Expression, purification, and inhibitory properties of human proteinase inhibitor

In a previous report, the cDNA for human proteinase inhibitor 8 (PI8) was first identified, isolated, and subcloned into a mammalian expression vector and expressed in baby hamster kidney cells. Initial studies indicated that PI8 was able to inhibit the amidolytic activity of trypsin and form an SDS-stable approximately 67-kDa complex with human thrombin [Sprecher, C. A., et al. (1995) J. Biol Chem. 270, 29854-29861]. In the present study, we have expressed recombinant PI8 in the methylotropic yeast Pichia pastoris, purified the inhibitor to homogeneity, and investigated its ability to inhibit a variety of proteinases. PI8 inhibited the amidolytic activities of porcine trypsin, human thrombin, human coagulation factor Xa, and the Bacillus subtilis dibasic endoproteinase subtilisin A through different mechanisms but failed to inhibit the Staphylococcus aureus endoproteinase Glu-C. PI8 inhibited trypsin in a purely competitive manner, with an equilibrium inhibition constant (Ki) of less than 3.8 nM. The interaction between PI8 and thrombin occurred with a second-order association rate constant (kassoc) of 1.0 x 10(5) M-1 s-1 and a Ki of 350 pM. A slow-binding kinetics approach was used to determine the kinetic constants for the interactions of PI8 with factor Xa and subtilisin A. PI8 inhibited factor Xa via a two-step mechanism with a kassoc of 7.5 x 10(4) M-1 s-1 and an overall Ki of 272 pM. PI8 was a potent inhibitor of subtilisin A via a single-step mechanism with a kassoc of 1.16 x 10(6) M-1 s-1 and an overall Ki of 8.4 pM. The interaction between PI8 and subtilisin A may be of physiological significance, since subtilisin A is an evolutionary precursor to the intracellular mammalian dibasic processing endoproteinases.

Human proteinase inhibitor 9 (PI9) is a potent inhibitor of subtilisin A

Serine proteinase inhibitors function as regulators of serine proteinase activity in a variety of physiological processes. Proteinase inhibitor 9 (PI9) is a 42 kDa member of the ovalbumin family of serpins that is expressed in placenta, lung, and cytotoxic lymphocytes. In this study, we have described the inhibitory mechanism of recombinant human PI9 towards the bacterial endoproteinase subtilisin A. PI9 inhibited the amidolytic activity of subtilisin A via a rapid, single step mechanism with an equilibrium inhibition constant of 3.6 pM and an overall second-order association rate constant of 2.4 x 10(6) M-1s-1, which is the strongest inhibitory mechanism of PI9 that has been described. The inhibitory action of PI9 towards subtilisin as a model proteinase may yield some indication of potential proteinases that may be regulated by PI9 in vivo.

Thrombopoietin is synergistic with other hematopoietic growth factors and physiologic platelet agonists for platelet activation in vitro

Thrombopoietin (TPO) is the primary physiologic regulator of platelet production. The effect of TPO on platelet function, both alone and in combination with other hematopoietic growth factors, adenosine diphosphate (ADP), and epinephrine, was investigated using fluorescent-labeled antibodies to the activation-dependent antigen CD62 (P-selectin) and flow cytometry. TPO stimulated CD62 expression on normal human platelets, and this expression was completely inhibited by the soluble extracellular domain of the TPO receptor, MPL. The growth factors granulocyte colony-stimulating factor (G-CSF) and erythropoietin (EPO), but not interleukin-3 (IL-3) or stem-cell factor (SCF), also stimulated platelet activation. The combination of EPO, SCF, ADP, and epinephrine with TPO were synergistic for platelet CD62 expression. These data further support a role for TPO in modulating platelet function.

Elevated tissue levels of interleukin-1 beta and tumor necrosis factor-alpha in vulvar vestibulitis

OBJECTIVE

To compare levels of two inflammatory cytokines, interleukin-1 beta(IL-1 beta) and tumor necrosis factor-alpha(TNF-alpha), in selected regions of the vulva, vestibule, and vagina in women with vulvar vestibulitis and in asymptomatic controls.

METHODS

Selective samplings of surgical specimens from 12 women undergoing perineoplasty for vulvar vestibulitis and ten pain-free subjects undergoing posterior vaginal repair were prepared into tissue homogenates and analyzed for concentrations of IL-1 beta and TNF-alpha. Interleukin-1 beta and TNF-alpha concentrations were measured by sandwich enzyme-linked immunosorbent assay. The results were reported after adjustment for total tissue protein concentration.

