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| C. Ciências Biológicas - 3. Bioquímica - 6. Bioquímica | ||
| SEA URCHIN FERTILIZATION IS INHIBITIED BY PLAT LECTINS
EXHIBITING DISTINCT CARBOHYDRATE BINDING COMPETENCES |
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| Nívea Maria Rocha Macedo 1 (niveamacedo@gmail.com), Letícia Veras Costa-Lotufo 2, Liezelotte Rezende Bomfim 1, Jefferson Soares de Oliveira 1, Cláudia do Ó Pessoa 2, Manoel Odorico de Moraes 2 e Márcio Viana Ramos 1 | ||
| (1. Depto. de Bioquímica e Biologia Molecular, Universidade Federal do Ceará – UFC; 2. Depto. de Fisiologia e Farmacologia, Universidade Federal do Ceará – UFC) | ||
| INTRODUÇÃO:
Reproductive biology represents an outstanding area for glycobiology investigation. Functional and structural analysis of glycoproteins operating in the fecundation suggests that oligosaccharides may act as essential functional groups that are required for success in fertilization. In animals in general, fertilization is mediated by interaction and fusion of two germinal cells (one egg and one sperm), trigging the initiation of cleavage, gastrulation and the species-specific developmental program that characterizes each organism. The sea urchin is one of the several organisms that have been used to decipher the basic cellular and molecular biology of animal fertilization. More is known about fertilization in sea urchins than is known about fertilization in most vertebrates because sea urchin is the model widespread used primarily due to substantial amount of sperms and eggs that can be obtained from species of this type and its embryogenesis can be easily followed. Previously studies indicate that several proteins and other molecules seem to be involved in sea urchin sperm-egg binding, but the basic model for the interaction is expected to be similar to mammalian gametes interaction. The aims of the present investigation were determine weather the soluble plant lectins purified from Canavalia brasiliensis (ConBr), Cratylia floribunda (CFL), Artocarpus integrifolia (Jacalin), Abrus precatorius (Abrin) and WGA could bind to sea urchin germinal cells and prevent fertilization. |
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| METODOLOGIA:
To fertilization, eggs (10.000 eggs/ml) or sperms (1%) were previously incubated with the lectins (active and heat-denatured) ConBr, CFL, Abrin, Jacalin and WGA at different concentrations for 30 minutes before mixing and the controls were done in the absence of them. The assays were stopped after 15 min by adding of 5 % formaldehyde and the fertilization rates were estimated by counting of eggs exhibiting visible fertilization membrane into 100 eggs on a comparative basis to the controls. The results were reported as mean ± S.E.M. of 4 determinations. Statistical significance (p < 0.05) was assessed by analysis of variance (ANOVA) followed by Boferroni’s test using GraphPad Prism 4.0 software (Graphpad Software, Inc). |
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| RESULTADOS:
Denatured lectins that were heat-treated during 45 min at 98 oC were ineffective upon sea urchin fertilization. It was noteworthy that all the active lectins were capable to bind at least one of sea urchin germinal cell types. The results showed that glucose/mannose-binding lectins differ among them because fertilization was fully inhibited by pre-incubation of ConBr with eggs while it was only partially inhibited by pre-incubation with CFL at similar conditions. The galactose/N-acetylgalactosamine-binding lectin Abrin was able to decrease sea urchin fertilization by pre-incubation with sperms while Jacalin that binds to alpha-galactose terminal structures, decreased fertilization rates when pre-incubated to eggs. The N-acetylglucosamine-binding lectin WGA seemed to be the sole lectin to bind both eggs and sperms since its pre-incubation with one of such gametes further decreased fecundation rates. The results suggest the presence of glycoconjugates with N-acetylglucasamine/sialic acid internal and terminal residues on N-glycan structures, high-mannose glycans and alpha-Gal terminal residues on N-glycan on egg surface and O-glycans and acetylglucosamine/sialic acid internal and terminal residues on N-glycan structures on sperm surface evolved to fertilization process. |
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| CONCLUSÕES:
The present study showed that the assayed lectins exhibiting distinct binding competences do bind sea urchin germinal cells diminishing fertilization rates. It seems that inhibition of fertilization owes to lectin binding to distinct glycoconjugates on gametes surface. However, inhibition would not be induced by competition between sperms and eggs ligands since the lectins used are drastically distinct in their binding properties. On the other hand, the lectins were able to detect unrelated glycan structures on gametes surfaces. The results stress the potential of lectins in glycobiology. |
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| Instituição de fomento: Supported by CNPq/PADCT, FUNCAP, and IFS. | ||
| Palavras-chave: Plant lectins; Glycoconjugates; Sea urchin fertilization. | ||
| Anais da 57ª Reunião Anual da SBPC - Fortaleza, CE - Julho/2005 |