FRET Visualization of Cyclic Stretch-Activated ERK via Calcium Channels Mechanosensation While Not Integrin β1 in Airway Smooth Muscle Cells

The underlying difference of metastatic and non-metastatic breast cancer cells in configuring type I collagen fibres to promote migration by cell mechanics

The progression of tumors is heavily influenced by mechanical properties of their microenvironment. In this work, we applied micropatterned models with varying distances and shapes to investigate the differences between metastatic MDA-MB-231 and non-metastatic MCF-7 breast cancer cells in reconfiguring extracellular matrix to promote cell migration induced by cell mechanics. Both cancer cells were able to rearrange type I collagen (COL) to form fibre threads, in which MDA-MB-231 consistently migrated more rapidly than MCF-7, ranging from geometrical square arrays with different spacings to complex polygonal models. MDA-MB-231 displayed higher capability of reorganizing fibre bundles at longer distance (800 ​μm). Further looking for differences in cell molecular mechanisms, siRNA knockdown inhibiting either integrin β1 or Piezo1 decreased fibre assembly and reduced the difference in COL remodeling and migration between two cancer cells. MDA-MB-231 showed inhibited migration with integrin knockdown, whereas scattering migration with Piezo1 knockdown, indicating cells losing directional mechanosensation. After inhibiting junctional E-cadherin with siRNA, MCF-7 cells migrated faster, resulting in reduced difference in comparison to MDA-MB-231 that didn't express E-cadherin. In summary, this work has explored the biomechanical differences between metastatic and non-metastatic breast cancer cells regarding COL fibre matrix remodeling and cell movements. The significant differences in E-cadherin expression in the two breast cancer cells had an effect on cell migrations. The results of this study provide research approaches for evaluating therapeutic effort on breast cancer.

The emerging roles of the endoplasmic reticulum in mechanosensing and mechanotransduction

Cells are continuously subjected to physical and chemical cues from the extracellular environment, and sense and respond to mechanical cues via mechanosensation and mechanotransduction. Although the role of the cytoskeleton in these processes is well known, the contribution of intracellular membranes has been long neglected. Recently, it has become evident that various organelles play active roles in both mechanosensing and mechanotransduction. In this Review, we focus on mechanosensitive roles of the endoplasmic reticulum (ER), the functions of which are crucial for maintaining cell homeostasis. We discuss the effects of mechanical stimuli on interactions between the ER, the cytoskeleton and other organelles; the role of the ER in intracellular Ca2+ signalling via mechanosensitive channels; and how the unfolded protein response and lipid homeostasis contribute to mechanosensing. The expansive structure of the ER positions it as a key intracellular communication hub, and we additionally explore how this may be leveraged to transduce mechanical signals around the cell. By synthesising current knowledge, we aim to shed light on the emerging roles of the ER in cellular mechanosensing and mechanotransduction.

Multiciliated cells adapt the mechanochemical Piezo1-Erk1/2-Yap1 cell proliferation axis to fine-tune centriole number

Multiciliated cells (MCCs) are specialized epithelial cells that undergo massive amplification of centrioles, constructing several motile cilia to propel fluid flow. The abundance of cilia is critical for efficient fluid flow, yet how MCCs regulate centriole/cilia numbers remains a major knowledge gap. We have shown that mechanical tension plays a central role in regulating apical area and centriole number in MCCs. Here, we demonstrate that centriole amplification is controlled by a mechanochemical pathway essential for cell proliferation in cycling cells. Specifically, MCCs under tension use Piezo1-mediated calcium signaling to drive Erk½ phosphorylation via PKC and subsequent Yap1 activation. Remarkably, MCCs use this pathway to activate a cilia-specific transcription program, influencing the expression of Foxj1, a master regulator of motile ciliogenesis. Our work is the first to identify a novel function for an important mechanochemical pathway in centriole amplification in MCCs, offering new insights into ciliopathies and cancer, where aberrant centriole numbers are implicated.

Teaser

This study demonstrates that multiciliated cells utilize the mechanochemical Piezo1-Erk1/2-Yap1 cell proliferation axis to activate the cilia-specific transcriptional factor Foxj1 and amplify centrioles in a tension- dependent manner.

CHRFAM7A diversifies human immune adaption through Ca2+ signalling and actin cytoskeleton reorganization

BACKGROUND

Human restricted genes contribute to human specific traits in the immune system. CHRFAM7A, a uniquely human fusion gene, is a negative regulator of the α7 nicotinic acetylcholine receptor (α7 nAChR), the highest Ca2+ conductor of the ACh receptors implicated in innate immunity. Understanding the mechanism of how CHRFAM7A affects the immune system remains unexplored.

METHODS

Two model systems are used, human induced pluripotent stem cells (iPSC) and human primary monocytes, to characterize α7 nAChR function, Ca2+ dynamics and decoders to elucidate the pathway from receptor to phenotype.

