Functional Integrin Regulation Through Interactions with Tetraspanin CD9

Integrins are adhesion receptors that mediate many intercellular and cell–extracellular matrix interactions with relevance in physiology and pathology. Unlike other cellular receptors, integrins critically require activation for ligand binding. Through interaction in cis with other molecules and the formation of tetraspanin-enriched membrane microdomains (TEMs), the tetraspanin CD9 regulates integrin activity and avidity. Here we present three techniques used to study CD9–integrin interactions and integrin activation.