A novel CD29-like protein expressed in Japanese lamprey (Lethenteron japonicum) and involved in immune response.

CD29 is the integrin beta1 subunit. Integrin family members are membrane receptors involved in cell adhesion and recognition in a variety of processes including embryogenesis, tissue repair and immune response. In this study, a novel CD29-like gene (LCD29) was identified and characterized in Japanese lamprey (Lethenteron japonicum), an agnathan that occupies a critical phylogenic position between cephalochordates and gnathostomes. After a partial cDNA sequence of LCD29 was found from the leucocyte cDNA library, the full-length cDNA was obtained by means of 3' and 5' RACE, respectively. LCD29 encodes 780 amino acids and shares high sequence homology with other vertebrates. Both real-time PCR and immunohistochemical assays have demonstrated the wide distribution of the LCD29 in lamprey tissues, and FACS analysis has shown that the expression level of this protein is higher in granulocytes than in lymphocytes. Furthermore, after the lampreys were stimulated with lipopolysaccharide, the levels of LCD29 mRNA were obviously up-regulated in the leucocytes, intestine, heart and gill tissues. Most importantly, an interaction between LCD29 and LCD9 in the intestine has been found with co-immunoprecipitation assays for the first time. The results obtained in the present study will help us to understand the function of LCD29 in immune response in jawless vertebrates.