Piezo1 belongs to mechano‐activatable cation channels serving as biological force sensors. However, the molecular events downstream of Piezo1 activation remain unclear. In this study, we used ...biosensors based on fluorescence resonance energy transfer (FRET) to investigate the dynamic modes of Piezo1‐mediated signaling and revealed a bimodal pattern of Piezo1‐induced intracellular calcium signaling. Laser‐induced shockwaves (LIS) and its associated shear stress can mechanically activate Piezo1 to induce transient intracellular calcium (Cai) elevation, accompanied by an increase in FAK activity. Interestingly, multiple pulses of shockwave stimulation caused a more sustained calcium increase and a decrease in FAK activity. Similarly, tuning the degree of Piezo1 activation by titrating either the dosage of Piezo1 ligand Yoda1 or the expression level of Piezo1 produced a similar bimodal pattern of FAK responses. Further investigations revealed that SHP2 serves as an intermediate regulator mediating this bimodal pattern in Piezo1 sensing and signaling. These results suggest that the degrees of Piezo1 activation induced by both mechanical LIS and chemical ligand stimulation may determine downstream signaling characteristics.
Synopsis
How activation of the mechano‐sensitive Piezo1 cation channel transmits signals remains incompletely understood. Here, the degree of Piezo1 activation induced by mechanical force or chemical ligand stimulation is found to determine downstream signaling characteristics.
FRET imaging in live cells monitors the effects of laser‐induced shockwaves (LIS) and their associated shear stress, and of Piezo1 stimulation by its chemical ligand Yoda1.
Mechanical or chemical activation of Piezo1 induces transient intracellular calcium elevation, accompanied by an increase in FAK activity.
Multiple pulses of shockwave stimulation cause a more sustained calcium increase and a decrease in FAK activity.
SHP2 can serve as an intermediate regulator mediating this bimodal pattern in Piezo1 sensing and signaling.
Combination of mechanical laser‐induced shockwave or chemical ligand Yoda1 stimulation and FRET imaging in live cells reveals that transient versus sustained calcium influx through mechano‐activatable channels has opposite effects on FAK kinase activity.
The initiation of an intestinal tumour is a probabilistic process that depends on the competition between mutant and normal epithelial stem cells in crypts
. Intestinal stem cells are closely ...associated with a diverse but poorly characterized network of mesenchymal cell types
. However, whether the physiological mesenchymal microenvironment of mutant stem cells affects tumour initiation remains unknown. Here we provide in vivo evidence that the mesenchymal niche controls tumour initiation in trans. By characterizing the heterogeneity of the intestinal mesenchyme using single-cell RNA-sequencing analysis, we identified a population of rare pericryptal Ptgs2-expressing fibroblasts that constitutively process arachidonic acid into highly labile prostaglandin E
(PGE
). Specific ablation of Ptgs2 in fibroblasts was sufficient to prevent tumour initiation in two different models of sporadic, autochthonous tumorigenesis. Mechanistically, single-cell RNA-sequencing analyses of a mesenchymal niche model showed that fibroblast-derived PGE
drives the expansion οf a population of Sca-1
reserve-like stem cells. These express a strong regenerative/tumorigenic program, driven by the Hippo pathway effector Yap. In vivo, Yap is indispensable for Sca-1
cell expansion and early tumour initiation and displays a nuclear localization in both mouse and human adenomas. Using organoid experiments, we identified a molecular mechanism whereby PGE
promotes Yap dephosphorylation, nuclear translocation and transcriptional activity by signalling through the receptor Ptger4. Epithelial-specific ablation of Ptger4 misdirected the regenerative reprogramming of stem cells and prevented Sca-1
cell expansion and sporadic tumour initiation in mutant mice, thereby demonstrating the robust paracrine control of tumour-initiating stem cells by PGE
-Ptger4. Analyses of patient-derived organoids established that PGE
-PTGER4 also regulates stem-cell function in humans. Our study demonstrates that initiation of colorectal cancer is orchestrated by the mesenchymal niche and reveals a mechanism by which rare pericryptal Ptgs2-expressing fibroblasts exert paracrine control over tumour-initiating stem cells via the druggable PGE
-Ptger4-Yap signalling axis.
