scholarly journals In silico Identification of Key Factors Driving the Response of Muscle Sensory Neurons to Noxious Stimuli

2021 ◽  
Vol 15 ◽  
Author(s):  
Sridevi Nagaraja ◽  
Luis F. Queme ◽  
Megan C. Hofmann ◽  
Shivendra G. Tewari ◽  
Michael P. Jankowski ◽  
...  
Keyword(s):  
Ion Channels ◽  
Computational Model ◽  
Neuronal Response ◽  
Integrated Approach ◽  
Electrical Signal ◽  
Sensitivity Analyses ◽  
Delayed Rectifier ◽  
Mechanical Stimuli ◽  
Mouse Muscle ◽  
Noxious Stimuli

Nociceptive nerve endings embedded in muscle tissue transduce peripheral noxious stimuli into an electrical signal [i.e., an action potential (AP)] to initiate pain sensations. A major contributor to nociception from the muscles is mechanosensation. However, due to the heterogeneity in the expression of proteins, such as ion channels, pumps, and exchangers, on muscle nociceptors, we currently do not know the relative contributions of different proteins and signaling molecules to the neuronal response due to mechanical stimuli. In this study, we employed an integrated approach combining a customized experimental study in mice with a computational model to identify key proteins that regulate mechanical nociception in muscles. First, using newly collected data from somatosensory recordings in mouse hindpaw muscles, we developed and then validated a computational model of a mechanosensitive mouse muscle nociceptor. Next, by performing global sensitivity analyses that simulated thousands of nociceptors, we identified three ion channels (among the 17 modeled transmembrane proteins and four endoplasmic reticulum proteins) as potential regulators of the nociceptor response to mechanical forces in both the innocuous and noxious range. Moreover, we found that simulating single knockouts of any of the three ion channels, delayed rectifier voltage-gated K+ channel (Kv1.1) or mechanosensitive channels Piezo2 or TRPA1, considerably altered the excitability of the nociceptor (i.e., each knockout increased or decreased the number of triggered APs compared to when all channels were present). These results suggest that altering expression of the gene encoding Kv1.1, Piezo2, or TRPA1 might regulate the response of mechanosensitive muscle nociceptors.

scholarly journals TACAN is an essential component of the mechanosensitive ion channel responsible for pain sensing

2018 ◽  
Author(s):  
L. Beaulieu-Laroche ◽  
M. Christin ◽  
AM Donoghue ◽  
F. Agosti ◽  
N. Yousefpour ◽  
...  
Keyword(s):  
Ion Channels ◽  
Heterologous Expression ◽  
Ion Channel ◽  
Behavioral Responses ◽  
Mechanical Stimuli ◽  
Thermal Pain ◽  
Fundamental Process ◽  
Mechanosensitive Ion Channel ◽  
Pain Stimuli ◽  
Essential Subunit

SummaryMechanotransduction, the conversion of mechanical stimuli into electrical signals, is a fundamental process underlying several physiological functions such as touch and pain sensing, hearing and proprioception. This process is carried out by specialized mechanosensitive ion channels whose identities have been discovered for most functions except pain sensing. Here we report the identification of TACAN (Tmem120A), an essential subunit of the mechanosensitive ion channel responsible for sensing mechanical pain. TACAN is expressed in a subset of nociceptors, and its heterologous expression increases mechanically-evoked currents in cell lines. Purification and reconstitution of TACAN in synthetic lipids generates a functional ion channel. Finally, knocking down TACAN decreases the mechanosensitivity of nociceptors and reduces behavioral responses to mechanical but not to thermal pain stimuli, without affecting the sensitivity to touch stimuli. We propose that TACAN is a pore-forming subunit of the mechanosensitive ion channel responsible for sensing mechanical pain.

Mechanotransduction in gastrointestinal smooth muscle cells: Role of mechanosensitive ion channels

2021 ◽  
Author(s):  
Vikram Joshi ◽  
Peter R Strege ◽  
Gianrico Farrugia ◽  
Arthur Beyder
Keyword(s):  
Smooth Muscle ◽  
Ion Channels ◽  
Smooth Muscle Cells ◽  
Muscle Cells ◽  
Tissue Level ◽  
Cytoskeletal Proteins ◽  
Cell Junction ◽  
Mechanical Stimuli ◽  
Junction Molecules

