Molecular cloning and expression analysis of P-selectin glycoprotein ligand-1 from zebrafish (Danio rerio).

To date, the best characterized glycoprotein ligand for P-selectin is P-selectin glycoprotein ligand-1 (PSGL-1). In this study, we cloned the full-length cDNA of PSGL-1 from zebrafish (Danio rerio). Zebrafish PSGl-1 cDNA is 1,594 bp and encodes a putative 284 amino acid protein with a theoretical molecular weight of 30.33 kDa and isoelectric point of 7.96. A signal peptide of 27 amino acids is predicted. The putative protein contains an extracellular mucin-like domain, a transmembrane domain and a cytoplasmic domain, with homology to mammalian PSGL-1. In the putative P-selectin binding region, there are 1 potential tyrosine sulfation site and 12 potential threonine O-glycosylation sites. A single extracellular cysteine, at the junction of the extracellular and transmembrane domains, suggests a disulfide-bonding pattern. The amino acid sequence of zebrafish PSGL-1 is 19-22% identical to that of mammalian PSGL-1. RT-PCR and whole-mount in situ hybridization analysis revealed that zebrafish PSGL-1 was expressed in early embryonic development, and the expression has an increased trend from 0.2 (1-cell stage) to 72 hpf. The results indicate that the general domain structure of PSGL-1 protein is conserved among species, and zebrafish PSGL-1 plays important roles in embryonic development and probably has similar biological function to that of mammalian PSGL-1.