The solution structure of the disulphide-linked homodimer of the human trefoil protein TFF1

Mucin networks: Dynamic structural assemblies controlling mucus function

Contrary to first appearances, mucus structural biology is not an oxymoron. Though mucus hydrogels derive their characteristics largely from intrinsically disordered, heavily glycosylated polypeptide segments, the secreted mucin glycoproteins that constitute mucus undergo an orderly assembly process controlled by folded domains at their termini. Recent structural studies revealed how mucin complexes promote disulphide-mediated polymerization to produce the mucus gel scaffold. Additional protein-protein and protein-glycan interactions likely tune the mesoscale properties, stability, and activities of mucins. Evidence is emerging that even intrinsically disordered glycosylated segments have specific structural roles in the production and properties of mucus. Though soft-matter biophysical approaches to understanding mucus remain highly relevant, high-resolution structural studies of mucins and other mucus components are providing new perspectives on these vital, protective hydrogels.

Association of functional genetic variants in TFF1 and nephrolithiasis risk in a Chinese population

Trefoil Factor 1 (TFF1) is considered to be able to inhibit the formation of kidney stone. However, genetic variants in TFF1 and corresponding function in kidney stone development are still not well studied. In this study, the discovery set including 230 cases and 250 controls was used to analyze the association between seven tagSNPs of TFF1 gene and the nephrolithiasis risk. Further evaluation was confirmed by the validation set comprising 307 cases and 461 controls. The consequences of the two-stage case–control study indicated that individuals with the rs3761376 A allele have significantly increased nephrolithiasis risk than those with the GG genotypes [adjusted odds ratio (OR) = 1.35, 95% confidence interval (CI) = 1.05–1.73]. Moreover, we also carried out a stratified analysis and found the increased nephrolithiasis risks at A allele among males, overweight individuals, no hypertensive individuals, nondiabetic individuals, smokers, and drinkers. In the following functional experiments, the notably lower expression of TFF1 was exhibited by the vectors carrying A allele compared with those carrying G allele in both luciferase (P = 0.022) and expression vectors (P = 0.041). In addition to tissue detection, we confirmed a significant inverse association of rs3761376 G > A and TFF1 gene expression (P < 0.001). These results suggest that TFF1 rs3761376 may serve as a potential biomarker to predict the risk of nephrolithiasis.

Trefoil Factor Family: A Troika for Lung Repair and Regeneration

Tissue damage in the upper and lower airways caused by mechanical abrasion, noxious chemicals, or pathogenic organisms must be followed by rapid restorative processes; otherwise, persistent immunopathology and disease may ensue. This review will discuss evidence for the important role served by trefoil factor (TFF) family members in healthy and diseased airways of humans and rodents. Collectively, these peptides serve to both maintain and restore homeostasis through their regulation of the mucous layer and their control of cell motility, cell differentiation, and immune function in the upper and lower airways. We will also discuss important differences in which trefoil member tracks with homeostasis and disease between humans and mice, which poses a challenge for research in this area. Moreover, we discuss new evidence supporting newly identified receptor binding partners in the leucine-rich repeat and immunoglobulin-like domain-containing NoGo (LINGO) family in mediating the biological effects of TFF proteins in mouse models of epithelial repair and infection. Recent advances in our knowledge regarding TFF peptides suggest that they may be reasonable therapeutic targets in the treatment of upper and lower airway diseases of diverse etiologies. Further work understanding their role in airway homeostasis, repair, and inflammation will benefit from these newly uncovered receptor-ligand interactions.

Chemical synthesis of human trefoil factor 1 (TFF1) and its homodimer provides novel insights into their mechanisms of action

TFF1 is a key peptide for gastrointestinal protection and repair. Its molecular mechanism of action remains poorly understood with synthetic intractability a recognised bottleneck. Here we describe the synthesis of TFF1 and its homodimer and their interactions with mucins and Helicobacter pylori. Synthetic access to TFF1 is an important milestone for probe and therapeutic development.

Structure, Function, and Therapeutic Potential of the Trefoil Factor Family in the Gastrointestinal Tract

Trefoil factor family peptides (TFF1, TFF2, and TFF3) are key players in protecting, maintaining, and repairing the gastrointestinal tract. Accordingly, they have the therapeutic potential to treat and prevent a variety of gastrointestinal disorders associated with mucosal damage. TFF peptides share a conserved motif, including three disulfide bonds that stabilize a well-defined three-loop-structure reminiscent of a trefoil. Although multiple functions have been described for TFF peptides, their mechanisms at the molecular level remain poorly understood. This review presents the status quo of TFF research relating to gastrointestinal disorders. Putative TFF receptors and protein partners are described and critically evaluated. The therapeutic potential of these peptides in gastrointestinal disorders where altered mucosal biology plays a crucial role in the underlying etiology is discussed. Finally, areas of investigation that require further research are addressed. Thus, this review provides a comprehensive update on TFF literature as well as guidance toward future research to better understand this peptide family and its therapeutic potential for the treatment of gastrointestinal disorders.

