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Ivor S. Douglas, Themistocles Dassopoulos
Published in Volume 117, Issue 9
J Clin Invest. 2007; 117(9):2391–2395 doi:10.1172/JCI33376
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Figure 1
The interaction of the 3 β-chain cation-binding sites of lymphocyte α4β7 integrin in the unliganded state and in the liganded conformation with endothelial cell MAdCAM-1.

Inside-out signaling coordinates cation-dependent allosteric conformational activation of the α4β7 integrin with the transition from a low-affinity binding state to an “open-hinge,” high-affinity binding state. This facilitates MAdCAM-1 binding and firm adhesion to α4β7. The orientation in the MAdCAM-1–liganded form of the linear cluster of 3 metal-binding sites (ligand-induced metal-binding site [LIMBS], metal ion–dependent adhesion site [MIDAS], and ADMIDAS) in the ligand-binding head region of the integrin β subunit von Willebrand factor type A (βA or I-like) domain are shown in green, red, and yellow, respectively. ADMIDAS and ligand-induced metal-binding site are regulators of adhesion and de-adhesion and contribute to adhesive rheo-tone. As reported by Park et al. (5) in this issue of the JCI, ADMIDAS regulates de-adhesion of the lymphocyte’s trailing edge integrins, thus facilitating transendothelial migration along chemokine gradients.