N-terminal sequence analysis of human placental protein 14, purified in high yield from decidual cytosol

Human placental protein 14 (PP14) has been purified in high yield from first trimester decidual cytosol. High-performance liquid chromatography on anion exchange, gel filtration and reverse-phase chromatography were used. The protein obtained is approximately 97% pure with an overall recovery of about 50% from the original tissue extract. The first 24 amino acids of the N-terminal were found to be Met-Asp-Ile-Pro-Gln-Thr-Lys-Gln-Asp-Leu-Glu-Leu-Pro-Lys-Leu-Ala-Gly-Thr-Glu-His - Glu-Met-Ala-Met. PP14 has been characterized in this study to be a dimeric glycoprotein of Mr 60,000, with homologous subunits having an Mr of 28,000.

Purification and characterization of placental protein 5

This report describes the purification of placental protein 5, PP5, from the human placenta by two affinity chromatography steps, the first with Heparin-Sepharose and the second with Sepharose-linked monoclonal anti-PP5 antibody. The final purification is achieved by reversed-phase high performance liquid chromatography. In SDS-polyacrylamide gel electrophoresis under reducing or nonreducing conditions, PP5 purified in this study migrates as one major band at 36 kD. The previously purified PP5 is more heterogeneous: under nonreducing conditions it migrates at 30 kD and, after reduction, it gives three bands at 16.8 kD, 18.3 kD, and 19.0 kD. In Western blot analysis, both purified proteins react with polyclonal and monoclonal anti-PP5 antibodies. Three N-terminal amino acid sequences are obtained for the previously purified PP5, whereas the N-terminal of PP5 purified in this study is blocked. These results suggest that PP5 previously purified in the absence of protease inhibitors, does not represent the native form of PP5. Computer comparison of the obtained amino acid sequences revealed no significant homology to known protein sequences.

Electron microscopic localization of the Pa and RT1.Aa antigens on the placenta of the rat

A major factor in the ability of the placenta to avoid allograft rejection is the differential expression of MHC class I antigens on its surface. Using monoclonal antibodies and the electron microscopic immunogold technique, we have demonstrated that only the pregnancy-associated (Pa) antigen, which carries a broadly shared antigenic determinant, is expressed on the placental surface in the rat, whereas the allele-specific classical transplantation antigens are not. Both types of antigens are, however, present in the cytoplasm of the basal trophoblast but completely absent from the labyrinthine trophoblast.

Interference of an alpha 2 component in immunological determinations of pregnancy-specific beta 1 glycoprotein in serum

Pregnancy-specific beta 1 glycoprotein (SP1-beta) was purified from human retroplacental blood by sequential anion exchange chromatography, gel chromatography and affinity chromatography. The final preparation appeared to be electrophoretically and immunochemically pure and was in particular free from any component with alpha mobility. The preparation was used as immunogen in rabbits as well as tracer and standard for radioimmunoassay and for cross- and rocket-immunoelectrophoresis. It was shown that this radioimmunoassay procedure, allowed quantitative determination of SP1-beta glycoprotein without interference by the alpha component.

Purification of decidual prolactin-releasing factor, a placental protein that stimulates prolactin release from human decidual tissue

Decidual prolactin-releasing factor (PRL-RF), a placental protein that stimulates the release of prolactin from human decidual tissue, has been purified from conditioned medium of human placental explants. The purification scheme consisted of ethanol extraction, anion exchange chromatography on DEAE-cellulose, size exclusion chromatography on Spherogel TSK-3000, and either a) immunoaffinity chromatography using an antiserum to a partially purified PRL-RF preparation or b) acetic acid-urea/SDS 2-dimensional PAGE. The apparent molecular weight of the purified releasing factor, estimated by SDS-PAGE, was 23,500 Da; and the half-maximal dose for the acute stimulation of prolactin release from human decidual cells was 0.05-0.1 ug/ml (2.2-4.4 nM).

