Identification of the first prokaryotic collagen sequence motif that mediates binding to human collagen receptors, integrins α 2β1 and α11β1

Abstract

Many pathogenic bacteria interact with human integrins to enter host cells and to augment host colonization. Group A Streptococcus (GAS) employs molecular mimicry by direct interactions between the cell surface streptococcal collagen-like protein-1 (Scl1) and the human collagen receptor, integrin α2β1. The collagen-like (CL) region of the Scl1 protein mediates integrin-binding, although, the integrin binding motif was not defined. Here, we used molecular cloning and site-directed mutagenesis to identify the GLPGER sequence as the α2β1 and the α11β1 binding motif. Electron microscopy experiments mapped binding sites of the recombinant α2- integrin-inserted domain to the GLPGER motif of the recombinant Scl (rScl) protein. rScl proteins and a synthetic peptide harboring the GLPGER motif mediated the attachment of C2C12-α2+ myoblasts expressing the α2β1 integrin as the sole collagen receptor. The C2C12-α11+ myoblasts expressing the α 11β1 integrin also attached to GLPGER-harboring rScl proteins. Furthermore, the C2C12-α11+ cells attached to rScl1 more efficiently than C2C12-α2+ cells, suggesting that the α11β1 integrin may have a higher binding affinity for the GLPGER sequence. Human endothelial cells and dermal fibroblasts adhered to rScl proteins, indicating that multiple cell types may recognize and bind the Scl proteins via their collagen receptors. This work is a stepping stone toward defining the utilization of collagen receptors by microbial collagen-like proteins that are expressed by pathogenic bacteria. © 2008 by The American Society for Biochemistry and Molecular Biology, Inc.