Mechanosensation, the ability to properly sense mechanical stimuli and transduce them into physiologic responses, is an essential determinant of gastrointestinal (GI) function. Abnormalities in this process result in highly prevalent GI functional and motility disorders. In the GI tract, several cell types sense mechanical forces and transduce them into electrical signals, which elicit specific cellular responses. Some mechanosensitive cells like sensory neurons act as specialized mechanosensitive cells that detect forces and transduce signals into tissue-level physiologic reactions. Non-specialized mechanosensitive cells like smooth muscle cells (SMCs) adjust their function in response to forces. Mechanosensitive cells utilize various mechanoreceptors and mechanotransducers. Mechanoreceptors detect and convert force into electrical and biochemical signals, and mechanotransducers amplify and direct mechanoreceptor responses. Mechanoreceptors and mechanotransducers include ion channels, specialized cytoskeletal proteins, cell junction molecules, and G-protein coupled receptors. SMCs are particularly important due to their role as final effectors for motor function. Myogenic reflex-the ability of smooth muscle to contract in response to stretch rapidly-is a critical smooth muscle function. Such rapid mechanotransduction responses rely on mechano-gated and -sensitive ion channels, which alter their ion pores' opening in response to force, allowing fast electrical and Ca2+ responses. Though GI SMCs express a variety of such ion channels, their identities remain unknown. Recent advancements in electrophysiological, genetic, in vivo imaging, and multi-omic technologies broaden our understanding of how SMC mechano-gated and -sensitive ion channels regulate GI functions. This review discusses GI SMC mechanosensitivity's current developments with a particular emphasis on mechano-gated and -sensitive ion channels.

scholarly journals Ginsenoside Rb1 exerts antiarrhythmic effects by inhibiting INa and ICaL in rabbit ventricular myocytes

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Zhipei Liu ◽  
Lv Song ◽  
Peipei Zhang ◽  
Zhenzhen Cao ◽  
Jie Hao ◽  
...  
Keyword(s):  
Ion Channels ◽  
Action Potential ◽  
Potassium Current ◽  
Ischemia Reperfusion ◽  
Calcium Currents ◽  
Delayed Rectifier ◽  
Dependent Manner ◽  
Ginsenoside Rb1 ◽  
Patch Clamp Technique ◽  
High Calcium

AbstractGinsenoside Rb1 exerts its pharmacological action by regulating sodium, potassium and calcium ion channels in the membranes of nerve cells. These ion channels are also present in cardiomyocytes, but no studies have been reported to date regarding the effects of Rb1 on cardiac sodium currents (INa), L-type calcium currents (ICaL) and action potentials (APs). Additionally, the antiarrhythmic potential of Rb1 has not been assessed. In this study, we used a whole-cell patch clamp technique to assess the effect of Rb1 on these ion channels. The results showed that Rb1 inhibited INa and ICaL, reduced the action potential amplitude (APA) and maximum upstroke velocity (Vmax), and shortened the action potential duration (APD) in a concentration-dependent manner but had no effect on the inward rectifier potassium current (IK1), delayed rectifier potassium current (IK) or resting membrane potential (RMP). We also designed a pathological model at the cellular and organ level to verify the role of Rb1. The results showed that Rb1 abolished high calcium-induced delayed afterdepolarizations (DADs), depressed the increase in intracellular calcium ([Ca2+]i), relieved calcium overload and protected cardiomyocytes. Rb1 can also reduce the occurrence of ventricular premature beats (VPBs) and ventricular tachycardia (VT) in ischemia-reperfusion (I-R) injury.

scholarly journals A computational model of pig ventricular cardiomyocyte electrophysiology and calcium handling: Translation from pig to human electrophysiology

2021 ◽  
Vol 17 (6) ◽  
pp. e1009137
Author(s):  
Namit Gaur ◽  
Xiao-Yan Qi ◽  
David Benoist ◽  
Olivier Bernus ◽  
Ruben Coronel ◽  
...  
Keyword(s):  
Computational Model ◽  
Ventricular Myocytes ◽  
Cell Model ◽  
Phase 1 ◽  
Ionic Currents ◽  
Pig Model ◽  
Calcium Handling ◽  
Human Model ◽  
Delayed Rectifier ◽  
Triggered Activity

