xP2, a new member of the P-domain peptide family of potential growth factors, is synthesized in Xenopus laevis skin

Expression Profiling along the Murine Intestine: Different Mucosal Protection Systems and Alterations in Tff1-Deficient Animals

Tff1 is a typical gastric peptide secreted together with the mucin, Muc5ac. Tff1-deficient (Tff1KO) mice are well known for their prominent gastric phenotype and represent a recognized model for antral tumorigenesis. Notably, intestinal abnormalities have also been reported in the past in these animals. Here, we have compared the expression of selected genes in Tff1KO mice and their corresponding wild-type littermates (RT-PCR analyses), focusing on different mucosal protection systems along the murine intestine. As hallmarks, genes were identified with maximum expression in the proximal colon and/or the duodenum: Agr2, Muc6/A4gnt/Tff2, Tff1, Fut2, Gkn2, Gkn3, Duox2/Lpo, Nox1. This is indicative of different protection systems such as Tff2/Muc6, Tff1-Fcgbp, gastrokines, fucosylation, and reactive oxygen species (ROS) in the proximal colon and/or duodenum. Few significant transcriptional changes were observed in the intestine of Tff1KO mice when compared with wild-type littermates, Clca1 (Gob5), Gkn1, Gkn2, Nox1, Tff2. We also analyzed the expression of Tff1, Tff2, and Tff3 in the pancreas, liver, and lung of Tff1KO and wild-type animals, indicating a cross-regulation of Tff gene expression. Furthermore, on the protein level, heteromeric Tff1-Fcgbp and various monomeric Tff1 forms were identified in the duodenum and a high-molecular-mass Tff2/Muc6 complex was identified in the proximal colon (FPLC, proteomics).

The Forms of the Lectin Tff2 Differ in the Murine Stomach and Pancreas: Indications for Different Molecular Functions

The lectin TFF2 belongs to the trefoil factor family (TFF). This polypeptide is typically co-secreted with the mucin MUC6 from gastric mucous neck cells, antral gland cells, and duodenal Brunner glands. Here, TFF2 fulfills a protective function by forming a high-molecular-mass complex with the MUC6, physically stabilizing the mucus barrier. In pigs and mice, and slightly in humans, TFF2 is also synthesized in the pancreas. Here, we investigated the murine stomach, pancreas, and duodenum by fast protein liquid chromatography (FPLC) and proteomics and identified different forms of Tff2. In both the stomach and duodenum, the predominant form is a high-molecular-mass complex with Muc6, whereas, in the pancreas, only low-molecular-mass monomeric Tff2 was detectable. We also investigated the expression of Tff2 and other selected genes in the stomach, pancreas, and the proximal, medial, and distal duodenum (RT-PCR analysis). The absence of the Tff2/Muc6 complex in the pancreas is due to a lack of Muc6. Based on its known motogenic, anti-apoptotic, and anti-inflammatory effects, we propose a protective receptor-mediated function of monomeric Tff2 for the pancreatic ductal epithelium. This view is supported by a report that a loss of Tff2 promotes the formation of pancreatic intraductal mucinous neoplasms.

Trefoil Factor Family (TFF) Peptides and Their Diverse Molecular Functions in Mucus Barrier Protection and More: Changing the Paradigm

Trefoil factor family peptides (TFF1, TFF2, TFF3) are typically co-secreted together with mucins. Tff1 represents a gastric tumor suppressor gene in mice. TFFs are also synthesized in minute amounts in the immune and central nervous systems. In mucous epithelia, they support rapid repair by enhancing cell migration ("restitution") via their weak chemotactic and anti-apoptotic effects. For a long time, as a paradigm, this was considered as their major biological function. Within recent years, the formation of disulfide-linked heterodimers was documented for TFF1 and TFF3, e.g., with gastrokine-2 and IgG Fc binding protein (FCGBP). Furthermore, lectin activities were recognized as enabling binding to a lipopolysaccharide of Helicobacter pylori (TFF1, TFF3) or to a carbohydrate moiety of the mucin MUC6 (TFF2). Only recently, gastric TFF1 was demonstrated to occur predominantly in monomeric forms with an unusual free thiol group. Thus, a new picture emerged, pointing to diverse molecular functions for TFFs. Monomeric TFF1 might protect the gastric mucosa as a scavenger for extracellular reactive oxygen/nitrogen species. Whereas, the TFF2/MUC6 complex stabilizes the inner layer of the gastric mucus. In contrast, the TFF3-FCGBP heterodimer (and also TFF1-FCGBP) are likely part of the innate immune defense of mucous epithelia, preventing the infiltration of microorganisms.

