Molecular cloning and genomic structure of an interleukin-8 receptor-like gene from homozygous clones of rainbow trout (Oncorhynchus mykiss)

Chemokines are small proteins (70-100 amino acids) which play an important role in recruitment and activation of leucocytes to migrate to the site of inflammation. Based on the position of the first two conserved cysteines, chemokines are classified into four subfamilies: C, CC, CXC and CX3C. To date, many members of CC and CXC have been found and studied extensively [1]. Chemokines exert effects on their target cell via chemokine receptors, which are G-protein coupled receptors containing seven transmembrane domains with an extracellular N-terminus and an intracellular C-terminus [2]. Interleukin 8 (IL-8) belongs to the CXC chemokine subfamily. It can activate and attract migratory neutrophils to an inflammation site. Two IL-8 receptors, CXCR1 and CXCR2, have been identified in mammals [3-6]; both of these receptors have high affinity for IL-8 and are expressed on the neutrophil. CXCR1 just binds IL-8; however, CXCR2 binds IL-8 and other structurally related chemokines such as growth-related oncogene (GRO) a, GRObeta, GROgamma, neutrophil-activating peptide-2 (NAP-2) and epithelial cell-derived neutrophil activating peptide-78 (ENA-78) [7, 8]. Several studies on fish chemokine receptors have been reported [9-11]. Thus far, however, IL-8 and CXCR1 and CXCR2 proteins from rainbow trout have not been reported: however, the sequence of a rainbow trout IL-8 has been noted (GenBank Accession No. AJ279069 [12]). Cloning of the IL-8 receptor is important to study the function of IL-8/CXCR1 and (CXCR2) in inflammation and signal transduction in fish. This paper reports the molecular cloning and genomic structure of an IL-8 receptor-like gene from four homozygous clones of rainbow trout: Oregon State University (OSU), Hot Creek (HC), Arlee (AR) and Swanson (SW).