Plasma proteins immunologically related to inter-alpha-trypsin inhibitor

SDS-polyacrylamide gel electrophoresis and immunoblot were applied to analysis of plasma proteins immunologically related to inter-alpha-trypsin inhibitor (ITI). In this system, anti-ITI sera were able to identify ITI and other components with an Mr near 120 kDa which would be degradation products of ITI by limited proteolysis. An anti-UTI (urinary trypsin-inhibitor) serum could detect, beside these derivatives, two minor components (Mr values near 90 and 60 kDa). Analysis of perchloric acid supernatants of plasma samples, using the same technic, induced visualization of a new component, similar to urinary trypsin inhibitor which could not be detected by direct analysis. This one was also characterized in a higher content in pathological samples (renal failure and infectious diseases).     

cDNA cloning of human inter-alpha-trypsin inhibitor discloses three different proteins

Inter-alpha-trypsin inhibitor (ITI) is a serum protein of unknown function. Part of the molecule (formerly called HI30) is closely related to a tumor-derived protein acting as a growth factor for endothelial cells. We screened a human liver cDNA expression library with antibodies raised against human ITI and isolated several clones which could be divided into three groups according to their DNA sequences. The cDNA of the first group codes for a protein composed of alpha 1-microglobulin (alpha 1M) and urinary trypsin inhibitor (UTI) and is identical to that encoded by a clone originally found by screening a human liver cDNA library with oligonucleotides derived from amino-acid sequences of the two Kunitz-type domains of UTI. The proteins derived from the cDNA of the second and the third group of clones are distantly related to each other, but unrelated to the protein derived from group 1 clones. Partial amino-acid sequencing of ITI isolated from serum allowed the verification of large parts of the cDNA-derived amino-acid sequences. The results favour the view that ITI is not a single chain protein, but rather a very tight complex of several components or a mixture of such complexes.     

Glycosaminoglycan-bound and free inter-alpha-trypsin inhibitor components of follicular fluid.

The proteinase inhibitor inter-alpha trypsin inhibitor (ITI) is a blood-derived protein necessary for normal female fertility. Absence of ITI leads to ovulation of naked oocytes that cannot fertilise. ITI consists of two heavy chains (ITI-HC) and bikunin linked by a chrondroitin sulphate. By binding to hyaluronate, ITI-HC stabilises the extracellular matrix, but ITI-HC also binds to proteoglycans in follicular fluid. In vivo concentrations of ITI components in preovulatory follicular fluid, free as well as bound to hyaluronate or proteoglycan, are unknown. In order to quantify these components, 58 follicular fluids and 13 blood samples were collected in connection with in vitro fertilisation and embryo transfer treatment of 13 women. Quantitation of glycosaminoglycan-bound ITI-HC was performed after separation from free ITI in agarose gel. ITI components were determined by immunoelectrophoresis and hyaluronate by an ELISA method. The follicular fluid concentration of ITI was on average 70% of that in plasma and the concentration of hyaluronate remained low despite follicular production, suggesting that the production of hyaluronate is the rate-limiting step in the formation of the extracellular matrix of the oocyte-cumulus complex. In follicular fluid, the concentration of free ITI-HC was higher than that of glycosaminoglycan-bound ITI-HC. Addition of exogeneous hyaluronate doubled the amount of hyaluronate-bound ITI-HC, further supporting the notion that ITI in follicular fluid is not rate-limiting for cumulus expansion in vivo.     

The effect of the glycosaminoglycan chain removal on some properties of the human urinary trypsin inhibitor

The major urinary trypsin inhibitor UTI I is a proteoglycan. UTI c (Mr 26,000), produced by chrondroitin lyase digestion of UTI I, was isolated and characterized. About 90% of the glycosaminoglycan chain was removed by this treatment without proteolytic modification, as assessed by amino-acid composition and N-terminal sequence of UTI c. Its electrophoretic mobilities on alkaline and SDS-PAGE are identical with those of UTI II which occurs in urine during storage. To study the role of the glycosaminoglycan chain on the inhibitory properties of UTI I, UTI I and UTI c were compared using different proteinases as target enzymes. The inhibitory activity towards bovine trypsin and chymotrypsin as well as human granulocytic cathepsin G did not differ significantly. However, towards human granulocytic elastase, the equilibrium dissociation constant (Ki) is 5 times higher for UTI c than for UTI I. Weak inhibitory activities were measured on human plasmin, UTI c being more efficient than UTI I. The acid-stability of UTI I is not modified after chrondroitin lyase treatment. UTI I and UTI c are equally sensitive to trypsinolysis indicating that the covalently bound glycosaminoglycan chain does not play an important role for the stability of UTI I.     