FINDINGS

CHRFAM7A/α7 nAChR is identified as a hypomorphic receptor with mitigated Ca2+ influx and prolonged channel closed state. This shifts the Ca2+ reservoir from the extracellular space to the endoplasmic reticulum (ER) leading to Ca2+ dynamic changes. Ca2+ decoder small GTPase Rac1 is then activated, reorganizing the actin cytoskeleton. Observed actin mediated phenotypes include cellular adhesion, motility, phagocytosis and tissue mechanosensation.

INTERPRETATION

CHRFAM7A introduces an additional, human specific, layer to Ca2+ regulation leading to an innate immune gain of function. Through the actin cytoskeleton it drives adaptation to the mechanical properties of the tissue environment leading to an ability to invade previously immune restricted niches. Human genetic diversity predicts profound translational significance as its understanding builds the foundation for successful treatments for infectious diseases, sepsis, and cancer metastasis.

FUNDING

This work is supported in part by the Community Foundation for Greater Buffalo (Kinga Szigeti) and in part by NIH grant R01HL163168 (Yongho Bae).

Characterization of PDGF-Induced Subcellular Calcium Regulation through Calcium Channels in Airway Smooth Muscle Cells by FRET Biosensors

The homeostasis of cellular calcium is fundamental for many physiological processes, while the calcium levels remain inhomogeneous within cells. During the onset of asthma, epithelial and inflammatory cells secrete platelet-derived growth factor (PDGF), inducing the proliferation and migration of airway smooth muscle (ASM) to the epidermal layer, narrowing the airway. The regulation of ASM cells by PDGF is closely related to the conduction of calcium signals. In this work, we generated subcellular-targeted FRET biosensors to investigate calcium regulation in the different compartments of ASM cells. A PDGF-induced cytoplasmic calcium [Ca2+]C increase was attributed to both extracellular calcium influx and endoplasmic reticulum (ER) calcium [Ca2+]ER release, which was partially regulated by the PLC-IP3R pathway. Interestingly, the removal of the extracellular calcium influx led to inhibited ER calcium release, likely through inhibitory effects on the calcium-dependent activation of the ER ryanodine receptor. The inhibition of the L-type calcium channel on the plasma membrane or the SERCA pump on the ER resulted in both reduced [Ca2+]C and [Ca2+]ER from PDGF stimulation, while IP3R channel inhibition led to reduced [Ca2+]C only. The inhibited SERCA pump caused an immediate [Ca2+]C increase and [Ca2+]ER decrease, indicating active calcium exchange between the cytosol and ER storage in resting cells. PDGF-induced calcium at the outer mitochondrial membrane sub-region showed a similar regulatory response to cytosolic calcium, not influenced by the inhibition of the mitochondrial calcium uniporter channel. Therefore, our work identifies calcium flow pathways among the extracellular medium, cell cytosol, and ER via regulatory calcium channels. Specifically, extracellular calcium flow has an essential function in fully activating ER calcium release.

High Stretch Modulates cAMP/ATP Level in Association with Purine Metabolism via miRNA-mRNA Interactions in Cultured Human Airway Smooth Muscle Cells

High stretch (>10% strain) of airway smooth muscle cells (ASMCs) due to mechanical ventilation (MV) is postulated to contribute to ventilator-induced lung injury (VILI), but the underlying mechanisms remain largely unknown. We hypothesized that ASMCs may respond to high stretch via regulatory miRNA-mRNA interactions, and thus we aimed to identify high stretch-responsive cellular events and related regulating miRNA-mRNA interactions in cultured human ASMCs with/without high stretch. RNA-Seq analysis of whole genome-wide miRNAs revealed 12 miRNAs differentially expressed (DE) in response to high stretch (7 up and 5 down, fold change >2), which target 283 DE-mRNAs as identified by a parallel mRNA sequencing and bioinformatics analysis. The KEGG and GO analysis further indicated that purine metabolism was the first enriched event in the cells during high stretch, which was linked to miR-370-5p-PDE4D/AK7. Since PDE4D/AK7 have been previously linked to cAMP/ATP metabolism in lung diseases and now to miR-370-5p in ASMCs, we thus evaluated the effect of high stretch on the cAMP/ATP level inside ASMCs. The results demonstrated that high stretch modulated the cAMP/ATP levels inside ASMCs, which could be largely abolished by miR-370-5p mimics. Together, these findings indicate that miR-370-5p-PDE4D/AK7 mediated high stretch-induced modulation of cAMP and ATP synthesis inside ASMCs. Furthermore, such interactive miRNA-mRNA pairs may provide new insights for the discovery of effective biomarkers/therapeutic targets for the diagnosis and treatment of VILI and other MV-associated respiratory diseases.