Trefoil factors share a lectin activity that defines their role in mucus

The mucosal epithelium secretes a host of protective disulfide-rich peptides, including the trefoil factors (TFFs). The TFFs increase the viscoelasticity of the mucosa and promote cell migration, though the molecular mechanisms underlying these functions have remained poorly defined. Here, we demonstrate that all TFFs are divalent lectins that recognise the GlcNAc-α-1,4-Gal disaccharide, which terminates some mucin-like O-glycans. Degradation of this disaccharide by a glycoside hydrolase abrogates TFF binding to mucins. Structural, mutagenic and biophysical data provide insights into how the TFFs recognise this disaccharide and rationalise their ability to modulate the physical properties of mucus across different pH ranges. These data reveal that TFF activity is dependent on the glycosylation state of mucosal glycoproteins and alludes to a lectin function for trefoil domains in other human proteins.

Trefoil factors (TFFs) protect the mucosa and have various reported binding activities, but whether they share a common interaction mechanism has remained unclear. Here, the authors provide structural and biochemical evidence that all three human TFFs are divalent lectins that recognise the same disaccharide.

Odyssey of trefoil factors in cancer: Diagnostic and therapeutic implications

Trefoil factors 1, 2, and 3 (TFFs) are a family of small secretory molecules involved in the protection and repair of the gastrointestinal tract (GI). TFFs maintain and restore epithelial structural integrity via transducing key signaling pathways for epithelial cell migration, proliferation, and invasion. In recent years, TFFs have emerged as key players in the pathogenesis of multiple diseases, especially cancer. Initially recognized as tumor suppressors, emerging evidence demonstrates their key role in tumor progression and metastasis, extending their actions beyond protection. However, to date, a comprehensive understanding of TFFs' mechanism of action in tumor initiation, progression and metastasis remains obscure. The present review discusses the structural, functional and mechanistic implications of all three TFF family members in tumor progression and metastasis. Also, we have garnered information from studies on their structure and expression status in different organs, along with lessons from their specific knockout in mouse models. In addition, we highlight the emerging potential of using TFFs as a biomarker to stratify tumors for better therapeutic intervention.

The Interaction of Helicobacter pylori with TFF1 and Its Role in Mediating the Tropism of the Bacteria Within the Stomach

Helicobacter pylori colonises the human stomach and has tropism for the gastric mucin, MUC5AC. The majority of organisms live in the adherent mucus layer within their preferred location, close to the epithelial surface where the pH is near neutral. Trefoil factor 1 (TFF1) is a small trefoil protein co-expressed with the gastric mucin MUC5AC in surface foveolar cells and co-secreted with MUC5AC into gastric mucus. Helicobacter pylori binds with greater avidity to TFF1 dimer, which is present in gastric mucus, than to TFF1 monomer. Binding of H. pylori to TFF1 is mediated by the core oligosaccharide subunit of H. pylori lipopolysaccharide at pH 5.0–6.0. Treatment of H. pylori lipopolysaccharide with mannosidase or glucosidase inhibits its interaction with TFF1. Both TFF1 and H. pylori have a propensity for binding to mucins with terminal non-reducing α- or β-linked N-acetyl-d-glucosamine or α-(2,3) linked sialic acid or Gal-3-SO₄²⁻. These findings are strong evidence that TFF1 has carbohydrate-binding properties that may involve a conserved patch of aromatic hydrophobic residues on the surface of its trefoil domain. The pH-dependent lectin properties of TFF1 may serve to locate H. pylori deep in the gastric mucus layer close to the epithelium rather than at the epithelial surface. This restricted localisation could limit the interaction of H. pylori with epithelial cells and the subsequent host signalling events that promote inflammation.

Binding of Helicobacter pylori to Human Gastric Mucins Correlates with Binding of TFF1

Helicobacter pylori binds to the gastric mucin, MUC5AC, and to trefoil factor, TFF1, which has been shown to interact with gastric mucin. We examined the interactions of TFF1 and H. pylori with purified gastrointestinal mucins from different animal species and from humans printed on a microarray platform to investigate whether TFF1 may play a role in locating H. pylori in gastric mucus. TFF1 bound almost exclusively to human gastric mucins and did not interact with human colonic mucins. There was a strong correlation between binding of TFF1 and H. pylori to human gastric mucins, and between binding of both TFF1 and H. pylori to gastric mucins with that of Griffonia simplicifolia lectin-II, which is specific for terminal non-reducing α- or β-linked N-acetyl-d-glucosamine. These results suggest that TFF1 may help to locate H. pylori in a discrete layer of gastric mucus and hence restrain their interactions with epithelial cells.

