Hydrophobic Signal Peptide Research Articles

Cloning and developmental expression of a family of pleurocidin-like antimicrobial peptides from winter flounder, Pleuronectes americanus (Walbaum)

Low molecular weight antimicrobial peptides are an important component of the innate immune system in animals, yet they have not been examined widely in fish. Of particular interest is their expression during development and in response to environmental conditions and disease. Here, we report the isolation of four genomic sequences encoding putative antimicrobial peptides from the winter flounder, Pleuronectes americanus (Walbaum), as well as reverse transcription-PCR products from two tissues that form the first defensive barrier to microbes — skin and intestine. Alignment of the predicted polypeptide sequences shows a conserved hydrophobic signal peptide of 22 amino acids followed by 25 amino acids that are identical (WF2) or homologous to the amino acid sequence of pleurocidin, followed by a conserved acidic portion. Southern hybridisation analysis indicates that related peptides are encoded in the genomes of other flatfish species. Northern and RT-PCR analyses of RNA from multiple tissues show that two of the pleurocidin genes are expressed predominantly in the skin whereas two other genes are expressed mainly in the intestine. RT-PCR assays of total RNA from larvae of different ages provide the first evidence of developmental expression of antimicrobial peptides in fish and indicate that the pleurocidin gene is first expressed at 13 days post-hatch in winter flounder.

Molecular characterization of the amplified carboxylesterase gene associated with organophosphorus insecticide resistance in the brown planthopper, Nilaparvata lugens.

Widespread resistance to organophosphorus insecticides (OPs) in Nilaparvata lugens is associated with elevation of carboxylesterase activity. A cDNA encoding a carboxylesterase, Nl-EST1, has been isolated from an OP-resistant Sri Lankan strain of N. lugens. The full-length cDNA codes for a 547-amino acid protein with high homology to other esterases/lipases. Nl-EST1 has an N-terminal hydrophobic signal peptide sequence of 24 amino acids which suggests that the mature protein is secreted from cells expressing it. The nucleotide sequence of the homologue of Nl-EST1 in an OP-susceptible, low esterase Sri Lankan strain of N. lugens is identical to Nl-EST1. Southern analysis of genomic DNA from the Sri Lankan OP-resistant and susceptible strains suggests that Nl-EST1 is amplified in the resistant strain. Therefore, resistance to OPs in the Sri Lankan strain is through amplification of a gene identical to that found in the susceptible strain.

Identification of a membrane targeting and degradation signal in the p42 protein of influenza C virus.

Two mRNA species are derived from the influenza C virus RNA segment six, (i) a colinear transcript containing a 374-amino-acid residue open reading frame (referred to herein as the seg 6 ORF) which is translated to yield the p42 protein, and (ii) a spliced mRNA which encodes the influenza C virus matrix (CM1) protein consisting of the first 242 amino acids of p42. The p42 protein undergoes proteolytic cleavage at a consensus signal peptidase cleavage site after residue 259, yielding the p31 and CM2 proteins. Translocation of p42 into the endoplasmic reticulum membrane occurs cotranslationally and requires the hydrophobic internal signal peptide (residues 239 to 259), as well as the predicted transmembrane domain of CM2 (residues 285 to 308). The p31 protein was found to undergo rapid degradation after cleavage from p42. Addition of the 26S proteasome inhibitor lactacystin to influenza C virus-infected or seg 6 ORF cDNA-transfected cells drastically reduced p31 degradation. Transfer of the 17-residue C-terminal region of p31 to heterologous proteins resulted in their rapid turnover. The hydrophobic nature, but not the specific amino acid sequence of the 17-amino-acid C terminus of p31 appears to act as the signal for targeting the protein to membranes and for degradation.

Identification of the gene encoding BmpB, a 30 kDa outer envelope lipoprotein of Brachyspira (Serpulina) hyodysenteriae, and immunogenicity of recombinant BmpB in mice and pigs.

