Mechanisms of integration of cells and extracellular matrices by integrins

While it is self-evident that all extracellular molecules are an integral part of a multicellular organism, it is paradoxical that they are often considered to be dissociated from cells. The reality is that a continuum of dynamic, bi-directional interactions links the intracellular environment through cell-surface receptors to multimolecular extracellular assemblies. These interactions not only control the behaviour of individual cells, but also determine tissue architecture. Adhesion receptor function is partly determined by an ability to tether the contractile cytoskeleton to the plasma membrane, but there is also evidence that integrin receptors modulate signalling events that are essential for cellular differentiation. A major challenge is now to integrate work at the atomic, molecular and cellular levels, and obtain holistic insights into the mechanisms controlling cell adhesion. In the present study, we review current knowledge of the molecular mechanisms employed by cells to integrate with the extracellular matrix. Two main topics are covered: the adaptation of integrin structure for bi-directional signalling and the integration of integrin signalling with other receptors.