Biology subjects

Baker, K. B.

Publications and source records attributed to Baker, K. B..

7 recordsLinked to original sources

bioRxiv2026

Talin controls the spatial distribution of vinculin tension in focal adhesions

Cells transmit force between the extracellular matrix and the actin cytoskeleton through integrin adhesion complexes centred on talin and vinculin. Vinculin binds talin through -helical vinculin-binding sites (VBS) that are exposed when talin rod domains unfold under force. Dissecting the significance of this interaction has relied heavily on the A50I mutation in vinculin, which has been widely used as a talin-binding-null mutant. Here we show that although the A50I mutation abolishes binding to the -catenin VBS, it retains nanomolar-affinity binding to multiple talin VBS. We therefore designed an improved mutant, I12K/A50I, that eliminates this residual talin binding. Biochemical assays and single-molecule stretching experiments demonstrate that I12K/A50I VD1 fails to bind talin even when VBS are exposed by force. Using vinculin tension and conformation sensors, we show that talin binding is required for efficient recruitment of vinculin to focal adhesions and for establishing spatial gradients of vinculin tension. However, vinculin can still experience mechanical load in the absence of talin binding. These results demonstrate that A50I is not a talin-binding-null and reveal that, while talin is not required for vinculin loading, it is essential for organising the spatial distribution of mechanical load within adhesion complexes.

cell biology↗

bioRxiv2026

An Aggregation Prone Region (APR) in talin controls talin self-interactions to regulate integrin adhesion complex dynamics

The tight regulation of the integrin family of extracellular matrix (ECM) receptors is essential for the coordination of most cellular processes. Talin regulates integrin function by binding to the cytoplasmic tail of the integrin beta subunit. Two integrin-binding sites (IBS) in talin have been reported, one in the talin head domain (IBS1), and a second in the C-terminal rod region of talin (IBS2), mapped to the R11-R12 domains. Whilst the structural details of integrin binding to IBS1 are well understood, IBS2s mode of binding integrin is less clear, and the biochemical details of this site have been elusive. Here we report that talin R11 contains a cryptic high affinity talin-binding site. We show that mechanical unfolding of R11 exposes an Aggregation Prone Region (APR) in Helix50 that oligomerizes with other talin R11s. Our data support a model whereby the process of mechanically unfolding one R11, exposes and maintains the APR in a high affinity conformation that drives unfolding of other R11 domains and oligomerisation. Atomic Force Microscopy confirms that the APR region alone forms micron long amyloid-like fibres, via a beta-sheet amyloid arrangement which can be abolished using a canonical "gatekeeper" point mutation, V2078K, that prevents APR interactions. Introducing this gatekeeper mutant in talin eliminates recruitment of talin IBS2 to integrin adhesion sites. The APR region in talin overlaps with a vinculin-binding site in Helix50, and we show a novel role for vinculin as a mechano-chaperone for talin, able to resolve the talin large species by binding to the VBS in Helix50. In light of this new information, we propose that the ability of R11-R12 to target to integrin adhesion complexes and enhance integrin activation can be better explained by a model where functional aggregation of talin serves to recruit and activate more talin molecules at the adhesion site leading to enhanced integrin activation. Whilst further work is required to fully exclude integrin binding to R11 we suggest that the name IBS2 might be a misnomer and propose the name Aggregation Prone Region 1 (APR1) for this talin oligomerisation motif.

cell biology↗

bioRxiv2023

The mechanical response of vinculin

Vinculin is a mechanosensitive adapter protein that links the actin network to cell-extracellular matrix adhesions and cell-cell adhesions. It is perhaps the best characterized mechanoeffector, as it is recruited to sites of adhesion in response to force on the mechanotransducers talin and alpha-catenin. Here we examined the mechanical properties of vinculin to assess its potential role as a mechanotransducer. We find that at physiological loading rates, the structural domains of vinculin unfold at forces in the 5-15 pN range and rapidly refold when forces are reduced back to 1 pN. Thus, vinculin domains also have the potential to act as force dependent molecular switches, akin to those in talin and alpha-catenin. As with the force dependent switches in talin, the unfolding of these domains in vinculin introduces large extension changes in the vinculin cytoskeletal linkage up to 150 nm with 20-30 nm steps of unfolding. Modelling of the tension-dependent interactions of the unstructured vinculin linker region with a model protein containing two SH3 domains indicated that even unstructured protein regions can mediate force-dependent interactions with ligands, where the binding of a dual-SH3 model protein is predicted to be significantly suppressed by forces greater than 10 pN. Together, these findings suggest that vinculin has a complex mechanical response with force-dependent interaction sites, suggesting it also acts as a mechanotransducer, recruiting partners in response to force.

