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Neuron Aug 2019Dorsal root ganglion (DRG) sensory neuron subtypes defined by their in vivo properties display distinct intrinsic electrical properties. We used bulk RNA sequencing of...
Dorsal root ganglion (DRG) sensory neuron subtypes defined by their in vivo properties display distinct intrinsic electrical properties. We used bulk RNA sequencing of genetically labeled neurons and electrophysiological analyses to define ion channel contributions to the intrinsic electrical properties of DRG neuron subtypes. The transcriptome profiles of eight DRG neuron subtypes revealed differentially expressed and functionally relevant genes, including voltage-gated ion channels. Guided by these data, electrophysiological analyses using pharmacological and genetic manipulations as well as computational modeling of DRG neuron subtypes were undertaken to assess the functions of select voltage-gated potassium channels (Kv1, Kv2, Kv3, and Kv4) in shaping action potential (AP) waveforms and firing patterns. Our findings show that the transcriptome profiles have predictive value for defining ion channel contributions to sensory neuron subtype-specific intrinsic physiological properties. The distinct ensembles of voltage-gated ion channels predicted to underlie the unique intrinsic physiological properties of eight DRG neuron subtypes are presented.
Topics: Action Potentials; Afferent Pathways; Animals; Computer Simulation; Ganglia, Spinal; Gene Expression Profiling; Gene Expression Regulation; High-Throughput Nucleotide Sequencing; Ion Channels; Mechanoreceptors; Mice; Mice, Transgenic; Models, Neurological; Nerve Tissue Proteins; Patch-Clamp Techniques; Potassium Channels, Voltage-Gated; RNA; Sensory Receptor Cells; Transcriptome
PubMed: 31248728
DOI: 10.1016/j.neuron.2019.05.039 -
Cell Death & Disease Mar 2021Hypertrophic scar (HS) formation is a skin fibroproliferative disease that occurs following a cutaneous injury, leading to functional and cosmetic impairment. To date,...
Hypertrophic scar (HS) formation is a skin fibroproliferative disease that occurs following a cutaneous injury, leading to functional and cosmetic impairment. To date, few therapeutic treatments exhibit satisfactory outcomes. The mechanical force has been shown to be a key regulator of HS formation, but the underlying mechanism is not completely understood. The Piezo1 channel has been identified as a novel mechanically activated cation channel (MAC) and is reportedly capable of regulating force-mediated cellular biological behaviors. However, the mechanotransduction role of Piezo1 in HS formation has not been investigated. In this work, we found that Piezo1 was overexpressed in myofibroblasts of human and rat HS tissues. In vitro, cyclic mechanical stretch (CMS) increased Piezo1 expression and Piezo1-mediated calcium influx in human dermal fibroblasts (HDFs). In addition, Piezo1 activity promoted HDFs proliferation, motility, and differentiation in response to CMS. More importantly, intradermal injection of GsMTx4, a Piezo1-blocking peptide, protected rats from stretch-induced HS formation. Together, Piezo1 was shown to participate in HS formation and could be a novel target for the development of promising therapies for HS formation.
Topics: Animals; Apoptosis; Calcium Signaling; Case-Control Studies; Cell Differentiation; Cell Movement; Cell Proliferation; Cells, Cultured; Cicatrix, Hypertrophic; Disease Models, Animal; Fibroblasts; Humans; Intercellular Signaling Peptides and Proteins; Ion Channels; Male; Mechanotransduction, Cellular; Membrane Proteins; Membrane Transport Modulators; Rats, Sprague-Dawley; Skin; Spider Venoms; Rats
PubMed: 33649312
DOI: 10.1038/s41419-021-03481-6 -
Nature Aug 2023PIEZOs are mechanosensitive ion channels that convert force into chemoelectric signals and have essential roles in diverse physiological settings. In vitro studies have...
