scholarly journals Swapping of transmembrane domains in the epithelial calcium channel TRPV6

2017 ◽  
Author(s):  
Appu K. Singh ◽  
Kei Saotome ◽  
Alexander I. Sobolevsky
Keyword(s):  
Ion Channels ◽  
Ion Channel ◽  
Calcium Channel ◽  
Transmembrane Domain ◽  
Transmembrane Domains ◽  
Domain Swapping ◽  
Structural Determinants ◽  
Disease States ◽  
Pore Domains

AbstractTetrameric ion channels have either swapped or non-swapped arrangements of the S1-S4 and pore domains. Here we show that mutations in the transmembrane domain of TRPV6 can result in conversion from a domain-swapped to non-swapped fold. These results reveal structural determinants of domain swapping and raise the possibility that a single ion channel subtype can fold into either arrangement in vivo, affecting its function in normal or disease states.

scholarly journals OSCA/TMEM63 are an evolutionarily conserved family of mechanically activated ion channels

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Swetha E Murthy ◽  
Adrienne E Dubin ◽  
Tess Whitwam ◽  
Sebastian Jojoa-Cruz ◽  
Stuart M Cahalan ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Ion Channels ◽  
Ion Channel ◽  
Molecular Mechanisms ◽  
Deep Insight ◽  
Evolutionarily Conserved ◽  
Bona Fide ◽  
Physical Forces ◽  
Insight Into

Mechanically activated (MA) ion channels convert physical forces into electrical signals, and are essential for eukaryotic physiology. Despite their importance, few bona-fide MA channels have been described in plants and animals. Here, we show that various members of the OSCA and TMEM63 family of proteins from plants, flies, and mammals confer mechanosensitivity to naïve cells. We conclusively demonstrate that OSCA1.2, one of the Arabidopsis thaliana OSCA proteins, is an inherently mechanosensitive, pore-forming ion channel. Our results suggest that OSCA/TMEM63 proteins are the largest family of MA ion channels identified, and are conserved across eukaryotes. Our findings will enable studies to gain deep insight into molecular mechanisms of MA channel gating, and will facilitate a better understanding of mechanosensory processes in vivo across plants and animals.

Carfilzomib-Induced Hypertension Is Mediated By Ion Channel Dysregulation in the Kidneys; The Potent Role of AMP-Activated Kinase α

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 34-35
Author(s):  
Panagiotis Efentakis ◽  
Sofia Lamprou ◽  
Polyzois Dimas ◽  
Constantinos Dimitriou ◽  
Manousos Makridakis ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Ion Channels ◽  
Ion Channel ◽  
Board Of Directors ◽  
Research Funding ◽  
Collecting Duct ◽  
Histological Evaluation ◽  
Advisory Committees ◽  
Induced Hypertension

