An outer-pore gate modulates the pharmacology of the TMEM16A channel

TMEM16A Ca2+-activated chloride channels are involved in multiple cellular functions and are proposed targets for diseases such as hypertension, stroke, and cystic fibrosis. This therapeutic endeavor, however, suffers from paucity of selective and potent modulators. Here, exploiting a synthetic small molecule with a biphasic effect on the TMEM16A channel, anthracene-9-carboxylic acid (A9C), we shed light on sites of the channel amenable for pharmacological intervention. Mutant channels with the intracellular gate constitutively open were generated. These channels were entirely insensitive to extracellular A9C when intracellular Ca2+ was omitted. However, when physiological Ca2+ levels were reestablished, the mutants regained sensitivity to A9C. Thus, intracellular Ca2+ is mandatory for the channel response to an extracellular modulator. The underlying mechanism is a conformational change in the outer pore that enables A9C to enter the pore to reach its binding site. The explanation of this structural rearrangement highlights a critical site for pharmacological intervention and reveals an aspect of Ca2+ gating in the TMEM16A channel.

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K2P2.1 (TREK-1) potassium channel activation protects against hyperoxia-induced lung injury

Scientific Reports ◽

10.1038/s41598-020-78886-y ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Tatiana Zyrianova ◽

Benjamin Lopez ◽

Riccardo Olcese ◽

John Belperio ◽

Christopher M. Waters ◽

...

Keyword(s):

Lung Injury ◽

Lung Compliance ◽

Alveolar Epithelial Cells ◽

Pharmacological Intervention ◽

Alveolar Epithelial ◽

Protein Levels ◽

Cell Counts ◽

Novel Approach ◽

Intracellular Ca ◽

Cell Depolarization

AbstractNo targeted therapies exist to counteract Hyperoxia (HO)-induced Acute Lung Injury (HALI). We previously found that HO downregulates alveolar K2P2.1 (TREK-1) K+ channels, which results in worsening lung injury. This decrease in TREK-1 levels leaves a subset of channels amendable to pharmacological intervention. Therefore, we hypothesized that TREK-1 activation protects against HALI. We treated HO-exposed mice and primary alveolar epithelial cells (AECs) with the novel TREK-1 activators ML335 and BL1249, and quantified physiological, histological, and biochemical lung injury markers. We determined the effects of these drugs on epithelial TREK-1 currents, plasma membrane potential (Em), and intracellular Ca2+ (iCa) concentrations using fluorometric assays, and blocked voltage-gated Ca2+ channels (CaV) as a downstream mechanism of cytokine secretion. Once-daily, intra-tracheal injections of HO-exposed mice with ML335 or BL1249 improved lung compliance, histological lung injury scores, broncho-alveolar lavage protein levels and cell counts, and IL-6 and IP-10 concentrations. TREK-1 activation also decreased IL-6, IP-10, and CCL-2 secretion from primary AECs. Mechanistically, ML335 and BL1249 induced TREK-1 currents in AECs, counteracted HO-induced cell depolarization, and lowered iCa2+ concentrations. In addition, CCL-2 secretion was decreased after L-type CaV inhibition. Therefore, Em stabilization with TREK-1 activators may represent a novel approach to counteract HALI.

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Redox-assisted regulation of Ca2+ homeostasis in the endoplasmic reticulum by disulfide reductase ERdj5

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1605818113 ◽

2016 ◽

Vol 113 (41) ◽

pp. E6055-E6063 ◽

Cited By ~ 41

Author(s):

Ryo Ushioda ◽

Akitoshi Miyamoto ◽

Michio Inoue ◽

Satoshi Watanabe ◽

Masaki Okumura ◽

...

Keyword(s):

