Project description:Muscle satellite cells (MuSCs), myogenic stem cells in skeletal muscles, play an essential role in muscle regeneration. After skeletal muscle injury, quiescent MuSCs are activated to enter the cell cycle and proliferate, thereby initiating regeneration; however, the mechanisms that ensure successful MuSC division, including chromosome segregation, remain unclear. Here, we show that PIEZO1, a calcium ion (Ca2+)-permeable cation channel activated by membrane tension, mediates spontaneous Ca2+ influx to control the regenerative function of MuSCs. Our genetic engineering approach in mice revealed that PIEZO1 is functionally expressed in MuSCs and that Piezo1 deletion in these cells delays myofibre regeneration after injury. These results are, at least in part, due to a mitotic defect in MuSCs. Mechanistically, this phenotype is caused by impaired PIEZO1-Rho signalling during myogenesis. Thus, we provide the first concrete evidence that PIEZO1, a bona fide mechanosensitive ion channel, promotes proliferation and regenerative functions of MuSCs through precise control of cell division.
Project description:Mutations that lead to muscular dystrophy often create deficiencies in cytoskeletal support of the muscle sarcolemma causing hyperactive mechanosensitive cation channel (MSC) activity and elevated intracellular Ca(2+). Caveolae are cholesterol-rich microdomains that form mechanically deformable invaginations of the sarcolemma. Mutations to caveolin-3, the main scaffolding protein of caveolae in muscle, cause Limbe-Girdle muscular dystrophy. Using genetic and acute chemical perturbations of developing myotubes we investigated whether caveolae are functionally linked to MSCs. MSC sensitivity was assayed using suction application to patches and probe-induced indentation during whole-cell recordings. Membrane mechanical stress in patches was monitored using patch capacitance/impedance. Cholesterol depletion disrupted caveolae and caused a large increase in MSC current. It also decreased the membrane mechanical relaxation time, likely reflecting cytoskeleton dissociation from the bilayer. Reduction of Cav3 expression with miRNA also increased MSC current and decreased patch relaxation time. In contrast Cav3 overexpression produced a small decrease in MSC currents. To acutely and specifically inhibit Cav3 interactions, we made a chimeric peptide containing the antennapedia membrane translocation domain and the Cav3 scaffolding domain (A-CSD3). A-CSD3 action was time dependent initially producing a mild Ca(2+) leak and increased MSC current, while longer exposures decreased MSC currents coinciding with increased patch stiffening. Images of GFP labeled Cav3 in patches showed that Cav3 doesn't enter the pipette, showing patch composition differed from the cell surface. However, disruption via cholesterol depletion caused Cav3 to become uniformly distributed over the sarcolemma and Cav3 appearance in the patch dome. The whole-cell indentation currents elicited under the different caveolae modifying conditions mirror the patch response supporting the role of caveolae in MSC function. These studies show that normal expression levels of Cav3 are mechanoprotective to the sarcolemma through multiple mechanisms, and Cav3 upregulation observed in some dystrophies may compensate for other mechanical deficiencies.
Project description:Transcranial low-intensity ultrasound is a promising neuromodulation modality, with the advantages of noninvasiveness, deep penetration, and high spatiotemporal accuracy. However, the underlying biological mechanism of ultrasonic neuromodulation remains unclear, hindering the development of efficacious treatments. Here, the well-known Piezo1 was studied through a conditional knockout mouse model as a major mediator for ultrasound neuromodulation ex vivo and in vivo. We showed that Piezo1 knockout (P1KO) in the right motor cortex of mice significantly reduced ultrasound-induced neuronal calcium responses, limb movement, and muscle electromyogram (EMG) responses. We also detected higher Piezo1 expression in the central amygdala (CEA), which was found to be more sensitive to ultrasound stimulation than the cortex was. Knocking out the Piezo1 in CEA neurons showed a significant reduction of response under ultrasound stimulation, while knocking out astrocytic Piezo1 showed no-obvious changes in neuronal responses. Additionally, we excluded an auditory confound by monitoring auditory cortical activation and using smooth waveform ultrasound with randomized parameters to stimulate P1KO ipsilateral and contralateral regions of the same brain and recording evoked movement in the corresponding limb. Thus, we demonstrate that Piezo1 is functionally expressed in different brain regions and that it is an important mediator of ultrasound neuromodulation in the brain, laying the ground for further mechanistic studies of ultrasound.
Project description:Mechanical load of the skeleton system is essential for the development, growth, and maintenance of bone. However, the molecular mechanism by which mechanical stimuli are converted into osteogenesis and bone formation remains unclear. Here we report that Piezo1, a bona fide mechanotransducer that is critical for various biological processes, plays a critical role in bone formation. Knockout of Piezo1 in osteoblast lineage cells disrupts the osteogenesis of osteoblasts and severely impairs bone structure and strength. Bone loss that is induced by mechanical unloading is blunted in knockout mice. Intriguingly, simulated microgravity treatment reduced the function of osteoblasts by suppressing the expression of Piezo1. Furthermore, osteoporosis patients show reduced expression of Piezo1, which is closely correlated with osteoblast dysfunction. These data collectively suggest that Piezo1 functions as a key mechanotransducer for conferring mechanosensitivity to osteoblasts and determining mechanical-load-dependent bone formation, and represents a novel therapeutic target for treating osteoporosis or mechanical unloading-induced severe bone loss.
Project description: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 Ca2+ 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 Ca2+ 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.
