Cloning and expression of a novel component of the CAP superfamily enhanced in the inflammatory response to LPS of the ascidian Ciona intestinalis.

The CAP Superfamily is a group of proteins which have been involved in several biological function like reproduction, cancer, and immune defence. A differential screening between LPS-challenged and naïve Ciona intestinalis has been performed to identify LPS induced genes. This strategy allowed the isolation of a full-length 1471 nn cDNA encoding for a 413 AA protein (CiCAP). In silico analysis has shown that this polypeptide displays a modular structure with similarities to vertebrate CAP-Superfamily proteins and to a collagen-binding adhesin of Streptococcus mutans. Domain organization analysis and alignment of CiCAP to other vertebrate CAP proteins showed a novel structure suggesting that this protein originated from a common ancestor gene which gave rise to many subfamilies of mosaic proteins with novel functions. Quantitative mRNA expression performed by Real Time PCR analysis demonstrated that this gene is rapidly activated in the pharynx of Ciona intestinalis a few hours after LPS injection. In addition, in situ hybridization has shown that CiCAP mRNA is highly expressed by haemocytes with large granules contained inside the pharynx vessels. These data show that the CiCAP represents a protein with novel structural domains involved in the ascidian immune responses.