A gene encoding a 30kDa outer envelope protein of the intestinal spirochaete Brachyspira (Serpulina) hyodysenteriae, was cloned and expressed in Escherichia coli strain XLOLR. Five phagemids containing DNA inserts encoding the protein were established and one clone (pSHA) was sequenced. An 816bp hypothetical open reading frame (ORF) was identified, with a potential ribosome binding site (AGGAG), and putative -10 (TATAAT) and -35 (TTGAAA) promoter regions upstream from the ATG start of the ORF. A 12bp inverted repeat sequence, possibly serving as a transcription terminator, was identified downstream from the TAA stop codon. Analysis of the amino acid sequence identified a 19 residue hydrophobic signal peptide, incorporating a potential signal peptidase cleavage site and membrane lipoprotein lipid attachment site. Further analysis of the amino acid usage of this lipoprotein, designated BmpB, showed its possible outer membrane localisation. Comparison of the gene encoding the lipoprotein, bmpB, with GenBank nucleotide sequences showed that it has homology with the gene (plp3) encoding Plp3, an outer membrane lipoprotein of Pasteurella haemolytica (54% identity in 735bp). Comparison of the deduced amino acid sequence with the SWISS-PROT amino acid database revealed greatest homology with the outer membrane lipoproteins (Plp1, 2, 3) of P. haemolytica (34% identity in 242 aa, 37% identity in 250 aa, and 39% identity in 272 aa, respectively), and lipoproteins (rcsF and lipoprotein-28) of E. coli (40% identity in 267 aa and 36% identity in 263 aa, respectively). Three of the recombinant E. coli clones (pSHA, pSHD, and pSHE) were formalinised and used to immunise mice. A bacterin preparation of one recombinant E. coli clone (pSHA) was used to immunise pigs. Sera from these mice and pigs recognised the 30kDa lipoprotein in outer membrane preparations of B. hyodysenteriae, indicating the immunogenicity of recombinant BmpB. Sera from pigs naturally infected with B. hyodysenteriae also reacted with recombinant BmpB expressed in E. coli.

The Thylakoid ΔpH-dependent Pathway Machinery Facilitates RR-independent N-Tail Protein Integration

The thylakoidal DeltapH-dependent and bacterial twin arginine transport systems are structurally and functionally related protein export machineries. These recently discovered systems have been shown to transport folded proteins but are not known to assemble integral membrane proteins. We determined the translocation pathway of a thylakoidal FtsH homologue, plastid fusion/protein translocation factor, which is synthesized with a chloroplast-targeting peptide, a hydrophobic signal peptide, and a hydrophobic membrane anchor. The twin arginine motif in its signal peptide and its sole integration requirement of a DeltapH suggested that plastid fusion/protein translocation factor employs the DeltapH pathway. Surprisingly, changing the twin arginine to twin lysine or deleting the signal peptide did not abrogate integration capability or characteristics. Nevertheless, three criteria argue that all three forms require the DeltapH pathway for integration. First, integration was competed by an authentic DeltapH pathway precursor. Second, antibodies to DeltapH pathway component Hcf106 specifically inhibited integration. Finally, chloroplasts from the hcf106 null mutant were unable to integrate Pftf into their thylakoids. Thus, DeltapH pathway machinery facilitates both signal peptide-directed and N-tail-mediated membrane integration and does not strictly require the twin arginine motif.

Purification and cDNA Cloning of Salmorin that Inhibits Fibrinogen Clotting

A new protein, salmorin, that inhibits fibrinogen clotting was purified to homogeneity from the snake venom of Agkistrodon halys brevicaudus. Salmorin was characterized to be a heterodimeric protein composed of 15 kDa and 14 kDa subunits. Purified salmorin inhibited not only thrombin-induced fibrinogen clotting but also factor Xa-induced prothrombin activation. Experimental evidence indicated that the hetero-dimeric protein does not bind to the thrombin catalytic site but binds to thrombin and prothrombin exosites. Analyses of the cDNA sequences encoding the two separate polypeptide chains revealed that the mature subunits are composed of 131 and 122 amino acids, respectively. In the isolated cDNAs, N-termini of both chains are preceded by hydrophobic signal peptides of 23 residues. The deduced amino acid sequence exhibited considerable identity with other snake venom C-type lectin-like proteins derived from various snake venoms.

