A 92-kDa human immunostimulatory protein

Surface aggregation of urinary proteins and aspartic Acid-rich peptides on the faces of calcium oxalate monohydrate investigated by in situ force microscopy

The growth of calcium oxalate monohydrate in the presence of Tamm-Horsfall protein (THP), osteopontin, and the 27-residue synthetic peptides (DDDS)(6)DDD and (DDDG)(6)DDD (D = aspartic acid, S = serine, and G = glycine) was investigated via in situ atomic force microscopy. The results show that these four growth modulators create extensive deposits on the crystal faces. Depending on the modulator and crystal face, these deposits can occur as discrete aggregates, filamentary structures, or uniform coatings. These proteinaceous films can lead to either the inhibition of or an increase in the step speeds (with respect to the impurity-free system), depending on a range of factors that include peptide or protein concentration, supersaturation, and ionic strength. While THP and the linear peptides act, respectively, to exclusively increase and inhibit growth on the (101) face, both exhibit dual functionality on the (010) face, inhibiting growth at low supersaturation or high modulator concentration and accelerating growth at high supersaturation or low modulator concentration. Based on analyses of growth morphologies and dependencies of step speeds on supersaturation and protein or peptide concentration, we propose a picture of growth modulation that accounts for the observations in terms of the strength of binding to the surfaces and steps and the interplay of electrostatic and solvent-induced forces at the crystal surface.

Tamm-Horsfall glycoprotein: biology and clinical relevance

Tamm-Horsfall glycoprotein (THP) is the most abundant urinary protein in mammals. Urinary excretion occurs by proteolytic cleavage of the large ectodomain of the glycosyl phosphatidylinositol-anchored counterpart exposed at the luminal cell surface of the thick ascending limb of Henle's loop. We describe the physical-chemical structure of human THP and its biosynthesis and interaction with other proteins and leukocytes. The clinical relevance of THP reported here includes: (1) involvement in the pathogenesis of cast nephropathy, urolithiasis, and tubulointerstitial nephritis; (2) abnormalities in urinary excretion in renal diseases; and (3) the recent finding that familial juvenile hyperuricemic nephropathy and autosomal dominant medullary cystic kidney disease 2 arise from mutations of the THP gene. We critically examine the literature on the physiological role and mechanism(s) that promote urinary excretion of THP. Some lines of research deal with the in vitro immunoregulatory activity of THP, termed uromodulin when isolated from urine of pregnant women. However, an immunoregulatory function in vivo has not yet been established. In the most recent literature, there is renewed interest in the capacity of urinary THP to compete efficiently with urothelial cell receptors, such as uroplakins, in adhering to type 1 fimbriated Escherichia coli. This property supports the notion that abundant THP excretion in urine is promoted in the host by selective pressure to obtain an efficient defense against urinary tract infections caused by uropathogenic bacteria.

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.

NEMO trimerizes through its coiled-coil C-terminal domain

NEMO/IkappaB kinase (IKK) gamma is the regulatory component of the IKK complex comprising the two protein kinases, IKKalpha and IKKbeta. To investigate the self-assembly properties of NEMO and to understand further the mechanism of activation of the IKK complex, we purified wild-type and mutant NEMO expressed in Escherichia coli. In the absence of its IKK partners, recombinant NEMO (rNEMO) is a metastable functional monomer correctly folded, according to its fluorescence and far-UV CD spectra, which is binding specifically to the IKK complex. A minor fraction of rNEMO was found tightly associated with DnaK (E. coli Hsp70). We also examined the interaction of NEMO with prokaryotic and eukaryotic Hsp70, and we showed that the Hsp70-NEMO complex forms a supramolecular structure probably corresponding to an assembly intermediate. In vivo cross-linking experiments indicate that native NEMO in association with IKK is in equilibrium between a dimeric and a trimeric form. Similarly to native NEMO, a NEMO mutant deleted from its IKK binding N-terminal domain (residues 242-388) forms a stable trimeric coiled-coil, suggesting that the association of NEMO with IKK or with Hsp70 prevents incorrect interdomain pairing reactions that could lead to aggregation or to an non-native oligomeric state of rNEMO. We propose a model in which the activation of the IKK complex occurs through the trimerization of NEMO upon binding to a not yet identified upstream activator.

The anti-tumoral activity of human glycoprotein HGP.92: a study with the mouse Lewis-lung-tumor cell

The ability of a purified human glycoprotein (HGP.92) to exert anti-tumor activity was investigated in a mouse model using long-term readout assays. In vitro, in the presence of inflammatory mouse macrophages incubated with HGP.92, the growth of the mouse Lewis-lung-tumor cells (3LL) was decreased. This effect was concentration-dependent and required direct contact between tumor targets and HGP.92-treated macrophages. In addition, if the macrophage monolayer was depleted of HGP.92 before addition of the target cells, no more cytostatic effect was observed. This anti-tumor activity of HGP.92-treated mouse macrophage was partially abrogated by addition of catalase in the culture medium, but not by superoxide dismutase or scavengers of the hydroxyl radical and singlet oxygen. Moreover, this tumor-cell growth reduction was not dependent on nitric oxide. In vivo, multiple i.v. injections of HGP.92 (5 times, 3 days apart) during the first week and a half exerted significant anti-tumor activity, as assessed by the reduction of both the number and the size of the lung nodules 3 weeks after i.v. inoculation of 3LL cells.