Develop Tandem Tension Sensor to Gauge Integrin-Transmitted Molecular Forces.

DNA-based tension sensors have innovated the imaging and calibration of mechanosensitive receptor-transmitted molecular forces, such as integrin tensions. However, these sensors mainly serve as binary reporters, only indicating if molecular forces exceed one predefined threshold. Here, we have developed tandem tension sensor (TTS), which comprises two consecutive force-sensing units, each with unique force detection thresholds and distinct fluorescence spectra, thereby enabling the quantification of molecular forces with dual reference levels. With TTS, we revealed that vinculin is not required for transmitting integrin tensions at approximately 10 pN (piconewtons) but is essential for elevating integrin tensions beyond 20 pN in focal adhesions (FAs). Such high tensions have emerged during the early stage of FA formation. TTS also successfully detected changes in integrin tensions in response to disrupted actin formation, inhibited myosin activity, and tuned substrate elasticity. We also applied TTS to examine integrin tensions in platelets and revealed two force regimes, with integrin tensions surpassing 20 pN at cell central regions and 13-20 pN integrin tensions at the cell edge. Overall, TTS, especially the construct consisting of a hairpin DNA (13 pN opening force) and a shearing DNA (20 pN opening force), stands as a valuable tool for the quantification of receptor-transmitted molecular forces within living cells.

RBM10 loss induces aberrant splicing of cytoskeletal and extracellular matrix mRNAs and promotes metastatic fitness.

RBM10 modulates transcriptome-wide cassette exon splicing. Loss-of-function RBM10 mutations are enriched in thyroid cancers with distant metastases. Analysis of transcriptomes and genes mis-spliced by RBM10 loss showed pro-migratory and RHO/RAC signaling signatures. RBM10 loss increases cell velocity. Cytoskeletal and ECM transcripts subject to exon-inclusion events included vinculin (VCL), tenascin C (TNC) and CD44. Knockdown of the VCL exon inclusion transcript in RBM10-null cells reduced cell velocity, whereas knockdown of TNC and CD44 exon-inclusion isoforms reduced invasiveness. RAC1-GTP levels were increased in RBM10-null cells. Mouse Hras G12V /Rbm1O KO thyrocytes develop metastases that are reversed by RBM10 or by combined knockdown of VCL, CD44 and TNC inclusion isoforms. Thus, RBM10 loss generates exon inclusions in transcripts regulating ECM-cytoskeletal interactions, leading to RAC1 activation and metastatic competency. Moreover, a CRISPR-Cas9 screen for synthetic lethality with RBM10 loss identified NFkB effectors as central to viability, providing a therapeutic target for these lethal thyroid cancers.

DNA-based ForceChrono probes for deciphering single-molecule force dynamics in living cells.

Understanding cellular force transmission dynamics is crucial in mechanobiology. We developed the DNA-based ForceChrono probe to measure force magnitude, duration, and loading rates at the single-molecule level within living cells. The ForceChrono probe circumvents the limitations of in vitro single-molecule force spectroscopy by enabling direct measurements within the dynamic cellular environment. Our findings reveal integrin force loading rates of 0.5-2 pN/s and durations ranging from tens of seconds in nascent adhesions to approximately 100 s in mature focal adhesions. The probe's robust and reversible design allows for continuous monitoring of these dynamic changes as cells undergo morphological transformations. Additionally, by analyzing how mutations, deletions, or pharmacological interventions affect these parameters, we can deduce the functional roles of specific proteins or domains in cellular mechanotransduction. The ForceChrono probe provides detailed insights into the dynamics of mechanical forces, advancing our understanding of cellular mechanics and the molecular mechanisms of mechanotransduction.

The TRIP6/LATS1 complex constitutes the tension sensor of α-catenin/vinculin at both bicellular and tricellular junctions.

