scholarly journals Piezo1 ion channels inherently function as independent mechanotransducers

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Amanda H Lewis ◽  
Jörg Grandl
Keyword(s):  
Ion Channels ◽  
Cell Types ◽  
Membrane Curvature ◽  
Stochastic Simulations ◽  
Open Probability ◽  
Cryo Electron Microscopy ◽  
Large Numbers ◽  
Entire Cell ◽  
Low Levels ◽  
Patch Clamp Electrophysiology

Piezo1 is a mechanically activated ion channel involved in sensing forces in various cell types and tissues. Cryo-electron microscopy has revealed that the Piezo1 structure is bowl-shaped and capable of inducing membrane curvature via its extended footprint, which indirectly suggests that Piezo1 ion channels may bias each other’s spatial distribution and interact functionally. Here, we use cell-attached patch-clamp electrophysiology and pressure-clamp stimulation to functionally examine large numbers of membrane patches from cells expressing Piezo1 endogenously at low levels and cells overexpressing Piezo1 at high levels. Our data, together with stochastic simulations of Piezo1 spatial distributions, show that both at endogenous densities (1–2 channels/μm2), and at non-physiological densities (10–100 channels/μm2) predicted to cause substantial footprint overlap, Piezo1 density has no effect on its pressure sensitivity or open probability in the nominal absence of membrane tension. The results suggest that Piezo channels, at densities likely to be physiologically relevant, inherently behave as independent mechanotransducers. We propose that this property is essential for cells to transduce forces homogeneously across the entire cell membrane.

scholarly journals Piezo1 ion channels inherently function as independent mechanotransducers

2021 ◽  
Author(s):  
Amanda H Lewis ◽  
Jorg Grandl
Keyword(s):  
Ion Channels ◽  
Cell Types ◽  
Substantial Effect ◽  
Membrane Curvature ◽  
Stochastic Simulations ◽  
Open Probability ◽  
Cryo Electron Microscopy ◽  
Large Numbers ◽  
Entire Cell ◽  
Patch Clamp Electrophysiology

Piezo1 is a mechanically activated ion channel involved in sensing forces in various cell types and tissues. Cryo-electron microscopy has revealed that the Piezo1 structure is bowl-shaped and capable of inducing membrane curvature via its extended footprint, which indirectly suggest that Piezo1 ion channels may bias each other's spatial distribution and interact functionally. Here, we use cell-attached patch-clamp electrophysiology and pressure-clamp stimulation to functionally examine large numbers of membrane patches from cells expressing Piezo1 endogenously at low levels and cells overexpressing Piezo1 at high levels. Our data, together with stochastic simulations of Piezo1 spatial distributions, show that both at endogenous densities (1-2 channels/μm2), and at non-physiological densities (10-20 channels/μm2) predicted to cause substantial footprint overlap, Piezo1 density has no substantial effect on its pressure sensitivity or open probability in the nominal absence of membrane tension. The results suggest that Piezo channels, at densities likely to be physiologically relevant, inherently behave as independent mechanotransducers. We propose this property is essential for cells to transduce forces homogeneously across the entire cell membrane.

scholarly journals Neural network aided approximation and parameter inference of non-Markovian models of gene expression

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Qingchao Jiang ◽  
Xiaoming Fu ◽  
Shifu Yan ◽  
Runlai Li ◽  
Wenli Du ◽  
...  
Keyword(s):  
Neural Network ◽  
Stochastic Dynamics ◽  
Stochastic Simulations ◽  
Parameter Inference ◽  
Biochemical Processes ◽  
Markovian Models ◽  
The Neural Network ◽  
Large Numbers ◽  
Small Set ◽  
Noisy Measurements

AbstractNon-Markovian models of stochastic biochemical kinetics often incorporate explicit time delays to effectively model large numbers of intermediate biochemical processes. Analysis and simulation of these models, as well as the inference of their parameters from data, are fraught with difficulties because the dynamics depends on the system’s history. Here we use an artificial neural network to approximate the time-dependent distributions of non-Markovian models by the solutions of much simpler time-inhomogeneous Markovian models; the approximation does not increase the dimensionality of the model and simultaneously leads to inference of the kinetic parameters. The training of the neural network uses a relatively small set of noisy measurements generated by experimental data or stochastic simulations of the non-Markovian model. We show using a variety of models, where the delays stem from transcriptional processes and feedback control, that the Markovian models learnt by the neural network accurately reflect the stochastic dynamics across parameter space.

