Toll-Like 3 Receptor In The Immune Response of Paracentrotus lividus Sea Urchin

Sea urchin innate immune response involves important proteins such as membrane receptors which trigger different intracellular signaling pathways. The discovery of the Toll-like receptors (TLRs) in immune cells of invertebrates such as the sea urchin, has renewed the interest in innate immunity and its potentiality in invertebrate models. The sea urchin coelomocytes are considered a good model to study the immune response (1, 2, 3, 4). In the sea urchin Strongylocentrotus purpuratus, these receptors are encoded by a large multigenic family which comprises 253 genes (5). Here we report the isolation, the protein analysis and the phylogeny of a partial cDNA encoding for Pl-tlr3 belonging to the family of Toll-like receptor from the coelomocytes of sea urchin Paracentrotus lividus, and its expression in response to LPS and poly-IC treatments. The analysis of the protein has allowed to understand that this receptor, localized into the endosome, is small in size and contains a small number of Leucine Rich Repeats. It is not involved in the immune response bacterial, given that its transcription, analyzed by QPCR, is not affected by the injection of LPS. On the contrary, poly-IC treatment, a chemical compound that mimes dsRNA, causes Pl-tlr3 overexpression. The phylogeny of the partial protein Pl-tlr3, compared with Tlr3 proteins from different classes of animals, give a vision of the evolutionary path that, most likely, this receptor has made in the course of millions of years, starting from simple organisms up to man. The study of the functions of Tlr3 genes in invertebrate may provide new perspectives on the knowledge of the TLR family of receptors in the immune response. 1 Pancer Z, et al. (2004) Nature, 430, 174. 2 Smith LC, et al. (2006) Inv. Surv. J., 3, 25-39. 3 Hibino T. et al. (2006) Dev. Biol., 300, 349. 4 Matranga V, et al (2005) Prog.Mol. Subcell. Biol., 39, 85. 5 Buckley KM and Rast JP. (2012) Front Immunol., 3, 136.