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

Abstract

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 αPS1βPS 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 αPS1βPS to αPS2βPS. During the switch, stress fibres increase their length and change orientation, first changing by 90° and then reorienting back. The normal rapid reorientation requires new expression of αPS2βPS, which also permits recruitment of the adaptor protein tensin. Unexpectedly, it is the extracellular portion of the αPS2 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.

The transmembrane protein Crumbs displays complex dynamics during follicular morphogenesis and is regulated competitively by Moesin and aPKC

“…In stage 11, they rapidly become squamous, doubling their apical and basal areas and trebling their perimeters in 20 min. Whereas external forces drive this squamous expansion as nurse cells empty their contents into the oocyte, the FCs must nevertheless actively remodel their junctions and membrane domains to maintain adhesion to the extracellular matrix (Delon and Brown, 2009;Schotman et al, 2008), cell-cell adhesion (Pope and Harris, 2008) and epithelial integrity. Because optical constraints make it difficult to image squamous cells in cross-section, we employed maximal projections encompassing the apical junctions and apical surface (see Materials and Methods and supplementary material Fig.…”

A central multifunctional role of integrin-linked kinase at muscle attachment sites

“…However, this cannot be a universal mechanism, as other sites of integrin adhesion lack Wech (Delon and Brown, 2009). Studies in vertebrate cells have identified additional ILK interactions that provide alternative mechanisms to link ILK to talin.…”

Distinct regulatory mechanisms control integrin adhesive processes during tissue morphogenesis

“…This idea is supported by previous work showing that a mutant bPS chimera that cannot transduce tension (comprising the cytoplasmic tail fused to an extracellular domain that cannot bind ECM ligands) can recruit talin but not PINCH or tensin . In addition, a recent Drosophila study illustrates that force may be required for the recruitment of IAC components, as the extracellular domain of aPS2-integrin is required for intracellular tensin recruitment in ovarian epithelial cells (Delon and Brown, 2009). Thus, force may play crucial roles in recruiting certain IAC components during tissue morphogenesis.…”