Molecular Cloning and Characterization of Chick CD9

Abstract

CD9 is a tetra-membrane-spanning glycoprotein involved in cell adhesion, migration, growth signaling and tumor cell metastasis. In this study a CD9 cDNA clone has been isolated from chick cDNA library. The chick CD9 clone contains an open reading frame of 224 amino acids. The deduced amino acid sequence from chick CD9 shows 63.3% identity with the human counterpart. Human and monkey CD9 upregulate the diphtheria toxin (DT) binding activity of human heparinbinding EGF-like growth factor, while chick CD9 lacks the ability to upregulate the DT binding activity. Comparison of the amino acid sequence of chick CD9 with that of human CD9 gives a clueto understanding the upregulation mechanism.