scholarly journals Synthesis and Evaluation of Novel α-Aminoamides Containing Benzoheterocyclic Moiety for the Treatment of Pain

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1716
Author(s):  
Kun Tong ◽  
Ruotian Zhang ◽  
Fengzhi Ren ◽  
Tao Zhang ◽  
Junlin He ◽  
...  
Keyword(s):  
Ion Channels ◽  
Patch Clamp ◽  
Formalin Test ◽  
Sodium Ion ◽  
Inhibitory Potency ◽  
Voltage Gated ◽  
Patch Clamp Electrophysiology ◽  
Sodium Ion Channels

Novel α-aminoamide derivatives containing different benzoheterocyclics moiety were synthesized and evaluated as voltage-gated sodium ion channels blocks the treatment of pain. Compounds 6a, 6e, and 6f containing the benzofuran group displayed more potent in vivo analgesic activity than ralfinamide in both the formalin test and the writhing assay. Interestingly, they also exhibited potent in vitro anti-Nav1.7 and anti-Nav1.8 activity in the patch-clamp electrophysiology assay. Therefore, compounds 6a, 6e, and 6f, which have inhibitory potency for two pain-related Nav targets, could serve as new leads for the development of analgesic medicines.

scholarly journals Lupeol Accumulation Correlates with Auxin in the Epidermis of Castor

Molecules ◽  
2021 ◽  
Vol 26 (10) ◽  
pp. 2978
Author(s):  
Donghai Li ◽  
Cheng Pan ◽  
Jianjun Lu ◽  
Wajid Zaman ◽  
Huayan Zhao ◽  
...  
Keyword(s):  
Auxin Transport ◽  
Biosynthesis Pathway ◽  
Comparative Transcriptome ◽  
Hormone Activity ◽  
Promoter Regions ◽  
Pentacyclic Triterpene ◽  
Large Numbers ◽  
Genes Encoding ◽  
Low Levels ◽  
Underlying Mechanisms

Lupeol, a natural lupane-type pentacyclic triterpene, possesses various pharmacological properties, and its production attracts attention. Significant quantities of lupeol are deposited on the castor aerial organ surface and are easily extractable as a predominant wax constituent. Thus, castor might be considered as a potential bioreactor for the production of lupeol. The lupeol biosynthesis pathway is well known, but how it is regulated remains largely unknown. Among large numbers of castor cultivars, we targeted one accession line (337) with high levels of lupeol on its stem surface and low levels thereof on its hypocotyl surface, implicating that lupeol synthesis is differentially regulated in the two organs. To explore the underlying mechanisms, we did comparative transcriptome analysis of the first internode of 337 stem and the upper hypocotyl. Our results show that large amounts of auxin-related genes are differentially expressed in both parts, implying some possible interactions between auxin and lupeol production. We also found that several auxin-responsive cis-elements are present in promoter regions of HMGR and LUS genes encoding two key enzymes involved in lupeol production. Furthermore, auxin treatments apparently induced the expression levels of RcHMGR and RcLUS. Furthermore, we observed that auxin treatment significantly increased lupeol contents, whereas inhibiting auxin transport led to an opposite phenotype. Our study reveals some relationships between hormone activity and lupeol synthesis and might provide a promising way for improving lupeol yields in castor.

scholarly journals Platelet and Erythrocyte Extravasation across Inflamed Corneal Venules Depend on CD18, Neutrophils and Mast Cell Degranulation

2021 ◽  
Vol 22 (14) ◽  
pp. 7360
Author(s):  
Angie De La Cruz ◽  
Aubrey Hargrave ◽  
Sri Magadi ◽  
Justin A. Courson ◽  
Paul T. Landry ◽  
...  
Keyword(s):  
Mast Cell ◽  
Cell Types ◽  
Mast Cell Degranulation ◽  
Wild Type ◽  
Delayed Wound Healing ◽  
Corneal Epithelial ◽  
Corneal Abrasion ◽  
Low Levels ◽  
Endothelial Pores

