Fibronectin matrix assembly at a glance

The organization and mechanics of extracellular matrix (ECM) protein polymers determine tissue structure and function. Secreted ECM components are assembled into polymers via a cell-mediated process. The specific mechanisms that cells use for assembly are crucial for generating tissue-appropriate matrices. Fibronectin (FN) is a ubiquitous and abundant ECM protein that is assembled into a fibrillar matrix by a receptor-mediated process, and the FN matrix provides a foundation for incorporation of many other proteins into the ECM. In this Cell Science at a Glance article and the accompanying poster, we describe the domain organization of FN and the events that initiate and propagate a stable insoluble network of FN fibrils. We also discuss intracellular pathways that regulate FN assembly and the impact of changes in assembly on disease progression.

Modularity-based mathematical modeling of ligand inter-nanocluster connectivity for unraveling reversible stem cell regulation

The native extracellular matrix is continuously remodeled to form complex interconnected network structures that reversibly regulate stem cell behaviors. Both regulation and understanding of its intricate dynamicity can help to modulate numerous cell behaviors. However, neither of these has yet been achieved due to the lack of designing and modeling such complex structures with dynamic controllability. Here we report modularity-based mathematical modeling of extracellular matrix-emulating ligand inter-cluster connectivity using the graph theory. Increasing anisotropy of magnetic nano-blockers proportionately disconnects arginine-glycine-aspartic acid ligand-to-ligand interconnections and decreases the number of ligand inter-cluster edges. This phenomenon deactivates stem cells, which can be partly activated by linearizing the nano-blockers. Remote cyclic elevation of high-anisotropy nano-blockers flexibly generates nano-gaps under the nano-blockers and augments the number of ligand inter-cluster edges. Subsequently, integrin-presenting stem cell infiltration is stimulated, which reversibly intensifies focal adhesion and mechanotransduction-driven differentiation both in vitro and in vivo. Designing and systemically modeling extracellular matrix-mimetic geometries opens avenues for unraveling dynamic cell-material interactions for tissue regeneration.

A new mechanism of fibronectin fibril assembly revealed by live imaging and super-resolution microscopy

Fibronectin (Fn1) fibrils have long been viewed as continuous fibers composed of extended, periodically aligned Fn1 molecules. However, our live-imaging and single-molecule localization microscopy data are inconsistent with this traditional view and show that Fn1 fibrils are composed of roughly spherical nanodomains containing six to eleven Fn1 dimers. As they move toward the cell center, Fn1 nanodomains become organized into linear arrays, in which nanodomains are spaced with an average periodicity of 105±17 nm. Periodical Fn1 nanodomain arrays can be visualized between cells in culture and within tissues; they are resistant to deoxycholate treatment and retain nanodomain periodicity in the absence of cells. The nanodomain periodicity in fibrils remained constant when probed with antibodies recognizing distinct Fn1 epitopes or combinations of antibodies recognizing epitopes spanning the length of Fn1. Treatment with FUD, a peptide that binds the Fn1 N-terminus and disrupts Fn1 fibrillogenesis, blocked the organization of Fn1 nanodomains into periodical arrays. These studies establish a new paradigm of Fn1 fibrillogenesis. This article has an associated First Person interview with the first author of the paper.

Hypoxia-induced blood-brain barrier dysfunction is prevented by pericyte-conditioned media via attenuated actomyosin contractility and claudin-5 stabilization

The blood-brain barrier (BBB) regulates molecular and cellular entry from the cerebrovasculature into the surrounding brain parenchyma. Many diseases of the brain are associated with dysfunction of the BBB, where hypoxia is a common stressor. However, the contribution of hypoxia to BBB dysfunction is challenging to study due to the complexity of the brain microenvironment. In this study, we used a BBB model with brain microvascular endothelial cells and pericytes differentiated from iPSCs to investigate the effect of hypoxia on barrier function. We found that hypoxia-induced barrier dysfunction is dependent upon increased actomyosin contractility and is associated with increased fibronectin fibrillogenesis. We propose a role for actomyosin contractility in mediating hypoxia-induced barrier dysfunction through modulation of junctional claudin-5. Our findings suggest pericytes may protect brain microvascular endothelial cells from hypoxic stresses and that pericyte-derived factors could be candidates for treatment of pathological barrier-forming tissues.