Endoplasmic Reticulum ◽

Disulfide Bond ◽

Plasma Membranes ◽

Dependent Manner ◽

Cellular Functions ◽

Endoplasmic Reticulum Calcium ◽

Disulfide Reductase ◽

Intracellular Ca ◽

Activity Dependent ◽

Er Calcium

Calcium ion (Ca2+) is an important second messenger that regulates numerous cellular functions. Intracellular Ca2+ concentration ([Ca2+]i) is strictly controlled by Ca2+ channels and pumps on the endoplasmic reticulum (ER) and plasma membranes. The ER calcium pump, sarco/endoplasmic reticulum calcium ATPase (SERCA), imports Ca2+ from the cytosol into the ER in an ATPase activity-dependent manner. The activity of SERCA2b, the ubiquitous isoform of SERCA, is negatively regulated by disulfide bond formation between two luminal cysteines. Here, we show that ERdj5, a mammalian ER disulfide reductase, which we reported to be involved in the ER-associated degradation of misfolded proteins, activates the pump function of SERCA2b by reducing its luminal disulfide bond. Notably, ERdj5 activated SERCA2b at a lower ER luminal [Ca2+] ([Ca2+]ER), whereas a higher [Ca2+]ER induced ERdj5 to form oligomers that were no longer able to interact with the pump, suggesting [Ca2+]ER-dependent regulation. Binding Ig protein, an ER-resident molecular chaperone, exerted a regulatory role in the oligomerization by binding to the J domain of ERdj5. These results identify ERdj5 as one of the master regulators of ER calcium homeostasis and thus shed light on the importance of cross talk among redox, Ca2+, and protein homeostasis in the ER.

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Do Calcium-Activated Chloride Channels Control Renin Secretion?

Physiology ◽

10.1152/physiologyonline.1990.5.2.43 ◽

1990 ◽

Vol 5 (2) ◽

pp. 43-46 ◽

Cited By ~ 1

Author(s):

A Kurtz

Keyword(s):

Chloride Channels ◽

Renin Secretion ◽

Volume Control ◽

Juxtaglomerular Cells ◽

Epithelioid Cells ◽

Intracellular Ca ◽

Cl Channels

The rate of renin secretion from renal juxtaglomerular epithelioid cells appears to be inversely correlated to intracellular Ca activity. Such a dependency of renin secretion on Ca activity could be controlled by Ca-activated Cl channels that may be involved in the volume control of juxtaglomerular cells.

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The role of SOX18 in bladder cancer and its underlying mechanism in mediating cellular functions

Life Sciences ◽

10.1016/j.lfs.2019.116614 ◽

2019 ◽

Vol 232 ◽

pp. 116614

Author(s):

Yin Huaqi ◽

Qin Caipeng ◽

Wang Qiang ◽

Du Yiqing ◽

Xu Tao

Keyword(s):

Bladder Cancer ◽

Underlying Mechanism ◽

Cellular Functions

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Small Interfering RNA Targeting Mitochondrial Calcium Uniporter Improves Cardiomyocyte Cell Viability in Hypoxia/Reoxygenation Injury by Reducing Calcium Overload

Oxidative Medicine and Cellular Longevity ◽

10.1155/2017/5750897 ◽

2017 ◽

Vol 2017 ◽

pp. 1-13 ◽

Cited By ~ 22

Author(s):

Yuriana Oropeza-Almazán ◽

Eduardo Vázquez-Garza ◽

Héctor Chapoy-Villanueva ◽

Guillermo Torre-Amione ◽

Gerardo García-Rivas

Keyword(s):

Underlying Mechanism ◽

Mitochondrial Calcium ◽

Mitochondrial Calcium Uniporter ◽

Calcium Uniporter ◽

Rna Targeting ◽

Intracellular Ca ◽

Pore Opening ◽

Reoxygenation Injury ◽

Interfering Rna ◽

Hypoxia Reoxygenation

Intracellular Ca2+mishandling is an underlying mechanism in hypoxia/reoxygenation (H/R) injury that results in mitochondrial dysfunction and cardiomyocytes death. These events are mediated by mitochondrial Ca2+(mCa2+) overload that is facilitated by the mitochondrial calcium uniporter (MCU) channel. Along this line, we evaluated the effect of siRNA-targeting MCU in cardiomyocytes subjected to H/R injury. First, cardiomyocytes treated with siRNA demonstrated a reduction of MCU expression by 67%, which resulted in significant decrease in mitochondrial Ca2+transport. siRNA treated cardiomyocytes showed decreased mitochondrial permeability pore opening and oxidative stress trigger by Ca2+overload. Furthermore, after H/R injury MCU silencing decreased necrosis and apoptosis levels by 30% and 50%, respectively, and resulted in reduction in caspases 3/7, 9, and 8 activity. Our findings are consistent with previous conclusions that demonstrate that MCU activity is partly responsible for cellular injury induced by H/R and support the concept of utilizing siRNA-targeting MCU as a potential therapeutic strategy.

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Proteolytic activation of prochemerin by kallikrein 7 breaks an ionic linkage and results in C-terminal rearrangement

Biochemical Journal ◽

10.1042/bj20121880 ◽

2013 ◽

Vol 452 (2) ◽

pp. 271-280 ◽

Cited By ~ 26

Author(s):

Stephan Schultz ◽

Anja Saalbach ◽

John T. Heiker ◽

Rene Meier ◽

Tristan Zellmann ◽

...