Cytochrome c6 from Cyanophora paradoxa

In the eukaryotic alga Cyanophora paradoxa, which does not contain plastocyanin, photosynthetic electron transport from the cytochrome b6/f complex to photosystem I is mediated by cytochrome c6. Cytochrome c6 was purified to homogeneity by column chromatography and FPLC. The relative molecular mass of the holoprotein was determined by two different mass spectrometric methods (californium-252 plasma desorption and UV matrix-assisted laser desorption ionization) giving 9251 +/- 3.3 Da. N-terminal Edman microsequencing yielded information on approx. 30 amino acid residues. Based on these data and on highly conserved regions of cytochromes c6, degenerate oligonucleotides were designed and used for PCR to amplify the genomic DNA of C. paradoxa. Screening of a C. paradoxa cDNA library yielded several clones coding for preapo-cytochrome c6. The deduced sequence of the mature protein was verified by plasma desorption mass spectrometric peptide mapping and shows high similarity to those of cytochromes c6 from cyanobacteria and algae. Cytochrome c6 appears to be encoded by a single nuclear gene (petJ) in C. paradoxa. As the mature protein is located in the lumen of the thylakoid membrane, it has to traverse three biological membranes as well as the unique peptidoglycan layer of the cyanelles before it reaches its final subcellular locale. Thus the transit sequence is composed of two different targeting signals: a stroma targeting peptide resembling those of higher plants with respect to hydropathy plots and amino acid composition and a hydrophobic signal peptide functioning as a thylakoid-traversing domain. There are indications for alternative sorting of part of the cyanelle cytochrome c6 pool to the periplasmic space. This is the first known bipartite transit sequence of a cyanelle precursor protein from C. paradoxa, a model organism concerning the endosymbiotic origin of plastids. Labeled precursor is efficiently imported into isolated cyanelles, then routed into thylakoids and processed to the mature protein. Hitherto, in vitro protein translocation was not reported for cyanobacterial-type thylakoids.

Crystal Structure of the Conserved Subdomain of Human Protein SRP54M at 2.1 Å Resolution: Evidence for the Mechanism of Signal Peptide Binding

Protein SRP54 is an integral part of the mammalian signal recognition particle (SRP), a cytosolic ribonucleoprotein complex which associates with ribosomes and serves to recognize, bind, and transport proteins destined for the membrane or secretion. The methionine-rich M-domain of protein SRP54 (SRP54M) binds the SRP RNA and the signal peptide as the nascent protein emerges from the ribosome. A focal point of this critical cellular function is the detailed understanding of how different hydrophobic signal peptides are recognized efficiently and transported specifically, despite considerable variation in sequence. We have solved the crystal structure of a conserved functional subdomain of the human SRP54 protein (hSRP54m) at 2.1Å resolution showing a predominantly alpha helical protein with a large fraction of the structure available for binding. RNA binding is predicted to occur in the vicinity of helices 4 to 6. The N-terminal helix extends significantly from the core of the structure into a large but constricted hydrophobic groove of an adjacent molecule, thus revealing molecular details of possible interactions between alpha helical signal peptides and human SRP54.

Biochemical analysis of mouse FKBP60, a novel member of the FKPB family

We have identified mouse and human FKBP60, a new member of the FKBP gene family. FKBP60 shares strongest homology with FKBP65 and SMAP. FKBP60 contains a hydrophobic signal peptide at the N-terminus, 4 peptidyl-prolyl cis/ trans isomerase (PPIase) domains and an endoplasmic reticulum retention motif (HDEL) at the C-terminus. Immunodetection of HA-tagged FKBP60 in NIH-3T3 cells suggests that FKBP60 is segregated to the endoplasmic reticulum. Northern blot analysis shows that FKBP60 is predominantly expressed in heart, skeletal muscle, lung, liver and kidney. With N-succinyl-Ala-Ala-Pro-Phe- p-nitroanilide as a substrate, recombinant GST-FKBP60 is shown to accelerate effectively the isomerization of the peptidyl-prolyl bond. This isomerization activity is inhibited by FK506. mFKBP60 binds Ca 2+ in vitro, presumably by its C-terminal EF-hand Ca 2+ binding motif, and is phosphorylated in vivo. hFKBP60 has been mapped to 7p12 and/or 7p14 by fluorescence in situ hybridization (FISH).

Cloning of the SmSPO-1 gene preferentially expressed in sporocyst during the life cycle of the parasitic helminth Schistosoma mansoni

Schistosomes are parasitic helminths with a complex life cycle in human and snail hosts. They express stage-specific genes that conceivably determine distinct properties of the parasite at different developmental stages. Here we report the stage-specific gene SmSPO-1, which is preferentially expressed in sporocysts residing in the snail host. The cDNA and the gene were cloned and sequenced. The cDNA, from cap site to the poly(A) addition site, is 498 bp long. It encodes a protein of 117 amino acids with a hydrophobic signal peptide of 18 residues, indicating that SmSPO-1 is a secreted or a membranal protein. In the gene the cDNA is split into four exons spread over 2.1 kb of chromosomal DNA.

A novel glycine-rich protein is associated with starch grain accumulation during anther development.

