Chemokine stimulation promotes enterocyte migration through laminin-specific integrins

Agle KA, Vongsa RA, Dwinell MB. Chemokine stimulation promotes enterocyte migration through laminin-specific integrins. Am J Physiol Gastrointest Liver Physiol 301: G968-G980, 2011. First published September 15, 2011; doi:10.1152/ajpgi.00208.2011.-Intestinal homeostasis is regulated in part by the single cell layer of the mucosal epithelium. This physical barrier is a prominent part of the innate immune system and possesses an intrinsic ability to heal damage and limit infection. The restitutive epithelial migration phase of healing requires dynamic integrin adhesion to the extracellular matrix. Previously, we have shown that the homeostatic chemokine CXCL12 utilizes intracellular calcium to increase enterocyte migration on laminin. The aim of these studies was to investigate integrin specificity and, in turn, functional responses elicited by CXCL12 stimulation. Analysis of cellular adhesion and spreading revealed CXCL12 preferentially activated laminin-specific integrins compared with collagen IV-binding integrins. Laminin-specific cell adhesion and spreading elicited by CXCL12 was dependent on intracellular calcium. CXCL12 increased activated beta 1-integrins on the surface of epithelial cells compared with untreated cells. RT-PCR confirmed expression of the laminin-binding integrins-alpha 3 beta 1, -alpha 6 beta 1, and -alpha 6 beta 4. Interestingly, shRNA-mediated depletion of laminin-specific alpha 3- or alpha 6-integrin subunits revealed differential functions. alpha 3-Integrin knockdown reduced basal as well as inducible restitution. Depletion of alpha 6-integrin specifically abolished CXCL12-stimulated, but not TGF-beta 1 or basal, migration. Depletion with either sh alpha 3-integrin or sh alpha 6-integrin prevented CXCL12-evoked cell spreading. Our data indicate that CXCL12 stimulates the inside-out activation of laminin-specific integrins to promote cell migratory functions. Together, our findings support the notion that extracellular mediators within the gastrointestinal mucosa coordinate cell-matrix interactions during epithelial restitution.