Phosphorylated paxillin and phosphorylated FAK constitute subregions within focal adhesions

Integrin-mediated adhesions are convergence points of multiple signaling pathways. Their inner structure and their diverse functions can be studied with super-resolution microscopy. Here, we examined the spatial organization within focal adhesion by analyzing several adhesion proteins with structured illumination microscopy (SIM). We found that phosphorylated paxillin (pPax) and phosphorylated focal adhesion kinase (pFAK) form spot-like, spatially defined clusters within adhesions in several cell lines and confirmed these findings with additional super-resolution techniques. These clusters showed a more regular separation from each other compared to more randomly distributed labels of general FAK or paxillin. Mutational analysis indicated that the active (open) FAK conformation is a prerequisite for the pattern formation of pFAK. Live-cell super-resolution imaging revealed that organization in clusters is preserved over time for FAK constructs; however, distance between clusters is dynamic for FAK, while paxillin is more stable. Combined, these data introduce spatial clusters of pPax and pFAK as substructures in adhesions and highlight the relevance of paxillin-FAK binding for establishing a regular substructure in focal adhesions.

Characterization of plasmatic proteins adsorption on poly(styrene sodium sulfonate) functionalized silicone surfaces

Proteins adsorption occurs spontaneously on biomaterial upon insertion within the body. The resulting protein layer influences biomaterial biocompatibility through enhanced bio-integration or, on the contrary, adverse reactions. Furthermore, upon adsorption, proteins can undergo modifications of their structure and, ultimately, their physicochemical properties and activity. Hence, the understanding of protein adsorption on implanted materials appears essential, as exemplified by silicone breast prostheses that might lead to serious health issues. Surface modifications with a bioactive polymer, poly(styrene sodium sulfonate)-polyNaSS, on a hydrophobic silicone surface that composes breast implants, have been successfully performed under UV irradiation by a radical surface polymerization. This strategy enhances cell biocompatibility and antibacterial features. Although detailed insights related to the mechanism are still scarce, polyNaSS is supposed to promote changes in the conformation and/or orientation of adsorbed plasma proteins, reducing the odd for a biofilm to form. The present work addresses more in-depth structural investigations of the adsorbed state of two plasma proteins: Bovine Serum Albumin (BSA), as a model protein, and fibronectin (FN), for its role in cell adhesion. Using Atomic force microscopy (AFM), we report that polyNaSS showed no significant impact on the BSA structure conversely to the FN one. However, imaging findings with AFM clearly outlined a change in the structural organization of FN, going from a nano fibrillar assembly with an average length of 130 nm to a globular one when the surface was grafted. Thus, it is highlighted that polyNaSS interacts specifically with FN. In addition, cell spreading assay of L929 fibroblasts on FN-coated surfaces with optical microscopy indicated no significant impact of the change in FN structure upon fibroblasts adhesion, which displayed active elongated shapes. The present features are crucial for understanding the cell adhesion mechanism induced by surface modification.

How did correlative atomic force microscopy and super-resolution microscopy evolve in the quest for unravelling enigmas in biology?

With the invention of the Atomic Force Microscope (AFM) in 1986 and the subsequent developments in liquid imaging and cellular imaging it became possible to study the topography of cellular specimens under nearly physiological conditions with nanometric resolution. The application of AFM to biological research was further expanded with the technological advances in imaging modes where topographical data can be combined with nanomechanical measurements, offering the possibility to retrieve the biophysical properties of tissues, cells, fibrous components and biomolecules. Meanwhile, the quest for breaking the Abbe diffraction limit restricting microscopic resolution led to the development of super-resolution fluorescence microscopy techniques that brought the resolution of the light microscope comparable to the resolution obtained by AFM. The instrumental combination of AFM and optical microscopy techniques has evolved over the last decades from integration of AFM with bright-field and phase-contrast imaging techniques at first to correlative AFM and wide-field fluorescence systems and then further to the combination of AFM and fluorescence based super-resolution microscopy modalities. Motivated by the many developments made over the last decade, we provide here a review on AFM combined with super-resolution fluorescence microscopy techniques and how they can be applied for expanding our understanding of biological processes.