Introduction: Carfilzomib (Cfz), an irreversible proteasome inhibitor (PI), is an approved agent against relapsed/refractory multiple myeloma (R/R MM). Cfz is associated with high incidence of cardiovascular adverse effects. Hypertension stands as the most frequent cardiovascular complication of Cfz. Even though thrombotic microangiopathy (TMA) is inculpated of Cfz's hypertensive phenotype, its exact pathophysiology is still elusive. In our previous work, we showed that Cfz establishes cardiotoxicity in vivo in a Protein Phosphatase 2A (PP2A)-AMP-activated kinase α (AMPKα)-dependent manner (Efentakis P et al. Blood. 2019;133(7):710-723) but does not lead to a permanent vascular deficit, indicating that hypertension is not vascular derived [Efentakis P et al. IJMS 2020;21(15):E5185]. Taking under consideration that renal homeostasis plays an important role in blood pressure regulation we sought to (i) characterize the dose-dependent manifestation of Cfz-induced hypertension; (ii) investigate the molecular signaling of Cfz in the kidneys by proteomic and immunoblotting analyses and (iii) study the renal ion channels regulation. Methods: Forty C57Bl/6 mice (12-14 weeks of age) were randomly assigned to: (i) Acute Protocol: a. Control [Normal Saline (N/S) 0.9%] and b. Cfz (8mg/kg) for two days and (ii) Sub-acute Protocol: a) Control (N/S 0.9%,) and b) Cfz (8mg/kg) for seven days. Intraperitoneal administration of N/S 0.9% and Cfz was performed at two consecutive and on alternate days for the acute and sub-acute protocols respectively. At baseline and endpoint of the experiments, systolic (SBP) and diastolic blood pressure (DBP) were measured, and subsequently mice were sacrificed for the collection of blood and renal samples. Blood samples were collected in citrate buffer for hematological/coagulation profiling [prothrombin time (PT) and INR estimation] and for cleaved Von Willebrand Factor (cl. VWF) immunoblotting assessment as well as for blood testing of white blood cells (WBCs) and platelets. Renal samples underwent histological proteomic and molecular analyses. Results: SBP and DBP were found to be elevated in Cfz group only in the sub-acute protocol compared to control (SBP: 78.5±2.0 vs 68.2±0.7, p<0.01 and DBP: 104.1±2.3 vs 97.4±2.4, p<0.05, respectively). Neutrophil count in the whole blood was elevated both in the acute and sub-acute protocols, while platelet count was decreased in the acute protocol and restored after sub-acute Cfz administration. Mice presented a thrombotic phenotype characterized by increased PT and INR and decreased cl. VWF after acute Cfz treatment, and a hemorrhagic phenotype with restored cl. VWF after sub-acute Cfz administration. However, the presence of TMA was not confirmed by histological evaluation of the kidneys in any of the protocols. Nonetheless histological evaluation of the kidneys revealed inflammation of the perirenal adipose tissue only in the sub-acute protocol. Proteomic analysis presented that proteasome regulation, metabolism and transport of organic anion processes are affected by Cfz administration. Molecular analysis of the renal tissue showed that Cfz induced an increase in the inducible nitric oxide synthase (iNOS) and microtubule-associated proteins 1A/1B light chain 3B (LC3-B) expression and a decreased AMPKα phosphorylation. Moreover, RT-PCR analysis of the renal samples revealed that collecting duct ion channels epithelial Na+ channel (ENaC), Na+/K+/ATPase and urea transporter 1 (UTA-1) mRNA levels were increased in Cfz group. Conclusion: Sub-acute Cfz treatment establishes a renal-derived hypertensive phenotype and a circulating inflammatory phenotype as indicated by the increased neutrophil and WBCs count in the blood. TMA does not seem to be implicated with the observed phenotype in vivo as investigated molecularly and histologically. Cfz-induced dephosphorylation of AMPKα and the subsequent dysregulation of the collecting duct renal ion channel homeostasis is found to be responsible for the observed effect. Therefore, Cfz seems to induce hypertension by a dysregulation of water-ion re-absorbance leading to increased cardiac preload. The latter comes in agreement with clinical data showing that some Cfz-treated patients present with fluid retention, which can be attributed to the aforementioned renal effects of the drug. Disclosures Efentakis: Amgen: Research Funding. Kastritis:Amgen: Consultancy, Honoraria, Research Funding; Genesis Pharma: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria. Dimopoulos:BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Personal fees; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Personal fees, Research Funding, Speakers Bureau; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Personal fees, Speakers Bureau; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Personal fees, Research Funding, Speakers Bureau; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Personal fees, Research Funding, Speakers Bureau. Andreadou:Amgen: Research Funding. Terpos:Amgen: Honoraria, Research Funding; Genesis pharma SA: Honoraria, Other: travel expenses , Research Funding; Janssen: Honoraria, Research Funding; Takeda: Honoraria, Other: travel expenses , Research Funding; Celgene: Honoraria; Sanofi: Honoraria; BMS: Honoraria.

scholarly journals Ion Channels in Cancer: Are Cancer Hallmarks Oncochannelopathies?

2018 ◽  
Vol 98 (2) ◽  
pp. 559-621 ◽  
Author(s):  
Natalia Prevarskaya ◽  
Roman Skryma ◽  
Yaroslav Shuba
Keyword(s):  
Ion Channels ◽  
Ion Channel ◽  
Human Cancer ◽  
Good Reason ◽  
Point Of View ◽  
Cancer Hallmarks ◽  
Disease States ◽  
Tight Association ◽  
Definition Of ◽  
Inherited Mutations

Genomic instability is a primary cause and fundamental feature of human cancer. However, all cancer cell genotypes generally translate into several common pathophysiological features, often referred to as cancer hallmarks. Although nowadays the catalog of cancer hallmarks is quite broad, the most common and obvious of them are 1) uncontrolled proliferation, 2) resistance to programmed cell death (apoptosis), 3) tissue invasion and metastasis, and 4) sustained angiogenesis. Among the genes affected by cancer, those encoding ion channels are present. Membrane proteins responsible for signaling within cell and among cells, for coupling of extracellular events with intracellular responses, and for maintaining intracellular ionic homeostasis ion channels contribute to various extents to pathophysiological features of each cancer hallmark. Moreover, tight association of these hallmarks with ion channel dysfunction gives a good reason to classify them as special type of channelopathies, namely oncochannelopathies. Although the relation of cancer hallmarks to ion channel dysfunction differs from classical definition of channelopathies, as disease states causally linked with inherited mutations of ion channel genes that alter channel's biophysical properties, in a broader context of the disease state, to which pathogenesis ion channels essentially contribute, such classification seems absolutely appropriate. In this review the authors provide arguments to substantiate such point of view.

