New tools to study the interaction between integrins and latent TGFbeta1

Transforming growth factor beta (TGF{beta}) 1 regulates cell differentiation and proliferation in different physiological settings, but is also involved in fibrotic progression and protects tumors from the immune system. Integrin V{beta}6 has been shown to activate latent TGF{beta}1 by applying mechanical forces onto the latency-associated peptide (LAP). While the extracellular binding between V{beta}6 and LAP1 is well characterized, less is known about the cytoplasmic adaptations that enable V{beta}6 to apply such forces. Here, we generated new tools to facilitate the analysis of this interaction. We combined the integrin-binding part of LAP1 with a GFP and the Fc chain of human IgG. This chimeric protein, sLAP1, revealed a mechanical rearrangement of immobilized sLAP1 by V{beta}6 integrin. This unique interaction was not observed between sLAP1 and other integrins. We also analyzed V{beta}6 integrin binding to LAP2 and LAP3 by creating respective sLAPs. Compared to sLAP1, integrin V{beta}6 showed less binding to sLAP3 and no rearrangement. These observations indicate differences in the binding of V{beta}6 to LAP1 and LAP3 that have not been appreciated so far. Finally, V{beta}6-sLAP1 interaction was maintained even at strongly reduced cellular contractility, highlighting the special mechanical connection between V{beta}6 integrin and latent TGF{beta}1.