Question

Explain the mechanism of integrin binding to the ECM and why this is biologically important.

Answer 1

Integrins are a large family of type I trans-membrane heterodimeric glycoprotein receptors that function as the major metazoan receptors for cell adhesion and connect the intracellular and extracellular environments. Integrins exist as two non-covalently bound a and b subunits, which pair to form hetero-dimers. There are 18a and 8b known sub-units, which combine to form at least 24 distinct integrin hetero-dimers. Integrin binding to ECM components including laminins, collagens, and fibronectin depends on the extracellular domains of the a and b integrin subunits. Each heterodimer consists of a large extracellular domain, which binds proteins in the extracellular environment. Integrins bind to extracellular matrix (ECM) glycol-proteins including collagens, fibronectins, laminins, and cellular receptors such as vascular cell adhesion molecule-1 and the intercellular cell adhesion molecule (ICAM) family.

When triggered, integrins in turn trigger chemical pathways to the interior such as the chemical composition and mechanical status of the ECM, which results in a response activation of transcription such as regulation of the cell cycle, cell shape, and motility; or new receptors being added to the cell membrane. This allows rapid and flexible responses to events at the cell surface