RESULTS

Median tissue levels of IL-1 beta and TNF-alpha were elevated 2.3-fold and 1.8-fold, respectively, in women with vulvar vestibulitis relative to pain-free women. Median IL-1 beta tissue levels were increased significantly from 1.3 pg/mg to 3.0 pg/mg total protein in women with vulvar vestibulitis compared to pain-free women. Median TNF-alpha tissue levels were increased from 83 pg/mg to 148 pg/mg total protein in women with vulvar vestibulitis compared to pain-free women. Analysis by selected anatomic site of women with vulvar vestibulitis revealed a significant 2.2-fold higher median level of TNF alpha at the vulvar site compared to the vestibule.

CONCLUSION

Concentrations of IL-1 beta and TNF-alpha were elevated in women with vulvar vestibulitis relative to those in asymptomatic controls. This elevation in inflammatory cytokines with vulvar vestibulitis varied according to anatomic site and was, paradoxically, lowest in the area of highest hyperalgesia, the vulvar vestibule. Inflammatory cytokine elevation may contribute to the pathophysiology of mucocutaneous hyperalgesia.

A mutation of the atrial natriuretic peptide (guanylyl cyclase-A) receptor results in a constitutively hyperactive enzyme

Mutation of an invariant glutamate residue found within the catalytic domain of guanylyl cyclases resulted in a dramatic 14-fold increase in the activity of the guanylyl cyclase-A receptor. Even in the presence of Mn2+/Triton X-100, a treatment previously thought to yield hormone-independent and maximum cyclase activity, the mutant enzyme remained 7-fold more active; to our knowledge, this is the first example of a protein modification or of an added agent that significantly increases cyclase activity in the presence of Mn2+/Triton X-100. Intracellular concentrations of cGMP in cells expressing the mutant (E974A) cyclase were only marginally elevated by the addition of atrial natriuretic peptide, and in broken-cell preparations, the mutant enzyme also was relatively insensitive to ligand/regulatory nucleotide. The marked increase in cyclase activity was not due to a relief of protein kinase domain inhibition, since the point mutation caused 7- to 13-fold elevations in guanylyl cyclase-A activity when the protein kinase homology domain was deleted. The E974A mutation also altered the kinetics from positive cooperative to linear with respect to MnGTP, suggesting disruption of subunit-subunit interactions. Thus, a single point mutation within the catalytic domain of a guanylyl cyclase results in a constitutively hyperactive enzyme that is independent of protein kinase domain regulation.

Factor VII central. A novel mutation in the catalytic domain that reduces tissue factor binding, impairs activation by factor Xa, and abolishes amidolytic and coagulant activity

Factor VII is a vitamin K-dependent zymogen of a serine protease that participates in the initial phase of blood coagulation. A factor VII molecular variant (factor VII Central) was identified in a 24-year-old male with severe factor VII deficiency and whose plasma factor VII antigen was 38% of normal, but expressed <1% factor VII procoagulant activity. DNA sequence analysis of the patient's factor VII gene revealed a thymidine to cytidine transition at nucleotide 10907 in exon VIII that results in a novel amino acid substitution of Phe328 to Ser. The patient was homozygous for this mutation, whereas each parent of the patient was heterozygous for this mutation. To investigate the molecular properties of this variant, a recombinant F328S factor VII mutant was prepared and analyzed in relation to wild-type factor VII. F328S factor VII exhibited <1% factor VII procoagulant activity and a 2-fold decreased affinity for tissue factor and failed to activate factor X or IX in the presence of tissue factor following activation by factor Xa. In addition, F328S factor VIIa exhibited no detectable amidolytic activity in the presence of tissue factor. The rate of F328S factor VII activation by factor Xa was markedly decreased relative to the rate of wild-type factor VII activation as revealed by densitometry scanning of SDS gels. Temporal analysis of this reaction by SDS-polyacrylamide gel electrophoresis also revealed the formation of two novel F328S factor VII degradation products (40 and 9 kDa) resulting from factor Xa proteolysis of the Arg315-Lys316 peptide bond in intact F328S factor VII. Computer modeling and molecular dynamics simulations of the serine protease domain of factor VIIa suggested that the inability of F328S factor VIIa to cleave substrates may result from the apparent formation of a hydrogen bond between Tyr377 and Asp338, a residue at the bottom of the substrate-binding pocket important for the interaction of substrate arginine side chains with the enzyme. These findings suggest that Phe328, which is conserved in prothrombin, factor IX, factor X, factor VII, and trypsin, is important for factor VIIa catalysis.

