Porcine SPLUNC1: Molecular cloning, characterization and expression analysis

SPLUNC1, originally named PLUNC for palate, lung and nasal epithelium clone, is a small protein which is secreted from the epithelial cells of the nasal cavity and the upper respiratory tract in humans, mice, rats and cows. SPLUNC1 is structurally homologous to the two key mediators of host defense against Gram-negative bacteria, lipopolysaccharide binding protein (LBP) and bactericidal permeability increasing protein (BPI). SPLUNC1 is therefore believed to play a role in the innate immune system. This work reports the cloning and analysis of the porcine (Sus scrofa) homologue of SPLUNC1. The SPLUNC1 cDNA was amplified by reverse transcriptase polymerase chain reaction (RT-PCR) using oligonucleotide primers derived from in silico sequences. The porcine cDNA codes for a protein of 249 amino acids which shows a high similarity to bovine (74%) and to human (69%) SPLUNC1. The predicted S. scrofa SPLUNC1, SsSPLUNC1, polypeptide contains a putative signal peptide of 19 residues. A similar signal sequence is also found in all other members of the PLUNC family. Expression analysis by RT-PCR demonstrated a very high expression level of the porcine SPLUNC1 homologue in trachea and lung tissue only. This airway-specific expression might be of particular interest in the study of airborne diseases in pig.