Cell-cell mechanotransduction regulates tissue development and homeostasis. α-catenin, the core component of adherens junctions, functions as a tension sensor and transducer by recruiting vinculin and transducing signals that influence cell behaviors. α-catenin/vinculin complex-mediated mechanotransduction regulates multiple pathways, such as Hippo pathway. However, their associations with the α-catenin-based tension sensors at cell junctions are still not fully addressed. Here, we uncovered the TRIP6/LATS1 complex co-localizes with α-catenin/vinculin at both bicellular junctions (BCJs) and tricellular junctions (TCJs). The localization of TRIP6/LATS1 complex to both TCJs and BCJs requires ROCK1 and α-catenin. Treatment by cytochalasin B, Y-27632 and blebbistatin all impaired the BCJ and TCJ junctional localization of TRIP6/LATS1, indicating that the junctional localization of TRIP6/LATS1 is mechanosensitive. The α-catenin/vinculin/TRIP6/LATS1 complex strongly localized to TCJs and exhibited a discontinuous button-like pattern on BCJs. Additionally, we developed and validated an α-catenin/vinculin BiFC-based mechanosensor that co-localizes with TRIP6/LATS1 at BCJs and TCJs. The mechanosensor exhibited a discontinuous distribution and motile signals at BCJs. Overall, our study revealed that TRIP6 and LATS1 are novel compositions of the tension sensor, together with the core complex of α-catenin/vinculin, at both the BCJs and TCJs.

Effect of Focal Adhesion Kinase and Vinculin Expression on Migration Parameters of Normal and Tumor Epitheliocytes.

Focal adhesions (FAs) are mechanosensory structures that transform physical stimuli into chemical signals guiding cell migration. Comprehensive studies postulate correlation between the FA parameters and cell motility metrics for individual migrating cells. However, which properties of the FAs are critical for epithelial cell motility in a monolayer remains poorly elucidated. We used high-throughput microscopy to describe relationship between the FA parameters and cell migration in immortalized epithelial keratinocytes (HaCaT) and lung carcinoma cells (A549) with depleted or inhibited vinculin and focal adhesion kinase (FAK) FA proteins. To evaluate relationship between the FA morphology and cell migration, we used substrates with varying stiffness in the model of wound healing. Cells cultivated on fibronectin had the highest FA area values, migration rate, and upregulated expression of FAK and vinculin mRNAs, while the smallest FA area and slower migration rate to the wound were specific to cells cultivated on glass. Suppression of vinculin expression in both normal and tumor cells caused decrease of the FA size and fluorescence intensity but did not affect cell migration into the wound. In contrast, downregulation or inactivation of FAK did not affect the FA size but significantly slowed down the wound closure rate by both HaCaT and A549 cell lines. We also showed that the FAK knockdown results in the FA lifetime decrease for the cells cultivated both on glass and fibronectin. Our data indicate that the FA lifetime is the most important parameter defining migration of epithelial cells in a monolayer. The observed change in the cell migration rate in a monolayer caused by changes in expression/activation of FAK kinase makes FAK a promising target for anticancer therapy of lung carcinoma.

Characterization of early and late events of adherens junction assembly.

Cadherins are transmembrane adhesion receptors. Cadherin ectodomains form adhesive 2D clusters through cooperative trans and cis interactions, whereas its intracellular region interacts with specific cytosolic proteins, termed catenins, to anchor the cadherin-catenin complex (CCC) to the actin cytoskeleton. How these two types of interactions are coordinated in the formation of specialized cell-cell adhesions, adherens junctions (AJ), remains unclear. We focus here on the role of the actin-binding domain of α-catenin (αABD) by showing that the interaction of αABD with actin generates actin-bound CCC oligomers (CCC/actin strands) incorporating up to six CCCs. The strands are primarily formed on the actin-rich cell protrusions. Once in cell-cell interface, the strands become involved in cadherin ectodomain clustering. Such combination of the extracellular and intracellular oligomerizations gives rise to the composite oligomers, trans CCC/actin clusters. To mature, these clusters then rearrange their actin filaments using several redundant pathways, two of which are characterized here: one depends on the α-catenin-associated protein, vinculin and the second one depends on the unstructured C-terminus of αABD. Thus, AJ assembly proceeds through spontaneous formation of trans CCC/actin clusters and their successive reorganization.

Cell-Material Interplay in Focal Adhesion Points.

