Talin2-mediated traction force drives matrix degradation and cell invasion

Inhibition of Talin2 dedifferentiates myofibroblasts and reverses lung and kidney fibrosis

Fibrosis is involved in 45% of deaths in the United States, and no treatment exists to reverse progression of the disease. To find novel targets for fibrosis therapeutics, we developed a model for the differentiation of monocytes to myofibroblasts that allowed us to screen for proteins involved in myofibroblast differentiation. Inhibition of a novel protein target generated by our model, talin2, reduces myofibroblast-specific morphology, α-smooth muscle actin content, and collagen I content and lowers the pro-fibrotic secretome of myofibroblasts. We find that knockdown of talin2 de-differentiates myofibroblasts and reverses bleomycin-induced lung fibrosis in mice, and further that Tln2-/- mice are resistant to bleomycin-induced lung fibrosis and resistant to unilateral ureteral obstruction-induced kidney fibrosis. Talin2 inhibition is thus a potential treatment for reversing lung and kidney fibroses.

Mechanical Load-Induced Upregulation of Talin2 through Non-Canonical Deubiquitination of OTUB1 Drives Facet Joint Osteoarthritis Pathogenesis

Facet joint osteoarthritis (FJOA) is a prevalent degenerative condition in the aging population; however, the underlying pathophysiological mechanisms remain poorly understood and current therapeutic strategies remain limited to palliative pain management. In this study, novel potential therapeutic targets and prevention paradigms for FJOA are systematically explored. Proteomic screening and validation show that Talin2 is specifically upregulated in FJOA samples. Immunoprecipitation-mass spectrometry, transcriptome RNA sequencing, and bioinformatics simulation analyses, combined with in vitro and in vivo experiments, are conducted to elucidate the molecular mechanism of the role of Talin2 in FJOA. Increased expression levels of Talin2 in FJOA promote the degradation of the extracellular matrix and inhibit its synthesis. Talin2 is found to be stabilized via non-canonical deubiquitination and direct interaction with ovarian tumor domain-containing ubiquitin aldehyde-binding protein 1 (OTUB1). C-C motif ligand 2 (CCL2), an inflammatory chemoattractant, is identified to be a target gene of Talin2. Furthermore, mechanical loading potentiates the Talin2/OTUB1 interaction, resulting in the stabilization of Talin2 and enhances non-canonical deubiquitination. Therefore, Talin2 regulates CCL2 expression and promotes FJOA. Given that Talin2 is stabilized and deubiquitinated by OTUB1, especially under mechanical load, the Talin2/OTUB1 interaction may be a promising therapeutic target for FJOA.

A Review of Talin- and Integrin-Dependent Molecular Mechanisms in Cancer Invasion and Metastasis

Cancer is the second most common cause of death in the world, representing one of the main economic burdens in health care and research. The effort of research has mainly focused on limiting the growth of a localized tumor, but most recently, there has been more attention focused on restricting the spreading of the cancer via invasion and metastasis. The signaling pathways behind these two processes share many molecules with physiological pathways regulating cell adhesion and migration, and, moreover, adhesion and migration processes themselves underlie tumor potential for invasion. In this work, we reviewed the latest literature about cancer development and invasion and their regulation by cell migration- and adhesion-related proteins, with a specific focus on talins and integrins. We also summarized the most recent developments and approaches to anti-cancer therapies, concentrating on cell migration-related therapies.

Differential stiffness between brain vasculature and parenchyma promotes metastatic infiltration through vessel co-option

In brain metastasis, cancer cells remain in close contact with the existing vasculature and can use vessels as migratory paths-a process known as vessel co-option. However, the mechanisms regulating this form of migration are poorly understood. Here we use ex vivo brain slices and an organotypic in vitro model for vessel co-option to show that cancer cell invasion along brain vasculature is driven by the difference in stiffness between vessels and the brain parenchyma. Imaging analysis indicated that cells move along the basal surface of vessels by adhering to the basement membrane extracellular matrix. We further show that vessel co-option is enhanced by both the stiffness of brain vasculature, which reinforces focal adhesions through a talin-dependent mechanism, and the softness of the surrounding environment that permits cellular movement. Our work reveals a mechanosensing mechanism that guides cell migration in response to the tissue's intrinsic mechanical heterogeneity, with implications in cancer invasion and metastasis.

Intercellular nanotube-mediated mitochondrial transfer enhances T cell metabolic fitness and antitumor efficacy

Mitochondrial loss and dysfunction drive T cell exhaustion, representing major barriers to successful T cell-based immunotherapies. Here, we describe an innovative platform to supply exogenous mitochondria to T cells, overcoming these limitations. We found that bone marrow stromal cells establish nanotubular connections with T cells and leverage these intercellular highways to transplant stromal cell mitochondria into CD8+ T cells. Optimal mitochondrial transfer required Talin 2 on both donor and recipient cells. CD8+ T cells with donated mitochondria displayed enhanced mitochondrial respiration and spare respiratory capacity. When transferred into tumor-bearing hosts, these supercharged T cells expanded more robustly, infiltrated the tumor more efficiently, and exhibited fewer signs of exhaustion compared with T cells that did not take up mitochondria. As a result, mitochondria-boosted CD8+ T cells mediated superior antitumor responses, prolonging animal survival. These findings establish intercellular mitochondrial transfer as a prototype of organelle medicine, opening avenues to next-generation cell therapies.