Trefoil Factor Family (TFF) Modules Are Characteristic Constituents of Separate Mucin Complexes in the Xenopus laevis Integumentary Mucus: In Vitro Binding Studies with FIM-A.1

The skin of the frog Xenopus laeevis is protected from microbial infections by a mucus barrier that contains frog integumentary mucins (FIM)-A.1, FIM-B.1, and FIM-C.1. These gel-forming mucins are synthesized in mucous glands consisting of ordinary mucous cells and one or more cone cells at the gland base. FIM-A.1 and FIM-C.1 are unique because their cysteine-rich domains belong to the trefoil factor family (TFF). Furthermore, FIM-A.1 is unusually short (about 400 amino acid residues). In contrast, FIM-B.1 contains cysteine-rich von Willebrand D (vWD) domains. Here, we separate skin extracts by the use of size exclusion chromatography and analyze the distribution of FIM-A.1 and FIM-C.1. Two mucin complexes were detected, i.e., a high-molecular-mass Complex I, which contains FIM-C.1 and little FIM-A.1, whereas Complex II is of lower molecular mass and contains the bulk of FIM-A.1. We purified FIM-A.1 by a combination of size-exclusion chromatography (SEC) and anion-exchange chromatography and performed first in vitro binding studies with radioactively labeled FIM-A.1. Binding of ¹²⁵I-labeled FIM-A.1 to the high-molecular-mass Complex I was observed. We hypothesize that the presence of FIM-A.1 in Complex I is likely due to lectin interactions, e.g., with FIM-C.1, creating a complex mucus network.

βγ-CAT, a non-lens betagamma-crystallin and trefoil factor complex, induces calcium-dependent platelet apoptosis

In recent years, it has been reported that apoptosis may occur in platelets and play a role in the clearance of effete platelets. βγ-CAT, a newly identified non-lens βγ-crystallin and trefoil factor complex from frog Bombina maxima skin secretions, caused several in vivo toxic effects on mammals. Through determined haematological parameters of rabbits, it has been found that βγ-CAT significantly reduced the number of platelets in a time-dependent manner. Here, in order to explore the effect of βγ-CAT on platelets, washed platelets were incubated with various concentrations of βγ-CAT for 30 minutes. We found that βγ-CAT induced several apoptosis events in human platelets, including caspase-3 activation, phosphatidylserine (PS) exposure, depolarisation of mitochondrial inner transmembrane potential (ΔΨm), cytochrome c re-lease and strong expression of pro-apoptotic Bax and Bak proteins. However, βγ-CAT did not significantly induce platelet activation as detected by P-selectin surface expression, GPIIb/IIIa activation and platelet aggregation. In addition, we observed that βγ-CAT-induced PS exposure and ΔΨm depolarisation in platelets are Ca2+-dependent. Taken together, βγ-CAT can induce Ca2+-dependent platelet apoptosis but does not cause platelet activation.

Host-defense and trefoil factor family peptides in skin secretions of the Mawa clawed frog Xenopus boumbaensis (Pipidae)

Peptidomic analysis of norepinephrine-stimulated skin secretions from the octoploid Mawa clawed frog Xenopus boumbaensis Loumont, 1983 led to the identification and characterization of 15 host-defense peptides belonging to the magainin (two peptides), peptide glycine-leucine-amide (PGLa; three peptides), xenopsin precursor fragment (XPF; three peptides), caerulein precursor fragment (CPF; two peptides), and caerulein precursor fragment-related peptide (CPF-RP; five peptides) families. In addition, caerulein and three peptides with structural similarity to the trefoil factor family (TFF) peptides, xP2 and xP4 from Xenopus laevis were also present in the secretions. Consistent with data from comparisons of the nucleotides sequence of mitochondrial and nuclear genes, the primary structures of the peptides suggest a close phylogenetic relationship between X. boumbaensis and the octoploid frogs Xenopus amieti and Xenopus andrei. As the three species occupy disjunct ranges within Cameroon, it is suggested that they diverged from a common ancestor by allopatric speciation.