The complex interplay between cells and materials is a key focus of this research, aiming to develop optimal scaffolds for regenerative medicine. The need for tissue regeneration underscores understanding cellular behavior on scaffolds, especially cell adhesion to polymer fibers forming focal adhesions. Key proteins, paxillin and vinculin, regulate cell signaling, migration, and mechanotransduction in response to the extracellular environment. This study utilizes advanced microscopy, specifically the AiryScan technique, along with advanced image analysis employing the Density-Based Spatial Clustering of Applications with Noise (DBSCAN) cluster algorithm, to investigate protein distribution during osteoblast cell adhesion to polymer fibers and glass substrates. During cell attachment to both glass and polymer fibers, a noticeable shift in the local maxima of paxillin and vinculin signals is observed at the adhesion sites. The focal adhesion sites on polymer fibers are smaller and elliptical but exhibit higher protein density than on the typical glass surface. The characteristics of focal adhesions, influenced by paxillin and vinculin, such as size and density, can potentially reflect the strength and stability of cell adhesion. Efficient adhesion correlates with well-organized, larger focal adhesions characterized by increased accumulation of paxillin and vinculin. These findings offer promising implications for enhancing scaffold design, evaluating adhesion to various substrates, and refining cellular interactions in biomedical applications.

Inhibition of vinculin activity has an adverse effect on porcine ovarian cells.

The existing knowledge of the involvement of vinculin (VCL) in the control of ovarian cell functions is insufficient. To understand the role of VCL in the control of basic porcine ovarian granulosa cell functions, we decreased VCL activity by small interfering RNA (VCL siRNA). The expression of VCL, accumulation of VCL protein, cell viability, proliferation (accumulation of PCNA and cyclin B1), proportion of proliferative active cells, apoptosis (accumulation of bax, caspase 3, p53, antiapoptotic marker bcl2, and bax/bcl-2 ratio), DNA fragmentation, and release of steroid hormones and IGF-I were analyzed by RT‒qPCR, Trypan blue exclusion test, quantitative immunocytochemistry, XTT assay, TUNEL assay, and ELISA. The suppression of VCL activity inhibited cell viability, the accumulation of the proliferation-related proteins PCNA and cyclin B1, the antiapoptotic protein bcl2, and the proportion of proliferative active cells. Moreover, VCL siRNA inhibited the release of progesterone, estradiol, and IGF-1. VCL siRNA increased the proportion of the proapoptotic proteins bax, caspase 3, p53, the proportion of DNA fragmented cells, and stimulated testosterone release. Taken together, the present study is the first evidence that inhibition of VCL suppresses porcine granulosa cell functions. Moreover, the results suggest that VCL can be a potent physiological stimulator of ovarian functions.

Role of the Ste20-like kinase SLK in podocyte adhesion.

SLK controls the cytoskeleton, cell adhesion, and migration. Podocyte-specific deletion of SLK in mice leads to podocyte injury as mice age and exacerbates injury in experimental focal segment glomerulosclerosis (FSGS; adriamycin nephrosis). We hypothesized that adhesion proteins may be substrates of SLK. In adriamycin nephrosis, podocyte ultrastructural injury was exaggerated by SLK deletion. Analysis of a protein kinase phosphorylation site dataset showed that podocyte adhesion proteins-paxillin, vinculin, and talin-1 may be potential SLK substrates. In cultured podocytes, deletion of SLK increased adhesion to collagen. Analysis of paxillin, vinculin, and talin-1 showed that SLK deletion reduced focal adhesion complexes (FACs) containing these proteins mainly in adriamycin-induced injury; there was no change in FAC turnover (focal adhesion kinase Y397 phosphorylation). In podocytes, paxillin S250 showed basal phosphorylation that was slightly enhanced by SLK; however, SLK did not phosphorylate talin-1. In adriamycin nephrosis, SLK deletion did not alter glomerular expression/localization of talin-1 and vinculin, but increased focal adhesion kinase phosphorylation modestly. Therefore, SLK decreases podocyte adhesion, but FAC proteins in podocytes are not major substrates of SLK in health and disease.

KANK1 shapes focal adhesions by orchestrating protein binding, mechanical force sensing, and phase separation.