PIEZOs are mechanosensitive ion channels that convert force into chemoelectric signals and have essential roles in diverse physiological settings. In vitro studies have proposed that PIEZO channels transduce mechanical force through the deformation of extensive blades of transmembrane domains emanating from a central ion-conducting pore. However, little is known about how these channels interact with their native environment and which molecular movements underlie activation. Here we directly observe the conformational dynamics of the blades of individual PIEZO1 molecules in a cell using nanoscopic fluorescence imaging. Compared with previous structural models of PIEZO1, we show that the blades are significantly expanded at rest by the bending stress exerted by the plasma membrane. The degree of expansion varies dramatically along the length of the blade, where decreased binding strength between subdomains can explain increased flexibility of the distal blade. Using chemical and mechanical modulators of PIEZO1, we show that blade expansion and channel activation are correlated. Our findings begin to uncover how PIEZO1 is activated in a native environment. More generally, as we reliably detect conformational shifts of single nanometres from populations of channels, we expect that this approach will serve as a framework for the structural analysis of membrane proteins through nanoscopic imaging.
Topics: Cell Membrane; Fluorescence; Ion Channels; Models, Molecular; Movement; Protein Conformation; Single-Cell Analysis
PubMed: 37587339
DOI: 10.1038/s41586-023-06427-4 -
Proceedings of the National Academy of... Jul 2023Osteoarthritis is a chronic disease that can be initiated by altered joint loading or injury of the cartilage. The mechanically sensitive PIEZO ion channels have been...
Osteoarthritis is a chronic disease that can be initiated by altered joint loading or injury of the cartilage. The mechanically sensitive PIEZO ion channels have been shown to transduce injurious levels of biomechanical strain in articular chondrocytes and mediate cell death. However, the mechanisms of channel gating in response to high cellular deformation and the strain thresholds for activating PIEZO channels remain unclear. We coupled studies of single-cell compression using atomic force microscopy (AFM) with finite element modeling (FEM) to identify the biophysical mechanisms of PIEZO-mediated calcium (Ca) signaling in chondrocytes. We showed that PIEZO1 and PIEZO2 are needed for initiating Ca signaling at moderately high levels of cellular deformation, but at the highest strains, PIEZO1 functions independently of PIEZO2. Biophysical factors that increase apparent chondrocyte membrane tension, including hypoosmotic prestrain, high compression magnitudes, and low deformation rates, also increased PIEZO1-driven Ca signaling. Combined AFM/FEM studies showed that 50% of chondrocytes exhibit Ca signaling at 80 to 85% nominal cell compression, corresponding to a threshold of apparent membrane finite principal strain of E = 1.31, which represents a membrane stretch ratio (λ) of 1.9. Both intracellular and extracellular Ca are necessary for the PIEZO1-mediated Ca signaling response to compression. Our results suggest that PIEZO1-induced signaling drives chondrocyte mechanical injury due to high membrane tension, and this threshold can be altered by factors that influence membrane prestress, such as cartilage hypoosmolarity, secondary to proteoglycan loss. These findings suggest that modulating PIEZO1 activation or downstream signaling may offer avenues for the prevention or treatment of osteoarthritis.
Topics: Humans; Chondrocytes; Ion Channels; Joints; Osteoarthritis; Mechanotransduction, Cellular; Calcium Signaling
PubMed: 37459546
DOI: 10.1073/pnas.2221958120 -
Physiological Reviews Jan 2024Cell excitability and its modulation by hormones and neurotransmitters involve the concerted action of a large repertoire of membrane proteins, especially ion channels.... (Review)
Review
Cell excitability and its modulation by hormones and neurotransmitters involve the concerted action of a large repertoire of membrane proteins, especially ion channels. Unique complements of coexpressed ion channels are exquisitely balanced against each other in different excitable cell types, establishing distinct electrical properties that are tailored for diverse physiological contributions, and dysfunction of any component may induce a disease state. A crucial parameter controlling cell excitability is the resting membrane potential (RMP) set by extra- and intracellular concentrations of ions, mainly Na, K, and Cl, and their passive permeation across the cell membrane through leak ion channels. Indeed, dysregulation of RMP causes significant effects on cellular excitability. This review describes the molecular and physiological properties of the Na leak channel NALCN, which associates with its accessory subunits UNC-79, UNC-80, and NLF-1/FAM155 to conduct depolarizing background Na currents in various excitable cell types, especially neurons. Studies of animal models clearly demonstrate that NALCN contributes to fundamental physiological processes in the nervous system including the control of respiratory rhythm, circadian rhythm, sleep, and locomotor behavior. Furthermore, dysfunction of NALCN and its subunits is associated with severe pathological states in humans. The critical involvement of NALCN in physiology is now well established, but its study has been hampered by the lack of specific drugs that can block or agonize NALCN currents in vitro and in vivo. Molecular tools and animal models are now available to accelerate our understanding of how NALCN contributes to key physiological functions and the development of novel therapies for NALCN channelopathies.