Project description:Piezo1 mechanosensitive ion channel (MSC) plays a significant role in human physiology. Despite several research on the function and expression of Piezo1 in the nervous system, its electrophysiological properties in neuroinflammatory astrocytes remain unknown. We tested whether astrocytic neuroinflammatory state regulates Piezo1 using electrical recordings, calcium imaging, and wound healing assays on cultured astrocytes. In this study, we determined whether neuroinflammatory condition regulates astrocytic Piezo1 currents in astrocytes. First, we performed electrophysiological recordings on the mouse cerebellum astrocytes (C8-S) under lipopolysaccharide (LPS)-induced neuroinflammatory condition. We found that LPS treatment significantly increased MSC currents in C8-S. The half-maximal pressure of LPS treated MSC currents was left-shifted but the slope sensitivity was not altered by LPS treatment. LPS-induced increase of MSC currents were further augmented by Piezo1 agonist, Yoda1 but were normalized by Piezo1 inhibitor, GsMTx4. Furthermore, silencing Piezo1 in LPS treated C8-S normalized not only MSC currents but also calcium influx and cell migration velocity. Together, our results show that LPS sensitized Piezo1 channel in C8-S astrocytes. These findings will suggest that astrocytic Piezo1 is a determinant of neuroinflammation pathogenesis and may in turn become the foundation of further research into curing several neuronal illnesses and injury related inflammation of neuronal cells.
Project description:Mechanosensitive Piezo1 channels are essential mechanotransduction proteins in eukaryotes. Their curved transmembrane domains, called arms, create a convex membrane deformation, or footprint, which is predicted to flatten in response to increased membrane tension. Here, using a hyperbolic tangent model, we show that, due to the intrinsic bending rigidity of the membrane, the overlap of neighboring Piezo1 footprints produces a flattening of the Piezo1 footprints and arms. Multiple all-atom molecular dynamics simulations of Piezo1 further reveal that this tension-independent flattening is accompanied by gating motions that open an activation gate in the pore. This open state recapitulates experimentally obtained ionic selectivity, unitary conductance, and mutant phenotypes. Tracking ion permeation along the open pore reveals the presence of intracellular and extracellular fenestrations acting as cation-selective sites. Simulations also reveal multiple potential binding sites for phosphatidylinositol 4,5-bisphosphate. We propose that the overlap of Piezo channel footprints may act as a cooperative mechanism to regulate channel activity.
Project description:The demand for a vaccine for coronavirus disease 2019 (COVID-19) highlighted gaps in our understanding of the requirements for B cell responses to antigens, particularly to membrane-presented antigens, as occurs in vivo. We found that human B cell responses to membrane-presented antigens required the function of Piezo1, a plasma membrane mechanosensitive cation channel. Simply making contact with a glass probe induced calcium (Ca2+) fluxes in B cells that were blocked by the Piezo1 inhibitor GsMTx4. When placed on glass surfaces, the plasma membrane tension of B cells increased, which stimulated Ca2+ influx and spreading of B cells over the glass surface, which was blocked by the Piezo1 inhibitor OB-1. B cell responses to membrane-presented antigens but not to soluble antigens were inhibited both by Piezo1 inhibitors and by siRNA-mediated knockdown of Piezo1. Thus, the activation of Piezo1 defines an essential event in B cell activation to membrane-presented antigens that may be exploited to improve the efficacy of vaccines.
Project description:Mechanosensitive ion channel Piezo1 is known to mediate a variety of inflammatory pathways and is also involved in the occurrence and development of many orthopedic diseases. Although its role in the inflammatory mechanism of knee osteoarthritis (KOA) has been reported, a systematic explanation is yet to be seen. This article aims to summarize the role of inflammatory responses in the pathogenesis of KOA and elucidate the mechanism by which the Piezo1-mediated inflammatory response contributes to the pathogenesis of KOA, providing a theoretical basis for the prevention and treatment of knee osteoarthritis. The results indicate that in the mechanism leading to knee osteoarthritis, Piezo1 can mediate the inflammatory response through chondrocytes and synovial cells, participating in the pathological progression of KOA. Piezo1 has the potential to become a new target for the prevention and treatment of this disease. Additionally, as pain is one of the most severe manifestations in KOA patients, the inflammatory response mediated by Piezo1, which causes the release of inflammatory mediators and pro-inflammatory factors leading to pain, can be further explored.
Project description:Cells can respond to mechanical stress by gating mechanosensitive ion channels (MSCs). The cloning of Piezo1, a eukaryotic cation selective MSC, defines a new system for studying mechanical transduction at the cellular level. Because Piezo1 has electrophysiological properties similar to those of endogenous cationic MSCs that are selectively inhibited by the peptide GsMTx4, we tested whether the peptide targets Piezo1 activity. Extracellular GsMTx4 at micromolar concentrations reversibly inhibited ∼80% of the mechanically induced current of outside-out patches from transfected HEK293 cells. The inhibition was voltage insensitive, and as seen with endogenous MSCs, the mirror image d enantiomer inhibited like the l. The rate constants for binding and unbinding based on Piezo1 current kinetics provided association and dissociation rates of 7.0 × 10(5) M(-1) s(-1) and 0.11 s(-1), respectively, and a K(D) of ∼155 nM, similar to values previously reported for endogenous MSCs. Consistent with predicted gating modifier behavior, GsMTx4 produced an ∼30 mmHg rightward shift in the pressure-gating curve and was active on closed channels. In contrast, streptomycin, a nonspecific inhibitor of cationic MSCs, showed the use-dependent inhibition characteristic of open channel block. The peptide did not block currents of the mechanical channel TREK-1 on outside-out patches. Whole-cell Piezo1 currents were also reversibly inhibited by GsMTx4, and although the off rate was nearly identical to that of outside-out patches, differences were observed for the on rate. The ability of GsMTx4 to target the mechanosensitivity of Piezo1 supports the use of this channel in high-throughput screens for pharmacological agents and diagnostic assays.