Platelet extravasation during inflammation is under-appreciated. In wild-type (WT) mice, a central corneal epithelial abrasion initiates neutrophil (PMN) and platelet extravasation from peripheral limbal venules. The same injury in mice expressing low levels of the β2-integrin, CD18 (CD18hypo mice) shows reduced platelet extravasation with PMN extravasation apparently unaffected. To better define the role of CD18 on platelet extravasation, we focused on two relevant cell types expressing CD18: PMNs and mast cells. Following corneal abrasion in WT mice, we observed not only extravasated PMNs and platelets but also extravasated erythrocytes (RBCs). Ultrastructural observations of engorged limbal venules showed platelets and RBCs passing through endothelial pores. In contrast, injured CD18hypo mice showed significantly less venule engorgement and markedly reduced platelet and RBC extravasation; mast cell degranulation was also reduced compared to WT mice. Corneal abrasion in mast cell-deficient (KitW-sh/W-sh) mice showed less venule engorgement, delayed PMN extravasation, reduced platelet and RBC extravasation and delayed wound healing compared to WT mice. Finally, antibody-induced depletion of circulating PMNs prior to corneal abrasion reduced mast cell degranulation, venule engorgement, and extravasation of PMNs, platelets, and RBCs. In summary, in the injured cornea, platelet and RBC extravasation depends on CD18, PMNs, and mast cell degranulation.

scholarly journals The inhibitory effect of Gβγ and Gβ isoform specificity on ENaC activity

2013 ◽  
Vol 305 (9) ◽  
pp. F1365-F1373 ◽  
Author(s):  
Ling Yu ◽  
Otor Al-Khalili ◽  
Billie Jeanne Duke ◽  
James D. Stockand ◽  
Douglas C. Eaton ◽  
...  
Keyword(s):  
Single Channel ◽  
Inhibitory Effect ◽  
G Protein Coupled Receptors ◽  
Open Probability ◽  
A6 Cells ◽  
Kinase C ◽  
Downstream Effectors ◽  
Isoform Specificity ◽  
Low Levels ◽  
G Protein Coupled

Epithelial Na+ channel (ENaC) activity, which determines the rate of renal Na+ reabsorption, can be regulated by G protein-coupled receptors. Regulation of ENaC by Gα-mediated downstream effectors has been studied extensively, but the effect of Gβγ dimers on ENaC is unclear. A6 cells endogenously contain high levels of Gβ1 but low levels of Gβ3, Gβ4, and Gβ5 were detected by Q-PCR. We tested Gγ2 combined individually with Gβ1 through Gβ5 expressed in A6 cells, after which we recorded single-channel ENaC activity. Among the five β and γ2 combinations, β1γ2 strongly inhibits ENaC activity by reducing both ENaC channel number ( N) and open probability ( Po) compared with control cells. In contrast, the other four β-isoforms combined with γ2 have no significant effect on ENaC activity. By using various inhibitors to probe Gβ1γ2 effects on ENaC regulation, we found that Gβ1γ2-mediated ENaC inhibition involved activation of phospholipase C-β and its enzymatic products that induce protein kinase C and ERK1/2 signaling pathways.

Control of secretion in anterior pituitary cells--linking ion channels, messengers and exocytosis

1988 ◽  
Vol 139 (1) ◽  
pp. 287-316
Author(s):  
W. T. Mason ◽  
S. R. Rawlings ◽  
P. Cobbett ◽  
S. K. Sikdar ◽  
R. Zorec ◽  
...  
Keyword(s):  
Ion Channels ◽  
Intracellular Calcium ◽  
Anterior Pituitary ◽  
Hormone Secretion ◽  
Cell Types ◽  
Pituitary Cell ◽  
Pituitary Cells ◽  
Calcium Activity ◽  
Anterior Pituitary Cells ◽  
Voltage Dependent