Immunohistochemical distribution of inter-alpha-trypsin inhibitor chains in normal and malignant human lung tissue.

The inter-alpha-trypsin inhibitor (ITI) family is a group of plasma proteins built up from heavy (HC1, HC2, HC3) and light (bikunin) chains synthesized in the liver. In this study we determined the distribution of ITI constitutive chains in normal and cancerous lung tissues using polyclonal antibodies. In normal lung tissue, H2, H3, and bikunin chains were found in polymorphonuclear cells, whereas H1 and bikunin proteins were found in mast cells. Bikunin was further observed in bronchoepithelial mucous cells. In lung carcinoma, similar findings were obtained on infiltrating polymorphonuclear and mast cells surrounding the tumor islets. Highly differentiated cancerous cells displayed strong intracytoplasmic staining with H1 and bikunin antiserum in both adenocarcinoma and squamous cell carcinoma. Moreover, weak but frequent H2 expression was observed in adenocarcinoma cells, whereas no H3-related protein could be detected in cancer cells. Local lung ITI expression was confirmed by RT-PCR. Although the respective role of inflammatory and tumor cells in ITI chain synthesis cannot be presently clarified, these results show that heavy chains as well as bikunin are involved in malignant transformation of lung tissue.(J Histochem Cytochem 47:1625-1632, 1999)     

Analysis of the proteoglycans synthesized by corneal explants from embryonic chicken. II. Structural characterization of the keratan sulfate and dermatan sulfate proteoglycans from corneal stroma

Radioisotopically labeled proteoglycans were isolated from a 4 M guanidine HCl, 2% Triton X-100 extract of corneal stroma from day 18 chicken embryos by anion-exchange chromatography. Two predominant proteoglycans in the sample were separated by octyl-Sepharose chromatography using a gradient elution of detergent in 4 M guanidine HCl. One proteoglycan had an overall mass of approximately 125 kDa, a single dermatan sulfate chain (approximately 85-90% chondroitin 4-sulfate, low iduronate content) of approximately 65 kDa, and a core protein after chondroitinase ABC digestion of approximately 45 kDa which also contained one to three N-linked oligosaccharides and one O-linked oligosaccharide. The other proteoglycan had an overall size of approximately 100 kDa, two to three keratan sulfate chains of approximately 15 kDa each, and a core protein following keratanase digestion of approximately 51 kDa which included two to three N-linked but no O-linked oligosaccharides. A larger size, a greater overall hydrophobicity (as measured by its interaction with octyl-Sepharose) and an absence of O-linked oligosaccharides argue that this core protein is a distinct gene product from the core protein of the dermatan sulfate proteoglycan.     

A chondroitin-sulfate chain is located on serine-10 of the urinary trypsin inhibitor.

1. The glycopeptide carrying the glycosaminoglycan chain of the urinary trypsin inhibitor (immunologically and structurally related to inter-alpha-trypsin inhibitor) was isolated. 2. The data from amino acid composition and part sequencing of this glycopeptide unambiguously demonstrate that the glycosaminoglycan is covalently linked to serine-10 of the peptide chain of UTI.     

Characterization of DLC-A and DLC-B, two families of cytoplasmic dynein light chain subunits.

Cytoplasmic dynein is a minus-end-directed, microtubule-dependent motor composed of two heavy chains (approximately 530 kDa), three intermediate chains (approximately 74 kDa), and a family of approximately 52-61 kDa light chains. Although the approximately 530 kDa subunit contains the motor and microtubule binding domains of the complex, the functions of the smaller subunits are not known. Using two-dimensional gel electrophoresis and proteolytic mapping, we show here that the light chains are composed of two major families, a higher M(r) family (58, 59, 61 kDa; dynein light chain group A [DLC-A]) and lower M(r) family (52, 53, 55, 56 kDa; dynein light chain group B [DLC-B]). Dissociation of the cytoplasmic dynein complex with potassium iodide reveals that all light chain polypeptides are tightly associated with the approximately 530 kDa heavy chain, whereas the approximately 74 kDa intermediate chain polypeptides are more readily extracted. Treatment with alkaline phosphatase alters the mobility of four of the light chain polypeptides, indicating that these subunits are phosphorylated. Sequencing of a cDNA clone encoding one member of the DLC-A family reveals a predicted globular structure that is not homologous to any known protein but does contain numerous potential phosphorylation sites and a consensus nucleotide-binding motif.     