Human placental anticoagulant protein: isolation and characterization

An anticoagulant protein was purified from the soluble fraction of human placenta by ammonium sulfate precipitation and column chromatography on DEAE-Sepharose, Sephadex G-75, and Mono S (Pharmacia). The yield of the purified protein was approximately 20 mg from one placenta. The purified protein gave a single band by sodium dodecyl sulfate-polyacrylamide gel electrophoresis with a molecular weight of 36,500. This protein prolonged the clotting time of normal plasma when clotting was induced either by brain thromboplastin or by kaolin in the presence of cephalin and Ca2+. It also prolonged the factor Xa induced clotting time of platelet-rich plasma but did not affect thrombin-induced conversion of fibrinogen to fibrin. The purified placental protein completely inhibited the prothrombin activation by reconstituted prothrombinase, a complex of factor Xa-factor Va-phospholipid-Ca2+. The placenta inhibitor had no effect on prothrombin activation when phospholipid was omitted from the above reaction. Also, it neither inhibited the amidolytic activity of factor Xa, nor did it bind to factor Xa. The placenta inhibitor, however, did bind specifically to phospholipid vesicles (20% phosphatidylserine and 80% phosphatidylcholine) in the presence of calcium ions. These results indicate that the placental anticoagulant protein (PAP) inhibits coagulation by binding to phospholipid vesicles. The amino acid sequences of three cyanogen bromide fragments of PAP aligned with those of two distinct regions of lipocortin I and II with a high degree of homology, showing that PAP is a member of the lipocortin family.

Calcium-sensitive, lipid-binding cytoskeletal proteins of the human placental microvillar region

In this study we describe a group of Ca2+-sensitive proteins located in the microvillar region of the human placental syncytiotrophoblast. By following the distribution of proteins between the particulate and supernatant phases of detergent-solubilized microvilli in the presence of defined concentrations of free Ca2+, we demonstrate a class of proteins of subunit molecular weights 72,000, 69,000, 38,000, 36,000, and 32,000 that associate with both the cytoskeleton and lipid at high concentrations of free Ca2+. These proteins can be released from microvilli using EGTA-containing buffers. Although they do not bind to phenyl-Sepharose, they will bind to phospholipids immobilized on phenyl-Sepharose columns in a Ca2+-dependent manner and show a marked preference for phospholipids with negatively charged headgroups. The results provide evidence for a sequence of events which may occur within the microvillus as the localized concentration of intracellular free Ca2+ rises.

Separation and characterisation of glycoproteins from normal, pregnancy, and acute inflammatory sera

A system of multiple chromatography combining anion-exchange, gel filtration, and affinity chromatography has been devised to separate several acute phase proteins from serum, including alpha 1 acid glycoprotein, transferrin, alpha 1-antichymotrypsin, alpha 1-antitrypsin and haemopexin. Only 5-15 ml of blood is required to provide milligram quantities of the purified proteins for further biochemical analysis. The system has been applied in a study of pregnancy and some diseases in order to investigate the changes in the serum protein profile and in individual proteins.

Purification of placental protein PP12 from human amniotic fluid and its comparison with PP12 from placenta by immunological, physicochemical and somatomedin-binding properties

Human amniotic fluid was found to contain a protein which is immunochemically indistinguishable from placental protein PP12. This protein was purified by gel filtration, hydrophobic interaction high performance liquid chromatography and anion-exchange chromatography. The relative molecular mass as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis was 34,000, and the isoelectric point was 4.9. Tryptic peptides of amniotic fluid PP12 as determined by reversed phase high performance liquid chromatography were similar to those of placental PP12. Both had the N-terminal amino acid sequence Ala-Pro-Trp-Gln-, which is the same as previously reported for a somatomedin-binding protein. Both placental PP12 and amniotic fluid PP12 were found to bind somatomedin C (IGF-I) with high affinity, Ka = 1 X 10(9) l/mol). Amniotic fluid is an ideal source of this somatomedin-binding protein, and the purification method described allows rapid isolation of PP12 under mild conditions which are essential for studies on its biological function.

Identification of a low molecular weight polypeptide of pregnant bovine uterine origin (LMW-UDF): influence on coagulation system in vitro. Part I

Acidified extracts of pregnant bovine uterus were found to contain a heparin-affinity polypeptide(s). The eluted peak was assayed in the Chandler loop method for whole blood and fibrin thrombus generation. Significant differences in the mean weight and size of whole blood thrombi (243.5 +/- 50 mg and 3.5 cm +/- 0.6 cm) occurred with 1 microgram of purified polypeptide when compared to control samples containing albumin (47.87 +/- .30 g and 0.8 cm +/- 0.3 cm). This activity was detected by the Chandler loop method with 100 ng to 10 micrograms of protein when analyzed in a dose-response fashion. When tested for fibrin thrombus formation this activity persisted. Experiments with 125I fibrinogen revealed no net increase or decrease of uptake into whole blood thrombi when purified polypeptide was added. The heparin-affinity polypeptide(s) possessed a molecular weight of approximately 6-4 kDa when examined by SDS-PAGE. We have therefore designated this polypeptide as low molecular weight-uterine derived factor (LMW-UDF).

