Peroxinectin, a cell adhesive protein associated with the proPO system from the black tiger shrimp, Penaeus monodon

Upon activation of the prophenoloxidase activating system in the shrimp, Pe naeus monodon, a cell adhesion activity in the haemolymph is generated. A c ell adhesion assay showed that a high number of granular cells (60%) adhere d to coverslips coated with a shrimp haemocyte lysate supernatant, whereas a very low number of cells adhered to coverslips coated with bovine serum a lbumin. Inhibition of adhesion by an antiserum against crayfish peroxinecti n, a cell adhesion protein, revealed that the cell adhesion activity detect ed in shrimp haemocyte lysate supernatant might result from a peroxinectin- like molecule in shrimp. A cDNA clone encoding shrimp peroxinectin was isol ated, which had an open reading frame of 2337 nucleotides, with a polyadeny lation sequence and a poly A tail. II encodes a protein of 778 amino acids including a 20 amino acid signal peptide. The mature protein (758 amino aci ds) has a predicted molecular mass of 84.8 kDa and an estimated pi of 9.0. Two putative integrin binding motifs, RGD (Arg-Gly-Asp) and KGD (Lys-Gly-As p), were found in shrimp peroxinectin. Sequence comparison shows that the s hrimp protein is similar to crayfish peroxinectin (69%) and to various pero xidases and putative peroxidases from invertebrates and vertebrates. The sh rimp peroxinectin cDNA also shows similarity (51%) to both Drosophila perox inectin-related protein (AAF78217) and peroxidasin (S46224), an extracellul ar matrix protein combining an active peroxidase domain as well as immunogl obulin domains, leucine rich repeats and procollagen-like motif. However, t he sequence similarity to both Drosophila molecules are mostly within the p eroxidase domain. Northern blot analysis, using a non-peroxidase region in peroxinectin as: a probe. revealed that peroxinectin is constitutively expr essed in shrimp haemocyte and was reduced significantly in shrimp injected with a beta -1,3-glucan,laminarin, to mimic an infection with a fungus. (C) 2001 Elsevier Science Ltd. All rights reserved.