Pro-α3(V) collagen chain is expressed in bone and its basic N-terminal peptide adheres to osteosarcoma cells

The third α-chain of type V collagen, α3(V) chain, was initially identified in the placenta more than 20 years ago, but was poorly characterized with regard to its expression and function. We generated a specific monoclonal antibody against the N-terminal domain of the pro-α3(V) chain and examined gene expression using immunohistochemical methods combined with in situ hybridization. The pro-α3(V) chain was seen in funis and amnion, but not chorionic villi and deciduas of mouse placenta. In mouse embryo, the transcripts of the pro-α3(V) gene were seen in tissues that were related to bone formation as well as developing muscle and nascent ligament previously reported (J. Biol. Chem. 275, 8749-8759, 2000). However, immunohistochemistry showed that pro-α3(V) protein accumulated rather in the developing bone of mouse embryo. On the other hand, the N-terminal globular domain of the pro-α3(V) chain has a unique structure that contains a highly basic segment of 23 amino acids. The peptide derived from the basic segment showed a specific adhesive feature to osteosarcoma cells but not to chondrosarcoma cells. The four heparin binding sites in the basic segment equally contribute toward adhesion to the osteosarcoma cells. Our data suggested that N-terminal globular domain of the pro-α3(V) chain influence bone formation of osteoblasts through proteoglycan on the cell surface during development or regeneration.