scholarly journals Fuel Cell Using Squid Axon Electrolyte and Its Proton Conductivity

2020 ◽  
Vol 11 (4) ◽  
pp. 86
Author(s):  
Tomoki Furuseki ◽  
Yasumitsu Matsuo
Keyword(s):  
Fuel Cell ◽  
Ion Channels ◽  
Ion Channel ◽  
Power Density ◽  
Proton Conductivity ◽  
Clean Energy ◽  
Squid Axon ◽  
High Proton Conductivity ◽  
High Proton

Fuel cells using biomaterials have the potential for environmentally friendly clean energy and have attracted a lot of interest. Moreover, biomaterials are expected to develop into in vivo electrical devices such as pacemakers with no side effects. Ion channels, which are membrane proteins, are known to have a fast ion transport capacity. Therefore, by using ion channels, the realization of fuel cell electrolytes with high-proton conductivity can be expected. In this study, we have fabricated a fuel cell using an ion channel electrolyte for the first time and investigated the electrical properties of the ion channel electrolyte. It was found that the fuel cell using the ion channel membrane shows a power density of 0.78 W/cm2 in the humidified condition. On the other hand, the power density of the fuel cell blocking the ion channel with the channel blocker drastically decreased. These results indicate that the fuel cell using the ion channel electrolyte operates through the existence of the ion channel and that the ion channel membrane can be used as the electrolyte of the fuel cell in humidified conditions. Furthermore, the proton conductivity of the ion channel electrolyte drastically increases above 85% relative humidity (RH) and becomes 2 × 10−2 S/m at 96% RH. This result indicates that the ion channel becomes active above 96%RH. In addition, it was deduced from the impedance analysis that the high proton conductivity of the ion channel electrolyte above 96% RH is caused by the activation of ion channels, which are closely related to the fractionalization of water molecule clusters. From these results, it was found that a fuel cell using the squid axon becomes a new fuel cell using the function of the ion channel above 96% RH.

scholarly journals Mining recent brain proteomic databases for ion channel phosphosite nuggets

2010 ◽  
Vol 137 (1) ◽  
pp. 3-16 ◽  
Author(s):  
Oscar Cerda ◽  
Je-Hyun Baek ◽  
James S. Trimmer
Keyword(s):  
Ion Channels ◽  
Ion Channel ◽  
Mammalian Brain ◽  
Phosphorylation Sites ◽  
Dynamic Regulation ◽  
Voltage Gated ◽  
Voltage Gated Ion Channels ◽  
Α Subunits

Voltage-gated ion channels underlie electrical activity of neurons and are dynamically regulated by diverse cell signaling pathways that alter their phosphorylation state. Recent global mass spectrometric–based analyses of the mouse brain phosphoproteome have yielded a treasure trove of new data as to the extent and nature of phosphorylation of numerous ion channel principal or α subunits in mammalian brain. Here we compile and review data on 347 phosphorylation sites (261 unique) on 42 different voltage-gated ion channel α subunits that were identified in these recent studies. Researchers in the ion channel field can now begin to explore the role of these novel in vivo phosphorylation sites in the dynamic regulation of the localization, activity, and expression of brain ion channels through multisite phosphorylation of their principal subunits.

scholarly journals Function and regulation of TRPP2 ion channel revealed by a gain-of-function mutant

2016 ◽  
Vol 113 (17) ◽  
pp. E2363-E2372 ◽  
Author(s):  
Mahmud Arif Pavel ◽  
Caixia Lv ◽  
Courtney Ng ◽  
Lei Yang ◽  
Parul Kashyap ◽  
...  
Keyword(s):  
Ion Channel ◽  
Transient Receptor Potential ◽  
Transmembrane Domain ◽  
Single Point ◽  
Receptor Potential ◽  
Cyst Formation ◽  
Activation Mechanism ◽  
Gain Of Function ◽  
Monovalent Ions