Cell Mechanics Regulates the Dynamic Anisotropic Remodeling of Fibril Matrix at Large Scale

Living tissues often have anisotropic and heterogeneous organizations, in which developmental processes are coordinated by cells and extracellular matrix modeling. Cells have the capability of modeling matrix in long distance; however, the biophysical mechanism is largely unknown. We investigated the dynamic remodeling of collagen I (COL) fibril matrix by cell contraction with designed patterns of cell clusters. By considering cell dynamic contractions, our molecular dynamics simulations predicted the anisotropic patterns of the observed COL bundling in experiments with various geometrical patterns without spatial limitation. The pattern of COL bundling was closely related to the dynamic remodeling of fibril under cell active contraction. We showed that cell cytoskeletal integrity (actin filaments and microtubules), actomyosin contractions, and endoplasmic reticulum calcium channels acting as force generations and transductions were essential for fiber bundling inductions, and membrane mechanosensory components integrin and Piezo played critical roles as well. This study revealed the underlying mechanisms of the cell mechanics-induced matrix remodeling in large scales and the associated cellular mechanism and should provide important guidelines for tissue engineering in potential biomedical applications.

Stretching the limits of extracellular signal-related kinase (ERK) signaling - Cell mechanosensing to ERK activation

Extracellular signal-regulated kinase (ERK) has been recognized as a critical regulator in various physiological and pathological processes. Extensive research has elucidated the signaling mechanisms governing ERK activation via biochemical regulations with upstream molecules, particularly receptor tyrosine kinases (RTKs). However, recent advances have highlighted the role of mechanical forces in activating the RTK-ERK signaling pathways, thereby opening new avenues of research into mechanochemical interplay in multicellular tissues. Here, we review the force-induced ERK activation in cells and propose possible mechanosensing mechanisms underlying the mechanoresponsive ERK activation. We conclude that mechanical forces are not merely passive factors shaping cells and tissues but also active regulators of cellular signaling pathways controlling collective cell behaviors.

Mechanical Ventilation-Related High Stretch Mainly Induces Endoplasmic Reticulum Stress and Thus Mediates Inflammation Response in Cultured Human Primary Airway Smooth Muscle Cells

Ventilator-induced lung injury (VILI) occurs in mechanically ventilated patients of respiratory disease and is typically characterized by airway inflammation. However, recent studies increasingly indicate that a major cause of VILI may be the excessive mechanical loading such as high stretch (>10% strain) on airway smooth muscle cells (ASMCs) due to mechanical ventilation (MV). Although ASMCs are the primary mechanosensitive cells in airways and contribute to various airway inflammation diseases, it is still unclear how they respond to high stretch and what mediates such a response. Therefore, we used whole genome-wide mRNA-sequencing (mRNA-Seq), bioinformatics, and functional identification to systematically analyze the mRNA expression profiles and signaling pathway enrichment of cultured human ASMCs exposed to high stretch (13% strain), aiming to screen the susceptible signaling pathway through which cells respond to high stretch. The data revealed that in response to high stretch, 111 mRNAs with count ≥100 in ASMCs were significantly differentially expressed (defined as DE-mRNAs). These DE-mRNAs are mainly enriched in endoplasmic reticulum (ER) stress-related signaling pathways. ER stress inhibitor (TUDCA) abolished high-stretch-enhanced mRNA expression of genes associated with ER stress, downstream inflammation signaling, and major inflammatory cytokines. These results demonstrate in a data-driven approach that in ASMCs, high stretch mainly induced ER stress and activated ER stress-related signaling and downstream inflammation response. Therefore, it suggests that ER stress and related signaling pathways in ASMCs may be potential targets for timely diagnosis and intervention of MV-related pulmonary airway diseases such as VILI.

Mechanical communication-associated cell directional migration and branching connections mediated by calcium channels, integrin β1, and N-cadherin

Cell–cell mechanical communications at a large spatial scale (above hundreds of micrometers) have been increasingly recognized in recent decade, which shows importance in tissue-level assembly and morphodynamics. The involved mechanosensing mechanism and resulted physiological functions are still to be fully understood. Recent work showed that traction force sensation in the matrix induces cell communications for self-assembly. Here, based on the experimental model of cell directional migration on Matrigel hydrogel, containing 0.5 mg/ml type I collagen, we studied the mechano-responsive pathways for cell distant communications. Airway smooth muscle (ASM) cells assembled network structure on the hydrogel, whereas stayed isolated individually when cultured on glass without force transmission. Cell directional migration, or network assembly was significantly attenuated by inhibited actomyosin activity, or inhibition of inositol 1,4,5-trisphosphate receptor (IP3R) calcium channel or SERCA pump on endoplasmic reticulum (ER) membrane, or L-type calcium channel on the plasma membrane. Inhibition of integrin β1 with siRNA knockdown reduced cell directional migration and branching assembly, whereas inhibition of cell junctional N-cadherin with siRNA had little effect on distant attractions but blocked branching assembly. Our work demonstrated that the endoplasmic reticulum calcium channels and integrin are mechanosensing signals for cell mechanical communications regulated by actomyosin activity, while N-cadherin is responsible for traction force-induced cell stable connections in the assembly.