Role of Integrin in Cellular Mechanotransduction

Chemical and physical cues from the extracellular matrix (ECM) are used as input for an integrated mechanochemical sensory system that controls cell behavior. Forces derived from the ECM have been implicated in various biological systems, including mesenchymal stem cell differentiation and tumor growth. Integrin transmembrane receptors connect the ECM network to the intracellular actomyosin network and are expected to play an important role in force sensing. Our group has previously shown that switching between two different integrin heterodimers ([alpha]5[beta]1 vs [alpha]v[beta]3), that bind the same ECM protein (fibronectin), causes remarkably distinct actin cytoskeletal organization. To investigate the role of these integrins in cellular mechanotransduction, we used fibronectin coated polyacrylamide substrates with varying rigidities and micropillar arrays. Data obtained thus far point to distinct rigidity thresholds for spreading and different distribution of ECM pulling forces for cells expressing either of these integrins. In order to further unravel the role of these integrins in cellular mechanotransduction we developed cyclic substrate stretcher technology coupled to real time confocal imaging.Toxicolog

Tumor-induced remote ECM network orientation steers angiogenesis

Tumor angiogenesis promotes tumor growth and metastasis. Here, we use automated sequential microprinting of tumor and endothelial cells in extracellular matrix (ECM) scaffolds to study its mechanical aspects. Quantitative reflection microscopy shows that tumor spheroids induce radial orientation of the surrounding collagen fiber network up to a distance of five times their radius. Across a panel of ~20 different human tumor cell lines, remote collagen orientation is correlated with local tumor cell migration behavior. Tumor induced collagen orientation requires contractility but is remarkably resistant to depletion of collagen-binding integrins. Microvascular endothelial cells undergo directional migration towards tumor spheroids once they are within the tumor-oriented collagen fiber network. Laser ablation experiments indicate that an intact physical connection of the oriented network with the tumor spheroid is required for mechanical sensing by the endothelial cells. Together our findings indicate that, in conjunction with described activities of soluble angiogenic factors, remote physical manipulation of the ECM network by the tumor can help to steer angiogenesis

The integrin expression profile modulates orientation and dynamics of force transmission at cell–matrix adhesions

Integrin adhesion receptors connect the extracellular matrix (ECM) to the cytoskeleton and serve as bidirectional mechanotransducers. During development, angiogenesis, wound healing and cancer progression, the relative abundance of fibronectin receptors, including integrins α5β1 and αvβ3, changes, thus altering the integrin composition of cell-matrix adhesions. Here, we show that enhanced αvβ3 expression can fully compensate for loss of α5β1 and other β1 integrins to support outside-in and inside-out force transmission. α5β1 and αvβ3 each mediate actin cytoskeletal remodeling in response to stiffening or cyclic stretching of the ECM. Likewise, α5β1 and αvβ3 support cellular traction forces of comparable magnitudes and similarly increase these forces in response to ECM stiffening. However, cells using αvβ3 respond to lower stiffness ranges, reorganize their actin cytoskeleton more substantially in response to stretch, and show more randomly oriented traction forces. Centripetal traction force orientation requires long stress fibers that are formed through the action of Rho kinase (ROCK) and myosin II, and that are supported by α5β1. Thus, altering the relative abundance of fibronectin-binding integrins in cell-matrix adhesions affects the spatiotemporal organization of force transmission.Toxicolog

Cellular adhesome screen identifies critical modulators of focal adhesion dynamics, cellular traction forces and cell migration behaviour

Computer Systems, Imagery and Medi

CD45RA(+)CCR7(-) CD8 T cells lacking co-stimulatory receptors demonstrate enhanced frequency in peripheral blood of NSCLC patients responding to nivolumab

Background Checkpoint inhibitors have become standard care of treatment for non-small cell lung cancer (NSCLC), yet only a limited fraction of patients experiences durable clinical benefit, highlighting the need for markers to stratify patient populations. Methods To prospectively identify patients showing response to therapy, we have stained peripheral blood samples of NSCLC patients treated with 2nd line nivolumab (n = 71), as well as healthy controls, with multiplex flow cytometry. By doing so, we enumerated 18 immune cell subsets and assessed expression for 28 T cell markers, which was followed by dimensionality reduction as well as rationale-based analyses. Results In patients with a partial response (PR), representing best overall response (BOR) according to RECIST v1.1, the number of CD8 T cells at baseline and during treatment is similar to those of healthy controls, but 2-fold higher than in patients with progressive and stable disease (PD and SD). CD8 T cell populations in PR patients show enhanced frequencies of T effector memory re-expressing CD45RA (TEMRA) cells, as well as T cells that express markers of terminal differentiatio