Focal adhesions (FAs) are dynamic protein assemblies that connect cytoskeletons to the extracellular matrix and are crucial for cell adhesion and migration. KANKs are scaffold proteins that encircle FAs and act as key regulators of FA dynamics, but the molecular mechanism underlying their specified localization and functions remains poorly understood. Here, we determine the KANK1 structures in complex with talin and liprin-ß, respectively. These structures, combined with our biochemical and cellular analyses, demonstrate how KANK1 scaffolds the FA core and associated proteins to modulate the FA shape in response to mechanical force. Additionally, we find that KANK1 undergoes liquid-liquid phase separation (LLPS), which is important for its localization at the FA edge and cytoskeleton connections to FAs. Our findings not only indicate the molecular basis of KANKs in bridging the core and periphery of FAs but also provide insights into the LLPS-mediated dynamic regulation of FA morphology.

Get a grip: Podosomes as potential players in phagocytosis.

Podosomes have been known for several decades as micron-sized, F-actin-rich structures that play a pivotal role in cell migration and invasion, as they are able to mediate both cell-matrix attachment as well as extracellular matrix degradation. Particularly in monocytic cells, podosomes have been shown to fulfill a variety of additional functions such as sensing of substrate rigidity and topography, or cell-cell fusion. Increasing evidence now points to the involvement of podosome-like structures also during phagocytosis by immune cells such as macrophages, dendritic cells, and neutrophils. Here, we compare the different cell models and experimental set ups where "phagocytic podosomes" have been described. We also discuss the composition and architecture of these structures, their potential involvement in mechanosensing and particle disruption, as well as the pros and cons for addressing them as bona fide podosomes.

Heart Failure with Recovered Ejection Fraction in Patients with Vinculin Loss-of-function Variants.

Predictors of myocardial recovery in heart failure (HF) are poorly understood. We explored if vinculin (VCL) variants are associated with myocardial recovery in dilated cardiomyopathy (DCM). Six infants with DCM with a VCL loss-of-function (LOF) variant were identified. Median age at diagnosis was 2 months, median LV ejection fraction was 24%, and median LV end-diastolic diameter z-score was 10.8. All patients received HF medications. Five patients (83%) showed normalization of LV function at a median age of 2.7 years. One patient progressed to end-stage HF requiring heart transplant. This case series identified a unique phenotype of HF with reduced ejection fraction at presentation that evolved to HF with recovered EF in over 80% of infant DCM cases with LOF VCL variants. These findings have prognostic implications for counseling and management of VCL-associated DCM and highlight a possible genetic basis for HF with recovered ejection fraction.

High Serum VE-Cadherin and Vinculin Concentrations Are Markers of the Disruption of Vascular Integrity during Type B Acute Aortic Dissection.

BACKGROUND: In the present study, we measured the serum vascular endothelial cadherin (VEC) and vinculin (Vcn) concentrations in patients with type B acute aortic dissection (TBAD) to evaluate their diagnostic value for this condition. METHODS: A total of 100 patients with TBAD and 90 matched controls were included in the study. The serum concentrations of VEC and Vcn were measured using enzyme-linked immunosorbent assays. RESULTS: The serum VEC and Vcn concentrations were significantly higher in participants with TBAD than in healthy controls. Compared with patients with acute myocardial infarction (AMI), the serum concentrations of VEC and Vcn in patients with TBAD were higher, and the Vcn showed significant difference, with statistical significance. Receiver operating characteristic analysis generated areas under the curves for VEC and Vcn that were diagnostic for TBAD (0.599 and 0.655, respectively). The optimal cut-off values were 3.975 ng/µL and 128.1 pg/mL, the sensitivities were 43.0% and 35.0%, and the specificities were 73.3% and 90.0%, respectively. In addition, the use of a combination of serum VEC and Vcn increased the AUC to 0.661, with a sensitivity of 33.0% and a specificity of 93.33%. A high serum Vcn concentration was associated with a higher risk of visceral malperfusion in participants with TBAD (odds ratio (OR) = 1.007, 95% confidence interval [CI]: 1.001-1.013, p = 0.014). In participants with refractory pain, the adjusted OR for the serum VEC concentration increased to 1.172 (95% CI: 1.010-1.361; p = 0.036), compared with participants without refractory pain. CONCLUSION: This study is the first to show the diagnostic value of serum VEC and Vcn for AAD and their relationships with the clinical characteristics of patients with TBAD. Thus, VEC and Vcn are potential serum markers of TBAD.

