Inhibitory role of α6β4-associated erbB-2 and phosphoinositide 3-kinase in keratinocyte haptotactic migration dependent on α3β1 integrin

Keratinocytes and other epithelial cells express two receptors for the basement membrane (BM) extracellular matrix component laminin-5 (Ln-5). integrins alpha3 beta1 and alpha6 beta4. While alpha3 beta1 mediates adhesion, spreading, and migration (Kreidberg, J.A. 2000. Curr: Opin. Cell Biol. 12:548-553), alpha6 beta4 is involved in BM anchorage via hemidesmosomes (Borradori, L., and A. Sonnenberg. 1999. J. Invest. Dermatol. 112:411-418). We investigated a possible regulatory interplay between alpha3 beta1 and alpha6 beta4 in cell motility using HaCaT keratinocytes as a model. We found that alpha6 beta4 antibodies inhibit alpha3 beta1-mediated migration on Ln-5, but only when migration is haptotactic (i.e., spontaneous or stimulated by alpha3 beta1 activation), and not when chemotactic (i.e., triggered by epidermal growth factor receptor). Inhibition of migration by alpha6 beta4 depends upon phosphoinositide 3-kinase (PI3-K) since it is abolished by PI3-K blockers and by dominant-negative PI3-K, and constitutively active PI3-K prevents haptotaxis. In HaCaT cells incubated with anti-alpha6 beta4 antibodies. activation of PI3-K is mediated by alpha6 beta4-associated erbB-2, as indicated by erbB-2 autophosphorylation and erbB-2/p85 PI3-K coprecipitation. Furthermore, dominant-negative erbB-2 abolishes inhibition of haptotaxis by anti-alpha6 beta4 antibodies. These results support a model whereby (a) haptotactic cell migration on Ln-5 is regulated by concerted action of alpha3 beta1 and alpha6 beta4 integrins, (b) alpha6 beta4-associated erbB-2 and PI3-K negatively affect haptotaxis, and (c) chemotaxis on Ln-5 is not affected by alpha6 beta4 antibodies and may require PI3-K activity. This model could be of general relevance to motility of epithelial cells in contact with BM.