Progesterone-associated proteins PP12 and PP14 in the human endometrium

Two proteins, designated as PP12 and PP14 were originally isolated from soluble extracts of the human placenta and its adjacent membranes. We have shown that they are synthesized by decidualized/secretory endometrium and not by placenta. Both proteins occur at high concentrations in human amniotic fluid, which is therefore an excellent source for purification. PP12 is a 34-kDa glycoprotein, which has an N-terminal amino acid sequence of Ala-Pro-Trp-Gln-Cys-Ala-Pro-Cys-Ser-Ala. This is identical with that of somatomedin-binding protein purified from the amniotic fluid. PP12 too binds somatomedin-C, or IGF-I (insulin-like growth factor-I). Human secretory endometrium synthesizes and secretes PP12, and progesterone stimulates its secretion. PP14 is a 28-kDa glycoprotein. Its N-terminal sequence shows homology to that of beta-lactoglobulins from various species. We have found PP14 in the human endometrium, serum and milk. Immunologically, PP14 is related to progestagen-associated endometrial protein (PEP), alpha-2 pregnancy-associated endometrial protein (alpha-2, PEG), endometrial protein 15 (EP15), alpha-uterine protein (AUP) and chorionic alpha-2 microglobulin (CAG-2). In ovulatory menstrual cycles, the concentration of PP14 increases in endometrial tissue as the secretory changes advance. In serum, the PP14 concentration begins to rise later than the progesterone levels, and high serum PP14 levels are maintained for the first days of the next cycle. By contrast, no elevation of serum PP14 level is seen in anovulatory cycles. Our results show that progesterone-associated proteins are synthesized by the human endometrium and appear in the peripheral circulation, where they can be quantitatively measured using immunochemical techniques.

Human pregnancy zone protein and alpha 2-macroglobulin. High-affinity binding of complexes to the same receptor on fibroblasts and characterization by monoclonal antibodies

Pregnancy zone protein (PZP) was isolated from late pregnancy serum and examined for binding to normal skin fibroblasts in culture. A high-affinity binding site on these cells is demonstrated for PZP reacted with methylamine. Experiments with alpha 2-macroglobulin (alpha 2M) and PZP, both modified by methylamine, showed this receptor to be identical to the previously characterized receptor for alpha 2M-proteinase complexes (Van Leuven, F., Cassiman, J.J., and Van den Berghe, H. (1979) J. Biol. Chem. 254, 5155-5160). With available monoclonal antibodies directed toward alpha 2M and prepared toward PZP, only a limited cross-reaction was observed. We obtained a monoclonal antibody which defines a neo-antigenic site on PZP-methylamine, completely analogous to the monoclonal antibody F2B2, which was previously shown to define a neo-antigenic site on alpha 2M complexes (Marynen, P., Van Leuven, F., Cassiman, J.J., and Van den Berghe, H. (1981) J. Immunol. 127, 1782-1786). These results provide evidence for the homologous function of alpha 2M and PZP as proteinase scavengers. The need for an extra proteinase inhibitor of the alpha 2M-type in pregnancy is discussed. The monoclonal antibodies now available will prove helpful in quantitation and eventually isolation of proteinase complexes of alpha 2M and PZP.

New placental proteins: chemistry, physiology and clinical use

In the past decade, several new placental proteins have been isolated and studied. The 'pregnancy-specific' beta 1-glycoprotein (SP1) is a major placental product with unusual physicochemical properties that has been extensively investigated, but its biological function remains uncertain. Pregnancy-associated plasma protein A (PAPP-A), a glycoprotein of mol. wt 400,000, has effects in vitro on the coagulation and complement cascades, probably by its properties of protease inhibition. Placental protein 5 (PP5) may be involved in the coagulation and fibrinolytic systems, and in follicle maturation and semen liquefaction. 'Placental protein 12' (PP12) is not a product of the placenta at all; it appears to be produced in the female genital tract under the influence of progesterone and may also be produced by proliferating liver cells. Further study may reveal new roles for these placental proteins beyond their traditional roles as tumour markers.