Talin2 binds to non-muscle myosin IIa and regulates cell attachment and fibronectin secretion

Talin2 is localized to large focal adhesions and is indispensable for traction force generation, invadopodium formation, cell invasion as well as metastasis. Talin2 has a higher affinity toward β-integrin tails than talin1. Moreover, disruption of the talin2-β-integrin interaction inhibits traction force generation, invadopodium formation and cell invasion, indicating that a strong talin2-β-integrin interaction is required for talin2 to fulfill these functions. Nevertheless, the role of talin2 in mediation of these processes remains unknown. Here we show that talin2 binds to the N-terminus of non-muscle myosin IIA (NMIIA) through its F3 subdomain. Moreover, talin2 co-localizes with NMIIA at cell edges as well as at some cytoplasmic spots. Talin2 also co-localizes with cortactin, an invadopodium marker. Furthermore, overexpression of NMIIA promoted the talin2 head binding to the β1-integrin tail, whereas knockdown of NMIIA reduced fibronectin and matrix metalloproteinase secretion as well as inhibited cell attachment on fibronectin-coated substrates. These results suggest that talin2 binds to NMIIA to control the secretion of extracellular matrix proteins and this interaction modulates cell adhesion.

Membrane-induced 2D phase separation of the focal adhesion protein talin

Focal adhesions form liquid-like assemblies around activated integrin receptors at the plasma membrane. How they achieve their flexible properties is not well understood. Here, we use recombinant focal adhesion proteins to reconstitute the core structural machinery in vitro. We observe liquid-liquid phase separation of the core focal adhesion proteins talin and vinculin for a spectrum of conditions and interaction partners. Intriguingly, we show that binding to PI(4,5)P2-containing membranes triggers phase separation of these proteins on the membrane surface, which in turn induces the enrichment of integrin in the clusters. We suggest a mechanism by which 2-dimensional biomolecular condensates assemble on membranes from soluble proteins in the cytoplasm: lipid-binding triggers protein activation and thus, liquid-liquid phase separation of these membrane-bound proteins. This could explain how early focal adhesions maintain a structured and force-resistant organization into the cytoplasm, while still being highly dynamic and able to quickly assemble and disassemble.

Talin mechanotransduction in disease

Talin protein (Talin 1/2) is a mechanosensitive cytoskeleton protein. The unique structure of the Talin plays a vital role in transmitting mechanical forces. Talin proteins connect the extracellular matrix to the cytoskeleton by linking to integrins and actin, thereby mediating the conversion of mechanical signals into biochemical signals and influencing disease progression as potential diagnostic indicators, therapeutic targets, and prognostic indicators of various diseases. Most studies in recent years have confirmed that mechanical forces also have a crucial role in the development of disease, and Talin has been found to play a role in several diseases. Still, more studies need to be done on how Talin is involved in mechanical signaling in disease. This review focuses on the mechanical signaling of Talin in disease, aiming to summarize the mechanisms by which Talin plays a role in disease and to provide references for further studies.

Talin2 and KANK2 functionally interact to regulate microtubule dynamics, paclitaxel sensitivity and cell migration in the MDA-MB-435S melanoma cell line

BACKGROUND

Focal adhesions (FAs) are integrin-containing, multi-protein structures that link intracellular actin to the extracellular matrix and trigger multiple signaling pathways that control cell proliferation, differentiation, survival and motility. Microtubules (MTs) are stabilized in the vicinity of FAs through interaction with the components of the cortical microtubule stabilizing complex (CMSC). KANK (KN motif and ankyrin repeat domains) family proteins within the CMSC, KANK1 or KANK2, bind talin within FAs and thus mediate actin-MT crosstalk. We previously identified in MDA-MB-435S cells, which preferentially use integrin αVβ5 for adhesion, KANK2 as a key molecule enabling the actin-MT crosstalk. KANK2 knockdown also resulted in increased sensitivity to MT poisons, paclitaxel (PTX) and vincristine and reduced migration. Here, we aimed to analyze whether KANK1 has a similar role and to distinguish which talin isoform binds KANK2.

METHODS

The cell model consisted of human melanoma cell line MDA-MB-435S and stably transfected clone with decreased expression of integrin αV (3αV). For transient knockdown of talin1, talin2, KANK1 or KANK2 we used gene-specific siRNAs transfection. Using previously standardized protocol we isolated integrin adhesion complexes. SDS-PAGE and Western blot was used for protein expression analysis. The immunofluorescence analysis and live cell imaging was done using confocal microscopy. Cell migration was analyzed with Transwell Cell Culture Inserts. Statistical analysis using GraphPad Software consisted of either one-way analysis of variance (ANOVA), unpaired Student's t-test or two-way ANOVA analysis.

RESULTS

We show that KANK1 is not a part of the CMSC associated with integrin αVβ5 FAs and its knockdown did not affect the velocity of MT growth or cell sensitivity to PTX. The talin2 knockdown mimicked KANK2 knockdown i.e. led to the perturbation of actin-MT crosstalk, which is indicated by the increased velocity of MT growth and increased sensitivity to PTX and also reduced migration.

