abolished its capacity to inhibit binding. Specific inhibition studies showed that N-acetylneuraminic (sialic) acid dose dependently displaced the binding of 125I-THP to immobilized PMN membranes at concentrations up to 100 mM. These results indicate that the reported activation of human PMN by THP is mediated through a single class of sialic acid-specific cell surface receptors.
43016577
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.
11810941
Release of gelatinase and superoxide from human mononuclear phagocytes in response to particulate Tamm Horsfall protein.
This study describes the in vitro activation of human mononuclear phagocytes by particulate Tamm Horsfall protein (THP). Peripheral blood monocytes phagocytosed THP particles with the accompanying release of superoxide radicals, N-acetyl-beta-D-glucosaminidase, and neutral metalloproteinase. Immunoprecipitation and substrate gel analysis identified the neutral proteinase as a 95-kd gelatinase. A comparison with other particulate ligands highlighted the specificity of the response to THP and showed that the magnitude of the response was comparable with that obtained with lipopolysaccharide (100 micrograms/ml). Parallel studies using peritoneal macrophages resulted in a similar pattern of enzyme release and reactive oxygen species synthesis. THP has been implicated in the pathogenesis of tubulointerstitial nephritis associated with reflux nephropathy. The present study indicates that an inflammatory response initiated by a neutrophil-THP interaction may be extended into a chronic phase via the activation of mononuclear phagocytes. The subsequent release of reactive oxygen metabolites and proteinases may contribute to the tissue damage and fibrosis associated with chronic immune-mediated tubulointerstitial nephritis.
27019797
Uromodulin and Tamm-Horsfall protein induce human monocytes to secrete TNF and express tissue factor.
Effects of uromodulin (URO) and Tamm-Horsfall protein (THP), the most abundant proteins in the urine of pregnant and normal women, respectively, on the induction of TNF-alpha secretion and tissue factor (TF) expression of human monocytes were studied. THP, URO, and its fragments stimulated human mononuclear cells to proliferate and secrete TNF-alpha. The release of URO and THP-induced TNF-alpha in monocytes was dependent upon protein tyrosine kinase activation that results in tyrosine phosphorylation. URO and THP also induced TF expression of human monocytes and monocytic cell line U937 in a dose-dependent manner. TF expression was transient, reached its peak at 6 h and declined toward basal levels by 24 h. Reverse transcriptase-PCR and dot-blot analysis confirmed the induction of TF mRNA synthesis. URO and THP-induced TF expression were inhibited by actinomycin D and pentoxifylline further supporting the requirement of de novo TF mRNA synthesis. The possibility of LPS contamination of URO and THP was excluded because: 1) URO and THP-induced TF expression were inhibited by specific Ab; 2) URO was less capable of inducing TF in HUVEC as compared with LPS; 3) polymyxin B blocked the induction of Limulus clotting by LPS but not by URO and THP; 4) both LPS-sensitive (C3H/HeN) and -resistant (C3H/HeJ) mice produced little or no TNF-alpha after URO challenge. Therefore, our findings suggest that URO and THP play a significant role in the innate immunity of the urinary system and that the immunostimulatory activity of URO is potentially useful for immunotherapy.
9466910
Tubulointerstitial immune complex nephritis in rats immunized with Tamm-Horsfall protein.
Rats immunized with Tamm-Horsfall protein (TH) developed autoantibodies to TH and tubulointerstitial nephritis with granular deposits of IgG, C3, and TH at the base of tubular cells of the thick ascending limb of Henle's loop and selective infiltration of leukocytes around this distal nephron segment. Selective IgG deposition at the base of cells in the tubular segment containing TH and the direct relationships of the amount of immune deposits and the severity of histologic lesions to serum levels of anti-TH antibodies suggest a pathogenetic role for the autoantibodies to TH. The immune deposits in this model of tubulointerstitial nephritis appear to be the consequence of in situ formation of immune complexes. This mechanism involves the diffusion of circulating antibodies to TH across tubular basement membranes and their combination with TH molecules associated with tubular cell surface membranes.