Extracellular matrix-associated serine protease inhibitors (Mr 33,000, 31,000, and 27,000) are single-gene products with differential glycosylation: cDNA cloning of the 33-kDa inhibitor reveals its identity to tissue factor pathway inhibitor-2

Recently, we reported the identification and partial characterization of three serine protease inhibitors (M(r) 33,000, 31,000, and 27,000) from the extracellular matrix (ECM) of human umbilical vein endothelial cells and skin cells. Here, we report that a full-length cDNA clone for the 33-kDa inhibitor from SV-40 transformed human skin fibroblasts (t12FB) is identical to a recombinant trypsin/tissue factor pathway inhibitor called TFPI-2 from placenta. By immunoblotting, the three inhibitors from ECM and cell lysates demonstrated cross-reactivity with an antiTFPI-2 IgG. To further elucidate how these inhibitors are related, pulse-chase labeling of t12FB with [35S]methionine followed by immunoprecipitation with antiTFPI-2 IgG was performed on ECM and cytosolic proteins. A precursor-product relationship did not exist between the three inhibitors from ECM. In contrast, the various species of inhibitors from cytosolic fractions demonstrated a precursor-product relationship. Within the cytosolic fraction, 26-, 29-, and 30-kDa inhibitors were detected in the early chases (0 and 15 min) but they form precursors to the synthesis of the 33-kDa inhibitor which accumulated in the later chases (30 min to 1 h). When pulse-chase experiments were performed in the presence of tunicamycin, synthesis as well as sequestration of the three inhibitors into ECM was completely inhibited. In the presence of tunicamycin, the cells synthesized and sequestered a single 25.5-kDa inhibitor into ECM. Peak quantities of the 25.5-kDa inhibitor appeared in the ECM after 6 h chase while they were 1 h for the 27- and 31-kDa inhibitors and 3 h for the 33-kDa inhibitor. To further support that the three inhibitors are related but only differ in the extent of glycosylation, the 33-kDa inhibitor from the t12FB ECM was deglycosylated with N-glycosidase F and the products were identified by immunoblotting with antiTFPI-2 IgG. The enzyme released the 31-, 27-, and 25.5-kDa inhibitors from the 33-kDa inhibitor. Collectively, these results demonstrate that the ECM-associated 33-, 31-, and 27-kDa inhibitors are biosynthetic products of a single gene with differential glycosylation. The 25.5-kDa inhibitor is unglycosylated, whereas 27- and 30- to 31-kDa inhibitors are partially glycosylated and the 33-kDa inhibitor is fully glycosylated. Inhibition of glycosylation significantly retarded the rate of secretion of the inhibitor but did not prevent its association with ECM. Quantitation of the inhibitors with cell-conditioned medium and ECM fractions reveals that 70-75% were ECM-associated and 25-30% cell-associated. None or very little of the inhibitors (0-2%) remained in a conditioned medium. Because they are primarily associated with ECM, the inhibitors may play a major role in ECM remodeling and turnover.

Antibodies against the N-terminus of IL-8 receptor A inhibit neutrophil chemotaxis

Neutrophil migration and activation are the cornerstones of the acute inflammatory response. Interleukin-8 triggers several functions of neutrophils in host defense: chemotaxis, degranulation and enzyme release, and superoxide production. Interleukin-8 is most potent as a chemoattractant, so chemotaxis is likely the most important of these functions. The effects of interleukin-8 on neutrophils are mediated through two receptors, IL-8RA and IL-8RB. To investigate the role of these receptors in neutrophil chemotaxis, we produced inhibitory antibodies to IL-8RA. These antibodies inhibit neutrophil chemotaxis toward IL-8 in vitro. These findings show that IL-8RA mediates a chemotactic signal in neutrophils and suggest that an anti-receptor strategy may be a useful approach to limit neutrophil migration in inflammation.