LIM14, originally identified as a lily gene associated with microsporogenesis, encodes a protein which has two distinct domains, one with glycine-serine repeats and the other with a hydrophobic signal peptide at the N-terminus. The putative LIM14 protein, however, is distinct from the glycine-rich cell wall proteins which have been described before. RNA analyses indicated that the LIM14 transcript is specifically detected in the anther from zygotene to young pollen stage. By using antibodies raised against recombinant LIM14 protein, we detected anther-specific 15 kDa protein. Immunofluorescence microscopy demonstrated that the LIM14 protein is associated with starch grains in the anther wall cells just prior to microspore mitosis and then accumulates at a higher level with the starch grains of immature pollen. We tagged LIM14 with the GUS and GFP reporter genes and introduced them into tobacco BY-2 cells. Analysis of the transformed cells revealed that the chimeric proteins are functional and specifically targeted to plastids. These results indicate that LIM14 is an anther-specific protein that may play a role in starch accumulation and amyloplast differentiation during anther development and pollen formation.

Multiple Functional Proteins Are Produced by Cleaving Asn-Gln Bonds of a Single Precursor by Vacuolar Processing Enzyme

Precursor-accumulating vesicles mediate transport of the precursors of seed proteins to protein storage vacuoles in maturing pumpkin seeds. We isolated the precursor-accumulating vesicles and characterized a 100-kDa component (PV100) of the vesicles. Isolated cDNA for PV100 encoded a 97,310-Da protein that was composed of a hydrophobic signal peptide and the following three domains: an 11-kDa Cys-rich domain with four CXXXC motifs, a 34-kDa Arg/Glu-rich domain composed of six homologous repeats, and a 50-kDa vicilin-like domain. Both immunocytochemistry and immunoblots with anti-PV100 antibodies showed that <10-kDa proteins and the 50-kDa vicilin-like protein were accumulated in the vacuoles. To identify the mature proteins derived from PV100, soluble proteins of the vacuoles were separated, and their molecular structures were determined. Mass spectrometry and peptide sequencing showed that two Cys-rich peptides, three Arg/Glu-rich peptides, and the vicilin-like protein were produced by cleaving Asn-Gln bonds of PV100 and that all of these proteins had a pyroglutamate at their NH2 termini. To clarify the cleavage mechanism, in vitro processing of PV100 was performed with purified vacuolar processing enzyme (VPE). Taken together, these results suggested that VPE was responsible for cleaving Asn-Gln bonds of a single precursor, PV100, to produce multiple seed proteins. It is likely that the Asn-Gln stretches not only provide cleavage sites for VPE but also produce aminopeptidase-resistant proteins. We also found that the Cys-rich peptide functions as a trypsin inhibitor. Our findings suggested that PV100 is converted into different functional proteins, such as a proteinase inhibitor and a storage protein, in the vacuoles of seed cells.

A novel cell wall protein specific to the mycelial form of Yarrowia lipolytica.

A cDNA clone specifying a cell wall protein was isolated from a Yarrowia lipolytica cDNA library. The cDNA library was constructed in the expression vector lambda gt 11, with the RNA isolated from actively growing mycelial cells. The deduced amino acid sequence shows that the encoded protein contains an N-terminal hydrophobic signal peptide. We have designated this protein YWP1 for Yarrowia lipolytica cell Wall Protein. Northern hybridization identified YWP1 transcript only when Y. lipolytica was growing in the mycelial form. The encoded protein seems to be covalently bound to the glucan cell wall since it is not released from the cell walls by sodium dodecyl sulphate extraction, but it is solubilized following partial degradation of beta-glucan by Zymolyase digestion. The protein is localized in the outer surface on the tip of the growing mycelial cells and is found partially cryptic in sub-apical locations, suggesting that it participates directly in the mycelial wall architecture.

Purification, characterization and cDNA cloning of soluble carbonic anhydrase from Chlorella sorokiniana grown under ordinary air.