Normal anterior pituitary cells, in their diversity and heterogeneity, provide a rich source of models for secretory function. However, until recently they have largely been neglected in favour of neoplastic, clonal tumour cell lines of pituitary origin, which have enabled a number of studies on supposedly homogeneous cell types. Because many of these lines appear to lack key peptide and neurotransmitter receptors, as well as being degranulated with accompanying abnormal levels of secretion, we have developed a range of normal primary anterior pituitary cell cultures using dispersion and enrichment techniques. By studying lactotrophs, somatotrophs and gonadotrophs we have revealed a number of possible transduction mechanisms by which receptors for hypothalamic peptides and neurotransmitters may control secretion. In particular, the transduction events controlling secretion from pituitary cells may differ fundamentally from those found in other cell types. Patch-clamp recordings in these various pituitary cell preparations have revealed substantial populations of voltage-dependent Na+, Ca2+ and K+ channels which may support action potentials in these cells. Although activation of these channels may gate Ca2+ entry to the cells under some conditions, our evidence taken with that of other laboratories suggests that peptide-receptor interactions leading to hormone secretion occur independently of significant membrane depolarization. Rather, secretion of hormone and rises in intracellular calcium measured with new probes for intracellular calcium activity, can occur in response to hypothalamic peptide activation in the absence of substantial changes in membrane potential. These changes in intracellular calcium activity almost certainly depend on both intracellular and extracellular calcium sources. In addition, strong evidence of a role for multiple intracellular receptors and modulators in the secretory event suggests we should consider the plasma membrane channels important for regulation of hormone secretion to be predominantly agonist-activated, rather than of the more conventional voltage-dependent type. Likewise, evidence from new methods for recording single ion channels suggests the existence of intracellular sites for channel modulation, implying they too may play an important role in secretory regulation. We shall consider new data and new technology which we hope will provide key answers to the many intriguing questions surrounding the control of pituitary hormone secretion. We shall highlight our work with recordings of single ion channels activated by peptides, and recent experiments using imaging of intracellular ionized free calcium.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Bradykinin acutely inhibits activity of the epithelial Na+ channel in mammalian aldosterone-sensitive distal nephron

2011 ◽  
Vol 300 (5) ◽  
pp. F1105-F1115 ◽  
Author(s):  
Oleg Zaika ◽  
Mykola Mamenko ◽  
Roger G. O'Neil ◽  
Oleh Pochynyuk
Keyword(s):  
Critical Role ◽  
Na Channel ◽  
Open Probability ◽  
Kinin System ◽  
Renal Kallikrein ◽  
Subsequent Activation ◽  
Patch Clamp Electrophysiology ◽  
B2 Receptors ◽  
Renal Tubular ◽  
Kallikrein Kinin System

Activation of the renal kallikrein-kinin system results in natriuresis and diuresis, suggesting its possible role in renal tubular sodium transport regulation. Here, we used patch-clamp electrophysiology to directly assess the effects of bradykinin (BK) on the epithelial Na+ channel (ENaC) activity in freshly isolated split-opened murine aldosterone-sensitive distal nephrons (ASDNs). BK acutely inhibits ENaC activity by reducing channel open probability ( Po) in a dose-dependent and reversible manner. Inhibition of B2 receptors with icatibant (HOE-140) abolished BK actions on ENaC. In contrast, activation of B1 receptors with the selective agonist Lys-des-Arg9-BK failed to reproduce BK actions on ENaC. This is consistent with B2 receptors playing a critical role in mediating BK signaling to ENaC. BK has little effect on ENaC Po when Gq/11 was inhibited with Gp antagonist 2A. Moreover, inhibition of phospholipase C (PLC) with U73122, but not saturation of cellular cAMP levels with the membrane-permeable nonhydrolysable cAMP analog 8-cpt-cAMP, prevents BK actions on ENaC activity. This argues that BK stimulates B2 receptors with subsequent activation of Gq/11-PLC signaling cascade to acutely inhibit ENaC activity. Activation of BK signaling acutely depletes apical PI( 4 , 5 )P2 levels. However, inhibition of Ca2+ pump SERCA of the endoplasmic reticulum with thapsigargin does not prevent BK signaling to ENaC. Furthermore, caffeine, while producing a similar rise in [Ca2+]i as in response to BK stimulation, fails to recapitulate BK actions on ENaC. Therefore, we concluded that BK acutely inhibits ENaC Po in mammalian ASDN via stimulation of B2 receptors and following depletion of PI( 4 , 5 )P2, but not increases in [Ca2+]i.