Purification of human secretory pregnancy-associated endometrial alpha 2-globulin (alpha 2-PEG) from cytosol of first trimester pregnancy endometrium

Pregnancy-associated endometrial alpha 2-globulin (alpha 2-PEG), the major secretory protein as assessed by in-vitro synthesis and secretion by the endometrium during the luteal phase of the menstrual cycle and early first trimester of pregnancy, has been purified from the cytosolic fraction of pregnancy endometrium. The purification schedule involved anion exchange chromatography (DE52), gel filtration (Sephacryl S-200), concanavalin A-Sepharose, chromatofocusing and negative immunoaffinity chromatography. On anion exchange chromatography alpha 2-PEG eluted at 0.11 M NaCl, on Sephacryl S-200 with an apparent Mr of 56 K, it bound to concanavalin A and eluted from a chromatofocusing column at a pH of 4.6. alpha 2-PEG was isolated with 98% purity, as assessed by one-dimensional sodium dodecyl sulphate (SDS)-gradient polyacrylamide gel electrophoresis (subunit Mr under reducing conditions 28 K), and a yield of 0.11 mg per g wet weight tissue. This purified alpha 2-PEG should enable in-vitro assessment of the function of this unique protein in implantation and pregnancy and provide antigenic material for the development of a radioimmunoassay.

Two human 35 kd inhibitors of phospholipase A2 are related to substrates of pp60v-src and of the epidermal growth factor receptor/kinase

We have purified two 35 kd phospholipase A2 inhibitors from human placenta, which we refer to as lipocortin I and II. Both proteins exhibit similar biochemical properties and occur in placenta at about 0.2% of the total protein. By peptide mapping, sequence, and immunological analyses, we show that lipocortin I and the 35 kd substrate for the EGF-receptor/kinase from A431 cells are the same protein. By similar criteria, we determine that lipocortin II is the human analogue of pp36, a major substrate for pp60src, which has been characterized in chicken embryo fibroblasts and in bovine brush border preparations. The amino acid sequences of lipocortin I and II that we deduced from cDNA clones share 50% homology, indicating that they probably evolved from a common gene.

Uromodulin: an immunoregulatory glycoprotein isolated from pregnancy urine that binds to and regulates the activity of interleukin 1

Uromodulin is an 85 kilodalton glycoprotein originally isolated from human pregnancy which has been shown to inhibit antigen specific T cell responses to recall antigens such as tetanus toxoid. We have also found that uromodulin is a high affinity ligand for interleukin 1 and is able to regulate the activity of interleukin 1 in vitro. Finally, we present data that free interleukin 2 receptor can be found in human pregnancy urine. We propose that a number of immunoregulatory phenomena associated with pregnancy are due to molecules able to specifically regulate interleukin 1 and interleukin 2.

A new trophoblast-derived growth factor from human placenta: purification and receptor identification

This paper describes the identification and characterization of a new peptide growth factor. The peptide was isolated from trophoblastic brush border membranes of human placenta. The purified preparation was homogeneous and consisted of a single polypeptide of Mr 34 000 with a pI of about 6.0. This peptide stimulated DNA replication in cultured fibroblasts. The following association was seen between activity and protein: During DEAE-cellulose chromatography, both the 34-kilodalton (kDa) protein and the mitogenic activity displayed identical binding and salt dependence of elution. Nondenaturing electrophoresis at pH 8.3 revealed a comigration of the 34-kDa protein and the DNA replication stimulatory activity. Identical electrophoretic mobilities were displayed for both activity and protein at pH 7.0. These results demonstrate that the preparation is homogeneous and show that growth factor activity is intrinsic to the 34-kDa polypeptide. Binding of the 125I-labeled 34-kDa mitogen to target fibroblastic cells was specific; i.e., nanomolar concentrations of the unlabeled 34-kDa protein competed effectively with the labeled protein, whereas a variety of well-characterized growth factors and hormones were unable to compete even at micromolar levels. Thus the 34-kDa protein interacts with target cells through highly specific surface receptors. Chemical cross-linking techniques were used to investigate the identity of the receptor for the 34-kDa mitogen. Cross-linking of fibroblastic cells containing bound 125I-labeled 34-kDa protein generated a radiolabeled complex of 86 kDa in all four cell types examined.(ABSTRACT TRUNCATED AT 250 WORDS)

A specific antibody to a new peptide growth factor from human placenta: immunocytochemical studies on its location and biosynthesis