The frog trefoil factor Bm-TFF2 activates human platelets via Gq and G12/13 signaling pathway

Bm-TFF2 is an amphibian trefoil factor purified from the Bombina maxima skin secretion that is highly toxic to mammals. We previously reported that Bm-TFF2 activates human platelets via protease-activated receptor 1. In this study, for a better understanding of platelet activation induced by Bm-TFF2, we used affinity chromatography and pharmacological inhibitors to investigate the downstream signaling pathway. Using Bm-TFF2-affinity chromatography, Gq was specifically eluted from the Bm-TFF2-coulped column. Pharmacological inhibitors such as U73122, Xestospongin C, BAPTA-AM and Gö6976 can significantly inhibit Bm-TFF2-induced platelet aggregation. These results suggested that Gq activation and the downstream PLCβ-IP3 receptor-cytoplasmic Ca(2+)-PKC signaling pathway is crucial for Bm-TFF2 to stimulate platelet aggregation. Furthermore, Bm-TFF2 induced strong platelet shape change at the concentrations of 5nM, in which the Ca(2+) mobilization of the platelets stimulated was not detectable. The p160(ROCK) inhibitorY27632 totally inhibited the shape change, indicating that Bm-TFF2 may activate the G12/13 pathway which leads to the activation of RhoA-p160(ROCK). In conclusion, Bm-TFF2 induced platelet activation mainly via the Gq and G12/13 signaling pathway. This study on the signaling pathway of Bm-TFF2 stimulation may help us understand the toxicity of B. maxima skin secretion to the human platelets.

Caerulein-and xenopsin-related peptides with insulin-releasing activities from skin secretions of the clawed frogs, Xenopus borealis and Xenopus amieti (Pipidae)

Caerulein-related peptides were identified in norepinephrine-stimulated skin secretions of the tetraploid frog Xenopus borealis and the octoploid frog Xenopus amieti using negative ion electrospray mass spectrometry and their primary structures determined by positive ion tandem (MS/MS) mass spectrometry. X. borealis caerulein-B1 (pGlu-Gln-Asp-Tyr(SO(3))-Gly-Thr-Gly-Trp-Met-Asp-Phe.NH2) contains an additional Gly(5) residue compared with X. laevis caerulein and caerulein-B2 (pGlu-Asp-Tyr(SO(3))-Thr-Gly-Trp-Met-Asp-Phe.NH2) contains a Gln(2) deletion. X. amieti caerulein was identical to the X. laevis peptide. In addition, xenopsin, identical to the peptide from X. laevis, together with xenopsin-AM2 (pGlu-Gly-Arg-Arg-Pro-Trp-Ile- Leu) that contains the substitution Lys(3)→Arg were isolated from X. amieti secretions. X. borealis caerulein-B1, and X. amieti xenopsin and xenopsin-AM2 produced significant (P<0.05) and concentration-dependent stimulations of insulin release from the rat BRIN-BD11 clonal β cell line at concentrations ⩾30nM. The peptides did not stimulate the release of lactate dehydrogenase at concentrations up to 3μM demonstrating that the integrity of the plasma membrane had been preserved. While their precise biological role is unclear, the caerulein- and xenopsin-related peptides may constitute a component of the animal's chemical defenses against predators.

Bm-TFF2, a toad trefoil factor, promotes cell migration, survival and wound healing

Toad skin is naked and continually confronted by various injurious factors. Constant skin renewal and repairs occur frequently. However, the mechanisms of the renewal and repair have not clearly elucidated. In our previous work, a trefoil factor (TFF), Bm-TFF2, has been purified from the Bombina maxima skin and characterized as a platelet agonist. The mRNA of TFFs in toad skin was up-regulated greatly during the metamorphosis, indicating a pivotal role of TFFs in amphibian skin. Here, we presented the effects of Bm-TFF2 on the cell migration, apoptosis and proliferation. Bm-TFF2 bound to epithelial cells and showed strong cell motility activity. At the concentrations of 1-100nM, Bm-TFF2-induced migration of human epithelial AGS and HT-29 cells, and rat intestinal epithelial IEC-6 cell lines. The in vitro wound healing assay also verified the activity of Bm-TFF2. Bm-TFF2 could also inhibit cell apoptosis induced by ceramide and sodium butyrate. The cell migration-promoting activity was abolished by MEK1 inhibitors, U0126 and PD98059, suggesting that ERK1/2 activation is crucial for Bm-TFF2 to stimulate cell migration. Taken together, Bm-TFF2 promoted wound healing by stimulating cell migration via MAPK pathway and preventing cell apoptosis. The potent biological activity of Bm-TFF2 makes it a useful molecular tool for further studies of structure-function relationship of the related human TFFs.

