Module 1: Figure integrin receptor
Integrin receptor activation by extracellular matrix (ECM) and cell-surface stimuli.
The integrin receptor is a heterodimer composed of an α- and a β-subunit. In the absence of stimulation (low-affinity state), the extracellular domains are bent over, but extend out to a high-affinity state following outside-in or inside-out signalling. During the former, the large extracellular domain interacts with various components of either the extracellular matrix (ECM) or cell-surface ligands. Integrins have very short cytoplasmic domains that lack enzyme activity. During receptor activation, the cytoplasmic domain of the β-subunit interacts with transducers such as focal adhesion kinase (FAK), which has tyrosine kinase (TK) activity, enabling an autophosphorylation to create binding sites to activate a number of transducing elements. During inside-out signalling, other receptors activate tyrosine kinases that phosphorylate FAK to induce a high-affinity state that then enables the integrin receptor to bind to other adhesion molecules.