Inhibitory properties of a novel human Kunitz-type protease inhibitor homologous to tissue factor pathway inhibitor

In a previous report, we described the molecular cloning, expression, and partial characterization of a second human tissue factor pathway inhibitor (TFPI), which we designated as TFPI-2 [Sprecher, C. A., et al. (1994) Proc. Natl. Acad. Sci. U.S.A. 91, 3353-3357]. Recombinant TFPI-2 inhibited the amidolytic activity of trypsin as well as that of factor VIIa in complex with tissue factor. TFPI-2 recently has been shown to be identical to placental protein 5 (PP5), a glycoprotein originally isolated from placenta that exhibits serine protease inhibitory activity. In the present study, we have examined TFPI-2/PP5 for its ability to inhibit a number of serine proteases involved in blood coagulation and fibrinolysis, inasmuch as TFPI-2/PP5 prolonged the coagulation time of human plasma induced by either tissue factor or contact activation in a dose-dependent manner. In addition to its ability to inhibit the amidolytic and proteolytic activities of the factor VIIa-tissue factor complex, TFPI-2/PP5 strongly inhibited the amidolytic activities of human factor XIa, human plasma kallikrein, and human plasmin with Ki values of 15, 25, and 3 nM, respectively. TFPI-2/PP5 was also a weak inhibitor of the activation of factor X by a complex of human factor IXa and poly(lysine) with an apparent Ki of 410 nM. Heparin markedly enhanced the ability of TFPI-2/PP5 to inhibit factor VIIa-tissue factor both in the solution phase and on cell surfaces. In addition, heparin augmented the inhibition of human factor Xa amidolytic activity at relatively high levels (10-100 nM) of TFPI-2/PP5. No significant inhibition of glandular kallikrein, urinary plasminogen activator, tissue plasminogen activator, human activated protein C, human factor Xa, human thrombin, or leukocyte elastase was observed when these proteases were incubated with TFPI-2 in the absence of heparin.

The inhibition of human factor VIIa-tissue factor by antithrombin III-heparin is enhanced by factor X on a human bladder carcinoma cell line

Previous studies have shown that antithrombin III-heparin effectively inhibited the factor VIIa-tissue factor complex. Herein, we show that the neutralization of factor VIIa in complex with the cell surface tissue factor by antithrombin III-heparin was markedly enhanced by plasma levels of factor X. Active site-mutated factor X (S376A factor X) and factor Xa previously inactivated with dansyl-Glu-Gly-Arg-chloromethyl ketone were as effective as plasma-derived factor X in this reaction, indicating that the active site serine residue of factor Xa was not involved in this mechanism. Furthermore, Gla-domainless factor X had no effect in this system, emphasizing the importance of the factor X Gladomain in this reaction. Antibody experiments revealed that this effect was not due to trace levels of a tissue factor pathway inhibitor contaminating either the factor X or antithrombin III preparations. The presence of heparin in this system was essential, as deletion of heparin resulted in a factor VIIa-tissue factor neutralization rate essentially identical to that observed for antithrombin III alone. Plasma levels of factor IX also accelerated the inhibition of factor VIIa-tissue factor by antithrombin III-heparin, although its effect was not as pronounced as that of factor X. Other vitamin K-dependent plasma proteins including protein S, protein C and prothrombin failed to augment the inhibition of factor VIIa-tissue factor by antithrombin III-heparin. Factor X did not enhance the neutralization rate of factor VIIa-tissue factor by antithrombin III-heparin when a carboxyl-terminal truncated tissue factor construct (TF1-219) was used, even in the presence of mixed phospholipids. Our collective finding suggest that antithrombin III and factor X bind to heparin at distinct sites on the heparin molecule resulting in a transient ternary complex of antithrombin III-heparin-factor X that represents the anticoagulant species. Factor X conceivably guides complex to a phosphatidylserine-rich site on the cell surface in close proximity to the factor VIIa-tissue factor complex and facilitates rapid neutralization of factor VIIa. Our findings also suggest that the effect of heparin on the regulation of the extrinsic pathway of blood coagulation may be more profound than previously recognized.

The guanylyl cyclase-A receptor transduces an atrial natriuretic peptide/ATP activation signal in the absence of other proteins

Attempts to activate partially purified preparations of the guanylyl cyclase-A (GC-A) receptor with atrial natriuretic peptide (ANP) have previously failed, leading to speculation that essential cofactors are lost during purification procedures. The receptor was modified to contain the FLAG epitope (DYKDDDDK), expressed in Sf9 cells, and purified to apparent homogeneity (4.3 mumol cyclic GMP formed/min/mg protein; 5.8 mmol 125I-ANP binding site/mg protein) by a combination of immunoaffinity, Q-Sepharose FF, and wheat germ agglutinin batch chromatography. High initial protein/detergent ratios, the presence of glycerol (40%), and the inclusion of protein phosphatase inhibitors in all buffers resulted in the purification of a receptor that continued to transduce the ANP/ATP activation signal. Both native and purified GC-A contained a single class of high affinity ANP binding sites (Kd = 60 pM) and an equivalent EC50 for ATP (0.3 mM). Positive cooperativity as a function of MnGTP was retained during purification. Thus, GC-A is capable of transducing a ligand binding signal in the absence of other proteins.

