Talin-vinculin precomplex drives adhesion maturation by accelerated force transmission and vinculin recruitment

Abstract

Talin, vinculin, and paxillin are mechanosensitive proteins that are recruited early to nascent integrin-based adhesions (NAs). Using machine learning, high-resolution traction force microscopy, single-particle-tracking and fluorescence fluctuation time-series analysis, we find that, only in the NAs that eventually mature to focal adhesions, all three molecules are recruited concurrently and in synchrony with force onset. Thereafter, vinculin assembles at ~5 fold higher rates than in non-maturing NAs. We identify a domain in talin, R8, which exposes a vinculinbinding-site (VBS) without requiring tension. Stabilizing this domain via mutation lowers tensionfree vinculin binding in conjunction with talin, impairs maturation of NAs, and reduces the rate of additional vinculin recruitment after force onset. Taken together, our data show that talin forms a complex with vinculin, before association with integrins, which is essential for NA maturation by talin's effective unfolding and exposure of additional VBSs that induce fast force growth and further vinculin binding. Cell-matrix adhesions are multi-molecular complexes that link the extracellular matrix (ECM), typically via integrin transmembrane receptors, to the actin cytoskeleton. Being both a forcetransmitter and a force-sensor, cell-matrix adhesions are critical to cell morphogenesis and mechanosensation (Discher et al., 2005;Parsons et al., 2010). Indeed, in response to ECM changes, adhesions undergo constant changes in morphology and motion that involve recruitment and recycling of a large number of adhesion molecules. For example, nascent adhesions (NAs) emerge within the actin-dense cell lamellipodia and then slide in the direction opposite to the protrusion as a result of polymerization-driven flow of the actin network (Parsons et al., 2010). Many of these NAs, which are less than 0.5 µm long, and thus in a light microscope only resolved as diffraction-limited spots, turn over early; but some of them mature into longer focal complexes (FCs, >0.5 µm in length) and focal adhesions (FAs, >2 µm in length) at the lamellipodia-lamella interface (Gardel et al., 2010;Parsons et al., 2010). During this progression, NAs go through multiple decision processes regarding fate and morphology. Compared to the well-studied FAs, for which the interconnection between structure, signaling, and force transmission is largely understood (Balaban et al.

Cancer associated talin point mutations disorganise cell adhesion and migration

“…Furthermore, reduced R7 stability will likely have a knock-on effect on R8 stability which may indirectly lead to signalling defects by perturbing R8 12 . The additional actin recruitment via vinculin could have a direct effect on FA dynamics by facilitating formation of talin-vinculin pre-complexes, necessary to enable efficient adhesion maturation 50 . This could also affect actomyosin contractility and Rho/ROCK signalling, which have been shown to regulate cell proliferation 51 .…”

Cancer associated talin point mutations disorganise cell adhesion and migration

“…The additional actin recruitment via vinculin could have a direct effect on FA dynamics by facilitating formation of talin-vinculin pre-complexes, necessary to enable efficient adhesion maturation 50 . This could also affect actomyosin contractility and Rho/ROCK signalling, which have been shown to regulate cell proliferation 51 .…”

<strong>The Mechanical Basis of Memory - the MeshCODE Theory</strong>

“…It might be that the Synaptic tagging observed in synapses (Frey and Morris, 1997;Martin et al, 1997;Martin and Kosik, 2002;Kelleher et al, 2004;Sajikumar and Frey, 2004;Redondo and Morris, 2011;Nonaka et al, 2014) is actually a similar process to the contractilitydependent growth of integrin adhesion complexes seen in other cells (Vicente-Manzanares and Horwitz, 2011;Sun et al, 2016;Gauthier and Roca-Cusachs, 2018;Han et al, 2019).…”