The pig is commonly used as an experimental model of human heart disease, including for the study of mechanisms of arrhythmia. However, there exist differences between human and porcine cellular electrophysiology: The pig action potential (AP) has a deeper phase-1 notch, a longer duration at 50% repolarization, and higher plateau potentials than human. Ionic differences underlying the AP include larger rapid delayed-rectifier and smaller inward-rectifier K+-currents (IKr and IK1 respectively) in humans. AP steady-state rate-dependence and restitution is steeper in pigs. Porcine Ca2+ transients can have two components, unlike human. Although a reliable computational model for human ventricular myocytes exists, one for pigs is lacking. This hampers translation from results obtained in pigs to human myocardium. Here, we developed a computational model of the pig ventricular cardiomyocyte AP using experimental datasets of the relevant ionic currents, Ca2+-handling, AP shape, AP duration restitution, and inducibility of triggered activity and alternans. To properly capture porcine Ca2+ transients, we introduced a two-step process with a faster release in the t-tubular region, followed by a slower diffusion-induced release from a non t-tubular subcellular region. The pig model behavior was compared with that of a human ventricular cardiomyocyte (O’Hara-Rudy) model. The pig, but not the human model, developed early afterdepolarizations (EADs) under block of IK1, while IKr block led to EADs in the human but not in the pig model. At fast rates (pacing cycle length = 400 ms), the human cell model was more susceptible to spontaneous Ca2+ release-mediated delayed afterdepolarizations (DADs) and triggered activity than pig. Fast pacing led to alternans in human but not pig. Developing species-specific models incorporating electrophysiology and Ca2+-handling provides a tool to aid translating antiarrhythmic and arrhythmogenic assessment from the bench to the clinic.

scholarly journals Fluorescence Microscopy of Piezo1 in Droplet Hydrogel Bilayers

2018 ◽  
Author(s):  
Oskar B. Jaggers ◽  
Pietro Ridone ◽  
Boris Martinac ◽  
Matthew A. B. Baker
Keyword(s):  
Ion Channels ◽  
Ion Channel ◽  
Simultaneous Recording ◽  
Mechanical Stimuli ◽  
Channel Activity ◽  
Channel Proteins ◽  
Mechanosensitive Ion Channel ◽  
Lymphatic Dysplasia ◽  
Hydrogel Bilayer

AbstractMechanosensitive ion channels are membrane gated pores which are activated by mechanical stimuli. The focus of this study is on Piezo1, a newly discovered, large, mammalian, mechanosensitive ion channel, which has been linked to diseases such as dehydrated hereditary stomatocytosis (Xerocytosis) and lymphatic dysplasia. Here we utilize an established in-vitro artificial bilayer system to interrogate single Piezo1 channel activity. The droplet-hydrogel bilayer (DHB) system uniquely allows the simultaneous recording of electrical activity and fluorescence imaging of labelled protein. We successfully reconstituted fluorescently labelled Piezo1 ion channels in DHBs and verified activity using electrophysiology in the same system. We demonstrate successful insertion and activation of hPiezo1-GFP in bilayers of varying composition. Furthermore, we compare the Piezo1 bilayer reconstitution with measurements of insertion and activation of KcsA channels to reproduce the channel conductances reported in the literature. Together, our results showcase the use of DHBs for future experiments allowing simultaneous measurements of ion channel gating while visualising the channel proteins using fluorescence.

scholarly journals The development of cooperative channels explains the maturation of hair cell’s mechanotransduction

2019 ◽  
Author(s):  
Francesco Gianoli ◽  
Thomas Risler ◽  
Andrei S. Kozlov
Keyword(s):  
Ion Channels ◽  
Hair Cell ◽  
Inner Ear ◽  
Hair Cells ◽  
Hair Bundle ◽  
Mechanical Stimuli ◽  
Biophysical Properties ◽  
Tip Link ◽  
Fast Adaptation ◽  
Kinetics Of

ABSTRACTHearing relies on the conversion of mechanical stimuli into electrical signals. In vertebrates, this process of mechano-electrical transduction (MET) is performed by specialized receptors of the inner ear, the hair cells. Each hair cell is crowned by a hair bundle, a cluster of microvilli that pivot in response to sound vibrations, causing the opening and closing of mechanosensitive ion channels. Mechanical forces are projected onto the channels by molecular springs called tip links. Each tip link is thought to connect to a small number of MET channels that gate cooperatively and operate as a single transduction unit. Pushing the hair bundle in the excitatory direction opens the channels, after which they rapidly reclose in a process called fast adaptation. It has been experimentally observed that the hair cell’s biophysical properties mature gradually during postnatal development: the maximal transduction current increases, sensitivity sharpens, transduction occurs at smaller hair-bundle displacements, and adaptation becomes faster. Similar observations have been reported during tip-link regeneration after acoustic damage. Moreover, when measured at intermediate developmental stages, the kinetics of fast adaptation varies in a given cell depending on the magnitude of the imposed displacement. The mechanisms underlying these seemingly disparate observations have so far remained elusive. Here, we show that these phenomena can all be explained by the progressive addition of MET channels of constant properties, which populate the hair bundle first as isolated entities, then progressively as clusters of more sensitive, cooperative MET channels. As the proposed mechanism relies on the difference in biophysical properties between isolated and clustered channels, this work highlights the importance of cooperative interactions between mechanosensitive ion channels for hearing.SIGNIFICANCEHair cells are the sensory receptors of the inner ear that convert mechanical stimuli into electrical signals transmitted to the brain. Sensitivity to mechanical stimuli and the kinetics of mechanotransduction currents change during hair-cell development. The same trend, albeit on a shorter timescale, is also observed during hair-cell recovery from acoustic trauma. Furthermore, the current kinetics in a given hair cell depends on the stimulus magnitude, and the degree of that dependence varies with development. These phenomena have so far remained unexplained. Here, we show that they can all be reproduced using a single unifying mechanism: the progressive formation of channel pairs, in which individual channels interact through the lipid bilayer and gate cooperatively.