Synthesis and localization of trefoil factor family (TFF) peptides in the human urinary tract and TFF2 excretion into the urine

Trefoil factor family (TFF) peptides promote regeneration and repair processes of mucous epithelia. They also probably play a key role in the remarkable regenerative capacity of the urinary tract epithelia. We have localized TFF1, TFF2, and TFF3 expression systematically in surgical specimens from the urinary tract by reverse transcription with the polymerase chain reaction, Western blot analysis, and immunohistochemistry. Urine samples from patients suffering from nephrolithiasis have been investigated and compared with those of healthy controls. TFF synthesis is detectable along the entire urinary tract epithelia. TFF3 synthesis is the most pronounced followed by TFF1, whereas TFF2 synthesis is occasionally detectable but only in trace amounts. In contrast, TFF2 is the predominant TFF peptide excreted into the urine, and significantly increased urinary TFF2 levels (together with occasionally raised TFF3 levels) have been observed in patients suffering from nephrolithiasis. Thus, we consider that TFF3 plays a major part in regeneration and restitution processes in urinary tract epithelia. TFF2 and probably also TFF3 are candidate biomarkers for nephrolithiasis and possibly other inflammatory conditions of the urinary tract.

A novel non-lens betagamma-crystallin and trefoil factor complex from amphibian skin and its functional implications

BACKGROUND

In vertebrates, non-lens betagamma-crystallins are widely expressed in various tissues, but their functions are unknown. The molecular mechanisms of trefoil factors, initiators of mucosal healing and being greatly involved in tumorigenesis, have remained elusive.

PRINCIPAL FINDINGS

A naturally existing 72-kDa complex of non-lens betagamma-crystallin (alpha-subunit) and trefoil factor (beta-subunit), named betagamma-CAT, was identified from frog Bombina maxima skin secretions. Its alpha-subunit and beta-subunit (containing three trefoil factor domains), with a non-covalently linked form of alphabeta(2), show significant sequence homology to ep37 proteins, a group of non-lens betagamma-crystallins identified in newt Cynops pyrrhogaster and mammalian trefoil factors, respectively. betagamma-CAT showed potent hemolytic activity on mammalian erythrocytes. The specific antiserum against each subunit was able to neutralize its hemolytic activity, indicating that the two subunits are functionally associated. betagamma-CAT formed membrane pores with a functional diameter about 2.0 nm, leading to K(+) efflux and colloid-osmotic hemolysis. High molecular weight SDS-stable oligomers (>240-kDa) were detected by antibodies against the alpha-subunit with Western blotting. Furthermore, betagamma-CAT showed multiple cellular effects on human umbilical vein endothelial cells. Low dosages of betagamma-CAT (25-50 pM) were able to stimulate cell migration and wound healing. At high concentrations, it induced cell detachment (EC(50) 10 nM) and apoptosis. betagamma-CAT was rapidly endocytosed via intracellular vacuole formation. Under confocal microscope, some of the vacuoles were translocated to nucleus and partially fused with nuclear membrane. Bafilomycin A1 (a specific inhibitor of the vacuolar-type ATPase) and nocodazole (an agent of microtuble depolymerizing), while inhibited betagamma-CAT induced vacuole formation, significantly inhibited betagamma-CAT induced cell detachment, suggesting that betagamma-CAT endocytosis is important for its activities.

CONCLUSIONS/SIGNIFICANCE

These findings illustrate novel cellular functions of non-lens betagamma-cyrstallins and action mechanism via association with trefoil factors, serving as clues for investigating the possible occurrence of similar molecules and action mechanisms in mammals.

Cloning and expression of xP1-L, a new marker gene for larval surface mucous cells of tadpole stomach in Xenopus laevis