Topics: Humans; Animals; Sodium Channels; Ion Channels; Membrane Potentials; Neurons; Sodium; Membrane Proteins
PubMed: 37615954
DOI: 10.1152/physrev.00014.2022 -
Nature Communications Jan 2022Mechanical overload of the vascular wall is a pathological hallmark of life-threatening abdominal aortic aneurysms (AAA). However, how this mechanical stress resonates...
Mechanical overload of the vascular wall is a pathological hallmark of life-threatening abdominal aortic aneurysms (AAA). However, how this mechanical stress resonates at the unicellular level of vascular smooth muscle cells (VSMC) is undefined. Here we show defective mechano-phenotype signatures of VSMC in AAA measured with ultrasound tweezers-based micromechanical system and single-cell RNA sequencing technique. Theoretical modelling predicts that cytoskeleton alterations fuel cell membrane tension of VSMC, thereby modulating their mechanoallostatic responses which are validated by live micromechanical measurements. Mechanistically, VSMC gradually adopt a mechanically solid-like state by upregulating cytoskeleton crosslinker, α-actinin2, in the presence of AAA-promoting signal, Netrin-1, thereby directly powering the activity of mechanosensory ion channel Piezo1. Inhibition of Piezo1 prevents mice from developing AAA by alleviating pathological vascular remodeling. Our findings demonstrate that deviations of mechanosensation behaviors of VSMC is detrimental for AAA and identifies Piezo1 as a novel culprit of mechanically fatigued aorta in AAA.
Topics: Aneurysm; Animals; Aorta, Abdominal; Aortic Aneurysm; Aortic Aneurysm, Abdominal; Biomedical Engineering; Biophysical Phenomena; Disease Models, Animal; Ion Channels; Male; Mice; Mice, Inbred C57BL; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Netrin-1; Phenotype; Stress, Mechanical; Vascular Remodeling
PubMed: 35082286
DOI: 10.1038/s41467-021-27874-5 -
Theranostics 2023Liver fibrosis is the common pathological pathway of chronic liver diseases and its mechanisms of which have not been fully declared. Macrophages play essential roles...
Liver fibrosis is the common pathological pathway of chronic liver diseases and its mechanisms of which have not been fully declared. Macrophages play essential roles in progression of liver fibrosis partially by sensing abnormal mechanical signals. The aim of the study is to investigate the functions of macrophage Piezo1, a mechano-sensitive ion channel, in liver fibrosis. Immunofluorescence in human and murine fibrotic liver samples revealed that expression of macrophage Piezo1 was increased. Myeloid-specific knockout () attenuated liver fibrosis by decreased collagen deposition and epithelial-mesenchymal transition (EMT). In mice, less inflammation during development of liver fibrosis was observed by lessened macrophage infiltration, decreased M1 polarization and expression of inflammatory cytokines. RNA-seq data showed macrophage Piezo1 regulated transcription of cathepsin S (CTSS). inhibited expression and activity of CTSS and and regulated T cell activity. Furthermore, inhibition of CTSS reversed macrophage inflammatory response driven by Piezo1 activation and LPS. Macrophage Piezo1 activation promoted CTSS secretion due to increased activity of Ca-dependent calpain protease induced by Ca influx to cleave lysosome-associated membrane protein-1 (LAMP1). Pharmacological inhibition of calpain activity partially blocked Piezo1 mediated CTSS secretion. Macrophage Piezo1 deficiency limits the progression of liver fibrosis by inhibited inflammatory response and decreased secretion of CTSS. These findings suggest that targeting Piezo1 channel may be a potential strategy for treating hepatic fibrosis.
