Fibronectin: The biological velcro

Abstract

This brief review of the salient structural and physiological properties of Fn might leave the impression that this essential glycoprotein leads a Jekyll-and-Hyde existence. In a positive sense, Fn is the foundation of the interstitial matrix and moderates cellular adhesion, migration, and growth as well as maintaining the integrity of basement membranes and mucosal surfaces. In addition Fn serves as an interface for a number of cell-mediated immunological activities. Under normal circumstances, the recognition of Fn by bacterial receptors serves to “locate” symbiotic organisms onto mucosal or cutaneous surfaces, thus establishing the protective normal bacterial flora. Fn can also act as a barrier to infection by selectively masking bacterial and viral receptors on mucosal and cell surfaces and by enhancing the clearance of microorganisms through opsonozation. The bad news is that Fn is found in increased concentrations in areas of fibrosis or inflammation. Damaged tissue resulting from a primary disease process or mechanical injury increases the likelihood of colonization and/or infection by organisms not usually capable of causing invasive disease. Some examples of this process might include pulmonary colonization and infection in the cystic fibrosis patient, bacterial endocarditis following rheumatic disease, group A streptococcal pharyngitis, and foreign body or surgical infections. The number of infectious agents that use Fn as a foothold for colonization and disease production is unknown but will indoubtedly increase because of the Velcro-like qualities of Fn. For a more extensive examination of this fascinating subject, the author highly recommends the excellent review recently complied by Proctor (37).