CONCLUSION

We conclude that KANK2 functionally interacts with talin2 and that the mechanism of increased sensitivity to PTX involves changes in microtubule dynamics. These data elucidate a cell-type-specific role of talin2 and KANK2 isoforms and we propose that talin2 and KANK2 are therefore potential therapeutic targets for improved cancer therapy.

RAD-TGTs: high-throughput measurement of cellular mechanotype via rupture and delivery of DNA tension probes

Mechanical forces drive critical cellular processes that are reflected in mechanical phenotypes, or mechanotypes, of cells and their microenvironment. We present here "Rupture And Deliver" Tension Gauge Tethers (RAD-TGTs) in which flow cytometry is used to record the mechanical history of thousands of cells exerting forces on their surroundings via their propensity to rupture immobilized DNA duplex tension probes. We demonstrate that RAD-TGTs recapitulate prior DNA tension probe studies while also yielding a gain of fluorescence in the force-generating cell that is detectable by flow cytometry. Furthermore, the rupture propensity is altered following disruption of the cytoskeleton using drugs or CRISPR-knockout of mechanosensing proteins. Importantly, RAD-TGTs can differentiate distinct mechanotypes among mixed populations of cells. We also establish oligo rupture and delivery can be measured via DNA sequencing. RAD-TGTs provide a facile and powerful assay to enable high-throughput mechanotype profiling, which could find various applications, for example, in combination with CRISPR screens and -omics analysis.

[Expression of miR-4324 and its targeted gene Talin2 in breast cancer]

OBJECTIVE

To investigate the regulatory effect of miR-4324 on ankyrin 2(Talin2) expression and biological behaviors of breast cancer cells and the clinical implications of changes in miR-4324 and Talin2 expressions in breast cancer.

METHODS

In breast cancer and adjacent tissues, the expressions of Talin2 and miR-4324 were examined with immunohistochemistry and qRT-PCR, respectively and the association of Talin2 expression levels with the prognosis and clinicopathological features of breast cancer patients was analyzed.The human breast cancer cell line SKBR-3 was transfected with miR-4324 mimic, miR-4324 inhibitor, si-Talin2, or both miR-4324 inhibitor and si-Talin2, and the changes in biological behaviors of the cells were examined; the cellular expression of Talin2at the mRNA and protein levels were detected with qRT-PCR and Western blotting.Dual luciferase reporter gene assay was used to verify the targeting relationship between miR-4324 and Talin2.The effect of miR-4324-mediated regulation of Talin2 on SKBR-3 cell migration was assessed using Transwell assays.

RESULTS

Talin2 expression was significantly higher in breast cancer tissues than in the adjacent tissues, and its expression level was correlated with lymph node metastasis and high HER-2 expression in breast cancer (P < 0.05) but not with the patient's age, clinical stage, histological grade or expressions of estrogen and progesterone receptors (P >0.05).The expression of miR-4324 was significantly reduced in breast cancer tissues as compared with the adjacent tissues (P < 0.01).In SKBR-3 cells, transfection with miR-4324 mimics significantly inhibited proliferation, migration and invasion (P < 0.05) and promoted apoptosis (P < 0.01) of the cells.Dual luciferase reporter gene assay confirmed that cotransfection with miR-4324 mimics significantly reduced luciferase activity of Talin2-3'-UTR WT reporter plasmid (P < 0.05).Transfection of the cells with miR-4324 mimics significantly reduced mRNA and protein expressions of Talin2(P < 0.05).Transwell migration assay showed that the migration ability of SKBR-3 cells was significantly enhanced after transfection with miR-4324 inhibitor (P < 0.01), lowered after transfection with si-Talin2(P < 0.01), and maintained at the intermediate level after co-transfection with miR-4324 inhibitor+si-Talin2 group (P < 0.05).

CONCLUSIONS

High expression of Talin2 is associated with lymph node metastasis and HER-2 overexpression in breast cancer patients.Down-regulation of miR-4324 inhibits the proliferation, invasion and migration and induces apoptosis of breast cancer cells, and the inhibitory effect of miR-4324 knockdown on breast cancer cell migration is mediated probably by targeted inhibition of Talin2 expression.

The aryl hydrocarbon receptor contributes to tissue adaptation of intestinal eosinophils in mice

Eosinophils are potent sources of inflammatory and toxic mediators, yet they reside in large numbers in the healthy intestine without causing tissue damage. We show here that intestinal eosinophils were specifically adapted to their environment and underwent substantial transcriptomic changes. Intestinal eosinophils upregulated genes relating to the immune response, cell-cell communication, extracellular matrix remodeling, and the aryl hydrocarbon receptor (AHR), a ligand-activated transcription factor with broad functions in intestinal homeostasis. Eosinophils from AHR-deficient mice failed to fully express the intestinal gene expression program, including extracellular matrix organization and cell junction pathways. AHR-deficient eosinophils were functionally impaired in the adhesion to and degradation of extracellular matrix, were more prone to degranulation, and had an extended life span. Lack of AHR in eosinophils had wider effects on the intestinal immune system, affecting the T cell compartment in nave and helminth-infected mice. Our study demonstrates that the response to environmental triggers via AHR partially shapes tissue adaptation of eosinophils in the small intestine.