Controlling Fibronectin Fibrillogenesis Using Visible Light

We previously developed a surface-assisted assay to image early steps of cell-induced plasma fibronectin (FN) fibrillogenesis by timelapse atomic force microscopy (AFM). Unexpectedly, complementary attempts to visualize FN fibrillogenesis using fluorescently labeled FN (Alexa Fluor 488 or 568) and live-cell light microscopy initially failed consistently. Further analysis revealed that fibrillar remodeling was inhibited efficiently in the focal area illuminated during fluorescence imaging, but progressed normally elsewhere on the substrate, suggesting photo sensitivity of the FN fibrillogenesis process. In agreement, active cell-driven fibrillar extension of FN could be stopped by transient illumination with visible light during AFM timelapse scanning. Phototoxic effects on the cells could be ruled out, because pre-illuminating the FN layer before cell seeding also blocked subsequent fibrillar formation. Varying the illumination wavelength range between 400 and 640 nm revealed strong inhibition across the visible spectrum up to 560 nm, and a decreasing inhibitory effect at longer wavelengths. The photo effect also affected unlabeled FN, but was enhanced by fluorophore labeling of FN. The inhibitory effect could be reduced when reactive oxygen species (ROS) were removed for the cell imaging medium. Based on these findings, FN fibrillogenesis could be imaged successfully using a labeling dye with a long excitation wavelength (Alexa Fluor 633, excitation at 632 nm) and ROS scavengers, such as oxyrase, in the imaging medium. Fibrillar remodeling of exposed cell-free FN layers by AFM scanning required higher scan forces compared to non-exposed FN, consisting with mechanical stiffing of the FN layer after illumination. In agreement with changes in FN mechanics, cells spreading on pre-exposed FN showed reduced migration speeds, altered focal adhesion arrangement, and changes in mechanosensitive signaling pathways, including reduced FAK (Y397) and paxillin (Y118) phosphorylation. Pre-exposure of FN to visible light prior to cell seeding thus provides a useful tool to delineate mechanosensitive signaling pathway related to FN fibrillogenesis. When using FN-coated cell adhesion substrates, care should be taken when comparing experimental results obtained on non-exposed FN layers in cell culture incubators, or during live-cell fluorescence imaging, as FN fibrillogenesis and mechanosensitive cellular signaling pathways may be affected differently.

Induction of ligand promiscuity of αVβ3 integrin by mechanical force

αVβ3 integrin can bind to multiple extracellular matrix proteins, including vitronectin (Vn) and fibronectin (Fn), which are often presented to cells in culture as homogenous substrates. However, in tissues, cells experience highly complex and changing environments. To better understand integrin ligand selection in such complex environments, we employed binary-choice substrates of Fn and Vn to dissect αVβ3 integrin-mediated binding to different ligands on the subcellular scale. Super-resolution imaging revealed that αVβ3 integrin preferred binding to Vn under various conditions. In contrast, binding to Fn required higher mechanical load on αVβ3 integrin. Integrin mutations, structural analysis and chemical inhibition experiments indicated that the degree of hybrid domain swing-out is relevant for the selection between Fn and Vn; only a force-mediated, full hybrid domain swing-out facilitated αVβ3-Fn binding. Thus, force-dependent conformational changes in αVβ3 integrin increased the diversity of available ligands for binding and therefore enhanced the ligand promiscuity of this integrin.This article has an associated First Person interview with the first author of the paper.

ILK supports RhoA/ROCK-mediated contractility of human intestinal epithelial crypt cells by inducing the fibrillogenesis of endogenous soluble fibronectin during the spreading process

BACKGROUND

Fibronectin (FN) assembly into an insoluble fibrillar matrix is a crucial step in many cell responses to extracellular matrix (ECM) properties, especially with regards to the integrin-related mechanosensitive signaling pathway. We have previously reported that the silencing of expression of integrin-linked kinase (ILK) in human intestinal epithelial crypt (HIEC) cells causes significant reductions in proliferation and spreading through concomitantly acquired impairment of soluble FN deposition. These defects in ILK-depleted cells are rescued by growth on exogenous FN. In the present study we investigated the contribution of ILK in the fibrillogenesis of FN and its relation to integrin-actin axis signaling and organization.

RESULTS

We show that de novo fibrillogenesis of endogenous soluble FN is ILK-dependent. This function seemingly induces the assembly of an ECM that supports increased cytoskeletal tension and the development of a fully spread contractile cell phenotype. We observed that HIEC cell adhesion to exogenous FN or collagen-I (Col-I) is sufficient to restore fibrillogenesis of endogenous FN in ILK-depleted cells. We also found that optimal engagement of the Ras homolog gene family member A (RhoA) GTPase/Rho-associated kinase (ROCK-1, ROCK-2)/myosin light chain (MLC) pathway, actin ventral stress fiber formation, and integrin adhesion complex (IAC) maturation rely primarily upon the cell's capacity to execute FN fibrillogenesis, independent of any significant ILK input. Lastly, we confirm the integrin α5β1 as the main integrin responsible for FN assembly, although in ILK-depleted cells αV-class integrins expression is needed to allow the rescue of FN fibrillogenesis on exogenous substrate.