biophysics↗

bioRxiv2022

Next generation protein-based materials capture and preserve projectiles from supersonic impacts

Extreme energy dissipating materials are essential for a range of applications. The military and police force require ballistic armour to ensure the safety of their personnel, while the aerospace industry requires materials that enable the capture, preservation and study of hypervelocity projectiles. However, current industry standards display at least one inherent limitation. To resolve these limitations we have turned to nature, utilising proteins that have evolved over millennia to enable effective energy dissipation. Specifically, a recombinant form of the mechanosensitive protein talin was incorporated into a monomeric unit and crosslinked, resulting in the production of the first reported example of a talin shock absorbing material (TSAM). When subjected to 1.5 km/s supersonic shots, TSAMs were shown not only to absorb the impact, but to capture/preserve the projectile, making TSAMs the first reported protein material to achieve this.

synthetic biology↗

bioRxiv2021

Cellular-resolution monitoring of ischemic stroke pathologies in the rat cortex

Stroke is a leading cause of disability in the Western world. Current post-stroke rehabilitation treatments are only effective in approximately half of the patients. Therefore, there is a pressing clinical need for developing new rehabilitation approaches for enhancing the recovery process, which requires the use of appropriate animal models. Here we study the activity patterns of multiple cortical regions in the rat brain using two-photon microscopy. We longitudinally recorded the fluorescence signal from thousands of neurons labeled with a genetically-encoded calcium indicator before and after an ischemic stroke injury, and found substantial functional changes across motor, somatosensory, and visual cortical regions during the post-stroke cortical reorganization period. We show that a stroke injury in the primary motor cortex has an effect on the activity patterns of neurons not only in the motor and somatosensory cortices, but also in the more distant visual cortex, and that these changes include modified firing rates and kinetics of neuronal activity patterns in response to a sensory stimulus. Changes in neuronal population activity provided animal-specific, circuit-level information on the poststroke cortical reorganization process, which may be essential for evaluating the efficacy of new approaches for enhancing the recovery process.

neuroscience↗

bioRxiv2021

Force-dependent interactions between talin and full-length vinculin

Talin and vinculin are part of a multi-component system involved in mechanosensing in cell-matrix adhesions. Both exist in auto-inhibited forms, and activation of vinculin requires binding to mechanically activated talin, yet how forces affect talins interaction with vinculin has not been investigated. Here by quantifying the force-dependent talin-vinculin interactions and kinetics using single-molecule analysis, we show that mechanical exposure of a single vinculin binding site (VBS) in talin is sufficient to relieve the autoinhibition of vinculin resulting in high-affinity binding. We provide evidence that the vinculin undergoes dynamic fluctuations between an auto-inhibited closed conformation and an open conformation that is stabilized upon binding to the VBS. Furthermore, we discover an additional level of regulation in which the mechanically exposed VBS binds vinculin significantly more tightly than the isolated VBS alone. Molecular dynamics simulations reveal the basis of this new regulatory mechanism, identifying a sensitive force-dependent change in the conformation of an exposed VBS that modulates binding. Together, these results provide a comprehensive understanding of how the interplay between force and autoinhibition provides exquisite complexity within this major mechanosensing axis.

biophysics↗

bioRxiv2018

TorC2 dependent phosphorylation modulates calcium regulation of fission yeast myosin.

All cells have the ability to respond to changes in their environment. Signalling networks modulate cytoskeleton and membrane organisation to impact cell cycle progression, polarised cell growth and multicellular development according to the environmental setting. Using diverse in vitro, in vivo and single molecule techniques we have explored the role of myosin-1 signalling in regulating endocytosis during both mitotic and meiotic cell cycles. We have established that a conserved serine within the neck region of the sole fission yeast myosin-1 is phosphorylated in a TORC2 dependent manner to modulate myosin function. Myo1 neck phosphorylation brings about a change in the conformation of the neck region and modifies its interaction with calmodulins, Myo1 dynamics at endocytic foci, and promotes calcium dependent switching between different calmodulin light chains. These data provide insight into a novel mechanism by which myosin neck phosphorylation modulates acto-myosin dynamics to control polarised cell growth in response to mitotic and meiotic cell-cycle progression and the cellular environment.

cell biology↗