A novel mouse β-defensin, mBD-6, predominantly expressed in skeletal muscle

Defensins comprise a family of cationic, antimicrobial peptides that is characterized by the conserved 6 cysteine residues. They are expressed in the epithelial cells of various organs and are identified as key elements in the host defense system at the mucosal surface. We isolated a novel mouse beta -defensin gene from the bacterial artificial chromosome DNA containing the mouse beta -defensin-3 gene. The full-length cDNA was cloned from skeletal muscle cDNA and called mouse beta -defensin-6 (mBD-6). The predicted peptide conserved the 6-cysteine motif and had 59% amino acid sequence identity with mouse beta -defensin-3 and 59% identity with mouse beta -defensin-4. We demonstrated the-expression of mBD-6 in skeletal muscle in addition to the esophagus, tongue, and trachea. In animal models of endotoxemia, mBD-6 expression was also induced in the lung. mBD-6 showed potent antimicrobial activity against Escherichia coli and would play an important role in host defense in the esophagus, airways, and skeletal muscle. mBD-6 is the first reported beta -defensin predominantly expressed in skeletal muscle. This unique tissue specificity suggests some, novel physiological roles of this peptide family.