Integrin α6β4-erbB2 Complex Inhibits Haptotaxis by Up-regulating E-cadherin Cell-Cell Junctions in Keratinocytes

Abstract

Keratinocyte integrins ␣6␤4 and ␣3␤1 bind laminin-5, a component of basement membranes. We previously demonstrated that in keratinocytes, haptotactic migration on laminin-5 was stimulated by anti-␤1 integrinactivating antibody TS2/16, whereas antibodies to ␣6 and ␤4, respectively, blocked TS2/16-induced, ␣3␤1-dependent migration. Moreover, ␣6␤4-associated haptotaxis inhibition was linked to a phosphatidylinositol 3-kinase (PI3K) pathway and required erbB2 activation. erbB2, the ligand-less member of the epidermal growth factor receptor family, was shown to form a complex with the hemidesmosomal integrin ␣6␤4. Here, we demonstrate that ␣6␤4 inhibitory effects on haptotaxis are abolished by an anti-E-cadherin antibody, which interferes with cell-cell adhesion. Furthermore, antibodies to ␣6 and ␤4 stimulated adhesion to an E-cadherin-Fc recombinant protein. In addition, anti-␣6/␤4 antibodies increased colony size in plated cells, stimulated cell-cell aggregation, and up-regulated E-cadherin localization to cell-cell contacts. These effects were abolished when erbB2 or PI3K were blocked. These results indicate that stimulation of ␣6␤4 increases E-cadherin-mediated cellcell adhesion and that this mechanism depends on erbB2 activation. The molecule that links ␣6␤4 with Ecadherin may be the small GTPase cdc42, an effector of PI3K, because dominant-negative cdc42 abolished the inhibitory effect of anti-␣6/␤4 antibodies and increased basal migration, whereas constitutively active cdc42 prevented the TS2/16-induced increase in haptotaxis. These findings suggest a model whereby ␣6␤4 can augment cell-cell adhesion and slow down haptotaxis over laminin-5 and point to the ␣6␤4-erbB2 heterodimer as an important signaling complex for the formation of cohesive keratinocyte layers.

Laminin-5-integrin interaction signals through PI 3-kinase and Rac1b to promote assembly of adherens junctions in HT-29 cells

“…This process might also occur in HT-29 cells. The more effective contribution of ␣ 6 ␤ 4 to the regulation of E-cadherin expression and function when HT-29 cells adhere onto laminin 5 is in agreement with the work of Hintermann and colleagues: in their system, the integrin ␣ 6 ␤ 4 can stimulate cell-cell aggregation, increase colony size in plated HaCaT keratinocytes, and upregulate E-cadherin localization at cellcell contacts (Hintermann et al, 2005). This effect was mediated by an increase in erbB-2 and PI 3-kinase activity, which in turn inhibits ␣ 3 ␤ 1 -controlled keratinocyte hypotaxis on laminin 5 (Hintermann et al, 2001).…”

Collagen VII plays a dual role in wound healing

“…This was not found in Col7a1-hypomorphic wounds, where strict collective migration was seen (data not shown). In light of these observations, it is interesting that integrin α6β4 has been suggested to delay haptotaxis by activating E-cadherin, leading to tighter cell-cell contacts (38). Our observations of altered migration behavior in integrin α6β4-overexpressing COL7A1-deficient keratinocytes support these studies.…”

Integrins stimulate E-cadherin-mediated intercellular adhesion by regulating Src-kinase activation and actomyosin contractility

“…In keratinocytes, integrins 64 and 31 stimulated E-cadherin homophilic interactions (Chartier et al, 2006;Hintermann and Quaranta, 2004;Hintermann et al, 2005). Both 21 integrin clustering and increased PKA activity are required to induce HT-1080 intercellular adhesion on collagen type IV (Whittard and Akiyama, 2001).…”