Trefoil Factor Peptides and Gastrointestinal Function

Trefoil factor (TFF) peptides, with a 40-amino acid motif and including six conserved cysteine residues that form intramolecular disulfide bonds, are a family of mucin-associated secretory molecules mediating many physiological roles that maintain and restore gastrointestinal (GI) mucosal homeostasis. TFF peptides play important roles in response to GI mucosal injury and inflammation. In response to acute GI mucosal injury, TFF peptides accelerate cell migration to seal the damaged area from luminal contents, whereas chronic inflammation leads to increased TFF expression to prevent further progression of disease. Although much evidence supports the physiological significance of TFF peptides in mucosal defenses, the molecular and cellular mechanisms of TFF peptides in the GI epithelium remain largely unknown. In this review, we summarize the functional roles of TFF1, 2, and 3 and illustrate their action mechanisms, focusing on defense mechanisms in the GI tract.

Functional expression of recombinant human trefoil factor 1 by Escherichia coli and Brevibacillus choshinensis

Background

Trefoil factor 1 (TFF1) mediates mucosal repair and belongs to a highly conserved trefoil factor family proteins which are secreted by epithelial cells in the stomach or colon mucous membrane. TFF1 forms a homodimer via a disulphide linkage that affects wound healing activity. Previous recombinant expressions of TFF1 were too low yield for industrial application. This study aims to improve the expression level of bioactive recombinant TFF1 (rTFF1) and facilitate application potency.

Methods

The rTFF1 gene rtff1 was synthesized, expressed by Escherichia coli and secreted by Brevibacillus choshinensis. The rTFF1s were purified. The polymeric patterns and wound healing capacities of purified rTFF1s were checked.

Results

In Escherichia coli, 21.08 mg/L rTFF1 was stably expressed as monomer, dimer and oligomer in soluble fraction. In Brevebacillus choshinensis, the rTFF1 was secreted extracellularly at high level (35.73 mg/L) and formed monomer, dimer and oligomer forms. Both proteins from different sources were purified by Ni-NTA chromatography and exhibited the wound healing activities. The rTFF1 produced by B. choshinensis had better wound healing capability than the rTFF1 produced by E. coli. After pH 2.4 buffer treatments, the purified rTFF1 formed more oligomeric forms as well as better wound healing capability. Glycosylation assay and LC-MS/MS spectrometry experiments showed that the rTFF1 produced by B. choshinensis was unexpectedly glycosylated at N-terminal Ser residue. The glycosylation may contribute to the better wound healing capacity.

Conclusions

This study provides a potent tool of rTFF1 production to be applied in gastric damage protection and wound healing. The protein sources from B. choshinensis were more efficient than rTFF1 produced by E. coli.

Electronic supplementary material

The online version of this article (doi:10.1186/s12896-015-0149-5) contains supplementary material, which is available to authorized users.

Trefoil factors (TFFs) are increased in bronchioalveolar lavage fluid from patients with chronic obstructive lung disease (COPD)

Trefoil factors (TFFs) 1, 2 and 3 are small polypeptides that are co-secreted with mucin throughout the body. They are up-regulated in cancer and inflammatory processes in the gastrointestinal system, where they are proposed to be involved in tissue regeneration, proliferation and protection. Our aim was to explore their presence in pulmonary secretions and to investigate whether they are up-regulated in pulmonary diseases characterized by mucin hypersecretion. Bronchioalveolar lavage fluid was obtained from 92 individuals referred to bronchoscopy. The patients were grouped according to diagnosis and pulmonary function. The concentrations of TFF1, TFF2 and TFF3 were measured by ELISA. All three peptides were detected in bronchioalveolar lavage fluid. Patients with chronic obstructive pulmonary disease had concentrations two to three times above the levels in the healthy reference group, and patients with pulmonary malignancies had concentrations of TFF1 and TFF2 three times that of the reference group. The results suggest that TFFs are involved in tissue regeneration, proliferation and protection in lung diseases.

Trefoil Factor 1 is involved in gastric cell copper homeostasis

Trefoil Factor 1 belongs to a group of small secreted proteins (the Trefoil Factor Family proteins), that are localized within the mucous granules and are expressed and secreted by epithelial cells that line mucous membranes. Trefoil factors are mainly expressed in the gastrointestinal tract, where they normally contribute to maintain the integrity of the mucosa. We recently demonstrated a selective binding ability of Trefoil Factor 1 for copper ions, through its carboxy-terminal tail, and we also observed that copper levels influence the equilibrium between the monomeric and homodimeric forms of Trefoil Factor 1, thus modulating its biological activity. Here we report that transcriptional regulation of Trefoil Factor 1 is also affected by copper levels, through the modulated binding of the copper-sensing transcription factor Sp1 onto the responsive elements present in the regulatory region of the gene. In addition we demonstrate that copper overload causes an accumulation of the trefoil protein in the Trans-Golgi Network and that Trefoil Factor 1 levels can influence copper excretion and copper related toxicity. These findings suggest that the protein might play a role in the overall complex mechanisms of copper homeostasis in the gastrointestinal tissues.

