Effects of substitution of conserved amino acid residues on the sugar-binding property of the tandem-repeat 32-kDa galectin of the nematode Caenorhabditis elegans

Expression and function of galectins in the endometrium and at the human feto-maternal interface

Galectins are classified as lectins that share structural similarities and bind β-galactosides via a conserved carbohydrate recognition domain. So far 16 out of 19 identified galectins were shown to be present in humans and numerous studies revealed galectins as pivotal modulators of cell death, differentiation and growth. Galectins were highlighted to interact with both the adaptive and innate immune response. In the field of reproductive medicine and placenta research different roles for galectins have been proposed. Several galectins, being abundantly present at the human feto-maternal interphase and endometrium, were hypothesized to significantly contribute to endometrial receptivity and pregnancy physiology. Hence, this review outlines selected aspects of galectin action within endometrial function and at the feto-maternal interphase. Further current knowledge on galectins in reproductive and pregnancy disorders like endometriosis, abortion or preeclampsia is summarized.

The second glutamic acid in the C-terminal CRD affects the carbohydrate-binding properties of recombinant galectins of Haemonchus contortus

The effects of the second glutamic acid (E) in the C-terminal CRDs on the hemagglutination and lactose-binding characteristics of the recombinant galectins of nematode Haemonchus contortus were observed using two isoforms of recombinant galectins as models, and the sugar-binding abilities of the N-terminal and C-terminal CRDs of the galectins were also compared. The second E in the CRD, WGNEER, of Hco-GAL-m was mutated to glycine acid (G) and resulted in a recombinant galectin (MG mutate) with a CRD of WGNEGR, identical to that of Hco-GAL-f. The G in Hco-GAL-f CRD, WGNEGR, was mutated to E and produced a recombinant galectin (FE mutate) equal to that of Hco-GAL-m. At the same time, the CRDs of the N-terminal (FNh,MNh) and C-terminal (FCh,MCh) of Hco-GAL-f, Hco-GAL-m were amplified by PCR. The abilities of carbohydrate binding and hemagglutination of the four galectins and the four CRDs were analysed, respectively, by alpha-lactose-agarose affinity chromatography and hemagglutination assay. The results showed that Hco-GAL-m and FE mutate bound effectively to alpha-lactose-agarose compared to Hco-GAL-f and MG mutate, which almost could not bind to the conjugate column. The hemagglutinating abilities of the Hco-GAL-m and FE mutate to human B type red blood cells were similar and were nearly two times higher than that of the Hco-GAL-f and MG mutate. The hemagglutinating ability of the MCh was five times to that of the MNh and FNh and almost two times to that of the FCh. The binding ability of the MCh and FCh were significantly reduced compared to that of the Hco-GAL-m and FE mutate, but still remained. As for the MNh and FNh, no elution peak was observed in the lactose-agarose affinity chromatography. These results suggested that the second amino acid E in the C-terminal CRD motif of H. contortus galectin was involved in carbohydrate binding and hemagglutination, and C-terminal CRDs had stronger carbohydrate ability than N-terminal CRDs.

Recombinant galectins of male and female Haemonchus contortus do not hemagglutinate erythrocytes of their natural host

Recombinant galectins of female and male adult worms of Haemonchus contortus were expressed in Escherichia coli and their hemagglutinating activities to human and different animal erythrocytes were analyzed. The results showed that female and male galectins could be highly expressed in E. coli using a temperature-sensitive plasmid, with the recombinant protein being mainly appeared in inclusion bodies. Hemagglutinating activity assays showed that both of the galectins hemagglutinated human A, B, O type, dog, rabbit, chicken and mouse erythrocytes at the high concentration of 40 microg/well, but did not hemagglutinate erythrocytes of the natural host of H. contortus, the goat. Sugar inhibition assays confirmed that, out of eight sugars tested, only lactose was effective to inhibit agglutination of human type B erythrocytes by the recombinant galectins.

Specific recognition of Leishmania major poly-beta-galactosyl epitopes by galectin-9: possible implication of galectin-9 in interaction between L. major and host cells

Leishmania parasites are the causative agents of leishmaniasis, manifesting itself in a species-specific manner. The glycan epitopes on the parasite are suggested to be involved in the Leishmania pathogenesis. One of such established species-unique glycan structures is the poly-beta-galactosyl epitope (Galbeta1-3)n found on L. major, which can develop cutaneous infections with strong inflammatory responses. Interestingly, the polygalactosyl epitope is also suggested to be involved in the development of the parasites in its host vector, sand fly. Thus, the recognition of the galactosyl epitope by lectins expressed in host or sand fly should be implicated in the species-specific manifestations of leishmaniasis and in the parasite life cycle, respectively. We recently reported that one host beta-galactoside-binding protein, galectin-3, can distinguish L. major from the other species through its binding to the poly-beta-galactosyl epitope, proposing a role for galectin-3 as an immunomodulator that could influence the L. major-specific immune responses in leishmaniasis. Here we report that galectin-9 can also recognize L. major by binding to the L. major-specific polygalactosyl epitope. Frontal affinity analysis with different lengths of poly-beta-galactosyllactose revealed that the galectin-9 affinity for polygalactose was enhanced in proportion to the number of Galbeta1-3 units present. Even though both galectins have comparable affinities toward the polygalactosyl epitopes, only galectin-9 can promote the interaction between L. major and macrophages, suggesting distinctive roles for the galectins in the L. major-specific development of leishmaniasis in the host.