Förster resonance energy transfer efficiency measurements on vinculin tension sensors at focal adhesions using a simple and cost-effective setup.

Significance: Forces inside cells play a fundamental role in tissue growth, affecting important processes such as cancer cell migration or tissue repair after injury. Förster resonance energy transfer (FRET)-based tension sensors are a remarkable tool for studying these forces and should be made easier to use. Aim: We prove that absolute FRET efficiency can be measured on a simple setup, an order of magnitude more cost-effective than a standard FRET microscopy setup, by applying it to vinculin tension sensors (VinTS) at the focal adhesions of live CHO-K1 cells. Approach: Our setup located at Université Paris-Saclay acquires donor and acceptor fluorescence in parallel on two low-cost CMOS cameras and uses two LEDs for rapid switching of the excitation wavelength at a reduced cost. The calibration required to extract FRET efficiency was achieved using a single construct (TSMod). FRET efficiencies were measured for VinTS and the tail-less control VinTL, lacking the actin-binding domain of vinculin. Measurements were confirmed on the same cell type using a more standard intensity-based setup located at Rutgers University. Results: The average FRET efficiency of VinTS (22.0%±4%) over more than 10,000 focal adhesions is significantly lower (p<10-6) than that of VinTL (30.4%±5%), our control that is insensitive to force, in agreement with the force exerted on vinculin at focal adhesions. Attachment of the CHO-K1 cells on fibronectin decreases FRET efficiency, thus increasing the force, compared with poly-lysine. FRET efficiency for the VinTL control is consistent with all measurements currently available in the literature, confirming the validity of our measurements and hence of our simpler setup. Conclusions: Force measurements, resolved spatially inside a cell, can be achieved using FRET-based tension sensors with a cost effective intensity-based setup. This will facilitate combining FRET with techniques for applying controlled forces such as optical tweezers.

Super-Resolution Spinning-Disk Confocal Microscopy Using Optical Photon Reassignment (SoRa) to Visualize the Actin Cytoskeleton in Macrophages.

Macrophages are motile, morphologically plastic cells that undergo substantial cytoskeletal remodeling to facilitate their roles in innate and adaptive immunity. Macrophages are adept at producing a variety of specialized actin-driven structures and processes including the formation of podosomes and the ability to engulf particles through phagocytosis and sample large amounts of extracellular fluid via micropinocytosis. Here, we describe techniques for immunostaining proteins and transfecting macrophages with plasmids for use with either fixed or live cell imaging. Furthermore, we discuss the use of spinning-disk super-resolution using optical reassignment to generate sub-diffraction limited structures using this type of confocal microscope.

Development of a Prediction Model for Short-Term Remission of Patients with Crohn's Disease Treated with Anti-TNF Drugs.

Therapy with anti-tumor necrosis factor (TNF) has dramatically changed the natural history of Crohn's disease (CD). However, these drugs are not without adverse events, and up to 40% of patients could lose efficacy in the long term. We aimed to identify reliable markers of response to anti-TNF drugs in patients with CD. A consecutive cohort of 113 anti-TNF naive patients with CD was stratified according to clinical response as short-term remission (STR) or non-STR (NSTR) at 12 weeks of treatment. We compared the protein expression profiles of plasma samples in a subset of patients from both groups prior to anti-TNF therapy by SWATH proteomics. We identified 18 differentially expressed proteins (p ≤ 0.01, fold change ≥ 2.4) involved in the organization of the cytoskeleton and cell junction, hemostasis/platelet function, carbohydrate metabolism, and immune response as candidate biomarkers of STR. Among them, vinculin was one of the most deregulated proteins (p < 0.001), whose differential expression was confirmed by ELISA (p = 0.054). In the multivariate analysis, plasma vinculin levels along with basal CD Activity Index, corticosteroids induction, and bowel resection were factors predicting NSTR.

Vinculin Y822 is an important determinant of ligand binding.