Topics: Animals; Humans; Mice; Calpain; Cytokines; Fibrosis; Ion Channels; Liver Cirrhosis; Macrophages
PubMed: 37908726
DOI: 10.7150/thno.86103 -
The International Journal of... Aug 2020In this review, we describe key signaling pathways regulating potassium channels present in the inner mitochondrial membrane. The signaling cascades covered here include... (Review)
Review
In this review, we describe key signaling pathways regulating potassium channels present in the inner mitochondrial membrane. The signaling cascades covered here include phosphorylation, redox reactions, modulation by calcium ions and nucleotides. The following types of potassium channels have been identified in the inner mitochondrial membrane of various tissues: ATP-sensitive, Ca-activated, voltage-gated and two-pore domain potassium channels. The direct roles of these channels involve regulation of mitochondrial respiration, membrane potential and synthesis of reactive oxygen species (ROS). Changes in channel activity lead to diverse pro-life and pro-death responses in different cell types. Hence, characterizing the signaling pathways regulating mitochondrial potassium channels will facilitate understanding the physiological role of these proteins. Additionally, we describe in this paper certain regulatory mechanisms, which are unique to mitochondrial potassium channels.
Topics: Adenosine Triphosphate; Animals; Calcium; Humans; Mitochondria; Mitochondrial Membranes; Oxidation-Reduction; Potassium Channels; Potassium Channels, Calcium-Activated; Potassium Channels, Tandem Pore Domain; Potassium Channels, Voltage-Gated; Reactive Oxygen Species; Signal Transduction
PubMed: 32574707
DOI: 10.1016/j.biocel.2020.105792 -
Annual Review of Biophysics May 2023Carefully orchestrated opening and closing of ion channels control the diffusion of ions across cell membranes, generating the electrical signals required for fast... (Review)
Review
Carefully orchestrated opening and closing of ion channels control the diffusion of ions across cell membranes, generating the electrical signals required for fast transmission of information throughout the nervous system. Inactivation is a parsimonious means for channels to restrict ion conduction without the need to remove the activating stimulus. Voltage-gated channel inactivation plays crucial physiological roles, such as controlling action potential duration and firing frequency in neurons. The ball-and-chain moniker applies to a type of inactivation proposed first for sodium channels and later shown to be a universal mechanism. Still, structural evidence for this mechanism remained elusive until recently. We review the ball-and-chain inactivation research starting from its introduction as a crucial component of sodium conductance during electrical signaling in the classical Hodgkin and Huxley studies, through the discovery of its simple intuitive mechanism in potassium channels during the molecular cloning era, to the eventual elucidation of a potassium channel structure in a ball-and-chain inactivated state.
Topics: Potassium Channels; Cell Membrane; Signal Transduction
PubMed: 36626766
DOI: 10.1146/annurev-biophys-100322-072921 -
Annual Review of Biochemistry Jun 2021Microorganisms contend with numerous and unusual chemical threats and have evolved a catalog of resistance mechanisms in response. One particularly ancient, pernicious... (Review)
Review
Microorganisms contend with numerous and unusual chemical threats and have evolved a catalog of resistance mechanisms in response. One particularly ancient, pernicious threat is posed by fluoride ion (F), a common xenobiotic in natural environments that causes broad-spectrum harm to metabolic pathways. This review focuses on advances in the last ten years toward understanding the microbial response to cytoplasmic accumulation of F, with a special emphasis on the structure and mechanisms of the proteins that microbes use to export fluoride: the CLC family of F/H antiporters and the Fluc/FEX family of F channels.
Topics: Antiporters; Chloride Channels; Cytoplasm; Fluorides; Ion Channels; Ion Transport; Membrane Proteins; Protein Conformation; Saccharomyces cerevisiae Proteins
PubMed: 33492991
DOI: 10.1146/annurev-biochem-071520-112507