The amphibian gastrointestinal tract is remodeled from a larval-type to an adult-type during metamorphosis. In the present study, we examined the products of subtractive hybridization between tadpole and frog stomach cDNAs of Xenopus laevis in order to identify genes expressed specifically in the larval stomach epithelium. A new gene homologous to xP1 was obtained and named xP1-L. In the genome database of Silurana tropicalis, we found a homologue of xP1-L and named it stP1-L. RT-PCR showed that the expression of xP1-L was detected in stage 41/42 tadpoles. In addition, in situ hybridization showed that xP1-L was localized to surface mucous cells of the larval stomach. The H(+)/K(+)-ATPase beta subunit, a marker gene for manicotto gland cells in the tadpole stomach, was also detected at the same time. However, adult marker genes such as xP1 for surface mucous cells and pepsinogen C (PgC) for oxynticopeptic cells were not expressed in the tadpole stages. The expression of xP1-L gradually decreased towards the metamorphic climax and disappeared after stage 61 when larval-type gastric epithelium is replaced by adult-type. We found that xP1-L was never expressed in surface mucous cells of the adult-type stomach, and xP1, instead of xP1-L, was expressed. During T3-induced metamorphosis, xP1-L expression decreased in the same manner as during natural metamorphosis. Thus, xP1-L is a useful marker for larval surface mucous cells in tadpole stomach. This is the first demonstration of a marker gene specific for the surface mucous cells of the larval stomach.

Bm-TFF2, a trefoil factor protein with platelet activation activity from frog Bombina maxima skin secretions

In mammals, trefoil factor family (TFF) proteins are involved in mucosal maintenance and repair, and they are also implicated in tumor suppression and cancer progression. A novel two domain TFF protein from frog Bombina maxima skin secretions (Bm-TFF2) has been purified and cloned. It activated human platelets in a dose-dependent manner and activation of integrin alpha(IIb)beta(3) was involved. Aspirin and apyrase did not largely reduce platelet response to Bm-TFF2 (a 30% inhibition), indicating that the aggregation is not substantially dependent on ADP and thromboxane A2 autocrine feedback. Elimination of external Ca(2+) with EGTA did not influence the platelet aggregation induced by Bm-TFF2, meanwhile a strong calcium signal (cytoplasmic Ca(2+) release) was detected, suggesting that activation of phospholipase C (PLC) is involved. Subsequent immunoblotting revealed that, unlike in platelets activated by stejnulxin (a glycoprotein VI agonist), PLCgamma2 was not phosphorylated in platelets activated by Bm-TFF2. FITC-labeled Bm-TFF2 bound to platelet membranes. Bm-TFF2 is the first TFF protein reported to possess human platelet activation activity.

Identification of excretory-secretory products of larval and adult Ostertagia ostertagi by immunoscreening of cDNA libraries

Excretory-secretory (ES) products of Ostertagia ostertagi, an abomasal nematode of cattle, are considered to be important for the development and survival of the parasite within the host. To gain insight in the composition of these ES products of both larval (L3, L4) and adult life stages of Ostertagia cDNA libraries of the parasite were immunoscreened with polyclonal rabbit serum raised against these ES products. This approach led to the identification of 41 proteins, amongst which are structural proteins such as actin, kinesin and vitellogenin, housekeeping proteins such as those involved in protein folding, different metabolic pathways or mitochondrial functioning and proteins associated with stress (heat shock protein) or antioxidantia (thioredoxin peroxidase). A large number of the isolated proteins were similar to hypothetical proteins of the model nematode Caenorhabditis elegans. Because somatic proteins can be non-specifically released during in vitro culturing as nematodes deteriorate, it was checked if the isolated proteins are genuinely secreted. The amino acid sequences of the translated cDNAs were investigated for signal peptides and monospecific antibodies against the isolated proteins were purified and used to develop Western blots of ES and somatic extracts. In this manner it could be proven that 15 cDNAs code for genuine secreted proteins. The identification of these ES antigens allows to select proteins with potential protective capacities, which are targets for vaccine development.

New member of the trefoil factor family of proteins is an alpha-macroglobulin protease inhibitor

The amino acid sequence of the monomeric alpha-macroglobulin (alphaM) from the American bullfrog, Rana catesbiana, was determined. The mature protein consisted of 1469 amino acid residues and shared sequence identity with other members of the alphaM family of protein. The central portion of the frog monomeric alphaM contained Cys residues positioned analogously to the Cys residues in human alpha(2)-macroglobulin (alpha(2)M), known to be involved in disulfide bridges. Additionally, the frog monomeric alphaM contained six Cys residues in a approximately 60 residue COOH-terminal extension not present in previously characterized alphaMs. The spacing of the Cys residues and the overall sequence identity of this COOH-terminal extension were consistent with a trefoil motif. This is the first time a member of the trefoil factor family has been identified in the circulatory system. The "bait region" was located between Arg(675)-Lys(685) and contained mainly basic amino acid residues. The COOH-terminal receptor-binding domain was not exposed prior to proteolysis of this highly susceptible region. The proximity of the receptor-binding and trefoil domains implied that the trefoil domain is similarly concealed before bait region cleavage.