Chondroitin/dermatan sulfate proteoglycan in human fetal membranes. Demonstration of an antigenically similar proteoglycan in fibroblasts

A proteoglycan was isolated from fetal membranes which had been separated from human postpartum placenta. The glycosaminoglycan side chains (Mr = 55,000) were found to be composed of 75% chondroitin sulfate and 23% dermatan sulfate as determined by chondroitinase ABC or AC II digestion. NH2-terminal microsequencing of the intact proteoglycan revealed a single amino acid sequence of (sequence; see text) A rabbit antiserum raised against the intact proteoglycan reacted in sodium dodecyl sulfate-polyacrylamide gel electrophoresis immunoblotting with Mr = 45,000 and 43,000 core polypeptides from chondroitinase-treated proteoglycan. Affinity-purified antibodies from this antiserum precipitated from human embryonic fibroblast culture fluid a proteoglycan which has an approximate Mr = 120,000 in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This proteoglycan has on the average two polysaccharide side chains. As defined by chondroitinase digestion, these chains consist of 66% dermatan sulfate and 20% chondroitin sulfate. Digestion of the glycosaminoglycan with chondroitinase ABC converted the proteoglycan to a Mr = 45,000 major and a Mr = 43,000 minor core polypeptide. Tissue immunofluorescence localized the proteoglycan to interstitial matrices, suggesting that it is a product of mesenchymal cells. The methods we have devised for the purification of the fetal membrane proteoglycan in chemical amounts and the antibodies we have prepared against it will allow studies on the structural and functional properties of the proteoglycan and on the expression of immunologically cross-reactive proteoglycans by various cells and tissues.     

Defect in SHAP-hyaluronan complex causes severe female infertility. A study by inactivation of the bikunin gene in mice

Hyaluronan (HA) associates with proteins and proteoglycans to form the extracellular HA-rich matrices that significantly affect cellular behaviors. So far, only the heavy chains of the plasma inter-alpha-trypsin inhibitor (ITI) family, designated as SHAPs (serum-derived hyaluronan-associated proteins), have been shown to bind covalently to HA. The physiological significance of such a unique covalent complex has been unknown but is of great interest, because HA and the ITI family are abundant in tissues and in plasma, respectively, and the SHAP-HA complex is formed wherever HA meets plasma. We abolished the formation of the SHAP-HA complex in mice by targeting the gene of bikunin, the light chain of the ITI family members, which is essential for their biosynthesis. As a consequence, the cumulus oophorus, an investing structure unique to the oocyte of higher mammals, had a defect in forming the extracellular HA-rich matrix during expansion. The ovulated oocytes were completely devoid of matrix and were unfertilized, leading to severe female infertility. Intraperitoneal administration of ITI, accompanied by the formation of the SHAP-HA complex, fully rescued the defects. We conclude that the SHAP-HA complex is a major component of the HA-rich matrix of the cumulus oophorus and is essential for fertilization in vivo.     

Biosynthesis of bikunin (urinary trypsin inhibitor) in rat hepatocytes.

One of the major sulfated proteins secreted by rat hepatocytes contains a low-sulfated chondroitin sulfate chain and its apparent molecular mass upon sodium dodecyl sulfate/polyacrylamide gel electrophoresis shifts from 40 to 28 kDa upon chondroitinase ABC treatment (E. M. Sj?berg and E. Fries, 1990, Biochem. J. 272, 113-118). These properties suggest that this protein is the rat homologue of the major trypsin inhibitor of human urine which was recently named bikunin. In serum, bikunin occurs mainly as a subunit of the pre-alpha-inhibitor and the inter-alpha-inhibitor; in these proteins it is covalently linked to the other polypeptides through its chondroitin sulfate chain. Bikunin has been shown to be synthesized by liver cells as a 42-kDa precursor, in which it is linked to alpha 1-microglobulin by two basic amino acids. We have isolated bikunin from rat urine and prepared antibodies against it. In rat hepatocytes pulse-labeled with [35S]methionine, these antibodies precipitated a labeled protein of 42 kDa. Upon chase, three different labeled proteins were recognized by the antibodies in the medium: one protein of 40 kDa (free bikunin), one of 125 kDa (presumably pre-alpha-inhibitor), and one greater than 240 kDa (possibly a protein related to the inter-alpha-inhibitor). Pulse-chase experiments with [35S]sulfate showed that these proteins occurred intracellularly as precursors containing alpha 1-microglobulin. These results demonstrate that the completion of the chondroitin sulfate chain and its coupling to other polypeptide chains occur before the cleavage of the alpha 1-microglobulin/bikunin precursor.     