Mutations in polycystin-1 and transient receptor potential polycystin 2 (TRPP2) account for almost all clinically identified cases of autosomal dominant polycystic kidney disease (ADPKD), one of the most common human genetic diseases. TRPP2 functions as a cation channel in its homomeric complex and in the TRPP2/polycystin-1 receptor/ion channel complex. The activation mechanism of TRPP2 is unknown, which significantly limits the study of its function and regulation. Here, we generated a constitutively active gain-of-function (GOF) mutant of TRPP2 by applying a mutagenesis scan on the S4–S5 linker and the S5 transmembrane domain, and studied functional properties of the GOF TRPP2 channel. We found that extracellular divalent ions, including Ca2+, inhibit the permeation of monovalent ions by directly blocking the TRPP2 channel pore. We also found that D643, a negatively charged amino acid in the pore, is crucial for channel permeability. By introducing single-point ADPKD pathogenic mutations into the GOF TRPP2, we showed that different mutations could have completely different effects on channel activity. The in vivo function of the GOF TRPP2 was investigated in zebrafish embryos. The results indicate that, compared with wild type (WT), GOF TRPP2 more efficiently rescued morphological abnormalities, including curly tail and cyst formation in the pronephric kidney, caused by down-regulation of endogenous TRPP2 expression. Thus, we established a GOF TRPP2 channel that can serve as a powerful tool for studying the function and regulation of TRPP2. The GOF channel may also have potential application for developing new therapeutic strategies for ADPKD.

scholarly journals Possible Magneto-Mechanical and Magneto-Thermal Mechanisms of Ion Channel Activation by Iron-Loaded Ferritin in Magnetogenetics

2019 ◽  
Author(s):  
Mladen Barbic
Keyword(s):  
Ion Channels ◽  
Magnetic Fields ◽  
Ion Channel ◽  
New Technology ◽  
Genetically Engineered ◽  
Channel Activation ◽  
Iron Storage ◽  
Magnetic Spin ◽  
Genetic Constructs

AbstractThe palette of tools for stimulation and regulation of neural activity is continually expanding. One of the new methods being introduced is magnetogenetics, where mechano-sensitive and thermo-sensitive ion channels are genetically engineered to be closely coupled to the iron-storage protein ferritin. Such genetic constructs could provide a powerful new way of non-invasively activating ion channels in-vivo using external magnetic fields that easily penetrate biological tissue. Initial reports that introduced this new technology have sparked a vigorous debate on the plausibility of physical mechanisms of ion channel activation by means of external magnetic fields. I argue that the initial criticisms leveled against magnetogenetics as being physically implausible were possibly based on the overly simplistic and unnecessarily pessimistic assumptions about the magnetic spin configurations of iron in ferritin protein. Additionally, all the possible magnetic-field-based mechanisms of ion channel activation in magnetogenetics might not have been fully considered. I present and propose several new magneto-mechanical and magneto-thermal mechanisms of ion channel activation by iron-loaded ferritin protein that may elucidate and clarify some of the mysteries that presently challenge our understanding of the reported biological experiments. Finally, I present some additional puzzles that will require further theoretical and experimental investigation.

Extracellular Hydraulic Resistance Enhances Cell Migration

2020 ◽  
Author(s):  
Debonil Maity ◽  
Kaustav Bera ◽  
Yizeng Li ◽  
Zhuoxu Ge ◽  
Yun Chen ◽  
...  
Keyword(s):  
Cell Migration ◽  
Ion Channels ◽  
Ion Channel ◽  
Hydraulic Resistance ◽  
High Viscosity ◽  
Vesicular Trafficking ◽  
Water Dynamics ◽  
Actin Dynamics ◽  
Fluid Viscosity

Abstract Cells migrating in vivo can encounter microenvironments with varying physical properties. One such physical variable is the viscosity of the fluid surrounding the cell. Increased fluid viscosity is expected to increase the hydraulic resistance experienced by the migrating cell and therefore decrease the cell speed. We demonstrate that contrary to this expected result, cells migrate faster in high viscosity media on 2D substrates. To reveal the molecular mechanism, we examined both actin dynamics and water dynamics driven by ion channel activity. Results show that cells increased in area in high viscosity and actomyosin dynamics remained similar, except that actin retrograde flow speed is reduced. Inhibiting ion channel fluxes in high viscosity media results in a large reduction in cell speed, suggesting that water flux contributes to the observed speed increase. Moreover, inhibiting actin-dependent vesicular trafficking that transports ion channels from the ER to the cell boundary changes ion channel spatial positioning and reduces cell speed in high viscosity media. Cells also displayed altered Ca2+-activity in high viscosity media, and when cytoplasmic Ca2+ is sequestered, cell speed reduction and altered ion channel positioning were observed. Taken together, we find that the cell cytoplasmic actin-phase and water-phase are coupled during cell migration in high viscosity media. Directional water fluxes are mediated by ion channels whose position depend on actin-based vesicular trafficking. There are no significant changes in ion channel total content in high viscosity, in agreement with physical modeling that also predicts the observed cell speedup in high viscosity environment.