Molecular cloning, expression, and partial characterization of two novel members of the ovalbumin family of serine proteinase inhibitors

A human placental lambda gt11 cDNA library was screened for sequences encoding proteins related to human proteinase inhibitor 6 (PI6), and two plaques were identified that displayed weak hybridization at high stringency. Isolation and characterization of the DNA inserts revealed two novel sequences encoding proteins composed of 376 and 374 amino acids with predicted molecular masses of approximately 42 kDa. The novel proteins displayed all of the structural features unique to the ovalbumin family of intracellular serpins including the apparent absence of a cleavable N-terminal signal sequence. The degree of amino acid sequence identity between the novel serpins and PI6 (63-68%) significantly exceeds that of any other combination of known intracellular serpins. The two novel serpins encoded by the two novel cDNA sequences have been designated as proteinase inhibitor 8 (PI8) and proteinase inhibitor 9 (PI9). The putative reactive center P1-P1' residues for PI8 and PI9 were identified as Arg339-Cys340 and Glu340-Cys341, respectively. PI9 appears to be unique in that it is the first human serpin identified with an acidic residue in the reactive center P1 position. In addition, the reactive center loop of PI9 exhibits 54% identity with residues found in the reactive center loop of the cowpox virus CrmA serpin. Two PI8 transcripts of 1.4 kilobases (kb) and 3.8 kb were detected by Northern analysis in equal and greatest abundance in liver and lung, while the 1.4-kb mRNA was in excess over the 3.8-kb mRNA in skeletal muscle and heart. Two PI9 transcripts of 3.4 and 4.4 kb were detected in equal and greatest abundance in lung and placenta and were weakly detected in all other tissues. PI8 and PI9 were expressed in baby hamster kidney and yeast cells, respectively. Immunoblot analyses using rabbit anti-PI6 IgG indicated the presence of PI8 in the cytosolic fraction of stably transfected cells that formed an SDS-stable 67-kDa complex with human thrombin. PI9 was purified to homogeneity from the yeast cell lysate by a combination of heparin-agarose chromatography and Mono Q fast protein liquid chromatography and migrated as a single band in SDS-polyacrylamide gel electrophoresis with an apparent molecular mass of 42 kDa. Purified recombinant PI9 failed to inhibit the amidolytic activities of trypsin, papain, thrombin, or Staphylococcus aureus endoproteinase Glu-C and did not form an SDS-stable complex when incubated with thrombin. The cognate intracellular proteinases that interact with PI8 and PI9 are unknown.

Recombinant ob protein reduces feeding and body weight in the ob/ob mouse

To determine whether the product of the recently cloned ob gene functions as an adipose-related satiety factor, recombinant murine ob protein was administered intraperitoneally to ob/ob mice. Monomeric ob protein given as single morning injections to groups of three animals at seven doses ranging from 5 to 100 micrograms reduced 24-h chow consumption in a dose-dependent manner from values of 81 +/- 6.8% of control (10-micrograms dose, P = 0.04) to 29 +/- 7.7% of control (100-micrograms dose, P < 0.0001). Daily injections of 80 micrograms of ob protein into six ob/ob mice for 2 wk led to an 11 +/- 1.6% decrease in body weight (P = 0.0009) and suppressed feeding to 26 +/- 4.9% of baseline (P < 0.0001), with significant reduction of serum insulin and glucose levels. The effect of recombinant ob protein on feeding was not augmented by cofactors secreted by adipose tissue, nor did exposure of adipose tissue to ob protein affect intracellular ob mRNA levels. Posttranslational modification of ob protein was not required for activity; however, addition of a hexahistidine tag to the amino terminus of the mature ob protein resulted in prolonged suppression of feeding after injection into ob/ob mice. These results demonstrate a direct effect of the ob protein to suppress feeding in the ob/ob mouse and suggest that this molecule plays a critical role in regulating total body fat content.