Trefoil factor peptides in serum and sputum from subjects with asthma and COPD

OBJECTIVE

Trefoil factor peptides (TFF) are secreted onto mucosal surfaces together with mucins and occur in high concentrations in pulmonary secretions from patients with chronic obstructive pulmonary disease (COPD). In the present study, we aimed to explore the concentrations of the peptides in serum and sputum in patients with COPD.

MATERIALS AND METHODS

Thirty-five individuals were included in the study, including 11 healthy individuals, 13 indivials with asthma and 11 individuals with COPD. TFF1, TFF2 and TFF3 were measured by enzyme-linked immunosorbent assay (ELISA) in sputum induced by hypertonic saline inhalation and in serum. Total protein content in sputum was also determined.

RESULTS

In the sputum samples from COPD patients, we observed an eightfold higher concentration of TFF1 and a fivefold higher concentration of TFF3 compared with controls. In the serum samples from COPD patients, we observed three-, three- and twofold higher concentrations of TFF1, TFF2 and TFF3 respectively compared with controls.

CONCLUSIONS

There is increased secretion of TFF peptides in the lungs of patients with COPD, as well as significant increases in serum levels. This suggests a role for TFF peptides in the pathogenesis of pulmonary diseases with mucus hypersecretion.

TFF3 is a normal breast epithelial protein and is associated with differentiated phenotype in early breast cancer but predisposes to invasion and metastasis in advanced disease

The trefoil protein TFF3 stimulates invasion and angiogenesis in vitro. To determine whether it has a role in breast tumor metastasis and angiogenesis, its levels were measured by immunohistochemistry in breast tissue with a specific monoclonal antibody raised against human TFF3. TFF3 is expressed in normal breast lobules and ducts, at higher levels in areas of fibrocystic change and papillomas, in all benign breast disease lesions, and in 89% of in situ and in 83% of invasive carcinomas. In well-differentiated tumor cells, TFF3 is concentrated at the luminal edge, whereas in poorly differentiated cells polarity is inverted and expression is directed toward the stroma. Expression was high in well-differentiated tumors and was associated significantly with low histological grade and with estrogen and progesterone receptor expression, accordant with induction of TFF3 mRNA by estrogen in breast cancer cells. Paradoxically, TFF3 expression was associated with muscle, neural, and lymphovascular invasion and the presence and number of involved lymph nodes, and it was an independent predictive marker of lymphovascular invasion and lymph node involvement. Consistent with an angiogenic function, TFF3 expression correlated strongly with microvessel density evaluated with CD31 and CD34. In conclusion, TFF3 is expressed in both the normal and diseased breast. Although associated with features of good prognosis, its profile of expression in invasive cancer is consistent with a role in breast tumor progression and tumor cell dissemination.

Activation of protease-activated receptor (PAR) 1 by frog trefoil factor (TFF) 2 and PAR4 by human TFF2

Trefoil factors (TFFs) promote epithelial cell migration to reseal superficial wounds after mucosal injury, but their receptors and the molecular mechanisms underlying this process are poorly understood. In this study, we showed that frog TFF2 activates protease-activated receptor (PAR) 1 to induce human platelet aggregation. Based on this result, we further tested the involvement of PARs in human TFF2 (hTFF2)-promoted mucosal healing. hTFF2-stimulated migration of epithelial HT-29 cells was largely inhibited by PAR4 depletion with small interfering RNAs but not by PAR1 or PAR2 depletion. The PAR4-negative epithelial cell lines AGS and LoVo were highly responsive to hTFF2 as assessed by phosphorylation of ERK1/2 and cell migration upon PAR4 expression. Our findings suggest that hTFF2 promotes cell migration via PAR4. These findings will be helpful in further investigations into the functions and molecular mechanisms of TFFs and PARs in physiology and disease.

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.

Copper binds the carboxy-terminus of trefoil protein 1 (TFF1), favoring its homodimerization and motogenic activity

Trefoil protein 1 (TFF1) is a small secreted protein belonging to the trefoil factor family of proteins, that are present mainly in the gastrointestinal (GI) tract and play pivotal roles as motogenic factors in epithelial restitution, cell motility, and other incompletely characterized biological processes. We previously reported the up-regulation of TFF1 gene in copper deficient rats and the unexpected property of the peptide to selectively bind copper. Following the previous evidence, here we report the characterization of the copper binding site by fluorescence quenching spectroscopy and mass spectrometric analyses. We demonstrate that Cys58 and at least three Glu surrounding residues surrounding it, are essential to efficiently bind copper. Moreover, copper binding promotes the TFF1 homodimerization, thus increasing its motogenic activity in in vitro wound healing assays. Copper levels could then modulate the TFF1 functions in the GI tract, as well as its postulated role in cancer progression and invasion.

