New tools to study the interaction between integrins and latent TGFβ1

Abstract

Transforming growth factor beta (TGFbeta) 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 alphaVbeta6 has been shown to activate latent TGFbeta1 by applying mechanical forces onto the latency-associated peptide (LAP). While the extracellular binding between alpha;beta6 and LAP1 is well characterized, less is known about the cytoplasmic adaptations that enable alphaVbeta6 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 alphaVbeta6 integrin. This unique interaction was not observed between sLAP1 and other integrins. We also analyzed alphaVbeta6 integrin binding to LAP2 and LAP3 by creating respective sLAPs. Compared to sLAP1, integrin alphaVbeta6 showed less binding to sLAP3 and no rearrangement. These observations indicate differences in the binding of alphaVbeta6 to LAP1 and LAP3 that have not been appreciated so far. Finally, alphaVbeta-sLAP1 interaction was maintained even at strongly reduced cellular contractility, highlighting the special mechanical connection between alphaVbeta6 integrin and latent TGFbeta1.