Calcium-induced changes in chondroitin sulfate chains of urinary trypsin inhibitor

Urinary trypsin inhibitor (UTI) has several roles other than protease inhibition. It is suggested that UTI inhibits calcium influx in cultured cells and that the chondroitin sulfate chain of UTI may play an important role. In order to clarify the mechanistic features of this phenomenon, the chondroitin sulfate chain of UTI was analyzed by (1)H-NMR. The samples were highly purified UTI dissolved in D(2)O in the presence or absence of Ca(2+), Mg(2+) and Na(+). 1D-spectra were obtained and T(1) values of detected signals were estimated from the inversion-recovery method. The addition of Ca(2+) to UTI caused a chemical shift to downfield, line broadening and a reduction of T(1) values at several signals from chondroitin sulfate moiety (especially at axial H-2 of GalNAc), whereas Mg(2+) and Na(+) had no significant effect. Some of the signals in the linkage region of chondroitin sulfate chain showed marked line broadening by Ca(2+). The reduction of T(1) values implies formation of a complex. It is suggested that Ca(2+) generates the sulfate salt and interacts with other polar groups in the chondroitin sulfate chain, thereby causing bridging between UTI molecules. Several properties of UTI may be related to this interaction of Ca(2+) with chondroitin sulfate chains.     

Human urinary proteinase inhibitor: inhibitory properties and interaction with bovine trypsin

The major urinary trypsin inhibitor (UTI) was found to inhibit bovine chymotrypsin and human leucocyte elastase strongly, cathepsin G weakly. No inhibition of porcine pancreatic elastase was observed. The stoichiometry of the inhibition of bovine trypsin by UTI was determined spectrophotometrically to be 1:2 (I/E molar ratio). After incubation of UTI with this enzyme in various molar ratios, two complexes (C1 and C2) could be visualized in alkaline polyacrylamide gel electrophoresis. C1 was isolated by affinity chromatography on Con-A Sepharose. In dodecyl sulfate polyacrylamide gel electrophoresis, C1 was dissociated to give an inhibitory band with the same electrophoretic mobility as native UTI. C2 released an active inhibitory fragment with Mr near 20000. A time-course study demonstrated that at a molar ratio I/E of 1.5:1, the C2 complex appears after two hours of incubation.     

The amino-acid sequence of the trypsin-released inhibitor from sheep inter-alpha-trypsin inhibitor

The amino-acid sequence of the inhibitory part of the sheep serum inter-alpha-trypsin inhibitor (ITI) was determined. The inhibitor is composed of two covalently linked Kunitz-type domains. The reactive site of the C-terminal antitryptic domain contains arginine in position 71 (P1) and glycine in position 73 (P'2), whereas ITI derived inhibitors hitherto investigated contain phenylalanine in these positions. The reactive site of the N-terminal elastase inhibiting domain contains leucine in position 15 (P1) and methionine in position 17 (P'2), as in ITI-derived inhibitors of pig and horse.     

Complex formation between regulatory and essential light chain on squid mantle myosin subfragment-1 revealed by thermal denaturation method.

Thermal treatment of squid myosin subfragment-1 (S-1) in the presence of EDTA results in a rapid inactivation of ATPase, a marked turbidity increase, and a dissociation of light chains. These effects were suppressed by addition of calcium ion. Different light chain binding in EDTA-medium from that in Ca-medium was demonstrated by the tryptic digestion of native squid S-1; the two types of light chain are both resistant to trypsinolysis in Ca-medium, whereas they are readily degraded in EDTA-medium. S-1 heavy chain was converted into three fragments with sizes of 27, 47, and 22 kDa in both media. However, trypsinolysis of S-1 inactivated in Ca-medium generated no such heavy chain fragments that survived, while the two types of light chain survived. These light chains were isolated as a complex lacking any heavy chain fragments, and the complex formation was Ca-sensitive. It is concluded that regulatory and essential light chains are present on S-1 as a complex whose formation is mediated by calcium ion, and this binding might alter the S-1 conformation so as to confer resistance to thermal treatment.     