CONCLUSION

Our study demonstrates that ILK specifically induces the initiation of FN fibrillogenesis during cell spreading, which promotes RhoA/ROCK-dependent cell contractility and maturation of the integrin-actin axis structures. However, the fibrillogenesis process and its downstream effect on RhoA signaling, cell contractility and spreading are ILK-independent in human intestinal epithelial crypt cells.

Cell Adhesion by Integrins

Integrins are heterodimeric cell surface receptors ensuring the mechanical connection between cells and the extracellular matrix. In addition to the anchorage of cells to the extracellular matrix, these receptors have critical functions in intracellular signaling, but are also taking center stage in many physiological and pathological conditions. In this review, we provide some historical, structural, and physiological notes so that the diverse functions of these receptors can be appreciated and put into the context of the emerging field of mechanobiology. We propose that the exciting journey of the exploration of these receptors will continue for at least another new generation of researchers.

Tspan8 is expressed in breast cancer and regulates E-cadherin/catenin signalling and metastasis accompanied by increased circulating extracellular vesicles

Tspan8 exhibits a functional role in many cancer types including pancreatic, colorectal, oesophagus carcinoma, and melanoma. We present a first study on the expression and function of Tspan8 in breast cancer. Tspan8 protein was present in the majority of human primary breast cancer lesions and metastases in the brain, bone, lung, and liver. In a syngeneic rat breast cancer model, Tspan8⁺ tumours formed multiple liver and spleen metastases, while Tspan8⁻ tumours exhibited a significantly diminished ability to metastasise, indicating a role of Tspan8 in metastases. Addressing the underlying molecular mechanisms, we discovered that Tspan8 can mediate up‐regulation of E‐cadherin and down‐regulation of Twist, p120‐catenin, and β‐catenin target genes accompanied by the change of cell phenotype, resembling the mesenchymal–epithelial transition. Furthermore, Tspan8⁺ cells exhibited enhanced cell–cell adhesion, diminished motility, and decreased sensitivity to irradiation. As a regulator of the content and function of extracellular vesicles (EVs), Tspan8 mediated a several‐fold increase in EV number in cell culture and the circulation of tumour‐bearing animals. We observed increased protein levels of E‐cadherin and p120‐catenin in these EVs; furthermore, Tspan8 and p120‐catenin were co‐immunoprecipitated, indicating that they may interact with each other. Altogether, our findings show the presence of Tspan8 in breast cancer primary lesion and metastases and indicate its role as a regulator of cell behaviour and EV release in breast cancer. © 2019 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

3D mapping of native extracellular matrix reveals cellular responses to the microenvironment

Cells and extracellular matrix (ECM) are mutually interdependent: cells guide self-assembly of ECM precursors, and the resulting ECM architecture supports and instructs cells. Though bidirectional signaling between ECM and cells is fundamental to cell biology, it is challenging to gain high-resolution structural information on cellular responses to the matrix microenvironment. Here we used cryo-scanning transmission electron tomography (CSTET) to reveal the nanometer- to micron-scale organization of major fibroblast ECM components in a native-like context, while simultaneously visualizing internal cell ultrastructure including organelles and cytoskeleton. In addition to extending current models for collagen VI fibril organization, three-dimensional views of thick cell regions and surrounding matrix showed how ECM networks impact the structures and dynamics of intracellular organelles and how cells remodel ECM. Collagen VI and fibronectin were seen to distribute in fundamentally different ways in the cell microenvironment and perform distinct roles in supporting and interacting with cells. This work demonstrates that CSTET provides a new perspective for the study of ECM in cell biology, highlighting labeled extracellular elements against a backdrop of unlabeled but morphologically identifiable cellular features with nanometer resolution detail.

