Integrin signaling couples binding and mechanical loading of an integrin to changes inside a cell. An integrin spans the cell membrane: extracellular binding to the extracellular matrix can promote intracellular assembly of adhesion complexes connected to actin. Conversely, intracellular regulation can change integrin affinity and clustering. Signalling therefore runs in both directions across the boundary. [ref]
A change in matrix stiffness can change how an attached cell bears load and activates downstream signals. This makes adhesion a source of information as well as a tether. Measuring adhesion strength, phosphorylation of a signalling component and eventual cell proliferation addresses different stages; none alone specifies the whole response.
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