Partial amino acid sequence of porcine elastase II. Active site and the activation peptide regions

The partial amino acid sequence of porcine elastase II, isolated from crude trypsin Type II, was determined. The enzyme consists of two polypeptide chains, a light chain composed of 11 residues, and a heavy chain (Mr = 23 500) with four intrachain disulfide bridges; the two chains are held together by one interchain disulfide bond. Elastase II was fragmented into several peptides by chemical cleavages with CNBr at the two methionine residues, 99 and 180 (chymotrypsinogen numbering), and with hydroxylamine at the peptide bond following DIP-Ser195. About 50% of the sequence was determined and the positions of 120 amino acids were located, including the light chain residues and most of the active site residues. The partial sequence shows 64% difference between porcine elastase II and elastase I and only 26% difference between porcine elastase II and bovine chymotrypsin B.     

Biosynthesis of small proteoglycan II (decorin) by chondrocytes and evidence for a procore protein

We have studied the biosynthesis of cartilage dermatan sulfate proteoglycan II (DS-PGII) (decorin) using in vitro translation of mRNA to determine the size of the primary gene product and by radiolabeling the protein in the presence of tunicamycin to inhibit the addition of Asn-linked oligosaccharides. Pulse-chase experiments were performed to examine post-translational processing and secretion. Inhibitors of oligosaccharide processing were used to determine whether DS-PGII molecules containing partially processed oligosaccharides could become proteoglycans and be secreted. Cell-free translation of sucrose gradient-fractionated RNA and subsequent immunoprecipitation of the core protein confirmed that the functional translated mRNA is in the size range of the two mRNA species observed by hybridization of chondrocyte RNA with a bone PGII cloned probe and that the translation product is a single protein with an apparent molecular mass of 42 kDa. Digestion of the intact proteoglycan (average molecular mass = 103 kDa) with chondroitinase ABC or AC results in an approximately 48-49-kDa product. Chondrocytes treated with tunicamycin to inhibit Asn-linked oligosaccharide addition synthesize and secrete a glycosaminoglycan (GAG)-substituted proteoglycan (average molecular mass = 86 kDa), yielding a 42-kDa core protein after chondroitinase ABC digestion, showing that Asn-linked oligosaccharides are not required for the addition of GAG chains or secretion. Following a short pulse (10 min) of [3H]leucine, three glycosylated forms of the DS-PGII core protein were observed, one of which is likely to be the precursor form of PGII predicted by the implied protein sequence of both bovine and human cDNA clones. Following the apparent cleavage of the propeptide, GAG-substituted intracellular core protein is detectable. Susceptibility to endoglycosidase H indicates that approximately one-third of the secreted core protein contains exclusively complex-type Asn-linked oligosaccharides and approximately two-thirds contain high mannose as well as complex-type oligosaccharides. Secreted DS-PGII appears to be fully substituted with three Asn-linked oligosaccharide chains. Inhibitors of oligosaccharide processing, however, permitted secretion of GAG-substituted DS-PGII that was fully (three chains) or incompletely (one or two chains) substituted with partially processed Asn-linked carbohydrate chains. By comparison of chondrocyte DS-PGII with fibroblast DS-PGII, we conclude that the addition and processing of Asn-linked carbohydrate chains are directed by the amino acid sequence of the core protein. The results reported here also suggest that the addition of xylose, the initial step in GAG chain synthesis, occurs early in biosynthesis and is determined by the primary amino acid sequence of the core protein.(ABSTRACT TRUNCATED AT 400 WORDS)     

Inhibition of human blood coagulation factor XIa by C-1 inhibitor

The inactivation of activated factor XI (factor XIa) and of its isolated light chain by C-1 inhibitor was studied. Irreversible inhibition was observed in a reaction in which no reversible enzyme-inhibitor complex was formed. The second-order rate constants for the inactivation of factor XIa or its light chain by C-1 inhibitor were 2.3 X 10(3) and 2.7 X 10(3) M-1 s-1, respectively. High molecular weight kininogen did not affect the rate of inactivation. The nature of the complexes formed between factor XIa or its light chain and C-1 inhibitor was studied by using sodium dodecyl sulfate gradient polyacrylamide slab gel electrophoresis. Under nonreducing conditions, two factor XIa-C-1 inhibitor complexes were observed with apparent molecular weights of 230,000 and 300,000. Reduction of these complexes resulted in the formation of a single band with a molecular weight of 130,000. This band is also formed in the reaction of the isolated light chain of factor XIa with C-1 inhibitor. These results demonstrate that two C-1 inhibitor molecules can become bound to the light chains of a factor XIa molecule. In addition, the mechanism of interaction of factor XIa or its isolated light chain with C-1 inhibitor appears identical, and the rate of inactivation of the enzyme by C-1 inhibitor is very similar. Neither the heavy chain of factor XIa nor high molecular weight kininogen is significantly involved in the inactivation of factor XIa by C-1 inhibitor.