scholarly journals Calnexin revealed as an ether-a-go-go chaperone by getting mutant worms up and going

2018 ◽  
Vol 150 (8) ◽  
pp. 1059-1061
Author(s):  
Jonathan T. Pierce
Keyword(s):  
Ion Channels ◽  
Dynamic Control ◽  
Cell Types ◽  
K Channel ◽  
Membrane Domains ◽  
Excitable Cells ◽  
Patch Clamp Recording ◽  
Cell Excitability ◽  
Distinct Membrane

The role of ion channels in cell excitability was first revealed in a series of voltage clamp experiments by Hodgkin and Huxley in the 1950s. However, it was not until the 1970s that patch-clamp recording ushered in a revolution that allowed physiologists to witness how ion channels flicker open and closed at angstrom scale and with microsecond resolution. The unexpectedly tight seal made by the patch pipette in the whole-cell configuration later allowed molecular biologists to suck up the insides of identified cells to unveil their unique molecular contents. By refining these techniques, researchers have scrutinized the surface and contents of excitable cells in detail over the past few decades. However, these powerful approaches do not discern which molecules are responsible for the dynamic control of the genesis, abundance, and subcellular localization of ion channels. In this dark territory, teams of unknown and poorly understood molecules guide specific ion channels through translation, folding, and modification, and then they shuttle them toward and away from distinct membrane domains via different subcellular routes. A central challenge in understanding these processes is the likelihood that these diverse regulatory molecules may be specific to ion channel subtypes, cell types, and circumstance. In work described in this issue, Bai et al. (2018. J. Gen. Physiol. https://doi.org/10.1085/jgp.201812025) begin to shed light on the biogenesis of UNC-103, a K+ channel found in Caenorhabditis elegans.

scholarly journals Generation of asymmetry during development. Segregation of type-specific proteins in Caulobacter.

1979 ◽  
Vol 81 (1) ◽  
pp. 123-136 ◽  
Author(s):  
N Agabian ◽  
M Evinger ◽  
G Parker
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Messenger Rna ◽  
Cell Types ◽  
Specific Protein ◽  
Soluble Proteins ◽  
Specific Cell ◽  
Daughter Cells ◽  
Specific Proteins ◽  
Entire Cell

An essential event in developmental processes is the introduction of asymmetry into an otherwise undifferentiated cell population. Cell division in Caulobacter is asymmetric; the progeny cells are structurally different and follow different sequences of development, thus providing a useful model system for the study of differentiation. Because the progeny cells are different from one another, there must be a segregation of morphogenetic and informational components at some time in the cell cycle. We have examined the pattern of specific protein segregation between Caulobacter stalked and swarmer daughter cells, with the rationale that such a progeny analysis would identify both structurally and developmentally important proteins. To complement the study, we have also examined the pattern of protein synthesis during synchronous growth and in various cellular fractions. We show here, for the first time, that the association of proteins with a specific cell type may result not only from their periodicity of synthesis, but also from their pattern of distribution at the time of cell division. Several membrane-associated and soluble proteins are segregated asymmetrically between progeny stalked and swarmer cells. The data further show that a subclass of soluble proteins becomes associated with the membrane of the progeny stalked cells. Therefore, although the principal differentiated cell types possess different synthetic capabilities and characteristic proteins, the asymmetry between progeny stalked and swarmer cells is generated primarily by the preferential association of specific soluble proteins with the membrane of only one daughter cell. The majority of the proteins which exhibit this segregation behavior are synthesized during the entire cell cycle and exhibit relatively long, functional messenger RNA half-lives.

Sign in / Sign up

Export Citation Format

Share Document