Structural Comparisons of Ligand-gated Ion Channels in Open, Closed, and Desensitized States Identify a Novel Propofol-binding Site on Mammalian γ-Aminobutyric Acid Type A Receptors

2015 ◽  
Vol 122 (4) ◽  
pp. 787-794 ◽  
Author(s):  
Nicholas P. Franks
Keyword(s):  
Ion Channel ◽  
Chloride Channel ◽  
Transmembrane Domain ◽  
Type A ◽  
Transmembrane Domains ◽  
Aminobutyric Acid ◽  
State Dependent ◽  
Novel Approach ◽  
Channel Opening ◽  
Acid Type

Abstract Background: Most anesthetics, particularly intravenous agents such as propofol and etomidate, enhance the actions of the neurotransmitter γ-aminobutyric acid (GABA) at the GABA type A receptor. However, there is no agreement as where anesthetics bind to the receptor. A novel approach would be to identify regions on the receptor that are state-dependent, which would account for the ability of anesthetics to affect channel opening by binding differentially to the open and closed states. Methods: The open and closed structures of the GABA type A receptor homologues Gloeobacter ligand–gated ion channel and glutamate-gated chloride channel were compared, and regions in the channels that move on channel opening and closing were identified. Docking calculations were performed to investigate possible binding of propofol to the GABA type A β3 homomer in this region. Results: A comparison between the open and closed states of the Gloeobacter ligand–gated ion channel and glutamate-gated chloride channel channels identified a region at the top of transmembrane domains 2 and 3 that shows maximum movement when the channels transition between the open and closed states. Docking of propofol into the GABA type A β3 homomer identified two putative binding cavities in this same region, one with a high affinity and one with a lower affinity. Both cavities were adjacent to a histidine residue that has been photolabeled by a propofol analog, and both sites would be disrupted on channel closing. Conclusions: These calculations support the conclusion of a recent photolabeling study that propofol acts at a site at the interface between the extracellular and transmembrane domains, close to the top of transmembrane domain 2.

scholarly journals Dynamic expression of homeostatic ion channels in differentiated cortical astrocytes in vitro

2021 ◽  
Author(s):  
Francesco Formaggio ◽  
Martina Fazzina ◽  
Raúl Estévez ◽  
Marco Caprini ◽  
Stefano Ferroni
Keyword(s):  
Ion Channels ◽  
Ion Channel ◽  
Defined Medium ◽  
Culture Conditions ◽  
Membrane Properties ◽  
Cortical Astrocytes ◽  
Cultured Astrocytes ◽  
Functional Features ◽  
Primary Cultured Astrocytes

AbstractThe capacity of astrocytes to adapt their biochemical and functional features upon physiological and pathological stimuli is a fundamental property at the basis of their ability to regulate the homeostasis of the central nervous system (CNS). It is well known that in primary cultured astrocytes, the expression of plasma membrane ion channels and transporters involved in homeostatic tasks does not closely reflect the pattern observed in vivo. The individuation of culture conditions that promotes the expression of the ion channel array found in vivo is crucial when aiming at investigating the mechanisms underlying their dynamics upon various physiological and pathological stimuli. A chemically defined medium containing growth factors and hormones (G5) was previously shown to induce the growth, differentiation, and maturation of primary cultured astrocytes. Here we report that under these culture conditions, rat cortical astrocytes undergo robust morphological changes acquiring a multi-branched phenotype that develop gradually during the 2-week period of culturing. The shape changes were paralleled by variations in passive membrane properties and background conductance owing to the differential temporal development of inwardly rectifying chloride (Cl−) and potassium (K+) currents. Confocal and immunoblot analyses showed that morphologically differentiated astrocytes displayed a robust increase in the expression of the inward rectifier Cl− and K+ channels ClC-2 and Kir4.1, respectively, which are relevant ion channels in vivo. Finally, they exhibited a large diminution of the intermediate filaments glial fibrillary acidic protein (GFAP) and vimentin which are upregulated in reactive astrocytes in vivo. Taken together the data indicate that long-term culturing of cortical astrocytes in this chemical-defined medium promotes a quiescent functional phenotype. This culture model could aid to address the regulation of ion channel expression involved in CNS homeostasis in response to physiological and pathological challenges.

Sign in / Sign up

Export Citation Format

Share Document