Cell type specific expression of secretory TFF peptides: colocalization with mucins and synthesis in the brain

The "TFF domain" is an ancient cysteine-rich shuffled module forming the basic unit for the family of secretory TFF peptides (formerly P-domain peptides and trefoil factors). It is also an integral component of mosaic proteins associated with mucous surfaces. Three mammalian TFF peptides are known (i.e., TFF1-TFF3); however, in Xenopus laevis the pattern is more complex (xP1, xP4.1, xP4.2, and xP2). TFF peptides are typical secretory products of a variety of mucin-producing epithelial cells (e.g., the conjunctiva, the salivary glands, the gastrointestinal tract, the respiratory tract, and the uterus). Each TFF peptide shows an unique expression pattern and different mucin-producing cells are characterized by their specific TFF peptide/secretory mucin combinations. TFF peptides have a pivotal role in maintaining the surface integrity of mucous epithelia in vivo. They are typical constituents of mucus gels, they modulate rapid mucosal repair ("restitution") by their motogenic and their cell scattering activity, they have antiapoptotic effects, and they probably modulate inflammatory processes. Pathological expression of TFF peptides occurs as a result of chronic inflammatory diseases or certain tumors. TFF peptides are also found in the central nervous system, at least in mammals. In particular, TFF3 is synthesized from oxytocinergic neurons of the hypothalamus and is released from the posterior pituitary into the bloodstream.

Mouse Trefoil factor genes: genomic organization, sequences and methylation analyses

The mammalian Trefoil Factors (TFFs), TFF1/pS2, TFF2/SP and TFF3/ITF, are expressed and secreted throughout the gastrointestinal tract with a specific and complementary pattern. These proteins exhibit common functions in the protection and repair process of the gastrointestinal epithelial barrier. Here, we report the clustered organization of the three mouse TFF genes in a 40 kb DNA segment, in a head to tail orientation in the following order: TFF1, TFF2, and TFF3. Computer comparison of the mouse TFF promoter sequences to their human counterparts revealed conserved boxes in both mouse and human genes. Promoter methylation analyses showed that, in tissues where these genes are normally expressed, the proximal promoters of TFF1 and TFF2 are specifically not methylated and that of TFF3 is partially demethylated. In contrast, in organs that do not express TFFs, the promoters of the three genes are methylated. These findings strongly argue for the involvement of epigenetic mechanisms in the regulation of TFF expression in normal and pathological conditions.

Molecular cloning and characterization of an antigenic protein with a repeating region from Clonorchis sinensis

In the course of immunoscreening of Clonorchis sinensis cDNA library, a cDNA CsRP12 containing a tandem repeat was isolated. The cDNA CsRP12 encodes two putative peptides of open reading frames (ORFs) 1 and 2 (CsRP12-1 and -2). The repetitive region is composed of 15 repeats of 10 amino acids. Of the two putative peptides, CsRP12-1 was proline-rich and found to have homologues in several organisms. Recombinant proteins of the putative peptides were bacterially produced and purified by an affinity chromatography. Recombinant CsRP12-1 protein was recognized by sera of clonorchiasis patients and experimental rabbits, but recombinant CsRP12-2 was not. One of the putative peptide, CsRP12-1, is designated CsPRA, proline-rich antigen of C. sinensis. Both the C-termini of CsRP12-1 and -2 were bacterially produced and analysed to show no antigenicity. Recombinant CsPRA protein showed high sensitivity and specificity. In experimental rabbits, IgG antibodies to CsPRA was produced between 4 and 8 weeks after the infection and decreased thereafter over one year. These results indicate that CsPRA is equivalent to a natural protein and a useful antigenic protein for serodiagnosis of human clonorchiasis.

