Integrin Receptors for Extracellular Matrix with Special Reference to Tenascin

Abstract

Integrins are a large family of transmembrane glycoproteins consisting of αβ heterodimers. Although the first members of this family were identified based on their ability to mediate cellular adhesion to components of the extracellular matrix, it is now clear that integrins can recognize a broad array of ligands including immunoglobulin family members, at least one member of the cadherin family, and probably other integrins. The functional significance of integrins binding to their ligands has now been extended well beyond simple cell adhesion with the recognition that integrins are true signaling receptors, inducing signals that can lead to numerous changes in cell behavior, including migration, proliferation, and induction of expression of a wide array of other cellular genes. At least 5 different integrins bind to the extracellular matrix protein, tenascin, at 3 distinct sites. Although the specific roles played by each of these integrins in cellular responses to tenascin have not been thoroughly investigated, preliminary evidence suggests that this structural diversity has functional significance. Because of the central role played by this protein family in development, inflammation, thrombosis, and tumorigenesis, integrins are among the most intensely studied proteins in biology.