The integrin adhesion complex changes its composition and function during morphogenesis of an epithelium

Cell adhesion to the extracellular matrix (ECM) is mediated by the integrin family of transmembrane receptors. Integrins link ECM ligands to the cytoskeleton, providing strong attachment to enable cell-shape change and tissue integrity. This connection is made possible by an intracellular complex of proteins, which links to actin filaments and controls signalling cascades that regulate cytoskeletal rearrangements. We have identified stress-fibre-associated focal adhesions that change their composition during tissue morphogenesis. Early expression of alpha PS1 alpha PS integrin decreases the levels of the actin-nucleating factors Enabled, Diaphanous and profilin, as well as downregulating the amount of F-actin incorporated into the stress fibres. As follicle cells mature in their developmental pathway and become squamous, the integrin in the focal adhesions changes from alpha PS1 alpha PS to alpha PS2 beta PS. During the switch, stress fibres increase their length and change orientation, first changing by 90 degrees and then reorienting back. The normal rapid reorientation requires new expression of alpha PS2 beta PS, which also permits recruitment of the adaptor protein tensin. Unexpectedly, it is the extracellular portion of the alpha PS2 subunit that provides the specificity for intracellular recruitment of tensin. Molecular variation of the integrin complex is thus a key component of developmentally programmed morphogenesis.