Structure of the Xenopus laevis TFF-gene xP4.1, differentially expressed to its duplicated homolog xP4.2

TFF-peptides (formerly P-domain peptides, trefoil factors) represent major secretory products of mucous epithelia in mammals and amphibia. The nucleotide sequence of a large portion of a gene encoding the TFF-peptide xP4.1 from Xenopus laevis and its genomic organization were determined in the present study. The peptide xP4.1 containing four TFF-domains is thought to represent the functional frog homolog of human TFF2 (formerly hSP). The xP4.1 gene analyzed spans a region of about 7 kb and consists of six exons. Each TFF-domain is encoded by a single exon flanked by type 1 introns typical of shuffled modules. The 5'-upstream region contains a TATA-box, and potential binding sites for hepatocyte nuclear factor 3 and AP-1. Furthermore, the cDNA sequence of a transcript named xP4.2 with 91% similarity to xP4.1 is presented. RT-PCR analysis revealed that xP4.1 and xP4.2 genes are differentially expressed. xP4.1 transcripts are detectable only in the stomach, but not in the esophagus, whereas xP4.2 transcripts are found both in the esophagus and in the stomach with a descending gradient from fundus to antrum.

Hepatocyte nuclear factor 3 (winged helix domain) activates trefoil factor gene TFF1 through a binding motif adjacent to the TATAA box

The winged helix transcription factors HNF-3/FKH (forkhead homologs) activate endodermal-derived and acute-phase gene expression and control gut development in Drosophila. Trefoil factor family (TFFs) peptides are vertebrate products secreted by mucin-producing epithelial cells of the gastrointestinal tract involved in restitution and repair of the mucosa. They are positively regulated in ulcerative and neoplastic conditions. We describe a consensus sequence in human and rodent TFF promoters close to the TATAA box showing striking similarity to the binding site of the HNF-3/FKH family. In gel retardation assays, HNF-3 alpha and beta bound predominantly to the site in TFF1 (formerly pS2) and, to a lesser extent, to the sites in TFF2 or TFF3. Mutations generated in this motif severely impaired transcription of TFF1 reporter genes. Cotransfection with expression vectors of HNF-3alpha and beta, but not the related HFH 11A and B, specifically activated the wild-type TFF1 reporter genes. Activation of endogenous expression of TFF1 by HNF-3 alpha and beta gene products was more than 1000 fold in the pancreatic cell line Capan-2 and fivefold in the gastric cell line MKN-45, whereas the intestinal cell lines HUTU 80 and HT-29 displayed no effect. Thus, HNF-3/FKH factors contribute causally to cell-specific regulation of TFF genes and may explain the acute-phase response of TFF peptides.

The pcd gene encoding piperideine-6-carboxylate dehydrogenase involved in biosynthesis of alpha-aminoadipic acid is located in the cephamycin cluster of Streptomyces clavuligerus

Three open reading frames (ORFs) have been located downstream of cefE in the cephamycin C gene cluster of Streptomyces clavuligerus. ORF13 (pcd) encodes a 496-amino-acid protein (molecular weight [MW], 52,488) with an N-terminal amino acid sequence identical to that of pure piperideine-6-carboxylate dehydrogenase. ORF14 (cmcT) encodes a 523-amino-acid protein (MW, 54,232) analogous to Streptomyces proteins for efflux and resistance to antibiotics. ORF15 (pbp74) encodes a high molecular weight penicillin-binding protein (MW, 74, 094).

The pS2/TFF1 trefoil factor, from basic research to clinical applications

pS2/TFF1 trefoil factor is normally expressed in the stomach, and is found ectopically in gastrointestinal inflammatory disorders and in various carcinomas. It is involved in stomach ontogenesis and in the maintenance of the integrity of the mucosa, and may represent a pharmacological tool for prevention and healing of gastrointestinal ulcerations. In breast cancer, it can be used to select patients suitable for hormone therapy. pS2/TFF1 is a pleiotropic factor involved in mucin polymerization, cell motility, cell proliferation and/or differentiation, and possibly in the nervous system.

Trefoil proteins: their role in normal and malignant cells

The three human trefoil proteins pS2, human intestinal trefoil factor (hITF), and human spasmolytic polypeptide (hSP) are expressed principally in the mucosa of the gastrointestinal tract. They are also expressed in a variety of other normal tissues and tumours. This review discusses the pattern of expression of trefoil proteins in cancer, current views on the biological functions of trefoil proteins, and the way in which the expression of trefoil proteins may influence the behaviour of cancer cells.

