Veterinary Immunology and Immunopathology

Annexins are Ca2+-dependent phospholipid-binding proteins. They are ubiquitous in living organisms and are involved in many cellular processes. In the course of studying Edwardsiella ictaluri pathogenesis in channel catfish, we identified that six annexin expressed sequence tags (A1, A2, A4, A5, A6 and A11) were up-regulated at the early stage of infection. In this study, we cloned and characterized these transcripts. The full-length nucleic acid sequences of channel catfish annexins ranges from1231 (annexinA1) to 2476 (annexin A6). Each transcript has one open reading, which appears to encode peptides ranges from 317 to 662 amino acid residues with the calculated molecular masses from 35.0 (annexin A5) to 74.5 kDa (annexin A6). Phylogenetic and sequence analyses demonstrate that each channel catfish annexin had a diversified amino terminus, and had four structurally conserved 70-amino acid repeats. In addition, several important features for annexin functions were conserved in channel catfish. For expression profile, channel catfish annexin A1, A4 and A6 transcripts were detected in spleen, anterior kidney, liver, intestine, skin and gill of fish examined. However, annexin A2, A5 and A11 cDNAs were variously detected in tissues of fish sampled. This result provides important information for further elucidating channel ctions catfish annexin fun Annexins, a protein superfamily, are ubiquitous and can be classified into five subfamilies: A subfamily for vertebrates, B for invertebrates, C for fungi and some unicellular eukaryotes, D for plants and E for protists (Gerke and Moss, 2002; Moss and Morgan, 2004; Mortimer et al., 2008). These proteins are biosynthesized as either in a soluble form in the cytosolic compartment or in associated with other proteins, such as with cytoskeleton (Moss and Morgan, 2004). After synthesis, they are undergoing a series of post-translational modification such as phosphorylation (Moss and Morgan, 2004). Two fundamental biochemical characteristics of annexins are (1) they bind ∗ Corresponding author. Tel.: +1 334 887 3741; fax: +1 334 887 2983. E-mail address: [email protected] (H.-Y. Yeh). 0165-2427/$ – see front matter. Published by Elsevier B.V. doi:10.1016/j.vetimm.2010.02.013 in vivo. Published by Elsevier B.V. to Ca2+-dependent, negatively charged phospholipids in a reversible manner and (2) they contain structurally conserved domains of about 70 amino acid repeats (Gerke and Moss, 2002; Gerke et al., 2005; Moss and Morgan, 2004). In human, 12 annexins have been identified, but their functions are largelyyet tobedetermined.AnnexinA1 (also called lipocortin I) plays key roles in mediating glucocorticoid anti-inflammatory and anti-migratory actions (for reviews, see Hannon et al., 2003; Perretti and Solito, 2004; Lim and Pervaiz, 2007; D’Acquisto et al., 2008; Perretti and D’Acquisto, 2009). Annexin A2 has been involved in (1) enhancement of osteoclast formation and bone resorption (Takahashi et al., 1994), (2) regulation of fibrin hemeostasis and neovascularization (Ling et al., 2004), and (3) regulationofphagocytosisofphotoreceptorouter segments in the retina (Law et al., 2009). Annexin A4 modulates the memH.-Y. Yeh, P.H. Klesius / Veterinary Immunology and Immunopathology 136 (2010) 176–183 177