Vinculin is an actin-binding protein present at cell-matrix and cell-cell adhesions, which plays a critical role in bearing force experienced by cells and dissipating it onto the cytoskeleton. Recently, we identified a key tyrosine residue, Y822, whose phosphorylation plays a critical role in force transmission at cell-cell adhesions. The role of Y822 in human cancer remains unknown, even though Y822 is mutated to Y822C in uterine cancers. Here, we investigated the effect of this amino acid substitution and that of a phosphodeficient Y822F vinculin in cancer cells. We observed that the presence of the Y822C mutation led to cells that proliferate and migrate more rapidly and contained smaller focal adhesions when compared to cells with wild-type vinculin. In contrast, the presence of the Y822F mutation led to highly spread cells with larger focal adhesions and increased contractility. Furthermore, we provide evidence that Y822C vinculin forms a disulfide bond with paxillin, accounting for some of the elevated phosphorylated paxillin recruitment. Taken together, these data suggest that vinculin Y822 modulates the recruitment of ligands.

An ensemble of cadherin-catenin-vinculin complex employs vinculin as the major F-actin binding mode.

The cell-cell adhesion cadherin-catenin complexes recruit vinculin to the adherens junction (AJ) to modulate the mechanical couplings between neighboring cells. However, it is unclear how vinculin influences the AJ structure and function. Here, we identified two patches of salt bridges that lock vinculin in the head-tail autoinhibited conformation and reconstituted the full-length vinculin activation mimetics bound to the cadherin-catenin complex. The cadherin-catenin-vinculin complex contains multiple disordered linkers and is highly dynamic, which poses a challenge for structural studies. We determined the ensemble conformation of this complex using small-angle x-ray and selective deuteration/contrast variation small-angle neutron scattering. In the complex, both α-catenin and vinculin adopt an ensemble of flexible conformations, but vinculin has fully open conformations with the vinculin head and actin-binding tail domains well separated from each other. F-actin binding experiments show that the cadherin-catenin-vinculin complex binds and bundles F-actin. However, when the vinculin actin-binding domain is removed from the complex, only a minor fraction of the complex binds to F-actin. The results show that the dynamic cadherin-catenin-vinculin complex employs vinculin as the primary F-actin binding mode to strengthen AJ-cytoskeleton interactions.

ConFERMing the role of talin in integrin activation and mechanosignaling.

Talin (herein referring to the talin-1 form), is a cytoskeletal adapter protein that binds integrin receptors and F-actin, and is a key factor in the formation and regulation of integrin-dependent cell-matrix adhesions. Talin forms the mechanical link between the cytoplasmic domain of integrins and the actin cytoskeleton. Through this linkage, talin is at the origin of mechanosignaling occurring at the plasma membrane-cytoskeleton interface. Despite its central position, talin is not able to fulfill its tasks alone, but requires help from kindlin and paxillin to detect and transform the mechanical tension along the integrin-talin-F-actin axis into intracellular signaling. The talin head forms a classical FERM domain, which is required to bind and regulate the conformation of the integrin receptor, as well as to induce intracellular force sensing. The FERM domain allows the strategic positioning of protein-protein and protein-lipid interfaces, including the membrane-binding and integrin affinity-regulating F1 loop, as well as the interaction with lipid-anchored Rap1 (Rap1a and Rap1b in mammals) GTPase. Here, we summarize the structural and regulatory features of talin and explain how it regulates cell adhesion and force transmission, as well as intracellular signaling at integrin-containing cell-matrix attachment sites.

Shigella IpaA mediates actin bundling through diffusible vinculin oligomers with activation imprint.

Upon activation, vinculin reinforces cytoskeletal anchorage during cell adhesion. Activating ligands classically disrupt intramolecular interactions between the vinculin head and tail domains that bind to actin filaments. Here, we show that Shigella IpaA triggers major allosteric changes in the head domain, leading to vinculin homo-oligomerization. Through the cooperative binding of its three vinculin-binding sites (VBSs), IpaA induces a striking reorientation of the D1 and D2 head subdomains associated with vinculin oligomerization. IpaA thus acts as a catalyst producing vinculin clusters that bundle actin at a distance from the activation site and trigger the formation of highly stable adhesions resisting the action of actin relaxing drugs. Unlike canonical activation, vinculin homo-oligomers induced by IpaA appear to keep a persistent imprint of the activated state in addition to their bundling activity, accounting for stable cell adhesion independent of force transduction and relevant to bacterial invasion.