Molecular and cellular analysis of rP1.B in the rat hypothalamus: in situ hybridization and immunohistochemistry of a new P-domain neuropeptide

P-domain peptides, a new family of secretory polypeptides, have been identified mainly in the gastroenteropancreatic tract of humans, rodents, and amphibians as well as in amphibian skin. In the present study, with PCR and RNA analysis a transcript has been discovered in rat brain termed rP1.B. The deduced polypeptide consists of a single P-domain and its amino acid sequence matches that of rat intestinal trefoil factor (rITF). Thus far, rP1.B is the only P-domain peptide expressed in neuronal cells of the CNS. Immunostained magnocellular perikarya were visible in the paraventricular, supraoptic and periventricular nuclei. Parvocellular rP1.B neurons were found in the arcuate nucleus. Additionally, specific hybridization signals with radiolabeled transcripts were observed in the same regions. rP1.B in the rat hypothalamus may be involved in the control of hypothalamo-hypophysial functions.

Trefoil peptides. Coming up clover

Now that information on trefoil domain structure is available from X-ray crystallographic and nuclear magnetic resonance spectroscopy studies, we can begin to understand the functions of these unusual protein motifs.

Pancreatic spasmolytic polypeptide: first three-dimensional structure of a member of the mammalian trefoil family of peptides

BACKGROUND

The trefoil peptides are a rapidly growing family of peptides, mainly found in the gastrointestinal tract. There is circumstantial evidence that they stabilize the mucus layer, and may affect the rate of healing of the mucosal epithelium.

RESULTS

We have determined the structure of porcine pancreatic spasmolytic polypeptide (PSP) to 2.5 A resolution. The polypeptide contains two trefoil domains. The domain structure is compact, and is composed of a central short antiparallel beta-sheet with one short helix above and one below it. This is a novel motif. The two domains are related by two-fold symmetry, and each domain contains a cleft.

CONCLUSIONS

The cleft within each domain could accommodate a polysaccharide chain, and may therefore be responsible for binding mucin glycoproteins. We suggest that PSP may cross-link glycoproteins, explaining its ability to stabilize the mucus layer.

Biosynthesis of frog skin mucins: cysteine-rich shuffled modules, polydispersities and genetic polymorphism

1. Frog integumentary mucins (FIM-A.1, FIM-B.1 and FIM-C.1) consist of typical threonine-rich highly O-glycosylated (semi)repetitive domains, and cysteine-rich modules, i.e. the P-domain, the short consensus repeat and a region with high similarity to the C-terminal end of von Willebrand factor (designated here CC29-motif). 2. These modules are thought to be involved in protein-protein interactions and they have been observed in a variety of extracellular proteins. In FIMs, these modules may be involved in oligomerization processes leading to an entangled mucin network. 3. Polydispersities have been detected in FIM-B.1 and FIM-C.1 within single individuals. Multiple transcripts are probably generated by alternative splicing of a huge array of different (semi)repetitive cassettes encoding the threonine-rich domains. 4. Furthermore, genetic polymorphism is observed between different individuals, probably due to allelic variations in the number of (semi)repetitive cassettes.

The P-domain or trefoil motif: a role in renewal and pathology of mucous epithelia?

By analogy with epidermal growth factor and EGF-like repeats, the P-domain, or trefoil motif, is a characteristic shuffled module containing six invariant cysteine residues that forms the basic unit for a family of mucin-associated peptides. These P-domain peptides are potential modulators of cell growth and they are also expressed under certain pathological conditions. Furthermore, P-domains have been found as components of extracellular mosaic proteins including certain mucins, where they are thought to play a role either in protein-protein or in lectin-like interactions.

Purification and characterization of the trefoil peptide human spasmolytic polypeptide (hSP) produced in yeast

Recombinant human spasmolytic polypeptide (r-hSP) has been produced in relatively large amounts in Saccharomyces cerevisiae. The two intronless trefoil domains of the hSP-DNA were cloned separately by PCR from human genomic DNA, and the remaining parts of the gene synthesized. Recombinant plasmids were constructed to encode a fusion protein consisting of a hybrid leader sequence and the hSP sequence. The leader sequence serves to direct the fusion protein into the secretory pathway of the cell and to expose it to the Kex 2 processing enzyme system. The secreted r-hSP was found in a glycosylated and an non-glycosylated form. The two forms of r-hSP were purified from the yeast fermentation broth by a combination of ion-exchange chromatography and preparative HPLC. The overall yield from 8 litres of fermentation broth was 160 mg r-hSP and 219 mg glycosylated r-hSP corresponding to 50% and 34%, respectively. The structure of the r-hSP and the glycosylated r-hSP was determined by amino acid analysis and carbohydrate composition analysis as well as by peptide mapping, amino acid sequencing and mass spectrometric analysis.