The beating heart possesses the intrinsic ability to adapt cardiac output to changes in mechanical load. The century-old Frank-Starling law and Anrep effect have documented that stretching the heart ...during diastolic filling increases its contractile force. However, the molecular mechanotransduction mechanism and its impact on cardiac health and disease remain elusive. Here we show that the mechanically activated Piezo1 channel converts mechanical stretch of cardiomyocytes into Ca
and reactive oxygen species (ROS) signaling, which critically determines the mechanical activity of the heart. Either cardiac-specific knockout or overexpression of Piezo1 in mice results in defective Ca
and ROS signaling and the development of cardiomyopathy, demonstrating a homeostatic role of Piezo1. Piezo1 is pathologically upregulated in both mouse and human diseased hearts via an autonomic response of cardiomyocytes. Thus, Piezo1 serves as a key cardiac mechanotransducer for initiating mechano-chemo transduction and consequently maintaining normal heart function, and might represent a novel therapeutic target for treating human heart diseases.
The Wnt signalling pathway is one of the central signalling pathways in bone development, homeostasis and regulation of bone mineral density. It consists of numerous Wnt ligands, receptors and ...co-receptors, which ensure tight spatiotemporal regulation of Wnt signalling pathway activity and thus tight regulation of bone tissue homeostasis. This enables maintenance of optimal mineral density, tissue healing and adaptation to changes in bone loading. While the role of the canonical/β-catenin Wnt signalling pathway in bone homeostasis is relatively well researched, Wnt ligands can also activate several non-canonical, β-catenin independent signalling pathways with important effects on bone tissue. In this review, we will provide a thorough overview of the current knowledge on different non-canonical Wnt signalling pathways involved in bone biology, focusing especially on the pathways that affect bone cell differentiation, maturation and function, processes involved in bone tissue structure regulation. We will describe the role of the two most known non-canonical pathways (Wnt/planar cell polarity pathways and Wnt/Ca
pathway), as well as other signalling pathways with a strong role in bone biology that communicate with the Wnt signalling pathway through non-canonical Wnt signalling. Our goal is to bring additional attention to these still not well researched but important pathways in the regulation of bone biology in the hope of prompting additional research in the area of non-canonical Wnt signalling pathways.
Intracellular calcium (Ca2+) signals are key regulators of multiple cellular functions, both healthy and physiopathological. It is therefore unsurprising that several cancers present a strong Ca2+ ...homeostasis deregulation. Among the various hallmarks of cancer disease, a particular role is played by metastasis, which has a critical impact on cancer patients’ outcome. Importantly, Ca2+ signalling has been reported to control multiple aspects of the adaptive metastatic cancer cell behaviour, including epithelial–mesenchymal transition, cell migration, local invasion and induction of angiogenesis (see Figure). In this context Ca2+ signalling is considered to be a substantial intracellular tool that regulates the dynamicity and complexity of the metastatic cascade. In the present study we review the spatial and temporal organization of Ca2+ fluxes, as well as the molecular mechanisms involved in metastasis, analysing the key steps which regulate initial tumour spread.
Model of the specific patterns of Ca2+ signals that are associated with different steps of cancer progression. It is important to note that most of the findings on Ca2+ signalling have been generated in vitro. Therefore, it is possible that in tissues, Ca2+ signals do not simply follow the same patterns.
To date, reconstitution of one of the fundamental methods of cell communication, the signaling pathway, has been unaddressed in the bottom-up construction of artificial cells (ACs). Such developments ...are needed to increase the functionality and biomimicry of ACs, accelerating their translation and application in biotechnology. Here, we report the construction of a de novo synthetic signaling pathway in microscale nested vesicles. Vesicle-cell models respond to external calcium signals through activation of an intracellular interaction between phospholipase A2 and a mechanosensitive channel present in the internal membranes, triggering content mixing between compartments and controlling cell fluorescence. Emulsion-based approaches to AC construction are therefore shown to be ideal for the quick design and testing of new signaling networks and can readily include synthetic molecules difficult to introduce to biological cells. This work represents a foundation for the engineering of multicompartment-spanning designer pathways that can be utilized to control downstream events inside an AC, leading to the assembly of micromachines capable of sensing and responding to changes in their local environment.