The trefoil factor interacting protein TFIZ1 binds the trefoil protein TFF1 preferentially in normal gastric mucosal cells but the co-expression of these proteins is deregulated in gastric cancer

The gastric tumour suppressor trefoil protein TFF1 is present as a covalently bound heterodimer with a previously uncharacterised protein, TFIZ1, in normal human gastric mucosa. The purpose of this research was firstly to examine the molecular forms of TFIZ1 present, secondly to determine if TFIZ1 binds other proteins apart form TFF1 in vivo, thirdly to investigate if TFIZ1 and TFF1 are co-regulated in normal gastric mucosa and fourthly to determine if their co-regulation is maintained or disrupted in gastric cancer. We demonstrate that almost all human TFIZ1 is present as a heterodimer with TFF1 and that TFIZ1 is not bound to either of the other two trefoil proteins, TFF2 and TFF3. TFIZ1 and TFF1 are co-expressed by the surface mucus secretory cells throughout the stomach and the molecular forms of each protein are affected by the relative abundance of the other. TFIZ1 expression is lost consistently, early and permanently in gastric tumour cells. In contrast, TFF1 is sometimes expressed in the absence of TFIZ1 in gastric cancer cells and this expression is associated with metastasis (lymph node involvement: p = 0.007). In conclusion, formation of the heterodimer between TFIZ1 and TFF1 is a specific interaction that occurs uniquely in the mucus secretory cells of the stomach, co-expression of the two proteins is disrupted in gastric cancer and expression of TFF1 in the absence of TFIZ1 is associated with a more invasive and metastatic phenotype. This indicates that TFF1 expression in the absence of TFIZ1 expression has potentially deleterious consequences in gastric cancer.

Identification of human urinary trefoil factor 1 as a novel calcium oxalate crystal growth inhibitor

Previous research on proteins that inhibit kidney stone formation has identified a relatively small number of well-characterized inhibitors. Identification of additional stone inhibitors would increase understanding of the pathogenesis and pathophysiology of nephrolithiasis. We have combined conventional biochemical methods with recent advances in mass spectrometry (MS) to identify a novel calcium oxalate (CaOx) crystal growth inhibitor in normal human urine. Anionic proteins were isolated by DEAE adsorption and separated by HiLoad 16/60 Superdex 75 gel filtration. A fraction with potent inhibitory activity against CaOx crystal growth was isolated and purified by anion exchange chromatography. The protein in 2 subfractions that retained inhibitory activity was identified by matrix-assisted laser desorption/ionization-time-of-flight MS and electrospray ionization-quadrupole-time-of-flight tandem MS as human trefoil factor 1 (TFF1). Western blot analysis confirmed the mass spectrometric protein identification. Functional studies of urinary TFF1 demonstrated that its inhibitory potency was similar to that of nephrocalcin. The inhibitory activity of urinary TFF1 was dose dependent and was inhibited by TFF1 antisera. Anti-C-terminal antibody was particularly effective, consistent with our proposed model in which the 4 C-terminal glutamic residues of TFF1 interact with calcium ions to prevent CaOx crystal growth. Concentrations and relative amounts of TFF1 in the urine of patients with idiopathic CaOx kidney stone were significantly less (2.5-fold for the concentrations and 5- to 22-fold for the relative amounts) than those found in controls. These data indicate that TFF1 is a novel potent CaOx crystal growth inhibitor with a potential pathophysiological role in nephrolithiasis.

The diurnal rhythm of the cytoprotective human trefoil protein TFF2 is reduced by factors associated with gastric mucosal damage: ageing, Helicobacter pylori infection, and sleep deprivation

OBJECTIVES

To determine if the normal TFF2 diurnal rhythm is disrupted in those with increased risk of gastric morbidity. Trefoil proteins protect the gastrointestinal mucosa from damage and aid its repair. TFF2 is considered the major cytoprotective gastric trefoil protein. There is a marked circadian variation in gastric luminal TFF2 in young healthy volunteers with peak levels present during the night.

METHODS

Gastric juice was aspirated at two hourly intervals over a 24-h period via a nasogastric tube. TFF2 was measured by quantitative western transfer analysis. Helicobacter pylori (H. pylori) status was measured by C13 urea breath test and by serology. The effects of H. pylori infection, sleep deprivation, and ageing, which cause increased gastric morbidity, on the TFF2 circadian rhythm were tested.