A receptor guanylyl cyclase expressed specifically in olfactory sensory neurons

We have cloned an additional member (GC-D) of the membrane receptor guanylyl cyclase [GTP pyrophosphate-lyase (cyclizing), EC 4.6.1.2] family that is specifically expressed in a subpopulation of olfactory sensory neurons. The extracellular, putative ligand-binding domain of the olfactory cyclase is similar in primary structure to two guanylyl cyclases expressed in the retina but diverges considerably from other known guanylyl cyclases. The expression of GC-D RNA is restricted to a small, randomly dispersed population of neurons that is within a single topographic zone in the olfactory neuroepithelium and resembles the pattern of the more diverse seven-transmembrane-domain odorant receptors. These observations suggest that GC-D may function directly in odor recognition or in modulating the sensitivity of a subpopulation of sensory neurons to specific odors.

Two membrane forms of guanylyl cyclase found in the eye

The cDNAs for two membrane guanylyl cyclases, designated E (GC-E) and F (GC-F, were isolated from a rat eye cDNA library. Their deduced topographic structures correspond to known members of the guanylyl cyclase receptor family, containing an extracellular domain, a single membrane-spanning domain, a protein kinase-like domain, and a cyclase catalytic domain. GC-E was expressed in the eye and the pineal gland, whereas GC-F expression was confined to the eye. Overproduction of GC-E and GC-F in COS cells resulted in expression of guanylyl cyclase activity, but ligands known to activate other guanylyl cyclase receptors failed to stimulate enzyme activity. Thus, both GC-E and GC-F remain orphan receptors. Amino acid sequence similarity between GC-E and GC-F in the extracellular region and homology with a cyclase expressed in olfactory neurons and retGC, a rod outer-segment-specific cyclase, suggest that there is another subfamily of guanylyl cyclase receptors, possibly restricted to sensory tissues.

Hepsin, a putative membrane-associated serine protease, activates human factor VII and initiates a pathway of blood coagulation on the cell surface leading to thrombin formation

Previous studies have shown that hepsin is a putative membrane-associated serine protease that is required for cell growth (Torres-Rosado, A., O'Shea, K. S., Tsuji, A., Chou, S.-H., and Kurachi, K. (1993) Proc. Natl. Acad. Sci. U.S. A. 90, 7181 7185). In the present study, we have transfected baby hamster kidney (BHK) cells with a plasmid containing the cDNA for human hepsin and examined these cells for their ability to activate several blood coagulation factors including factors X, IX, VII, prothrombin, and protein C. Little, if any, proteolytic activation of factors X, IX, prothrombin, or protein C was observed when these clotting factors were incubated with hepsin-transfected cells. On the other hand, hepsin-transfected cells proteolytically activated significant concentrations of human factor VII in a time- and calcium-dependent manner, whereas essentially no activation of factor VII was observed in BHK cells transfected with plasmid lacking the cDNA for hepsin. The factor VII activating activity in the hepsin-transfected BHK cell line was confined exclusively to the total membrane fraction and was inhibited > 95% by antibody raised against a fusion protein consisting of maltose-binding protein and the extracellular domain of human hepsin. An active site factor VII mutant, S344A factor VII, was cleaved as readily as plasma-derived factor VII by hepsin-transfected cells, indicating that factor VII was not converted to factor VIIa autocatalytically on the cell surface. In contrast, an activation cleavage site factor VII mutant, R152E factor VII, was not cleaved by hepsin-transfected cells, suggesting that factor VII and S344A factor VII were activated on these cells by cleavage of the Arg152-Ile153 peptide bond. In the copresence of factor VII and factor X, hepsin-transfected BHK cells supported the formation of factor Xa. In addition, in the copresence of factor VII, factor X, and prothrombin, hepsin-transfected BHK cells supported the formation of thrombin. These results strongly suggest that membrane-associated hepsin converts zymogen factor VII to factor VIIa, which in turn, is capable of initiating a coagulation pathway on the cell surface that ultimately leads to thrombin formation.

Human thrombopoietin: gene structure, cDNA sequence, expression, and chromosomal localization

Thrombopoietin (TPO), a lineage-specific cytokine affecting the proliferation and maturation of megakaryocytes from committed progenitor cells, is believed to be the major physiological regulator of circulating platelet levels. Recently we have isolated a cDNA encoding a ligand for the murine c-mpl protooncogene and shown it to be TPO. By employing a murine cDNA probe, we have isolated a gene encoding human TPO from a human genomic library. The TPO locus spans over 6 kb and has a structure similar to that of the erythropoietin gene (EPO). Southern blot analysis of human genomic DNA reveals a hybridization pattern consistent with a single gene locus. The locus was mapped by in situ hybridization of metaphase chromosome preparations to chromosome 3q26-27, a site where a number of chromosomal abnormalities associated with thrombocythemia in cases of acute myeloid leukemia have been mapped. A human TPO cDNA was isolated by PCR from kidney mRNA. The cDNA encodes a protein with 80% identity to previously described murine TPO and is capable of initiating a proliferative signal to murine interleukin 3-dependent BaF3 cells expressing the murine or human TPO receptor.