Cellular senescence and the senescence-associated secretory phenotype (SASP) are implicated in aging and age-related disease, and SASP-related inflammation is thought to contribute to tissue ...dysfunction in aging and diseased animals. However, whether and how SASP factors influence the regenerative capacity of tissues remains unclear. Here, using intestinal organoids as a model of tissue regeneration, we show that SASP factors released by senescent fibroblasts deregulate stem cell activity and differentiation and ultimately impair crypt formation. We identify the secreted N-terminal domain of Ptk7 as a key component of the SASP that activates non-canonical Wnt / Ca
signaling through FZD7 in intestinal stem cells (ISCs). Changes in cytosolic Ca
elicited by Ptk7 promote nuclear translocation of YAP and induce expression of YAP/TEAD target genes, impairing symmetry breaking and stem cell differentiation. Our study discovers secreted Ptk7 as a factor released by senescent cells and provides insight into the mechanism by which cellular senescence contributes to tissue dysfunction in aging and disease.
•PRL activity was regulated by the circadian rhythm.•PRL-induced signaling was significantly decreased in CLOCK−/− mice.•SOCS was up-regulated in CLOCK−/− mice.
The circadian molecular Clock is an ...internal time-keeping system, which regulates various physiological processes. The circadian Clock may be involved in all biological processes. The circadian Clock is closely related to prolactin’s activities. However, until now, the effect of circadian Clock dysregulation on PRL’s bioactivities remains unclear. Clock protein is an essential component in circadian Clock and necessary for Clock function. Therefore, Clock gene knockout mice (CLOCK −/− mice) was used to explore the effect of circadian Clock dysfunction on PRL’s activities. The in vitro and in vivo experimental results showed that PRLR-mediated signaling was significantly down-regulated. PRL-induced JAK2-STAT5 signaling in Clock-/- mice was significantly decreased compared to control mice in vivo. In vitro, PRL/PRLR-mediated signaling in mammary epithelial cell that Clock was knocked down by siRNA was significantly down-regulated compared to control cells. Mechanistically, the expression levels of negative regulatory molecule (the suppressor of cytokine signaling (SOCS) was upregulated in vitro and in vivo, which may be one of the factors that causes the PRL-signaling downregulation. Taken together, the current work indicates that the circadian Clock affects the PRL’s activities. This finding lays the foundation for studying the relationship between the circadian Clock and PRL’s biological activities.
Fibro/Adipogenic Progenitors (FAPs) are muscle-interstitial progenitors mediating pro-myogenic signals that are critical for muscle homeostasis and regeneration. In myopathies, the ...autocrine/paracrine constraints controlling FAP adipogenesis are released causing fat infiltrates. Here, by combining pharmacological screening, high-dimensional mass cytometry and in silico network modeling with the integration of single-cell/bulk RNA sequencing data, we highlighted the canonical WNT/GSK/β-catenin signaling as a crucial pathway modulating FAP adipogenesis triggered by insulin signaling. Consistently, pharmacological blockade of GSK3, by the LY2090314 inhibitor, stabilizes β-catenin and represses PPARγ expression abrogating FAP adipogenesis ex vivo while limiting fatty degeneration in vivo. Furthermore, GSK3 inhibition improves the FAP pro-myogenic role by efficiently stimulating, via follistatin secretion, muscle satellite cell (MuSC) differentiation into mature myotubes. Combining, publicly available single-cell RNAseq datasets, we characterize FAPs as the main source of WNT ligands inferring their potential in mediating autocrine/paracrine responses in the muscle niche. Lastly, we identify WNT5a, whose expression is impaired in dystrophic FAPs, as a crucial WNT ligand able to restrain the detrimental adipogenic differentiation drift of these cells through the positive modulation of the β-catenin signaling.
Neutrophils form cellular clusters or swarms in response to injury or pathogen intrusion. Yet, intracellular signaling events favoring this coordinated response remain to be fully characterized. ...Here, we show that calcium signals play a critical role during mouse neutrophil clustering around particles of zymosan, a structural fungal component. Pioneer neutrophils recognizing zymosan or live
displayed elevated calcium levels. Subsequently, a transient wave of calcium signals in neighboring cells was observed followed by the attraction of neutrophils that exhibited more persistent calcium signals as they reached zymosan particles. Calcium signals promoted LTB4 production while the blocking of extracellular calcium entry or LTB4 signaling abrogated cluster formation. Finally, using optogenetics to manipulate calcium influx in primary neutrophils, we show that calcium signals could initiate recruitment of neighboring neutrophils in an LTB4-dependent manner. Thus, sustained calcium responses at the center of the cluster are necessary and sufficient for the generation of chemoattractive gradients that attract neutrophils in a self-reinforcing process.
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