Purified Pseudomonas aeruginosa PA-I lectin induces gut growth when orally ingested by rats

Plant as a plenteous reserve of lectin

Lectins are clusters of glycoproteins of nonimmune foundation that combine specifically and reversibly to carbohydrates, mainly the sugar moiety of glycoconjugates, resulting in cell agglutination and precipitation of glycoconjugates. They are universally distributed in nature, being established in plants, fungi, viruses, bacteria, crustacea, insects, and animals, but leguminacae plants are rich source of lectins. The present review reveals the structure, biological properties, and application of plant lectins.

PA-I lectin from Pseudomonas aeruginosa binds acyl homoserine lactones

The study analyses the binding affinities of Pseudomonas aeruginosa PA-I lectin (PA-IL) to three N-acyl homoserine lactones (AHSL), quorum sensing signal molecules responsible for cell-cell communication in bacteria. It shows that like some plant lectins, PA-IL has a dual function and, besides its carbohydrate-binding capacity, can accommodate AHLS. Formation of complexes between PA-IL and AHSL with acyl side chains composed of 4, 6 or 12 methyl groups is characterized by changes in the emissions of two incorporated fluorescent markers, TNS and IAEDANS, both derivatives of naphthalene sulfonic acid. PA-IL shows increasing affinities to lactones with longer aliphatic side chains. The values of the apparent dissociation constants (K(d)), which are similar to the previously determined K(d) for the adenine high affinity binding, and the similar effects of lactones and adenine on the TNS emission indicate one identical binding site for these ligands, which is suggested to represent the central cavity of the oligomeric molecule formed after the association of the four identical subunits of PA-IL. Intramolecular distances between the fluorescent markers and protein Trp residues are determined by fluorescence resonance energy transfer (FRET).

Interactions of Pseudomonas aeruginosa PA-IIL lectin with quail egg white glycoproteins

Pseudomonas aeruginosa produces several lectins, including the galactophilic PA-IL and the fucose- and mannose-binding PA-IIL. The great advantage of these two lectins is their stability in purified preparations. Following observations that pigeon egg white blocks Escherichia coli P-fimbriae and PA-IL, we examined the interactions of diverse avian egg white components with PA-IIL. This lectin may represent both mannose- and fucose-specific microbial adhesins. For comparison, Con A (which also binds mannose) and Ulex europaeus lectin (UEA-I, which binds fucose) were analyzed in parallel. The lectin interactions with chicken, quail, and pigeon egg whites and several purified chicken egg white glycoproteins were examined by a hemagglutination inhibition test and Western blotting. Both analyses showed that like Con A and unlike UEA-I, which was not sensitive to any of these three egg whites, PA-IIL most strongly reacted with the quail egg white. However, in contrast with Con A, its interactions with the chicken egg white components, excluding avidin, were very poor. The results of this study might indicate the possibility that some of the egg white components that interacted with the above two mannose-binding lectins (exhibiting individual heterogeneity) might be associated with the innate immunity against mannose-specific microbial or viral adhesion during the fowl embryonic period.Key words: Pseudomonas aeruginosa, microbial lectin, PA-IIL lectin, avian egg white.

The hemagglutinating activities of Pseudomonas aeruginosa lectins PA-IL and PA-IIL exhibit opposite temperature profiles due to different receptor types

The two Pseudomonas aeruginosa lectins PA-IL and PA-IIL, which are very similar in subunit size, composition and properties, but differ in carbohydrate specificity, were shown to exhibit opposite temperature profiles in hemagglutination tests. The galactophilic PA-IL, which interacts with the erythrocyte I antigen (together with B or P system antigens), resembles Ii system-specific 'cold hemagglutinins' (including antibodies and lectins of animals and plants) in low (4 degrees C) temperature optimum, while the hemagglutination by the fucose- and mannose-binding PA-IIL (like that of antibodies and lectins which do not bind to these antigens) increases on raising the temperature from 4 to 37 degrees C and even to 42 degrees C. The preferential production of both P. aeruginosa lectins at 28 degrees C and their much stronger interaction with enzyme (protease or sialidase)-damaged cells, as well as the lower temperature optimum (4 degrees C) of PA-IL-binding to the host cells, may be associated with the saprophytic rather than parasitic designation of this bacterium.