RESULTS

H. pylori infection attenuated the increase in TFF2 that occurs during the night. The TFF2 diurnal rhythm was reduced in older people and both the TFF2 level reached and the time at which the maximum TFF2 concentration occurs were associated inversely with age (p < 0.005). Sleep deprivation delayed the normal night time increase in gastric TFF2 and resulted in an overall reduction in TFF2 secretion.

CONCLUSIONS

H. pylori infection, ageing, and sleep deprivation cause a reduction in the TFF2 diurnal rhythm. The demonstration that the TFF2 rhythm is impaired in cohorts of individuals known to suffer gastric symptoms suggests that interventions to restore the normal TFF2 rhythm in those with poor mucosal protection could reduce morbidity.

Luminal and parenteral TFF2 and TFF3 dimer and monomer in two models of experimental colitis in the rat

BACKGROUND

Peptides of the trefoil factor family (TFF1, TFF2 and TFF3) are cosecreted with mucus from mucus-producing cells in most organ systems and are believed to interact with mucus to form high-viscosity stable gel complexes. In the gastrointestinal tract, they sustain the mucosal barrier, and both injected and orally administered TFF peptide have protective and healing functions in the gastric mucosa.

AIM

To investigate the possible treatment effect of luminally and parenterally administered TFF peptides in experimental colitis in rats.

METHODS

Colitis was induced by administration of 5% dextran sodium sulphate in the drinking water or by one intraperitoneal injection of mitomycin C, 3.75 mg/kg. TFF peptides were administered as subcutaneous injections or directly into the lumen via a catheter placed in the proximal colon. Treatments were saline, TFF2, TFF3 monomer or TFF3 dimer 5 mg/kg twice per day throughout the study [dextran sulphate sodium (DSS)] or from day 4 to 7 (mitomycin C). Colitis severity was scored in a stereomicroscope and histologically.

RESULTS

Luminal treatment with TFF3 in its dimeric form significantly improved the colitis score in both colitis models, whereas TFF2 had positive effect only in DSS-induced colitis. The TFF3 monomer was without any effects in both models. Treatment effect was most pronounced in the middle part of the colon, closest to the tip of the catheter. Injected TFF peptides, especially the TFF3 monomer, aggravated the colitis score in both colitis models.

CONCLUSIONS

Intracolonic administration of TFF3 dimer and TFF2 improves experimentally induced colitis in rats. The TFF3 monomer has no effect. Parenteral administration of TFF peptides aggravates the colitis especially the TFF3 monomer.

Interaction between TFF1, a Gastric Tumor Suppressor Trefoil Protein, and TFIZ1, a Brichos Domain-Containing Protein with Homology to SP-C

TFF1 is a gastric tumor suppressor that protects gastric epithelial cells from damage but can promote invasive properties of tumor cells. Antibodies were raised against correctly folded TFF1 protein. These showed that the 6.67 kDa secreted trefoil protein is present as an approximately 25 kDa complex in normal human gastric mucosa. The TFF1 complex was immunopurified from human gastric mucosa and shown to comprise two proteins joined by a disulfide bond. Both were identified by amino-terminal sequencing and MALDI TOF mass spectrometry. The TFF1 protein partner is a previously unknown protein that we have called TFIZ1 for trefoil factor interactions(z) 1. TFIZ1 is expressed and secreted in normal gastric mucosa. TFIZ1 mRNA was cloned from gastric mucosa and sequenced. TFIZ1 is an 18.31 kDa protein and contains an approximately 100 amino acid brichos domain and homology with smart00019.10, SF_P. This is the first demonstration that a member of the trefoil factor family of proteins is bound covalently to a brichos domain-containing protein. The apparent molecular mass of the TFF1:TFIZ1 heterodimer is remarkably close to the theoretical molecular mass of 24.98 kDa. In conclusion, the heterodimer comprises one molecule each of TFF1 and TFIZ1, and the disulfide bond between TFF1 and TFIZ1 is the most important factor stabilizing the heterodimer.

Trefoil factor family peptide 3 prevents the development and promotes healing of ischemia-reperfusion injury in weanling rats

BACKGROUND/PURPOSE

Although the pathogenesis of necrotizing enterocolitis (NEC) is not completely defined, ischemia appears to be one of the most important causative factors. Trefoil factor family peptide 3 (TFF3) is a peptide normally expressed in the small bowel and colon and is involved in the maintenance and repair of mucosal integrity. The authors hypothesized that monomeric (TFF3 Ser57) and dimeric (TFF3 Cys57) recombinant TFF3 may prevent the development and accelerate healing of intestinal ischemia-reperfusion injury in weanling rats.