Mechanical Stimulus-Related Risk Signature Plays a Key Role in the Prognostic Nomogram For Endometrial Cancer

Background

Tumor biomechanics correlates with the progression and prognosis of endometrial carcinoma (EC). The objective of this study is to construct a risk model using the mechanical stimulus-related genes in EC.

Methods

We retrieved the transcriptome profiling and clinical data of EC from The Cancer Genome Atlas (TCGA) and Molecular Signatures Database (MSigDB). Differentially expressed mechanical stimulus-related genes were extracted from the databases, and then the least absolute shrinkage and selection operator (LASSO) regression analysis was used to construct a risk model. A nomogram integrating the genes and the clinicopathological characteristics was established and validated using the Kaplan-Meier survival and receiver operating characteristic (ROC) curves to estimate the overall survival (OS) of EC patients. Protein profiling technology and immunofluorescence technique were performed to verify the connection between biomechanics and EC.

Results

In total, 79 mechanical stimulus-related genes were identified by analyzing the two databases. Based on the LASSO regression analysis, 7 genes were selected for the establishment of the risk model. This model showed a good performance in terms of the prognostic accuracy in high- and low-risk groups. The area under the ROC curves (AUC) of this model was 0.697, 0.712 and 0.723 for 3-, 5- and 7-year OS, respectively. Then, a nomogram integrating the genes of the risk model and clinical features was constructed. The nomogram could accurately predict the OS (AUC = 0.779, 0.812 and 0.806 for 3-, 5- and 7-year OS, respectively). The results of the protein profiling technology and immunofluorescence revealed the expression of cytoskeleton proteins to be correlated with the Matrigel stiffness degree.

Conclusions

In summary, a risk model of 7 mechanical stimulus-related genes was identified in EC. A nomogram based on this risk model and combining the clinicopathological features to assess the overall survival of EC showed high practical value.

CRISPR-Based Activation of Endogenous Expression of TPM1 Inhibits Inflammatory Response of Primary Human Coronary Artery Endothelial and Smooth Muscle Cells Induced by Recombinant Human Tumor Necrosis Factor α

Tumor necrosis factor α (TNFα) is one of the most important proinflammatory cytokines, which affects many processes associated with the growth and characteristics of endothelial, smooth muscle, and immune system cells. However, there is no correlation between most in vivo and in vitro studies on its role in endothelial cell proliferation and migration. In this study, we examined the effect of recombinant human (rh) TNFα produced in HEK293 cells on primary human coronary artery endothelial cells (pHCAECs) in the context of F-actin organization and such processes as migration and adhesion. Furthermore, we evaluated the possibility of the inhibition of the endothelial inflammatory response by the CRISPR-based regulation of TPM1 gene expression. We showed that TNFα-induced activation of pHCAECs was related to the reorganization of the actin cytoskeleton into parallel-arranged stress fibers running along the longer axis of pHCAECs. It allowed for the directed and parallel motion of the cells during coordinated migration. This change in F-actin organization promoted strong but discontinuous cell–cell contacts involved in signalization between migrating cells. Moreover, this form of intercellular connections together with locally increased adhesion was related to the formation of migrasomes and further migracytosis. Stabilization of the actin cytoskeleton through the CRISPR-based activation of endogenous expression of TPM1 resulted in the inhibition of the inflammatory response of pHCAECs following treatment with rh TNFα and stabilization of cell–cell junctions through reduced cleavage of vascular endothelial cadherin (VE-cadherin) and maintenance of the stable levels of α- and β-catenins. We also showed that CRISPR-based activation of TPM1 reduced inflammatory activation, proliferation, and migration of primary human coronary artery smooth muscle cells. Therefore, products of the TPM1 gene may be a potential therapeutic target for the treatment of proinflammatory vascular disorders.

The multiple roles of actin-binding proteins at invadopodia

Invadopodia are actin-rich membrane protrusions that facilitate cancer cell dissemination by focusing on proteolytic activity and clearing paths for migration through physical barriers, such as basement membranes, dense extracellular matrices, and endothelial cell junctions. Invadopodium formation and activity require spatially and temporally regulated changes in actin filament organization and dynamics. About three decades of research have led to a remarkable understanding of how these changes are orchestrated by sequential recruitment and coordinated activity of different sets of actin-binding proteins. In this chapter, we provide an update on the roles of the actin cytoskeleton during the main stages of invadopodium development with a particular focus on actin polymerization machineries and production of pushing forces driving extracellular matrix remodeling.