The use of conserved cellulase family-specific sequences to clone cellulase homologue cDNAs from Fusarium oxysporum

Five cDNAs from the cellulolytic fungi Fusarium oxysporum that code for five distinct cellulase homologues have been cloned and sequenced. The cloning strategy exploited the hydrophobic cluster analysis-based cellulase family classification of Henrissat and Bairoch [Biochem. J. 293 (1993) 781-788] to design degenerate oligodeoxyribonucleotides (oligos) that encoded amino-acid sequences conserved in an intra-family, but not inter-family, manner among cellulases from different species. Polymerase chain reaction (PCR) experiments using F. oxysporum genomic DNA primed with these 'family-specific' oligos were used to rapidly generate PCR fragments which were in turn used to probe cDNA libraries. Two distinct cDNAs coding for cellulase C-family homologues and one cDNA each coding for homologues to the B, F and K families, were isolated in this manner. This approach is an example of the power of multiple sequence analysis to generate cross-species, homology-based probes to rapidly clone homologues in a species of interest.

The structure, biology and potential therapeutic applications of recombinant thrombopoietin

Platelets, an integral component of hemostasis, are produced by megakaryocytes derived from the differentiation of pluripotent stem cells in the bone marrow or spleen. After decades of study, the regulation of this process is still not well understood. However, the recent cloning and characterization of thrombopoietin, a ligand for the receptor encoded by the c-mpl proto-oncogene, provides new insights into the humoral regulation of megakaryocytopoiesis and platelet production. Consistent with the proposed role as a major physiological regulator of megakaryocytopoiesis, thrombopoietin has potent effects on megakaryocytopoiesis in vitro and in vivo. In addition to the original supposition that thrombopoietin functions as a late-acting megakaryocyte maturation factor, recombinant thrombopoietin proves also to be a potent stimulator of hematopoietic progenitor cells, inducing them to undergo proliferation and differentiation into megakaryocytic colonies. When administered to mice, thrombopoietin causes an increase in peripheral platelet numbers to previously unattainable levels within a few days. Studies of the efficacy of thrombopoietin are underway. It is envisaged that this new cytokine will have widespread applications as a therapeutic agent for the management of bleeding due to thrombocytopenias, in particular those resulting from cancer chemo- or irradiation therapy.

Molecular cloning, expression, and partial characterization of a second human tissue-factor-pathway inhibitor

Previous studies have shown that tissue-factor-pathway inhibitor (TFPI) is an important regulator of the extrinsic pathway of blood coagulation through its ability to inhibit factor Xa and factor VIIa-tissue factor activity. We describe the molecular cloning and expression of a full-length cDNA that encodes a molecule, designated TFPI-2, that has a similar overall domain organization and considerable primary amino acid sequence homology to TFPI. After a 22-residue signal peptide, the mature protein contains 213 amino acids with 18 cysteines and two canonical N-linked glycosylation sites. The deduced sequence of mature TFPI-2 revealed a short acidic amino-terminal region, three tandem Kunitz-type domains, and a carboxyl-terminal tail highly enriched in basic amino acids. Northern analysis indicates that TFPI-2 is transcribed in umbilical vein endothelial cells, liver, and placenta. TFPI-2 was expressed in baby hamster kidney cells and purified from the serum-free conditioned medium by a combination of heparin-agarose chromatography, Mono Q FPLC, Mono S FPLC, and Superose 12 FPLC. Purified TFPI-2 migrated as a single band in SDS/PAGE and exhibited a molecular mass of 32 kDa in the presence and absence of reducing agent. The amino-terminal sequence of recombinant TFPI-2 was identical to that predicted from the cDNA. Despite its structural similarity to TFPI, the purified recombinant TFPI-2 failed to react with polyclonal anti-TFPI IgG. Preliminary studies indicated that purified recombinant TFPI-2 strongly inhibited the amidolytic activities of trypsin and the factor VIIa-tissue factor complex. In addition, the inhibition of factor VIIa-tissue factor amidolytic activity by recombinant TFPI-2 was markedly enhanced in the presence of heparin. TFPI-2 at high concentrations weakly inhibited the amidolytic activity of human factor Xa, but had no measurable effect on the amidolytic activity of human thrombin.

