Crustacean immunity : Characterization of some crayfish blood proteins

Abstract: The cDNA sequence and some properties of a previously purified #x03B2;-1,3-glucan binding protein are reported here. The putative amino acid sequence (predicted molecular mass: 152 kDa) of the protein did not show any significant similarity to any known protein, but an RGD motif and a region with slight similarity to bacterial glucanase was found. The RDG motif may be involved in the blood cell degranulating activity of this molecule although it was not possible to prevent binding of the protein to crayfish blood cells (haemocytes) by pre-treating cells with a short peptide containing RGD. No glucanase activity could be detected. Carbohydrate analysis showed that the protein is a glycoprotein with mannose as the main sugar constituent. It was also found that this protein can function as an opsonin.With in situ hybridisation the expression of prophenoloxidase was detected in the circulating haemocytes, but not in the haematopoietic tissue of crayfish. Thus, cells are not fully developed in the haematopoietic tissue. With an injection of laminarin, a #x03B2;-1,3-glucan, it was possible to increase expression of proPO in haemoyctes in the species Astacus astacus, but not in Pacifastacus Ieniusculus. The chronic infection of the crayfish plague, Aphanomyces astaci, in P. leniusculus might already have induced the immune system, thus no further increase is possible. In contrast, A. astacus with a latent infection of the parasite Psorospermium haeckeli did not show any upregulation in the expression of proPO compared to control animals.Cloning and purification of a 23 kDa Kasal proteinase inhibitor from haemocytes are re-ported. The activity against chymotrypsin and subtilisin suggests a possible role as inhibitorof microbe proteinases.A high mobility group-1/2 protein was cloned from a cDNA library made from crayfishblood cells. The predicted amino acid sequence with a mass of 23 kDa has two so-calledHMG-boxes and an acid C-terminal tail. The transcript is present in haemocytes, muscle,and hepatopancreas in adult animals. It shows highest similarity to the dorsal switch protein(DSP1) found in Drosophila melanogaster.