Tumor Cellular and Microenvironmental Cues Controlling Invadopodia Formation

During the metastatic progression, invading cells might achieve degradation and subsequent invasion into the extracellular matrix (ECM) and the underlying vasculature using invadopodia, F-actin-based and force-supporting protrusive membrane structures, operating focalized proteolysis. Their formation is a dynamic process requiring the combined and synergistic activity of ECM-modifying proteins with cellular receptors, and the interplay with factors from the tumor microenvironment (TME). Significant advances have been made in understanding how invadopodia are assembled and how they progress in degradative protrusions, as well as their disassembly, and the cooperation between cellular signals and ECM conditions governing invadopodia formation and activity, holding promise to translation into the identification of molecular targets for therapeutic interventions. These findings have revealed the existence of biochemical and mechanical interactions not only between the actin cores of invadopodia and specific intracellular structures, including the cell nucleus, the microtubular network, and vesicular trafficking players, but also with elements of the TME, such as stromal cells, ECM components, mechanical forces, and metabolic conditions. These interactions reflect the complexity and intricate regulation of invadopodia and suggest that many aspects of their formation and function remain to be determined. In this review, we will provide a brief description of invadopodia and tackle the most recent findings on their regulation by cellular signaling as well as by inputs from the TME. The identification and interplay between these inputs will offer a deeper mechanistic understanding of cell invasion during the metastatic process and will help the development of more effective therapeutic strategies.

Phosphoinositides regulate force-independent interactions between talin, vinculin, and actin

Focal adhesions (FA) are large macromolecular assemblies which help transmit mechanical forces and regulatory signals between the extracellular matrix and an interacting cell. Two key proteins talin and vinculin connecting integrin to actomyosin networks in the cell. Both proteins bind to F-actin and each other, providing a foundation for network formation within FAs. However, the underlying mechanisms regulating their engagement remain unclear. Here, we report on the results of in vitro reconstitution of talin-vinculin-actin assemblies using synthetic membrane systems. We find that neither talin nor vinculin alone recruit actin filaments to the membrane. In contrast, phosphoinositide-rich membranes recruit and activate talin, and the membrane-bound talin then activates vinculin. Together, the two proteins then link actin to the membrane. Encapsulation of these components within vesicles reorganized actin into higher-order networks. Notably, these observations were made in the absence of applied force, whereby we infer that the initial assembly stage of FAs is force independent. Our findings demonstrate that the local membrane composition plays a key role in controlling the stepwise recruitment, activation, and engagement of proteins within FAs.

Long Noncoding RNA Lnc-TLN2-4:1 Suppresses Gastric Cancer Metastasis and Is Associated with Patient Survival

Gastric cancer (GC) is one of the most common malignancies worldwide, and the tumor metastasis leads to poor outcomes of GC patients. Long noncoding RNAs (lncRNAs) have emerged as new regulatory molecules that play a crucial role in tumor metastasis. However, the biological function and underlying mechanism of numerous lncRNAs in GC metastasis remain largely unclear. Here, we report a novel lncRNA, lnc-TLN2-4:1, whose expression is decreased in GC tissue versus matched normal tissue, and its low expression is involved in the lymph node and distant metastases of GC, as well as poor overall survival rates of GC patients. We further found that lnc-TLN2-4:1 inhibits the ability of GC cells to migrate and invade but does not influence GC cell proliferation and confirmed that lnc-TLN2-4:1 is mainly located in the cytoplasm of GC cells. We then found that lnc-TLN2-4:1 increases the mRNA and protein expression of TLN2 in GC cells and there is a positive correlation between the expression of lnc-TLN2-4:1 and TLN2 mRNA in GC tissue. Collectively, we identified a novel lncRNA, lnc-TLN2-4:1, in GC, where lnc-TLN2-4:1 represses cell migration and invasion. The low expression of lnc-TLN2-4:1 is associated with poor overall survival rates of GC patients. These suggest that lnc-TLN2-4:1 may be a tumor suppressor during GC metastasis.

Mix and (mis-)match - The mechanosensing machinery in the changing environment of the developing, healthy adult and diseased heart

The composition and the stiffness of cardiac microenvironment change during development and/or in heart disease. Cardiomyocytes (CMs) and their progenitors sense these changes, which decides over the cell fate and can trigger CM (progenitor) proliferation, differentiation, de-differentiation or death. The field of mechanobiology has seen a constant increase in output that also includes a wealth of new studies specific to cardiac or cardiomyocyte mechanosensing. As a result, mechanosensing and transduction in the heart is increasingly being recognised as a main driver of regulating the heart formation and function. Recent work has for instance focused on measuring the molecular, physical and mechanical changes of the cellular environment - as well as intracellular contributors to the passive stiffness of the heart. On the other hand, a variety of new studies shed light into the molecular machinery that allow the cardiomyocytes to sense these properties. Here we want to discuss the recent work on this topic, but also specifically focus on how the different components are regulated at various stages during development, in health or disease in order to highlight changes that might contribute to disease progression and heart failure.

Cyanidin-3-glucoside binds to talin and modulates colon cancer cell adhesions and 3D growth

Cyanidin-3-glucoside (C3G) is a natural pigment, found in many colorful fruits and vegetables. It has many health benefits, including anti-inflammation, cancer prevention, and anti-diabetes. Although C3G is assumed to be an antioxidant, it has been reported to affect cell-matrix adhesions. However, the underlying molecular mechanism is unknown. Here, we show that the expression of talin1, a key regulator of integrins and cell adhesions, negatively correlated with the survival rate of colon cancer patients and that depletion of talin1 inhibited 3D spheroid growth in colon cancer cells. Interestingly, C3G bound to talin and promoted the interaction of talin with β1A-integrin. Molecular docking analysis shows that C3G binds to the interface of the talin-β-integrin complex, acting as an allosteric regulator and altering the interaction between talin and integrin. Moreover, C3G promoted colon cancer cell attachment to fibronectin. While C3G had no significant effect on colon cancer cell proliferation, it significantly inhibited 3D spheroid growth in fibrin gel assays. Since C3G has no or very low toxicity, it could be potentially used for colon cancer prevention or therapy.