Keyword(s):

Human Skin ◽

Underlying Mechanism ◽

Structural Rearrangement ◽

Proteolytic Activation ◽

Psoriasis Therapy ◽

Specific Protease ◽

Skin Biopsies ◽

Processing Protease ◽

Excessive Accumulation

The excessive accumulation of adipose tissue in obesity is associated with multiple inflammatory dermatological diseases. Chemerin, a chemoattractant adipokine, dependent on proteolytical activation, is highly expressed in skin. Different proteases have been reported to activate prochemerin, but none is inherently expressed in human skin. In the present study, we identified a tissue-specific protease and investigated the underlying mechanism of activation at the molecular level. We characterized human KLK7 (kallikrein 7) as a prochemerin processing protease in vitro converting prochemerin into active chemerinF156. The activating truncation by the protease might trigger a structural rearrangement leading to an increased affinity of chemerin to CMKLR1 (chemokine-like receptor 1). Molecular modelling and experimental data suggest an underlying ionic interaction in prochemerin C-terminal domains. These findings provide a general molecular basis for the necessity of C-terminal processing of prochemerin. Moreover, immunohistochemistry was used to investigate prochemerin, KLK7 and the recently identified KLK7 inhibitor vaspin expression in human skin biopsies, and distinct co-localization in psoriatic biopsies was observed. On the basis of these results, it is hypothesized that KLK7 activity may contribute to the development of psoriatic lesions as a consequence of excessive chemerin activation and impaired protease activity regulation by vaspin. Therefore this interaction represents an interesting target for psoriasis therapy and treatment of other obesity-related diseases.

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Neutrophil activation in response to monomeric myeloperoxidase

Biochemistry and Cell Biology ◽

10.1139/bcb-2017-0290 ◽

2018 ◽

Vol 96 (5) ◽

pp. 592-601 ◽

Cited By ~ 5

Author(s):

Irina V. Gorudko ◽

Daria V. Grigorieva ◽

Alexey V. Sokolov ◽

Ekaterina V. Shamova ◽

Valeria A. Kostevich ◽

...

Keyword(s):

Acute Inflammation ◽

Neutrophil Activation ◽

Human Neutrophils ◽

Calcium Stores ◽

Cellular Functions ◽

Leukocyte Accumulation ◽

Cytoskeleton Reorganization ◽

Neutrophil Degranulation ◽

Intracellular Ca ◽

Normal Human

Myeloperoxidase (MPO) is an oxidant-producing enzyme that can also regulate cellular functions via its nonenzymatic effects. Mature active MPO isolated from normal human neutrophils is a 145 kDa homodimer, which consists of 2 identical protomers, connected by a single disulfide bond. By binding to CD11b/CD18 integrin, dimeric MPO induces neutrophil activation and adhesion augmenting leukocyte accumulation at sites of inflammation. This study was performed to compare the potency of dimeric and monomeric MPO to elicit selected neutrophil responses. Monomeric MPO (hemi-MPO) was obtained by treating the dimeric MPO by reductive alkylation. Analysis of the crucial signal transducer, intracellular Ca2+, showed that dimeric MPO induces Ca2+ mobilization from the intracellular calcium stores of neutrophils and influx of extracellular Ca2+ whereas the effect of monomeric MPO on Ca2+ increase in neutrophils was less. It was also shown that monomeric MPO was less efficient than dimeric MPO at inducing actin cytoskeleton reorganization, cell survival, and neutrophil degranulation. Furthermore, we have detected monomeric MPO in the blood plasma of patients with acute inflammation. Our data suggest that the decomposition of dimeric MPO into monomers can serve as a regulatory mechanism that controls MPO-dependent activation of neutrophils and reduces the proinflammatory effects of MPO.

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Evidence for an interaction between Golli and STIM1 in store-operated calcium entry

Biochemical Journal ◽

10.1042/bj20100650 ◽

2010 ◽

Vol 430 (3) ◽

pp. 453-460 ◽

Cited By ~ 45

Author(s):

Ciara M. Walsh ◽

Mary K. Doherty ◽

Alexei V. Tepikin ◽

Robert D. Burgoyne

Keyword(s):