scholarly journals Piezo1 Induces Local Curvature in a Mammalian Membrane and Forms Specific Protein-Lipid Interactions

2019 ◽  
Author(s):  
Amanda Buyan ◽  
Charles D. Cox ◽  
James Rae ◽  
Jonathan Barnoud ◽  
Jinyuan Li ◽  
...  
Keyword(s):  
Ion Channels ◽  
Pressure Control ◽  
Specific Protein ◽  
Mechanical Stimuli ◽  
Membrane Composition ◽  
Local Curvature ◽  
Force Detection ◽  
Electrical Currents ◽  
Lipid Environment ◽  
Gated Ion Channels

SummaryTouch, hearing, and blood pressure control require mechanically-gated ion channels that convert mechanical stimuli into electrical currents. Piezo1 and Piezo2 were recently identified as essential eukaryotic mechanically-gated ion channels, yet how they respond to physical forces remains poorly understood. Here we use a multi-disciplinary approach to interrogate the interaction of Piezo1 with its lipid environment. We show that individual Piezo1 channels induce significant local curvature in the membrane that is magnified in a cooperative manner to generate larger curved ‘Piezo1 pits.’ Curvature decreases under lateral membrane tension, consistent with a hypothesis that force detection can involve sensing changes to local curvature. The protein alters its local membrane composition, enriching specific lipids and forming essential binding sites for phosphoinositides and cholesterol that are functionally relevant and often related to Piezo1-mediated pathologies. Finally, we show that Piezo1 alters the expression of lipid-regulating proteins and modifies the cellular lipidome. In short, we find that lipids influence Piezo1 activity and Piezo1 influences the local morphology and composition of the bilayer as well as the cellular lipidome.

Ion Channel Compartments in Photoreceptors: Evidence From Salamander Rods With Intact and Ablated Terminals

2007 ◽  
Vol 98 (1) ◽  
pp. 86-95 ◽  
Author(s):  
Peter R. MacLeish ◽  
Colin A. Nurse
Keyword(s):  
Ion Channels ◽  
Imaging Techniques ◽  
Cell Voltage ◽  
Ionic Currents ◽  
Simultaneous Recording ◽  
Delayed Rectifier ◽  
Sensory Cells ◽  
Before And After ◽  
Voltage Dependent ◽  
Highly Correlated

Vertebrate photoreceptors are highly polarized sensory cells in which several different ionic currents have been characterized. In the present study we used whole cell voltage-clamp and optical imaging techniques, the former combined with microsurgical manipulations, and simultaneous recording of membrane current and intracellular calcium signals to investigate the spatial distribution of ion channels within isolated salamander rods. In recordings from intact rods with visible terminals, evidence for five previously identified ionic currents was obtained. These include two Ca2+-dependent, i.e., a Ca2+-dependent chloride current [ ICl(Ca)] and a large-conductance Ca2+- and voltage-dependent K+ or BK current [ IK(Ca)], and three voltage-dependent currents, i.e., a delayed-rectifier type current [ IK(V)], a hyperpolarization-activated cation current ( Ih), and a dihydropyridine-sensitive L-type calcium current ( ICa). Of these, ICl(Ca) was highly correlated with the presence of a terminal; rods with visible terminals expressed ICl(Ca) without exception ( n = 125), whereas approximately 71% of rods (40/56) without visible terminals lacked ICl(Ca). More significantly, ICl(Ca) was absent from all rods ( n = 33) that had their terminals ablated, and recordings from the same cell before and after terminal ablation led, in all cases ( n =10), to the loss of ICl(Ca). In contrast, IK(Ca), IK(V), and Ih remained largely intact after terminal ablation, suggesting that they arose principally from ion channels located in the soma and/or inner segment. The outward IK(Ca) in terminal-ablated rods was reversibly suppressed on “puffing” a Ca2+-free extracellular solution over the soma and was appreciably enhanced by the L-type Ca2+ channel agonist, Bay K 8644 (0.1–2 μM). These data indicate that rod photoreceptors possess discrete targeting mechanisms that preferentially sort ion channels mediating ICl(Ca) to the terminal.

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