Dysfunctional Mechanotransduction through the YAP/TAZ/Hippo Pathway as a Feature of Chronic Disease

In order to ascertain their external environment, cells and tissues have the capability to sense and process a variety of stresses, including stretching and compression forces. These mechanical forces, as experienced by cells and tissues, are then converted into biochemical signals within the cell, leading to a number of cellular mechanisms being activated, including proliferation, differentiation and migration. If the conversion of mechanical cues into biochemical signals is perturbed in any way, then this can be potentially implicated in chronic disease development and processes such as neurological disorders, cancer and obesity. This review will focus on how the interplay between mechanotransduction, cellular structure, metabolism and signalling cascades led by the Hippo-YAP/TAZ axis can lead to a number of chronic diseases and suggest how we can target various pathways in order to design therapeutic targets for these debilitating diseases and conditions.

MT1-MMP directs force-producing proteolytic contacts that drive tumor cell invasion

Unraveling the mechanisms that govern the formation and function of invadopodia is essential towards the prevention of cancer spread. Here, we characterize the ultrastructural organization, dynamics and mechanical properties of collagenotytic invadopodia forming at the interface between breast cancer cells and a physiologic fibrillary type I collagen matrix. Our study highlights an uncovered role for MT1-MMP in directing invadopodia assembly independent of its proteolytic activity. Electron microscopy analysis reveals a polymerized Arp2/3 actin network at the concave side of the curved invadopodia in association with the collagen fibers. Actin polymerization is shown to produce pushing forces that repel the confining matrix fibers, and requires MT1-MMP matrix-degradative activity to widen the matrix pores and generate the invasive pathway. A theoretical model is proposed whereby pushing forces result from actin assembly and frictional forces in the actin meshwork due to the curved geometry of the matrix fibers that counterbalance resisting forces by the collagen fibers.

The mechanism of force production by invadopodia is unclear. Here, the authors show that cell surface MT1-MMP when in contact with collagen, induces Arp2/3 branched actin polymerisation on the concave side of invadopodia, which generates a pushing force along with collagen cleavage by MT1-MMP to invade.

The Interplay Between Cell-Cell and Cell-Matrix Forces Regulates Cell Migration Dynamics

Cells in vivo encounter and exert forces as they interact with the extracellular matrix (ECM) and neighboring cells during migration. These mechanical forces play crucial roles in regulating cell migratory behaviors. Although a variety of studies have focused on describing single-cell or the collective cell migration behaviors, a fully mechanistic understanding of how the cell-cell (intercellular) and cell-ECM (extracellular) traction forces individually and cooperatively regulate single-cell migration and coordinate multicellular movement in a cellular monolayer is still lacking. Here, we developed an integrated experimental and analytical system to examine both the intercellular and extracellular traction forces acting on individual cells within an endothelial cell colony as well as their roles in guiding cell migratory behaviors (i.e., cell translation and rotation). Combined with force, multipole, and moment analysis, our results revealed that traction force dominates in regulating cell active translation, whereas intercellular force actively modulates cell rotation. Our findings advance the understanding of the intricacies of cell-cell and cell-ECM forces in regulating cellular migratory behaviors that occur during the monolayer development and may yield deeper insights into the single-cell dynamic behaviors during tissue development, embryogenesis, and wound healing.

Talin-2 regulates integrin functions in exosomes

Integrins on exosomes have been shown to mediate binding to recipient cells, potentially playing important roles in controlling exosomal internalization and organ distributions. Although the ability of cellular integrins to mediate cell adhesion is known to be regulated by the cytoplasmic adaptor protein talin, whether the activity of exosomal integrins is similarly regulated by talin remains to be elucidated. Here we have studied this question in T-cell exosomes that surface express the integrins αLβ2 and α4β7. T-cells and T-cell exosomes engineered to lack talin-2 showed reduced binding to the integrin ligand ICAM-1 and MAdCAM-1 compared with control T-cells and exosomes, despite the fact that those T cells and exosomes express intact levels of the other isoform talin-1. In addition, talin-2-deficient T-cell exosomes were less efficiently internalized by endothelial cells, compared with control exosomes. These results suggest that the mechanisms of talin-mediated integrin regulation operate similarly in cells and exosomes.

Matrix mechanical plasticity regulates cancer cell migration through confining microenvironments

Studies of cancer cell migration have found two modes: one that is protease-independent, requiring micron-sized pores or channels for cells to squeeze through, and one that is protease-dependent, relevant for confining nanoporous matrices such as basement membranes (BMs). However, many extracellular matrices exhibit viscoelasticity and mechanical plasticity, irreversibly deforming in response to force, so that pore size may be malleable. Here we report the impact of matrix plasticity on migration. We develop nanoporous and BM ligand-presenting interpenetrating network (IPN) hydrogels in which plasticity could be modulated independent of stiffness. Strikingly, cells in high plasticity IPNs carry out protease-independent migration through the IPNs. Mechanistically, cells in high plasticity IPNs extend invadopodia protrusions to mechanically and plastically open up micron-sized channels and then migrate through them. These findings uncover a new mode of protease-independent migration, in which cells can migrate through confining matrix if it exhibits sufficient mechanical plasticity.