Hela Cells ◽

Underlying Mechanism ◽

Binding Assays ◽

Cellular Functions ◽

Store Depletion ◽

Store Operated Calcium Entry ◽

Oligodendrocyte Precursor ◽

Ca2 Channels

SOCCs (store-operated Ca2+ channels) are highly selective ion channels that are activated upon release of Ca2+ from intracellular stores to regulate a multitude of diverse cellular functions. It was reported previously that Golli-BG21, a member of the MBP (myelin basic protein) family of proteins, regulates SOCE (store-operated Ca2+ entry) in T-cells and oligodendrocyte precursor cells, but the underlying mechanism for this regulation is unknown. In the present study we have discovered that Golli can directly interact with the ER (endoplasmic reticulum) Ca2+-sensing protein STIM1 (stromal interaction molecule 1). Golli interacts with the C-terminal domain of STIM1 in both in vitro and in vivo binding assays and this interaction may be modulated by the intracellular Ca2+ concentration. Golli also co-localizes with full-length STIM1 and Orai1 complexes in HeLa cells following Ca2+ store depletion. Overexpression of Golli reduces SOCE in HeLa cells, but this inhibition is overcome by overexpressing STIM1. We therefore suggest that Golli binds to STIM1–Orai1 complexes to negatively regulate the activity of SOCCs.

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Phosphatidylinositol-(4, 5)-bisphosphate regulates calcium gating of small-conductance cation channel TMEM16F

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1718728115 ◽

2018 ◽

Vol 115 (7) ◽

pp. E1667-E1674 ◽

Cited By ~ 30

Author(s):

Wenlei Ye ◽

Tina W. Han ◽

Layla M. Nassar ◽

Mario Zubia ◽

Yuh Nung Jan ◽

...

Keyword(s):

Cellular Functions ◽

Charged Amino Acids ◽

Cation Current ◽

Intracellular Ca ◽

Phospholipid Scrambling ◽

Calcium Gating ◽

Phosphatidylinositol 4 ◽

Open Question ◽

Small Conductance ◽

Positively Charged

TMEM16F, which is activated by elevation of intracellular calcium to trigger phospholipid scrambling and the collapse of lipid bilayer asymmetry to mediate important cellular functions such as blood coagulation, also generates a small-conductance calcium-activated cation current. How TMEM16F activation may be regulated is an open question. By recording TMEM16F Ca2+-activated current, we found that the TMEM16F Ca2+-response is desensitized by a brief exposure to high intracellular Ca2+, which is associated with depletion of phosphatidylinositol-(4, 5)-bisphosphate (PIP2) from the inner leaflet of the membrane. Application of artificial or natural PIP2 restores TMEM16F channel activity. PIP2 modulation of TMEM16F requires the presence of several positively charged amino acids in its cytoplasmic N-terminal domain. TMEM16F interaction with PIP2 works synergistically with membrane depolarization to facilitate Ca2+-gating of TMEM16F. Our study reveals the dependence of TMEM16F activity on phosphoinositides and provides one mechanism for TMEM16F activation to be strictly regulated in the cell membrane.

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Function- and agonist-specific Ca2+signalling: The requirement for and mechanism of spatial and temporal complexity in Ca2+signals

Biochemistry and Cell Biology ◽

10.1139/o00-012 ◽

2000 ◽

Vol 78 (3) ◽

pp. 217-240 ◽

Cited By ~ 33

Author(s):

James D Johnson ◽

John P Chang

Keyword(s):

Secretory Granules ◽

Hormone Secretion ◽

Large Body ◽

Cellular Functions ◽

Vast Number ◽

Temporal Complexity ◽

Cellular Processes ◽

Intracellular Ca ◽

Influx Pathways ◽

Basic Features

Calcium signals have been implicated in the regulation of many diverse cellular processes. The problem of how information from extracellular signals is delivered with specificity and fidelity using fluctuations in cytosolic Ca2+concentration remains unresolved. The capacity of cells to generate Ca2+signals of sufficient spatial and temporal complexity is the primary constraint on their ability to effectively encode information through Ca2+. Over the past decade, a large body of literature has dealt with some basic features of Ca2+-handling in cells, as well as the multiplicity and functional diversity of intracellular Ca2+stores and extracellular Ca2+influx pathways. In principle, physiologists now have the necessary information to attack the problem of function- and agonist-specificity in Ca2+signal transduction. This review explores the data indicating that Ca2+release from diverse sources, including many types of intracellular stores, generates Ca2+signals with sufficient complexity to regulate the vast number of cellular functions that have been reported as Ca2+-dependent. Some examples where such complexity may relate to neuroendocrine regulation of hormone secretion/synthesis are discussed. We show that the functional and spatial heterogeneity of Ca2+stores generates Ca2+signals with sufficient spatiotemporal complexity to simultaneously control multiple Ca2+-dependent cellular functions in neuroendocrine systems.Key words: signal coding, IP3receptor, ryanodine receptor, endoplasmic reticulum, Golgi, secretory granules, mitochondria, exocytosis.

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