The Molecular Dance of Fibronectin: Conformational Flexibility Leads to Functional Versatility

Fibronectin, a large multimodular protein and one of the major fibrillar components of the extracellular matrix, has been the subject of study for many decades and plays critical roles in embryonic development and tissue homeostasis. Moreover, fibronectin has been implicated in the pathology of many diseases, including cancer, and abnormal depositions of fibronectin have been identified in a number of amyloid and nonamyloid lesions. The ability of fibronectin to carry all these diverse functionalities depends on interactions with a large number of molecules, including adhesive and signaling cell surface receptors, other components of the extracellular matrix, and growth factors and cytokines. The regulation and integration of such large number of interactions depends on the modular architecture of fibronectin, which allows a large number of conformations, exposing or destroying different binding sites. In this Review, we summarize the current knowledge regarding the conformational flexibility of fibronectin, with an emphasis on how it regulates the ability of fibronectin to interact with various signaling molecules and cell-surface receptors and to form supramolecular assemblies and fibrillar structures.

A Selective Extracellular Matrix Proteomics Approach Identifies Fibronectin Proteolysis by A Disintegrin-like and Metalloprotease Domain with Thrombospondin Type 1 Motifs (ADAMTS16) and Its Impact on Spheroid Morphogenesis

Secreted and cell-surface proteases are major mediators of extracellular matrix (ECM) turnover, but their mechanisms and regulatory impact are poorly understood. We developed a mass spectrometry approach using a cell-free ECM produced in vitro to identify fibronectin (FN) as a novel substrate of the secreted metalloprotease ADAMTS16. ADAMTS16 cleaves FN between its (I)5 and (I)6 modules, releasing the N-terminal 30 kDa heparin-binding domain essential for FN self-assembly. ADAMTS16 impairs FN fibrillogenesis as well as fibrillin-1 and tenascin-C assembly, thus inhibiting formation of a mature ECM by cultured fibroblasts. Furthermore ADAMTS16 has a marked morphogenetic impact on spheroid formation by renal tubule-derived MDCKI cells. The N-terminal FN domain released by ADAMTS16 up-regulates MMP3, which cleaves the (I)5-(I)6 linker of FN similar to ADAMTS16, therefore creating a proteolytic feed-forward mechanism. Thus, FN proteolysis not only regulates FN turnover, but also FN assembly, with potential long-term consequences for ECM assembly and morphogenesis.

Fibroblast-fibronectin patterning and network formation in 3D fibrin matrices

PURPOSE

We previously reported that fibroblasts migrating within 3-D collagen matrices move independently, whereas fibroblasts within 3-D fibrin matrices form an interconnected network. Similar networks have been identified previously during in vivo corneal wound healing. In this study, we investigate the role of fibronectin in mediating this mechanism of collective cell spreading, migration and patterning.

METHODS

To assess cell spreading, corneal fibroblasts were plated within fibrillar collagen or fibrin matrices. To assess migration, compacted cell-populated collagen matrices were nested inside cell-free fibrin matrices. Constructs were cultured in serum-free media containing PDGF, with or without RGD peptide, anti-α5 or anti-fibronectin blocking antibodies. In some experiments, LifeAct and fluorescent fibronectin were used to allow dynamic assessment of cell-induced fibronectin reorganization. 3-D and 4-D imaging were used to assess cell mechanical behavior, connectivity, F-actin, α5 integrin and fibronectin organization.

RESULTS

Corneal fibroblasts within 3-D fibrin matrices formed an interconnected network that was lined with cell-secreted fibronectin. Live cell imaging demonstrated that fibronectin tracks were formed at the leading edge of spreading and migrating cells. Furthermore, fibroblasts preferentially migrated through fibronectin tracks laid down by other cells. Interfering with cell-fibronectin binding with RGD, anti α5 integrin or anti fibronectin antibodies inhibited cell spreading and migration through fibrin, but did not affect cell behavior in collagen.

CONCLUSIONS

In this study, a novel mode of cell patterning was identified in which corneal fibroblasts secrete and attach to fibronectin via α5β1 integrin to facilitate spreading and migration within 3-D fibrin matrices, resulting in the formation of localized fibronectin tracks. Other cells use these fibronectin tracks as conduits, resulting in an interconnected cell-fibronectin network.

