Force interacts with macromolecular structure in activation of TGF-β

Abstract

Summary We show how integrin αVβ6 binds a macromolecular ligand, pro-TGF-β1, in an orientation biologically relevant for force-dependent release of TGF-β from latency. The conformation of the prodomain integrin-binding motif differs in presence and absence of integrin binding; differences extend well outside the interface and illustrate how integrins can remodel extracellular matrix. Remodeled residues outside the interface stabilize the integrin-bound conformation, adopt a conformation similar to earlier evolving family members, and show how macromolecular components outside the binding motif contribute to integrin recognition. Regions in and outside the highly interdigitated interface stabilize a specific integrin-pro-TGF-β orientation that defines the pathway through these macromolecules that actin cytoskeleton-generated tensile force takes when applied through the integrin β-subunit. Simulations of force-dependent activation of TGF-β demonstrate evolutionary specializations for force application through the TGF-β prodomain and through the β and not α-subunit of the integrin.

Atypical interactions of integrin α V β 8 with pro-TGF-β1

“…Clonal cell lines were selected and protein was purified as described (14). Human pro-TGF-β1 with a R249A cleavage site mutation was prepared as described (15). Negative-stain EM was as described (19,30,31).…”

Intracellular and extracellular TGF-β signaling in cancer: some recent topics

“…β1-LAP and β3-LAP contain an Arg-Gly-Asp (RGD) sequence, the recognition motif for integrins, and bind to cell surface integrins, particularly αvβ1, αvβ6, and αvβ8, while LTBPs anchor the latent TGF-β complex in the ECM [204]. Biological and structural studies demonstrate that the molecular tension mediated by the physical stretch between the β-LAP- integrin interaction at the cell surface and LTBP anchorage in the ECM is responsible for the release of active TGF-β1 from the latent TGF-β1 complex [203][204][205]. It should be noted that the RGD sequence is not present in β2-LAP, and therefore, the latent TGF-β2 complex may not be activated by the interaction with integrins.…”

Single-molecule force spectroscopy of protein-membrane interactions

“…Protein-membrane interactions play pivotal roles in numerous biological processes, including membrane protein folding (Yu et al, 2017;Popot and Engelman, 2016;Min et al, 2015), lipid metabolism and transport (Giordano et al, 2013;Reinisch and De Camilli, 2016;Hammond and Balla, 2015;Wong et al, 2017), membrane trafficking (Zhou et al, 2017;Pérez-Lara et al, 2016;Wu et al, 2017;Hurley, 2006;Shen et al, 2012;McMahon and Gallop, 2005), signal transduction (Dong et al, 2017;Aggarwal and Ha, 2016;Lemmon, 2008;Das et al, 2015), and cell motility (Wang and Ha, 2013;Tsujita and Itoh, 2015). Studying these interactions is often difficult, especially when they involve multiple intermediates, multiple ligands, mechanical force, large energy changes, or protein aggregation (Dong et al, 2017;Pérez-Lara et al, 2016;Arauz et al, 2016).…”

“…Studying these interactions is often difficult, especially when they involve multiple intermediates, multiple ligands, mechanical force, large energy changes, or protein aggregation (Dong et al, 2017;Pérez-Lara et al, 2016;Arauz et al, 2016). Traditional experimental approaches based on an ensemble of protein molecules often fail to reveal the intermediates, energetics, and kinetics of protein-membrane binding, due to difficulties in synchronizing the reactions and in applying force to proteins or membranes (Zhang et al, 2013).…”