Effects of a panel of dietary lectins on cholecystokinin release in rats

We previously showed that soybean lectin (SBL) releases cholecystokinin (CCK) and have now asked whether other dietary lectins have this effect and if extracellular calcium is involved. Lectins and vehicle were first infused into the duodenum of anesthetized rats. The CCK response to vehicle was 3.1 +/- 0.6 pmol/l (P < 0.05 vs. basal). SBL and peanut lectin (PNL) (84 microg/ml) significantly increased plasma CCK concentrations from 2.0 +/- 0.4 pmol/l to a maximum of 8.4 +/- 0.5 pmol/l (P < 0.01 vs. vehicle, mean +/- SE) and from 1.9 +/- 0.5 to 7.0 +/- 0.6 pmol/l (P < 0.05 vs. vehicle, mean +/- SE), respectively. Wheat germ lectin (WGL) (840 microg) also increased plasma CCK levels from 1.5 +/- 0.3 pmol/l to a maximum of 9.7 +/- 1.3 pmol/l (P < 0.05 vs. vehicle, mean +/- SE). Corresponding increases in pancreatic protein output occurred. Broad bean lectin (BBL) had no effect on either parameter. Dose-dependent responses were seen with SBL, PNL, and WGL (1, 10, and 100 microg/ml) in perifused rat intestinal cells. These responses were abolished in calcium-free medium and in the presence of the competing sugars of the lectins. Therefore, SBL, PNL, and WGL, which bind to motifs including N-acetyl-D-galactosamine, galactose, and N-acetylglucosamine, respectively, released CCK, but BBL, which binds to mannose and glucose, did not. Ingestion of lectins may have major CCK-mediated effects on gastrointestinal function and growth.

The molecular basis of intractable diarrhoea of infancy

The intractable diarrhoeas of infancy present very major problems of clinical management. However, the conceptual importance of these conditions lies in the information that they may provide about normal small-intestinal function in humans: among such infants will be found the human equivalents of the 'knock-out' mice, in which targeted gene disruption allows sometimes unexpected insight into the regulation of intestinal function. The challenge posed by the intractable diarrhoeal syndromes, of working backwards from an apparently common phenotype to probably multiple genotypes, is, however, immense. Very few of these conditions have been described at the genetic level, although the molecular basis of pathogenesis has been better explored in recent years. The two major groups of intractable diarrhoea are due to (1) primary epithelial abnormalities (which usually present within the first few days of life) and (2) immunologically mediated (which generally present after the first few weeks). The high prevalence of autoimmune enteropathy among infantile autoimmune disease, in contrast to adult autoimmunity, is intriguing and may reflect constitutive abnormality of extrathymic lymphocyte maturation. The use of potent immunosuppressive drugs and increasing expertise with parenteral nutrition are improving the outlook of these previously fatal conditions. Viewed globally, however, the pressing problem is to treat effectively the millions of infants who die from severe persistent diarrhoea and wasting, which would certainly not be considered intractable in wealthy countries.

Salmonella typhimurium and Salmonella enteritidis induce gut growth and increase the polyamine content of the rat small intestine in vivo

The effects of infection by Salmonella enteritidis and S. typhimurium on the small and large intestines, liver, spleen and mesenteric nodules of rats were studied in vivo. Both Salmonella serotypes persisted and proliferated in the gastrointestinal tract and invaded sub-epithelial tissues, mainly the ileum, leading to the systemic distribution of these pathogens. Coincidental with infection, the rate of crypt cell proliferation increased resulting in substantial growth of the small intestine. The extent of this and the accompanying accumulation of polyamines was particularly dramatic in the ileum where there was also some disruption of the villus epithelium. It is possible that these effects of the infection on the metabolism and morphology of the small bowel, which strongly resembled the changes induced by some plant lectins, may facilitate the colonisation and invasion of the gut by Salmonellae.