The tale of two talins - two isoforms to fine-tune integrin signalling

Talins are cytoplasmic adapter proteins essential for integrin-mediated cell adhesion to the extracellular matrix. Talins control the activation state of integrins, link integrins to cytoskeletal actin, recruit numerous signalling molecules that mediate integrin signalling and coordinate recruitment of microtubules to adhesion sites via interaction with KANK (kidney ankyrin repeat-containing) proteins. Vertebrates have two talin genes, TLN1 and TLN2. Although talin1 and talin2 share 76% protein sequence identity (88% similarity), they are not functionally redundant, and the differences between the two isoforms are not fully understood. In this Review, we focus on the similarities and differences between the two talins in terms of structure, biochemistry and function, which hint at subtle differences in fine-tuning adhesion signalling.

The role of talin2 in breast cancer tumorigenesis and metastasis

Recent studies show that talin2 has a higher affinity to β-integrin tails and is indispensable for traction force generation and cell invasion. However, its roles in cell migration, cancer cell metastasis and tumorigenesis remain to be determined. Here, we used MDA-MB-231 human breast cancer cells as a model to define the roles of talin2 in cell migration, invasion, metastasis and tumorigenesis. We show here that talin2 knockdown (KD) inhibited cell migration and focal adhesion dynamics, a key step in cell migration, and that talin2 knockout (KO) inhibited cell invasion and traction force generation, the latter is crucial for cell invasion. Re-expression of talin2^WT in talin2-KO cells restored traction force generation and cell invasion, but that of talin2^S339C, a β-integrin-binding deficient mutant, did not. Moreover, talin2 KO (or KD) suppressed tumorigenesis and metastasis in mouse xenograft models. However, surprisingly, re-expression of talin2^WT in talin2-KO cells did not rescue tumorigenesis. Thus, talin2 is required for breast cancer cell migration, invasion, metastasis and tumorigenesis, although exogenous expression of high levels of talin2 could inhibit tumorigenesis.

Single and collective cell migration: the mechanics of adhesions

Chemical and physical properties of the environment control cell proliferation, differentiation, or apoptosis in the long term. However, to be able to move and migrate through a complex three-dimensional environment, cells must quickly adapt in the short term to the physical properties of their surroundings. Interactions with the extracellular matrix (ECM) occur through focal adhesions or hemidesmosomes via the engagement of integrins with fibrillar ECM proteins. Cells also interact with their neighbors, and this involves various types of intercellular adhesive structures such as tight junctions, cadherin-based adherens junctions, and desmosomes. Mechanobiology studies have shown that cell-ECM and cell-cell adhesions participate in mechanosensing to transduce mechanical cues into biochemical signals and conversely are responsible for the transmission of intracellular forces to the extracellular environment. As they migrate, cells use these adhesive structures to probe their surroundings, adapt their mechanical properties, and exert the appropriate forces required for their movements. The focus of this review is to give an overview of recent developments showing the bidirectional relationship between the physical properties of the environment and the cell mechanical responses during single and collective cell migration.

Mechanical stability of talin rod controls cell migration and substrate sensing

Cells adhere to the surrounding tissue and probe its mechanical properties by forming cell-matrix adhesions. Talin is a critical adhesion protein and participates in the transmission of mechanical signals between extracellular matrix and cell cytoskeleton. Force induced unfolding of talin rod subdomains has been proposed to act as a cellular mechanosensor, but so far evidence linking their mechanical stability and cellular response has been lacking. Here, by utilizing computationally designed mutations, we demonstrate that stepwise destabilization of the talin rod R3 subdomain decreases cellular traction force generation, which affects talin and vinculin dynamics in cell-matrix adhesions and results in the formation of talin-rich but unstable adhesions. We observed a connection between talin stability and the rate of cell migration and also found that talin destabilization affects the usage of different integrin subtypes and sensing of extracellular matrix proteins. Experiments with truncated forms of talin confirm the mechanosensory role of the talin R3 subdomain and exclude the possibility that the observed effects are caused by the release of talin head-rod autoinhibition. In conclusion, this study provides evidence into how the controlled talin rod domain unfolding acts as a key regulator of adhesion structure and function and consequently controls central cellular processes such as cell migration and substrate sensing.

Molecular stretching modulates mechanosensing pathways

For individual cells in tissues to create the diverse forms of biological organisms, it is necessary that they must reliably sense and generate the correct forces over the correct distances and directions. There is considerable evidence that the mechanical aspects of the cellular microenvironment provide critical physical parameters to be sensed. How proteins sense forces and cellular geometry to create the correct morphology is not understood in detail but protein unfolding appears to be a major component in force and displacement sensing. Thus, the crystallographic structure of a protein domain provides only a starting point to then analyze what will be the effects of physiological forces through domain unfolding or catch-bond formation. In this review, we will discuss the recent studies of cytoskeletal and adhesion proteins that describe protein domain dynamics. Forces applied to proteins can activate or inhibit enzymes, increase or decrease protein-protein interactions, activate or inhibit protein substrates, induce catch bonds and regulate interactions with membranes or nucleic acids. Further, the dynamics of stretch-relaxation can average forces or movements to reliably regulate morphogenic movements. In the few cases where single molecule mechanics are studied under physiological conditions such as titin and talin, there are rapid cycles of stretch-relaxation that produce mechanosensing signals. Fortunately, the development of new single molecule and super-resolution imaging methods enable the analysis of single molecule mechanics in physiologically relevant conditions. Thus, we feel that stereotypical changes in cell and tissue shape involve mechanosensing that can be analyzed at the nanometer level to determine the molecular mechanisms involved.