Stretch-dependent changes in molecular conformation in fibronectin nanofibers

Fibronectin (FN) is an extracellular matrix (ECM) glycoprotein that plays an important role in a wide range of biological processes including embryonic development, wound healing, and fibrosis. Recent evidence has demonstrated that FN is mechanosensitive, where the application of force induces conformational changes within the FN molecule to expose otherwise cryptic binding domains. However, it has proven technically challenging to dynamically monitor how the nanostructure of FN fibers changes as a result of force-induced extension, due in part to the inherent complexity of FN networks within tissue and cell-generated extracellular matrix (ECM). This has limited our understanding of FN matrix mechanobiology and the complex bi-directional signaling between cells and the ECM, and de novo FN fiber fabrication strategies have only partially addressed this. Towards addressing this need, we have developed a modified surface-initiated assembly (SIA) technique to engineer FN nanofibers that we can uniaxially stretch to >7-fold extensions and subsequently immobilize them in the stretched state for high resolution atomic force microscopy (AFM) imaging. Using this approach, we analyzed how the nanostructure of FN molecules within the nanofibers changed with stretch. In fully contracted FN nanofibers, we observed large, densely packed, isotropically-oriented nodules. With intermediate extension, uniaxially-aligned fibrillar regions developed and nodules became progressively smaller. At high extension, the nanostructure consisted of highly aligned fibrils with small nodules in a beads-on-a-string arrangement. In summary, we have established a methodology to uniaxially stretch FN fibers and monitor changes in nanostructure using AFM. Our results provide new insight into how FN fiber extension can affect the morphology of the constituent FN molecules.

Atomic Force Microscopy in Characterizing Cell Mechanics for Biomedical Applications: A Review

Cell mechanics is a novel label-free biomarker for indicating cell states and pathological changes. The advent of atomic force microscopy (AFM) provides a powerful tool for quantifying the mechanical properties of single living cells in aqueous conditions. The wide use of AFM in characterizing cell mechanics in the past two decades has yielded remarkable novel insights in understanding the development and progression of certain diseases, such as cancer, showing the huge potential of cell mechanics for practical applications in the field of biomedicine. In this paper, we reviewed the utilization of AFM to characterize cell mechanics. First, the principle and method of AFM single-cell mechanical analysis was presented, along with the mechanical responses of cells to representative external stimuli measured by AFM. Next, the unique changes of cell mechanics in two types of physiological processes (stem cell differentiation, cancer metastasis) revealed by AFM were summarized. After that, the molecular mechanisms guiding cell mechanics were analyzed. Finally the challenges and future directions were discussed.

Progress in the Correlative Atomic Force Microscopy and Optical Microscopy

Atomic force microscopy (AFM) has evolved from the originally morphological imaging technique to a powerful and multifunctional technique for manipulating and detecting the interactions between molecules at nanometer resolution. However, AFM cannot provide the precise information of synchronized molecular groups and has many shortcomings in the aspects of determining the mechanism of the interactions and the elaborate structure due to the limitations of the technology, itself, such as non-specificity and low imaging speed. To overcome the technical limitations, it is necessary to combine AFM with other complementary techniques, such as fluorescence microscopy. The combination of several complementary techniques in one instrument has increasingly become a vital approach to investigate the details of the interactions among molecules and molecular dynamics. In this review, we reported the principles of AFM and optical microscopy, such as confocal microscopy and single-molecule localization microscopy, and focused on the development and use of correlative AFM and optical microscopy.

AMPK negatively regulates tensin-dependent integrin activity

Georgiadou et al. show that the major metabolic sensor AMPK regulates integrin activity and integrin-dependent processes in fibroblasts by modulating tensin levels. Loss of AMPK up-regulates tensin expression, triggering enhanced integrin activity in fibrillar adhesions, fibronectin remodeling, and traction stress.

Tight regulation of integrin activity is paramount for dynamic cellular functions such as cell matrix adhesion and mechanotransduction. Integrin activation is achieved through intracellular interactions at the integrin cytoplasmic tails and through integrin–ligand binding. In this study, we identify the metabolic sensor AMP-activated protein kinase (AMPK) as a β1-integrin inhibitor in fibroblasts. Loss of AMPK promotes β1-integrin activity, the formation of centrally located active β1-integrin– and tensin-rich mature fibrillar adhesions, and cell spreading. Moreover, in the absence of AMPK, cells generate more mechanical stress and increase fibronectin fibrillogenesis. Mechanistically, we show that AMPK negatively regulates the expression of the integrin-binding proteins tensin1 and tensin3. Transient expression of tensins increases β1-integrin activity, whereas tensin silencing reduces integrin activity in fibroblasts lacking AMPK. Accordingly, tensin silencing in AMPK-depleted fibroblasts impedes enhanced cell spreading, traction stress, and fibronectin fiber formation. Collectively, we show that the loss of AMPK up-regulates tensins, which bind β1-integrins, supporting their activity and promoting fibrillar adhesion formation and integrin-dependent processes.