Recently, we isolated a new peptide growth factor of Mr 34 000 from synctial membranes of human placenta. In its polypeptide molecular weight and receptor binding specificity it is unlike several known growth factors. In this paper we described immunocytochemical studies on its cellular location and biosynthesis. A rabbit antiserum was raised against a homogeneous preparation of the placental peptide. The specificity of the antibody was established by immunoprecipitation and immunoblot analyses. The antibody recognized both the native and denatured 34-kilodalton (kDa) peptide but showed no binding to a variety of other growth factors and hormones tested. The antibody was used to investigate the genesis and location of the 34-kDa membranous mitogen. Immunoperoxidase staining of placental tissue slices revealed a restricted localization of the antigen in the cytoplasmic organelles of cytotrophoblasts and in the brush border membranes of syncytiotrophoblasts. No other placental structures contained the antigen. A developmentally regulated appearance of the mitogen was suggested by the fact that first trimester placenta consistently stained far more strongly than term placenta. These studies show that the 34-kDa mitogenic protein originates in placenta from embryo-derived cellular structures and suggest that in its strategic location it may influence trophoblastic growth in an autocrine manner. In other studies we investigated the presence and biosynthesis of the 34-kDa peptide in the A431 vulval carcinoma cell line, which was shown earlier to contain a membrane-associated 34-kDa growth factor. The studies demonstrate that this cell line, as well as some other human carcinomas of breast and bladder origin, actively expresses this peptide.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of an SP-1-like protein in non-pregnancy serum: isolation using a monoclonal antibody

Human SP-1, a glycoprotein synthesized by the placenta during pregnancy, was shown to exist as polymers in maternal serum by a rapid passive transfer immunoblotting technique following conventional agarose electrophoresis. Moreover, the SP-1 polymers in serum were shown to dissociate into one main component upon treatment with 8 M urea prior to electrophoresis. However, an unexpected observation was the existence of an SP-1-like immunoreactive species in male serum with the sensitive immunoblotting technique. This SP-1-like protein in male serum had similar properties to its placentally derived counterpart in pregnancy serum, namely a propensity for complex formation and a reduced electrophoretic mobility following neuraminidase treatment. The relationship between the two SP-1 proteins was demonstrated by isolating them from their respective sera using an immobilized monoclonal antibody raised to purified SP-1 from pregnancy serum. Immunoblotting after sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed the existence of two major SP-1 species in pregnancy serum. These two SP-1 species had apparent molecular weights of 68,000 and 64,000. In addition, there were two minor bands at 35,000 and 32,000. These smaller SP-1 species did not appear to be subunits of the larger entities since they were detectable in the absence of reducing conditions. SDS-PAGE and immunoblotting showed that the immunoaffinity-purified SP-1 species from male and pregnancy sera had similar, but not identical, molecular weights.

Detection of a pregnancy-associated protein

Monospecific antiserum was produced with the use of a placental extract showing high activity of a proteinase which hydrolyses a synthetic substrate, N-benzoyl-D,L-arginine p-nitroanilide, used for measuring tryptic activity. An immunological study showed that antibodies were not generated against the component with this activity but against an antigen which was not related to several well-known pregnancy-associated proteins. Pregnancy sera contained an antigen which immunologically was completely identical to the antigen of placental origin. Single radial immunodiffusion showed an elevated level of reactive antigen in pregnant subjects: 70% of 333 cases were positive. Cross-reacting antigen was also detected in sera as well as ascitic fluid from cases of advanced ovarian cancer. Sephadex G-200 gel filtration indicated that the antigen has an apparent molecular weight of 94000, and immunoelectrophoresis showed the molecule to be of beta-mobility. These properties suggest that the substance may represent an additional pregnancy-associated protein entity. Partial purification and some immunological properties of this antigen are described.

An endogenous activator protein in human placenta for enzymatic degradation of glucosylceramide

An endogenous, heat-stable and pronase-sensitive activator for enzymatic hydrolysis of glucosylceramide was detected in the crude lysosome-mitochondria fraction of human placenta. Its properties differ distinctly in several important respects from those of the previously described glucosylceramidase activator. The activator reported here had no effect on crude glucosylceramidase with either glucosylceramide or 4-methylumbelliferyl-beta-D-glucopyranoside as the substrate in the presence of either sodium taurocholate or phosphatidylserine. On the contrary, glucosylceramide hydrolysis by the enzyme partially purified through Octyl-Sepharose 4B chromatography was stimulated by this activator 6-9-fold in the presence of either sodium taurocholate or phosphatidylserine. The Km for glucosylceramide in the presence of the activator was 1/3 of that without the activator. In the crude enzyme fraction, the activator was present in a 16-fold excess over the minimum amount necessary for full activation of the enzyme. Hydrolysis of the fluorogenic substrate by the post-Octyl-Sepharose enzyme, however, was not stimulated by the activator. Similarly, hydrolysis of galactosylceramide by galactosylceramidase obtained from the same Octyl-Sepharose chromatography was not stimulated. Our observations are consistent with the idea that glucosylceramidase is saturated by, or perhaps tightly associated with, this activator in the placenta and that they are dissociated by the Octyl-Sepharose chromatography. In fact, the properties of the combined post-Octyl-Sepharose enzyme and activator closely mimic those of the crude enzyme without added activator.

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.