Novel Linear Peptides with High Affinity to αvβ3 Integrin for Precise Tumor Identification

Development of alternative linear peptides for targeting αvβ3 integrin has attracted much attention, as the traditional peptide ligand, cyclic RGD, is limited by inferior water-solubility and complex synthesis. Using pharmacophore-based virtual screening and high-throughput molecular docking, we identified two novel linear small peptides RWr and RWrNM with high affinity and specificity to αvβ3 integrin. The competitive binding with cyclic RGD (c(RGDyK)) and cellular uptake related to the integrin expression levels verified their affinity to αvβ3 integrin. The intermolecular interaction measurement and dynamics simulation demonstrated the high binding affinity and stability, especially for RWrNM. In vivo peptide-guided tumor imaging and targeted therapy further confirmed their specificity. Results indicated that the newly identified small linear peptide RWrNM, with high affinity and specificity to αvβ3 integrin, better water-solubility, and simplified synthetic process, could overcome limitations of the current cyclic RGD peptides, paving the way for diverse use in diagnosis and therapy.

The molecular basis of talin2's high affinity toward β1-integrin

Talin interacts with β-integrin tails and actin to control integrin activation, thus regulating focal adhesion dynamics and cell migration. There are two talin genes, Tln1 and Tln2, which encode talin1 and talin2, and it is generally believed that talin2 functions redundantly with talin1. However, we show here that talin2 has a higher affinity to β1-integrin tails than talin1. Mutation of talin2 S339 to leucine, which can cause Fifth Finger Camptodactyly, a human genetic disease, completely disrupted its binding to β–integrin tails. Also, substitution of talin1 C336 with Ser enhanced the affinity of talin1, whereas substitution of talin2 S339 with Cys diminished that of talin2. Further computational modeling analysis shows that talin2 S339 formed a hydrogen bond with E353, which is critical for inducing key hydrogen bonds between talin2 N326 and β1-integrin R760, and between talin2 K327 and β1-integrin D759. Mutation at any of these residues significantly diminished the interaction of talin2 with β1- integrin tails. These hydrogen bonds were not observed in talin1/β1-integrin, but did exist in talin1^C336S/β1-integrin complex. These results suggest that talin2 S339 forms a hydrogen bond with E353 to mediate its high affinity to β1-integrin.

CRISPR-Cas9 Mediated NOX4 Knockout Inhibits Cell Proliferation and Invasion in HeLa Cells

Increased expression of NOX4 protein is associated with cancer progression and metastasis but the role of NOX4 in cell proliferation and invasion is not fully understood. We generated NOX4 knockout HeLa cell lines using the CRISPR-Cas9 gene editing system to explore the cellular functions of NOX4. After transfection of CRISPR-Cas9 construct, we performed T7 endonuclease 1 assays and DNA sequencing to generate and identify insertion and deletion of the NOX4 locus. We confirmed the knockout of NOX4 by Western blotting. NOX4 knockout cell lines showed reduced cell proliferation with an increase of sub-G1 cell population and the decrease of S/G2/M population. Moreover, NOX4 deficiency resulted in a dramatic decrease in invadopodium formation and the invasive activity. In addition, NOX4 deficiency also caused a decrease in focal adhesions and cell migration in HeLa cells. These results suggest that NOX4 is required for both efficient proliferation and invasion of HeLa cells.

p70S6K1 (S6K1)-mediated Phosphorylation Regulates Phosphatidylinositol 4-Phosphate 5-Kinase Type I γ Degradation and Cell Invasion

Phosphatidylinositol 4-phosphate 5-kinase type I γ (PIPKIγ90) ubiquitination and subsequent degradation regulate focal adhesion assembly, cell migration, and invasion. However, it is unknown how upstream signals control PIPKIγ90 ubiquitination or degradation. Here we show that p70S6K1 (S6K1), a downstream target of mechanistic target of rapamycin (mTOR), phosphorylates PIPKIγ90 at Thr-553 and Ser-555 and that S6K1-mediated PIPKIγ90 phosphorylation is essential for cell migration and invasion. Moreover, PIPKIγ90 phosphorylation is required for the development of focal adhesions and invadopodia, key machineries for cell migration and invasion. Surprisingly, substitution of Thr-553 and Ser-555 with Ala promoted PIPKIγ90 ubiquitination but enhanced the stability of PIPKIγ90, and depletion of S6K1 also enhanced the stability of PIPKIγ90, indicating that PIPKIγ90 ubiquitination alone is insufficient for its degradation. These data suggest that S6K1-mediated PIPKIγ90 phosphorylation regulates cell migration and invasion by controlling PIPKIγ90 degradation.