Resistance to inhibition by alpha-1-anti-trypsin and species specificity of a chimeric human/bovine protein C

Human activated protein C (APC) has been shown to be physiologically susceptible to inhibition by the abundant serpin inhibitor alpha-1-anti-trypsin (AAT). Studies on the inactivation by AAT [Heeb, M. J., & Griffin, J. H. (1988) J. Biol. Chem. 263, 11613-11616] have shown that the calculated rate of this inactivation matches that of the observed half-life of APC in vivo [Wydro, R., Oppenheimer, C., Rodger, R., & Miemi, S. (1988) Clin. Res. 36, 329A] and complex formation therefore probably represents a physiologic regulation process for APC. In this study we observed that bovine APC, in contrast to human APC, is nearly completely resistant to inactivation by human AAT. An additional difference between human and bovine APC is that human APC is a potent anticoagulant in human plasma, whereas bovine APC is only minimally active in human plasma. These functional differences exist despite considerable structural similarity between the human and bovine molecules. In order to identify specific molecular regions responsible for function, a chimeric molecule consisting of the light chain of human protein C (PC) and the heavy chain of bovine PC was constructed, expressed, and characterized. The activated chimeric PC is similar to human APC in having potent anticoagulant activity in human plasma, but displays nearly identical resistance to AAT inhibition with the bovine molecule. The similarity between the chimeric and bovine molecules in resistance to AAT inhibition indicates that the structural determinants for inhibitor interactions reside within the heavy chain (serine protease) domain.(ABSTRACT TRUNCATED AT 250 WORDS)

Protein kinase C activators inhibit receptor-mediated potocytosis by preventing internalization of caveolae

Potocytosis is an endocytic pathway that utilizes glycosylphosphatidylinositol-anchored membrane proteins and caveolae to concentrate and internalize small molecules. We now report that activators of protein kinase C are potent inhibitors of potocytosis. Activators such as phorbol-12-myristate-13-acetate (PMA) inhibit the internalization of receptors for 5-methyltetrahydrofolate but allow the internal receptor pool to return to the cell surface. PMA does not affect the clustering of the folate receptor but instead markedly reduces the number of caveolae. Exposure to PMA totally blocks the intracellular accumulation of 5-methyltetrahydrofolate without affecting receptor-independent uptake or the formation of polyglutamylated species of 5-methyltetrahydrofolate in the cytoplasm. These data suggest that PMA inhibits uptake by inactivating caveolae internalization.

Expression, purification and characterization of a Kunitz-type protease inhibitor domain from human amyloid precursor protein homolog

The Kunitz-type protease inhibitor domain from a recently identified homolog of the Alzheimer amyloid precursor protein (APPH KPI) was expressed in yeast, purified and characterized. Its inhibition profile towards several serine proteases was studied and compared to that of APP KPI, the Kunitz domain from the Alzheimer amyloid precursor protein. APPH KPI was shown to inhibit proteases with trypsin-like specificity with an inhibitor profile resembling that of the APP KPI domain. The KPI domains from APP and APPH inhibited trypsin (Ki = 0.02 nM), and plasma kallikrein (Ki = 86 nM) with approximal equal affinity. In comparison to APP KPI (Ki = 82 nM) the KPI domain of the homolog, APPH KPI, (Ki = 8.8 nM) was a more potent inhibitor of glandular kallikrein. APPH KPI was a less potent inhibitor of chymotrypsin than APP KPI (Ki = 78 nM as compared to Ki = 6 nM), plasmin (Ki = 81 nM as compared to 42 nM), and factor XIa (Ki = 14 nM as compared to Ki = 0.7 nM). The affinity of factor XIa for APPH KPI is sufficiently high to allow for an interaction in the blood. It is, however, well possible that the physiological protease ligand for the receptor-like APPH protein has yet to be identified.

Vulvitis and vaginitis

Although the vulva and vagina are embryologically and histologically different, proximity results in inflammatory conditions which commonly affect both regions. Patients often confuse 'vulvitis' and 'vaginitis' in characterizing symptoms. It is the job of the clinician to recognize inflammatory conditions specific to vulva and vagina, as well as to understand that inflammatory conditions can often involve both areas. This review of recent literature does not pretend to be comprehensive. Rather, it highlights specific conditions and research questions of recent interest.