31058782
Tubulointerstitial nephritis and immunologic responses to Tamm-Horsfall protein in rabbits challenged with homologous urine or Tamm-Horsfall protein.
Tubulointerstitial nephritis was produced in 19 of 23 New Zealand White rabbits challenged i.v. with adjuvant-free homologous urine for greater than or equal to 16 wk and 11 of 14 challenged with adjuvant-free rabbit Tamm-Horsfall protein for 2 to 24 wk. Lesions were identical in the two groups of rabbits and were characterized by focal mononuclear infiltrates and microscopic scarring localized to distal nephron segments identified as the thick ascending limb of the loop of Henle. Concomitant immunoglobulin deposition was not detected despite antecedent elevations in serum IgG antibody directed against Tamm-Horsfall protein in 17 of 19 and 10 of 11 affected rabbits, respectively. Peripheral lymphocytes from affected rabbits were found to be cytotoxic and underwent blast transformation in the presence of homologous urine or Tamm-Horsfall protein in vitro. These lymphocytes were shown to produce a soluble cytotoxic product upon exposure to Tamm-Horsfall protein. Neither tubulointerstitial nephritis nor this pattern of cellular and humoral immune response to Tamm-Horsfall protein was found in two age-matched control groups: one unchallenged, and the other challenged i.v. with urine that had been selectively depleted of Tamm-Horsfall protein by 95%. It is concluded that the tubulointerstitial nephritis produced in rabbits by injection of urine or Tamm-Horsfall protein is the result of a predominately cellular immune response directed against Tamm-Horsfall protein.
8641372
GP-2/THP gene family encodes self-binding glycosylphosphatidylinositol-anchored proteins in apical secretory compartments of pancreas and kidney.
A family of homologous genes is shown to encode GP-2, the major glycosylphosphatidylinositol (GPI)-linked glycoprotein of pancreatic zymogen granule membranes, and Tamm-Horsfall protein (THP), a GPI-linked glycoprotein associated with apical vesicles in kidney thick ascending limb of Henle (TALH) cells. The C-terminal regions of GP-2 (Asp54-Phe530) and THP (Asp175-His644) from rat show 53% identity, 86% similarity, and 26 conserved cysteine residues including one epidermal growth factor motif. The unique N-terminal domain of rat THP (unique-THP, Pro29-Gln174) shows four conserved epidermal growth factor motifs, three in tandem and one in reverse orientation. GP-2 homologues are observed in a wide variety of epithelial cells, several of which contain highly regulated secretory processes. GP-2 released from zymogen granule membranes with phosphatidylinositol phospholipase C reacts with anti-cross-reactive determinant antibody (anti-CRD), confirming the GPI nature of the pancreatic homologue. In contrast, GP-2 and THP, released endogenously from pancreas and kidney, respectively, do not react with anti-cross-reactive determinant antibody, suggesting alternative enzymatic mechanisms for their physiological release. Globular domains of GP-2 and THP, but not albumin, show pH- and ion-dependent self-association in vitro. The GP-2/THP family appears to represent a newly discovered class of GPI-anchored proteins, which may utilize pH- and ion-dependent self-association mechanisms for establishing membrane (micro)domains targeted to intracellular secretory compartments.
28192676
Cytochemical and immunocytochemical characterization of a fibrillar network (GP2) in pancreatic juice: possible role as a sieve in the pancreatic ductal system.