METHODS

Intestinal injury was induced in 18-day-old rats by occlusion of the superior mesenteric vessels for 60 minutes. To examine the protective effect, rats were given 3 microg/g of TFF3 Ser57 or TFF3 Cys57 by subcutaneous or enteral administration 30 minutes before the vascular occlusion. To examine the healing effect, rats were given 3 microg/g of TFF3 Ser57 or TFF3 Cys57 by subcutaneous or enteral administration 60 minutes after the beginning of reperfusion. Samples from small bowel and colon were collected for morphometric analysis after 3 hours of reperfusion. Mucosal damage was assessed by the Chiu score.

RESULTS

Both forms of TFF3 reduced the amount of damage when administered before the ischemia. Administration of TFF3 Ser57 and TFF3 Cys57 after the beginning of reperfusion significantly increased the villous height and decreased the Chiu score in the small intestine and colon.

CONCLUSIONS

TFF3 Ser57 monomer and TFF3 Cys57 dimer prevent the development and promote healing of ischemia-reperfusion injury in weanling rats. There are no differences between the routes of administration of TFF3.

Solution structure of the disulfide-linked dimer of human intestinal trefoil factor (TFF3): the intermolecular orientation and interactions are markedly different from those of other dimeric trefoil proteins

The trefoil protein TFF3 forms a homodimer (via a disulfide linkage) that is thought to have increased biological activity over the monomer. The solution structure of the TFF3 dimer has been determined by NMR and compared with the structure of the TFF3 monomer and with other trefoil dimer structures (TFF1 and TFF2). The most significant structural differences between the trefoil domain in the monomer and dimer TFF3 are in the orientations of the N-terminal 3(10)-helix (residues 10-12) and in the presence in the dimer of an additional 3(10)-helix (residues 53-55) outside of the core region. The TFF3 dimer forms a more compact structure as compared with the TFF1 dimer where the two trefoil domains are connected by a flexible region with the monomer units being at variable distances from each other and in many different orientations. Although TFF2 is also a compact structure, the dispositions of its monomer units are very different from those of TFF3. The structural differences between the dimers result in the two putative receptor/ligand binding sites that remain solvent exposed in the dimeric structures having very different dispositions in the different dimers. Such differences have significant implications for the mechanism of action and functional specificity for the TFF class of proteins.

Helicobacter pylori interacts with the human single-domain trefoil protein TFF1

Why Helicobacter pylori colonizes only gastric tissue is unknown. It is found on gastric mucus-secreting cells and in the overlying gastric mucus but not deep in gastric glands. This localization mirrors the expression of trefoil factor 1, TFF1. We hypothesized that H. pylori interacting with TFF1 could explain the tropism of this bacteria for gastric tissue. Recombinant human TFF1 expressed in Escherichia coli was purified by affinity chromatography, ion-exchange chromatography, and gel filtration. Binding of H. pylori was assessed by using flow cytometry and the BIAcore system, which allows real-time monitoring of molecular interactions. In flow cytometry, H. pylori bound to the TFF1 dimer, but Campylobacter jejuni strains and the laboratory strain of E. coli, HB101, did not bind. When the BIAcore system was used, H. pylori bound strongly to TFF1-coated dextran chips compared with uncoated chips. Binding was inhibited by a TFF1 monoclonal antibody and by soluble TFF1. H. pylori bound to porcine gastric mucin only if it was pretreated with TFF1. In conclusion, H. pylori interacts avidly with the dimeric form of TFF1, and this interaction enables binding to gastric mucin, suggesting that TFF1 may act as a receptor for the organism in vivo. This interaction may underline the previously unexplained tropism of this organism for gastric tissue and its colocalization with the gastric mucin MUC5AC.

Development of a two-site ELISA assay for the dimeric form of human TFF1

TFF1 is one of three human trefoil proteins expressed principally in the gastrointestinal tract in normal tissues. TFF1 protects the gastric mucosa against damage as a result of its ability to facilitate reconstitution of damaged gastric mucosa and its involvement in the secretion and structure of gastric mucus. The most biologically active molecular form in cell culture and animal models tested is a dimer formed by a disulfide bond between two cysteine residues close to the C terminus of the protein. We have therefore developed an assay for this form of TFF1 which should facilitate its measurement in biological samples.

Expression and motogenic activity of TFF2 in human breast cancer cells

The expression of TFF2 in breast cancer cells and the effect of recombinant TFF2 on breast cancer cell migration were assessed. TFF2 expression was detected by PCR in estrogen receptor-negative and at lower levels in estrogen receptor-positive breast cancer cells. TFF2 expression was detected in nine out of 10 primary breast tumors but its expression was not related to that of the estrogen receptor. Focal expression was observed in normal and tumor cells by immunohistochemistry. TFF2 stimulated the migration of estrogen-responsive MCF-7 and non-responsive MDA-MB231 cells. We conclude that TFF2 is expressed in normal and malignant breast epithelial cells and that it stimulates the migration of breast cancer cells.

