Identification of a beta 2 (CD18) molecule in a teleost species, Ictaluruspunctatus Rafinesque

Beta 2, in combination with the alpha subunit, is responsible for tight adh esion of leukocytes, especially neutrophils and macrophages, in areas of in flammation. Although identified in mammalian and avian species; the beta 2 or CD18 molecule has yet to be identified in fish. The present investigatio n has identified a full-length channel catfish. Ictalurus punctatus, cDNA b eta 2 molecule composed of 2.8 kb and a deduced amino acid sequence of 772 amino acids. The catfish molecule has an amino acid homology ranging from 5 4 to 63% with mouse, bovine, rabbit, human and chicken. The channel catfish molecule retains several characteristics of mammalian beta 2 molecules, su ch as cysteine-rich repeat regions, N-linked glycosylation sites, and sever al proposed signal sequences. Expression of the beta 2 molecule on the catf ish neutrophil cytoplasmic membranes is increased upon phorbol dibutyrate s timulation of the cells. Based on Western blotting and the immunoprecipitat ion test, the channel catfish beta 2 molecule has a molecular mass of appro ximately 95 kD, essentially the same as that for mammalian species. However , two additional molecules, perhaps or chains, of unexpected molecular mass appear to co-precipitate in the SPIT with the 95 kD CD18 molecule. These r esults confirm the existence and expression of a beta 2 gene in channel cat fish, a species phylogenetically distant from mammalian species. (C) 1999 E lsevier Science Ltd, All rights reserved.