The secretory product of the exocrine pancreas contains sedimentable and non-sedimentable materials. Electron microscopy of the pellet obtained after ultracentrifugation reveals two major components: microvesicles (pancreasomes) and a fibrillar network of small mesh size. Negative staining of an unfixed pellet demonstrated that these structures are not fixation artifacts. Cytochemical analysis showed that pancreasomes are reactive to osmication and uranyl acetate staining, whereas the fibrillar network was unreactive thereby indicating that the latter does not contain lipids; however, lead citrate staining reveals the network. Alcian blue, known to bind sulfate groups of mucosubstances, reacted strongly with the fibrillar network. The pellet was also characterized by immunocytochemistry with specific antibodies to amylase and glycoprotein 2 (GP2). Both antibodies were located only on the fibrillar network. Washing of the pellet with 100 mM KCl-250 mM NaBr had little effect on GP2 content, but reduced considerably alpha-amylase associated with the reticular matrix. It appeared that GP2 was the major component of the scaffolding that gives rise to the fibrillar network and that other proteins such as alpha-amylase could reversibly bind to it. When double-labeling immunocytochemistry was carried out on the unwashed pellet, labeling of the first antigen reduced the labeling of the second. Removal of amylase by washing the pellet increased the GP2 signal. These results indicate that amylase is bound on the GP2 network. Although the function of the GP2 network is still not clearly defined several possibilities could be envisaged at the level of the pancreatic duct system: 1) The network could drain off any aggregates or precipitates forming in small ducts. 2) The small mesh of the network would present a physical barrier to infecting bacteria that could enter into the duct system from the intestine, especially in conditions of low flow rates. 3) The network may exert a mechanical pressure on the membranes bordering the acinar lumen and small ducts thereby preventing their collapse in basal conditions.
32761214
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.
25523095
Tamm-Horsfall glycoprotein: ultrastructural immunoperoxidase localization in rat kidney.
Tamm-Horsfall urinary glycoprotein (TH) is the primary constituent of urinary casts. The intracellular distribution of TH in normal rat kidney was determined by immunoelectron microscopy using horseradish peroxidase-labeled antibodies and compared with morphologic localization of TH by immunofluorescence and light immunoperoxidase microscopy. Electron microscopy revealed an intracellular localization of TH restricted to the thick ascending limb of the loop of Henle (ALH). In this nephron segment, TH was distributed on and between adjacent intercellular membranes and infolding intracellular membranes at the base of these cells, within Golgi vacuoles, apical vesicles, and on the luminal membranes. Macula densa cells were negative, although typical ALH cells across the lumen of the same tubular segment were positive. Other renal segments were negative for intracellular TH. The unique distribution of TH is consistent with the known function of the ALH as the diluting segment of the nephron. We speculate that the aggregation and gel formation of TH on and between ALH surface membranes may restrict water movement across the ALH. This influence on permeability would be an important role for TH in the generation of concentration gradients for the countercurrent multiplier system of the kidney.
12206931
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.
78610241
Goodman and Gilman's The Pharmacological Basis of Therapeutics
Being asked to review Goodman and Gilman is a lot like being asked to comment on motherhood. The stature of " G & G ," the "blue bible" of pharmacology, is intimidating. For a reviewer reared in its teachings, it is difficult to find fault. Luckily, in keeping with the textbook's tradition, this new edition is virtually without fault. The book covers an everincreasing body of knowledge in crisp, clear language and its time-honored, familiar format. The eighth edition marks the 50th anniversary of the textbook. As mentioned in the preface by the senior editor, Alfred Goodman Gilman, the primary objectives of the book have remained the same since his father and Dr Goodman wrote the first edition in 1940: the correlation of pharmacology with related medical sciences, the continual reinterpretation of the actions and uses of drugs in view of medical advances, and the emphasis on applying pharmacodynamics to therapeutics. Dr
45720920
Factors affecting urate excretion following diuretic administration in man.
Abstract In order to investigate the mechanism of diuretic-induced urate retention and hyperuricemia, renal clearance studies were performed in normal subjects, utilizing furosemide and ethacrynic acid. After the intravenous administration of either diuretic, uric acid excretion always increased, at least transiently. However, during the second hour following furosemide or ethacrynic acid, uric acid excretion decreased during diuretic-induced extracellular fluid volume contraction, but remained near or above control levels when urinary losses were simultaneously replaced with isotonic saline solution. The extremely low rates of uric acid excretion in the volume-depleted subjects suggested that tubular secretion was impaired. Since the diminution in uric acid excretion occurred only after volume depletion, a direct effect of these diuretics on tubular secretion is unlikely. Instead, it is postulated that stimulatory and suppressive effects of furosemide and ethacrynic acid on urate secretion could be mediated indirectly through altered renal blood flow and angiotensin release, respectively.