Role of Integrin in Cellular Mechanotransduction

Chemical and physical cues from the extracellular matrix (ECM) are used as input for an integrated mechanochemical sensory system that controls cell behavior. Forces derived from the ECM have been implicated in various biological systems, including mesenchymal stem cell differentiation and tumor growth. Integrin transmembrane receptors connect the ECM network to the intracellular actomyosin network and are expected to play an important role in force sensing. Our group has previously shown that switching between two different integrin heterodimers ([alpha]5[beta]1 vs [alpha]v[beta]3), that bind the same ECM protein (fibronectin), causes remarkably distinct actin cytoskeletal organization. To investigate the role of these integrins in cellular mechanotransduction, we used fibronectin coated polyacrylamide substrates with varying rigidities and micropillar arrays. Data obtained thus far point to distinct rigidity thresholds for spreading and different distribution of ECM pulling forces for cells expressing either of these integrins. In order to further unravel the role of these integrins in cellular mechanotransduction we developed cyclic substrate stretcher technology coupled to real time confocal imaging.Toxicolog

Tumor-induced remote ECM network orientation steers angiogenesis

10.1038/srep22580Scientific Reports62258

Tumor-induced remote ECM network orientation steers angiogenesis

Tumor angiogenesis promotes tumor growth and metastasis. Here, we use automated sequential microprinting of tumor and endothelial cells in extracellular matrix (ECM) scaffolds to study its mechanical aspects. Quantitative reflection microscopy shows that tumor spheroids induce radial orientation of the surrounding collagen fiber network up to a distance of five times their radius. Across a panel of ~20 different human tumor cell lines, remote collagen orientation is correlated with local tumor cell migration behavior. Tumor induced collagen orientation requires contractility but is remarkably resistant to depletion of collagen-binding integrins. Microvascular endothelial cells undergo directional migration towards tumor spheroids once they are within the tumor-oriented collagen fiber network. Laser ablation experiments indicate that an intact physical connection of the oriented network with the tumor spheroid is required for mechanical sensing by the endothelial cells. Together our findings indicate that, in conjunction with described activities of soluble angiogenic factors, remote physical manipulation of the ECM network by the tumor can help to steer angiogenesis

Substrate rigidity modulates traction forces and stoichiometry of cell–matrix adhesions

In cell-matrix adhesions, integrin receptors and associated proteins provide a dynamic coupling of the extracellular matrix (ECM) to the cytoskeleton. This allows bidirectional transmission of forces between the ECM and the cytoskeleton, which tunes intracellular signaling cascades that control survival, proliferation, differentiation, and motility. The quantitative relationships between recruitment of distinct cell-matrix adhesion proteins and local cellular traction forces are not known. Here, we applied quantitative super-resolution microscopy to cell-matrix adhesions formed on fibronectin-stamped elastomeric pillars and developed an approach to relate the number of talin, vinculin, paxillin, and focal adhesion kinase (FAK) molecules to the local cellular traction force. We find that FAK recruitment does not show an association with traction-force application, whereas a ∼60 pN force increase is associated with the recruitment of one talin, two vinculin, and two paxillin molecules on a substrate with an effective stiffness of 47 kPa. On a substrate with a fourfold lower effective stiffness, the stoichiometry of talin:vinculin:paxillin changes to 2:12:6 for the same ∼60 pN traction force. The relative change in force-related vinculin recruitment indicates a stiffness-dependent switch in vinculin function in cell-matrix adhesions. Our results reveal a substrate-stiffness-dependent modulation of the relationship between cellular traction-force and the molecular stoichiometry of cell-matrix adhesions.Biological and Soft Matter Physic

Substrate Rigidity Modulates the Composition in Cell-Matrix Adhesions

Toxicolog