Soluble carbonic anhydrase (CA, EC 4.2.1.1) inducible by low levels of CO2 was purified from the unicellular green alga Chlorella sorokiniana grown at alkaline pH. The purified CA had a specific activity of 2,300 units (mg protein)-1. The molecular mass of the CA was found to be 100 kDa by non-dissociating (native)-polyacrylamide gel electrophoresis and 50 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The 50-kDa subunit was recognized by concanavalin A. These results suggest that the protein has a dimeric form with two 50-kDa subunits that are glycosylated in an asparagine-linked manner. The native CA was revealed by isoelectric focusing to be a very acidic protein with an isoelectric point of 4.2. About 60% of the CA activity was inhibited by 0.5 M NaCl. The enzyme was inactivated over 95% by preincubation with 50 mM dithiothreitol but not with 1 mM dithiothreitol. After partial amino acid sequence analysis, a cDNA clone of the CA was isolated and characterized. The cloned cDNA fragment encoded a 348-amino-acid polypeptide (36,709 Da) including an NH2-terminal hydrophobic signal peptide composed of 35 amino acids (3,725 Da). Conserved regions of sequences found in animal CAs, in the periplasmic (pCA) and the intracellular CAs of Chlamydomonas, and in the plasma-membrane-bound CA of Dunaliella (Dca) were also found in this Chlorella CA. The signal sequence was significantly homologous to the pCA and the Dca. The internal signal sequence between the large and the small subunits reported for pCA was not found in this Chlorella CA. The soluble CA of this alga was an alpha-type CA with salt-sensitive, periplasm-locating and acidic properties and very different from pCA and Dca with their salt-sensitive/neutral and salt-resistant/acidic properties, respectively.

Human Ecalectin, a Variant of Human Galectin-9, Is a Novel Eosinophil Chemoattractant Produced by T Lymphocytes

A 1.6-kilobase pair cDNA was isolated from a human T-cell-derived expression library that encodes a novel eosinophil chemoattractant (designated ecalectin) expressed during allergic and parasitic responses. Based on its deduced amino acid sequence, ecalectin is a 36-kDa protein consisting of 323 amino acids. Although ecalectin lacks a hydrophobic signal peptide, it is secreted from mammalian cells. Ecalectin is not related to any known cytokine or chemokine but rather is a variant of human galectin-9, a member of the large family of animal lectins that have affinity for beta-galactosides. Recombinant ecalectin, expressed in COS cells and insect cells, exhibited potent eosinophil chemoattractant activity and attracted eosinophils in vitro and in vivo in a dose-dependent manner but not neutrophils, lymphocytes, or monocytes. The finding that the ecalectin transcript is present in abundance in various lymphatic tissues and that its expression increases substantially in antigen-activated peripheral blood mononuclear cells suggests that ecalectin is an important T-cell-derived regulator of eosinophil recruitment in tissues during inflammatory reactions. We believe that this is the first report of the expression of an immunoregulatory galectin expressed by a T-cell line that is selective for eosinophils.

DNaseY: A Rat DNaseI-like Gene Coding for a Constitutively Expressed Chromatin-Bound Endonuclease‡

A rat gene, designated DNaseY, encoding a 36 kDa endonuclease was identified and cloned. Sequence analysis of the cDNA showed it to be the rat homologue of human DNAS1L3. The DNaseY gene product had 42% identity to DNaseI, including conserved critical active site residues, the essential disulfide bridge, the calcium binding domain, and a signal peptide, as well as 2 of the 3 signature boxes. Significantly, DNaseY had 2 nuclear localization signals and was more basic (pI 9.5) than DNaseI (pI 4.8). The DNaseY gene contained a number of exons similar to that of DNaseI, separated by much larger introns, resulting in a gene of >17 kb compared to <4 kb gene of DNaseI. The 36 kDa DNaseY gene product was catalytically inactive but was converted to an active 33 kDa endonuclease following processing of the hydrophobic signal peptide. Antibody generated against peptides representing the predicted amino acid sequence of DNaseY cross-reacted with a 33 kDa nuclear protein which possessed endonucleolytic activity. The enzyme was active over a broad pH range (optimum pH 7-8), was Ca2+/Mg2+-dependent, was inhibited by Zn2+, and was capable of both single- and double-stranded DNA cleavage, producing DNA fragments with 3'-OH ends. Furthermore, the DNaseY gene was expressed constitutively in all cells and tissues tested, but it was not transcriptionally up-regulated in apoptotic cells. All these features were consistent with a role in the early stages of apoptotic DNA fragmentation.

Cloning and sequencing of a novel murine liver carboxylesterase cDNA

Carboxylesterases (EC 3.1.1.1) comprise a group of serine hydrolases with at least 20 genetically distinct loci in mice. Here, we describe differential display PCR-based cloning of a cDNA, encoding a novel murine carboxylesterase termed ES-x, which was expressed predominantly in liver but also in kidney and lung. The cDNA of ES-x spanned a 2249-bp sequence with an open reading frame encoding 565 amino acids, including an N-terminal hydrophobic signal peptide which directs the synthesis into microsomal lumen and a C-terminal HVEL consensus sequence for retaining the protein in the lumen of the endoplasmic reticulum. The predicted amino acid sequence of ES-x exhibited 75% identity with rat liver pI 6.1 esterase. We further demonstrate that feeding mice with diets containing cholestyramine or sodium cholate increases mRNA-expression of ES-x in liver 2.5- to 3-fold.

