Molecular cloning and characterisation of a homologue of the alpha inhibitor of NF-kappaB in the griffon vulture (Gyps fulvus)

NF-kappaB has been found to play roles in many different compartments of the immune system during differentiation of immune cells and development of lymphoid organs and during immune activation. The activity of NF-kappaB is primarily regulated by a family of structurally related proteins known as the IkappaB proteins. Herein, we report the molecular cloning and characterisation of a griffon vulture (Gyps fulvus) orthologue of the alpha inhibitor of NF-kappaB (IkappaBalpha). The full-length cDNA consists of 1553 bp with an ORF encoding a 313 amino acids protein (GenBank accession number EU161944). The putative G. fulvus IkappaBalpha protein (Gf-IkappaBalpha) possesses the characteristic organization of the mammalian IkappaBalpha proteins. Gf-IkappaBalpha contains an N-terminal signalling receiver domain, a central ankyrin repeat domain, required for its interaction with NF-kappaB, and a putative PEST-like sequence in the C-terminus. Quantitative real-time RT-PCR (qRT-PCR) analysis indicated that Gf-IkappaBalpha mRNA levels were higher in vulture heart, lung, artery and PBMC cells than in small and large intenstine and kidney. The predicted amino acid sequence of Gf-IkappaBalpha was 73% identical to human IkappaBalpha, and 91% identical to chicken IkappaBalpha. These results confirm the existence of the NF-kappaB signalling pathway in vulture and suggest a similar functional interaction between IkappaBalpha and NF-kappaB. Based on the results and the homology to the vertebrate NF-kappaB cascade, these studies help to highlight a potentially important regulatory pathway for the study of the related functions in vulture immune system.