Abstract
Integrin and receptor tyrosine kinase signalling networks cooperate to regulate various biological functions. The molecular details underlying the integration of both signalling networks remain largely uncharacterized. Here we identify a signalling module composed of a fibronectin-α5β1-integrin-integrin-linked-kinase (ILK) complex that, in concert with epidermal growth factor (EGF) cues, cooperatively controls the formation of transient actin-based circular dorsal ruffles (DRs) in fibroblasts. DR formation depends on the precise spatial activation of Src at focal adhesions by integrin and EGF receptor signals, in an ILK-dependent manner. In a SILAC-based phosphoproteomics screen we identified the tumour-suppressor Cyld as being required for DR formation induced by α5β1 integrin and EGF receptor co-signalling. Furthermore, EGF-induced Cyld tyrosine phosphorylation is controlled by integrin-ILK and Src as a prerequisite for DR formation. This study provides evidence for a novel function of integrin-ILK and EGF signalling crosstalk in mediating Cyld tyrosine phosphorylation and fast actin-based cytoskeletal rearrangements.
Highlights
Cells are exposed to a wide variety of mechanical and chemical stimuli that must be integrated at the molecular level to achieve an appropriate biological response
integrin-linked kinase (ILK) is crucial for dorsal ruffles (DRs) formation We generated ILK-floxed (ILKf/f) and ILK-deficient (ILK2/2) fibroblasts to investigate the consequence of ILK deletion in vitro (Sakai et al, 2003)
To study this effect under defined conditions in the presence of specific growth factors, we measured epidermal growth factor (EGF)-triggered DR formation in serum-starved ILKf/f and ILK2/2 fibroblasts that were seeded on FN-coated surfaces
Summary
Cells are exposed to a wide variety of mechanical and chemical stimuli that must be integrated at the molecular level to achieve an appropriate biological response. More than 180 signalling and scaffolding molecules have been identified that can be recruited to large integrin-based signalling hubs called focal adhesions (FAs) (Legate and Fassler, 2009; ’Schiller et al, 2011; Kuo et al, 2011; Zaidel-Bar and Geiger, 2010). Among these molecules, integrin-linked kinase (ILK) is a key player that directly binds the b1 and b3 integrin cytoplasmic tails (Hannigan et al, 1996; Pasquet et al, 2002). The analysis of constitutive and conditional deletion of the Ilk gene in mice, Drosophila melanogaster and Caenorhabditis elegans revealed that ILK controls the organization of the F-actin cytoskeleton, cell polarity, differentiation and proliferation (Esfandiarei et al, 2010; Grashoff et al, 2003; Hannigan et al, 1996; Legate and Fassler, 2009; Lorenz et al, 2007; Mackinnon et al, 2002; Sakai et al, 2003; Wang et al, 2008; Zervas et al, 2001)
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