Molecular cloning, characterization and tissue expression of prophenoloxidase cDNA from the mosquito Armigeres subalbatus inoculated with Dirofilaria immitis microfilariae.

A cDNA encoding mosquito Armigeres subalbatus prophenol oxidase (As-pro-PO) was obtained by rapid amplification of cDNA ends-polymerase chain reaction (RACE-PCR) after Dirofilaria immitis inoculation. The 2205 bp As-pro-PO cDNA contains a 32 bp 5'-noncoding region, a 2055 bp open reading frame (685 amino acids), and a 118 bp 3'-noncoding region. Hydrophobic signal peptide for the endoplasmic reticulum targeting is not found in the NH2-terminal region. Two potential copper-binding domains, amino acids 197-245 and 345-412, are highly homologous to those of the other insect pro-POs. A 2.2 kb As-pro-PO transcript was identified by Northern blot analysis using D. immitis microfilariae-inoculated A. subalbatus. Both in situ hybridization and Northern blot analysis demonstrated that As-pro-PO mRNA was synthesized in mosquito haemocytes but not in other tissues, i.e. fat bodies, midguts and ovaries, etc.

An ERp60-like protein from the filarial parasite Dirofilaria immitis has both transglutaminase and protein disulfide isomerase activity.

Transglutaminases (TGases; EC 2.3.2.13) are a family of enzymes that catalyze calcium-dependent covalent cross-linking of cellular proteins by establishing epsilon-(gamma-glutamyl)lysine isopeptide bonds. These covalent isopeptide bonds are of great physiological significance because they are highly resistant to proteolysis, denaturants, and reducing agents. Prior studies have demonstrated the presence of isopeptide bonds in the sheath and cuticle of filarial parasites, suggesting an important role for TGase-catalyzed reactions during the growth and development of filarial nematodes. Herein we report the identification and cloning of a cDNA encoding a TGase from the dog heartworm Dirofilaria immitis (DiTG). The DiTG expressed in Escherichia coli (recombinant DiTG) was able to catalyze calcium-dependent cross-linking reactions. The derived amino acid sequence of the DiTG cDNA (pDiTG) predicts a protein of 57.1 kDa and includes an N-terminal hydrophobic signal peptide. The pDiTG has no sequence similarity with any of the known TGases, but it has significant homology to protein disulfide isomerase (PDI) and, particularly, to the PDI-related endoplasmic reticulum protein ERp60, a PDI isoform found in the lumen of endoplasmic reticulum. As predicted from the amino acid sequence homology, recombinant DiTG catalyzed the isomerization of intramolecular disulfide/sulfhydryl bonds in denatured RNase in vitro as effectively as did mammalian PDI. Conversely, purified PDI from bovine liver could catalyze protein cross-linking reactions in a Ca(2+)-dependent manner. This report describes the dual catalytic activity of TGase and PDI in post- and/or cotranslational modification of newly synthesized proteins. These TGase-catalyzed posttranslational modifications may play a pivotal role in the synthesis of new cuticle during the growth and maturation of filarial parasites.

The possible role of vascular endothelial growth factor (VEGF) in gastric ulcer healing: effect of sofalcone on VEGF release in vitro.

Angiogenesis plays an important role in gastric ulcer repair. Several growth factors are involved in angiogenesis and, of these, vascular endothelial growth factor (VEGF) has received considerable attention because it is the only factor that acts specifically on endothelial cells and, unlike other angiogenic growth factors, has the hydrophobic signal peptide required for extracellular transport according to classical secretory pathways. We have lately demonstrated the role of VEGF in gastric ulcer repair. Previous reports confirmed that sofalcone has remarkable effects on gastric ulcer healing, which may be mediated by its stimulatory effect on prostaglandin (PG) release in gastric cells. Our data indicate that PGs stimulate VEGF expression in gastric fibroblasts. In this report we hypothesize that the clinical effect of sofalcone is mediated by VEGF expression and we demonstrate that sofalcone stimulates VEGF release by gastric fibroblasts in primary culture.