Injected TFF1 and TFF3 bind to TFF2-immunoreactive cells in the gastrointestinal tract in rats

Peptides of the trefoil factor family (TFF1, TFF2 and TFF3) are co-secreted with mucus in most organ systems and are believed to interact with mucins to produce high-viscosity, stable gel complexes. We have previously demonstrated that cells in the GI tract possess binding sites to TFF2 and that injected TFF2 ends up in the mucus layer. In the present study, tissue binding and metabolism of parenterally administered human TFF1 and TFF3 in rats were described and compared to the immunohistochemical localization of the TFF peptides. 125I-TFF1 monomer and 125I-TFF3 mono- and dimer were given intravenously to female Wistar rats. The tissue distribution was assessed by gamma counting of organ samples and by autoradiography of histological sections. The degradation of 125I-TFF3 was studied by means of trichloracetic acid (TCA) precipitation and the saturability of the binding by administration of excess unlabelled peptide. The TFF peptides were localized in histologic sections from the GI tract by immunohistochemistry. Injected TFF3 dimer (12%) was taken up by the GI tract. At autoradiography, grains were localized to the same cells that were immunoreactive to TFF2. The binding could be displaced by excess TFF3. Similar binding was observed for the TFF1 and TFF3 monomers apart from binding in the stomach, where the uptake was only 15% in comparison to the dimer. There was no specific binding outside the GI tract and no binding to TFF1 or TFF3 immunoreactive cells. In conclusion, the TFF2-binding cells in the gastrointestinal tract seem to have basolateral, receptor-like activity to all three TFF peptides. The mucous neck cells of the stomach predominantly take up TFFs with two trefoil domains, indicating a different receptor-like activity in the stomach compared to the rest of the GI tract.

The closely related estrogen-regulated trefoil proteins TFF1 and TFF3 have markedly different hydrodynamic properties, overall charge, and distribution of surface charge

The human trefoil proteins TFF1 and TFF3 are expressed predominantly in the gastrointestinal tract. They are also expressed and regulated by estrogens in malignant breast epithelial cells. TFF1 and TFF3 are small cysteine-rich acidic secreted proteins of 60 and 59 amino acids with similar isoelectric points of 4.75 and 3.94, respectively. Each contains one trefoil domain that is characterized by several conserved features including six cysteine residues with conserved spacing. TFF1 and TFF3 form intermolecular disulfide bonds via an extra-trefoil domain cysteine residue and are present in vivo as monomers and homodimers and as complexes with other proteins. The TFF1 dimer is more active than the TFF1 monomer. In the present study the hydrodynamic and charge properties of TFF1 and TFF3 monomers and homodimers have been compared and shown to differ markedly. Notably, TFF1 is significantly more asymmetric than TFF3 (frictional coefficients 1.25 and 1.12, respectively, p < 0.001), and homodimerization of TFF1 results in a greater increase in asymmetry than for TFF3. The overall charges of TFF1 and TFF3 are very different at neutral pH. Titration curves predicted significant differences in charge across a wide pH range that agreed well with experimental data. The locations of charged amino acids in the primary sequences and in the tertiary structures of TFF1 and TFF3 were examined. This revealed interesting divergence in both the distribution and local topology of charged amino acid side chains. The significant differences between the shape, size, and surface charge of these two closely related molecules may account for their divergent biological activities.

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.

The estrogen-regulated protein, TFF1, stimulates migration of human breast cancer cells

The human trefoil protein TFF1 is a small cysteine-rich secreted protein that is frequently expressed in breast tumors under the control of estrogen. The function of TFF1 in breast cancer is unknown. To test the hypothesis that it promotes tumor dissemination, we produced recombinant TFF1 and assessed its ability to stimulate the movement of breast cancer cells by using in vitro wounding and migration assays. Recombinant TFF1 stimulated migration at concentrations of TFF1 found in culture medium. Migration of MCF-7 breast cancer cells, which secrete TFF1, was stimulated by lower concentrations of TFF1 than MDA MB231 cells that do not produce TFF1. Dimeric TFF1, linked by a disulfide bond, and monomeric TFF1 are produced by estrogen-responsive breast cancer cell lines. Recombinant TFF1 dimer was eightfold more potent than TFF1 monomer, implying that the interaction of TFF1 with its receptor is facilitated by dimerization. The majority of TFF1-stimulated migration resulted from chemotaxis, but dimeric TFF1 stimulated some chemokinesis. These results show that estrogens can stimulate the motility of breast cancer cells via the induction of TFF1 and suggest that one reason for the efficacy of hormonal therapies is their ability to reduce expression of TFF1 and, hence, the migration of breast tumor cells.