scholarly journals Voltage-gated proton channels exist in the plasma membrane of human oocytes

2019 ◽  
Vol 34 (10) ◽  
pp. 1974-1983 ◽  
Author(s):  
R Ya Smith ◽  
D Morgan ◽  
L Sharma ◽  
V V Cherny ◽  
N Tidswell ◽  
...  
Keyword(s):  
Large Scale ◽  
Human Sperm ◽  
Proton Channel ◽  
Human Oocytes ◽  
Proton Channels ◽  
Voltage Gated ◽  
Registration Number ◽  
Heterologous Expression Systems ◽  
Competing Interest ◽  
Proton Currents

Abstract STUDY QUESTION Do human oocytes express voltage-gated proton channels? SUMMARY ANSWER Human oocytes exhibit voltage-gated proton currents. WHAT IS KNOWN ALREADY Voltage-gated proton currents have been reported in human sperm, where they contribute to capacitation and motility. No such studies of human oocytes exist. STUDY DESIGN, SIZE, DURATION Voltage-clamp studies were undertaken using entire oocytes and vesicles derived from oocytes and in excised patches of membrane from oocytes. PARTICIPANTS/MATERIALS, SETTING, METHODS Frozen, thawed human metaphase II oocytes were obtained from material donated to the gamete repository at the Rush Center for Advanced Reproductive Care. Prior to patch clamping, oocytes were warmed and equilibrated. Formation of an electrically tight seal requires exposing bare oolemma. Sections of the zona pellucida (ZP) were removed using a laser, followed by repeated pipetting, to further separate the oocyte from the ZP. Patch-clamp studies were performed using the whole-cell configuration on oocytes or vesicles derived from oocytes, and using inside-out patches of membrane, under conditions optimized to detect voltage-gated proton currents. MAIN RESULTS AND THE ROLE OF CHANCE Proton currents are present at significant levels in human oocytes where they exhibit properties similar to those reported in other human cells, as well as those in heterologous expression systems transfected with the HVCN1 gene that codes for the voltage-gated proton channel. LARGE SCALE DATA N/A LIMITATIONS, REASONS FOR CAUTION Human oocytes are large cells, which limits our ability to control the intracellular solution. Subtle effects of cryopreservation by vitrification and subsequent warming on properties of HVCN1, the HVCN1 gene product, cannot be ruled out. WIDER IMPLICATIONS OF THE FINDINGS Possible functions for voltage-gated proton channels in human oocytes may now be contemplated. STUDY FUNDING/COMPETING INTEREST(S) NIH R35GM126902 (TED), Bears Care (DM). No competing interests. TRIAL REGISTRATION NUMBER N/A.

Voltage-gated proton channels help regulate pHi in rat alveolar epithelium

2005 ◽  
Vol 288 (2) ◽  
pp. L398-L408 ◽  
Author(s):  
Ricardo Murphy ◽  
Vladimir V. Cherny ◽  
Deri Morgan ◽  
Thomas E. DeCoursey
Keyword(s):  
Epithelial Cells ◽  
Ph Regulation ◽  
Alveolar Epithelial Cell ◽  
Alveolar Epithelium ◽  
Alveolar Epithelial Cells ◽  
Proton Channel ◽  
Resting Cells ◽  
Proton Channels ◽  
Voltage Gated ◽  
Alveolar Epithelial

Voltage-gated proton channels are expressed highly in rat alveolar epithelial cells. Here we investigated whether these channels contribute to pH regulation. The intracellular pH (pHi) was monitored using BCECF in cultured alveolar epithelial cell monolayers and found to be 7.13 in nominally HCO3−-free solutions [at external pH (pHo) 7.4]. Cells were acid-loaded by the NH4+ prepulse technique, and the recovery was observed. Under conditions designed to eliminate the contribution of other transporters that alter pH, addition of 10 μM ZnCl2, a proton channel inhibitor, slowed recovery about twofold. In addition, the pHi minimum was lower, and the time to nadir was increased. Slowing of recovery by ZnCl2 was observed at pHo 7.4 and pHo 8.0 and in normal and high-K+ Ringer solutions. The observed rate of Zn2+-sensitive pHi recovery required activation of a small fraction of the available proton conductance. We conclude that proton channels contribute to pHi recovery after an acid load in rat alveolar epithelial cells. Addition of ZnCl2 had no effect on pHi in unchallenged cells, consistent with the expectation that proton channels are not open in resting cells. After inhibition of all known pH regulators, slow pHi recovery persisted, suggesting the existence of a yet-undefined acid extrusion mechanism in these cells.

scholarly journals Proton channels and renal hypertensive injury: a key piece of the Dahl salt-sensitive rat puzzle?

2016 ◽  
Vol 310 (8) ◽  
pp. R679-R690 ◽  
Author(s):  
Paul M. O'Connor ◽  
Avirup Guha ◽  
Carly A. Stilphen ◽  
Jingping Sun ◽  
Chunhua Jin
Keyword(s):  
Experimental Studies ◽  
Proton Channel ◽  
Thick Ascending Limb ◽  
Phagocytic Cells ◽  
Proton Channels ◽  
Voltage Gated ◽  
Medullary Thick Ascending Limb ◽  
Current Controversy ◽  
Experimental Approaches ◽  
Species Production

Hv1 is a voltage-gated proton channel highly expressed in phagocytic cells, where it participates in the NADPH oxidase-dependent respiratory burst. We have recently identified Hv1 as a novel renal channel, expressed in the renal medullary thick ascending limb that appears to importantly contribute to the pathogenesis of renal hypertensive injury in the Dahl salt-sensitive rat model. The purpose of this review is to describe the experimental approaches that we have undertaken to identify the source of excess reactive oxygen species production in the renal outer medulla of Dahl salt-sensitive rats and the resulting evidence that the voltage-gated proton channel Hv1 mediates augmented superoxide production and contributes to renal medullary oxidative stress and renal injury. In addition, we will attempt to point out areas of current controversy, as well as propose areas in which further experimental studies are likely to move the field forward. The content of the following review was presented as part of the Water and Electrolyte Homeostasis Section New Investigator Award talk at Experimental Biology 2014.

scholarly journals Functionality of the voltage-gated proton channel truncated in S4

2009 ◽  
Vol 107 (5) ◽  
pp. 2313-2318 ◽  
Author(s):  
Souhei Sakata ◽  
Tatsuki Kurokawa ◽  
Morten H. H. Nørholm ◽  
Masahiro Takagi ◽  
Yoshifumi Okochi ◽  
...  
Keyword(s):  
Voltage Sensor ◽  
Proton Channel ◽  
Voltage Sensing ◽  
Proton Channels ◽  
Voltage Gated ◽  
Transmembrane Segments ◽  
Cysteine Scanning ◽  
Dog Pancreas ◽  
Voltage Gated Ion Channels ◽  
Channel Properties

The voltage sensor domain (VSD) is the key module for voltage sensing in voltage-gated ion channels and voltage-sensing phosphatases. Structurally, both the VSD and the recently discovered voltage-gated proton channels (Hv channels) voltage sensor only protein (VSOP) and Hv1 contain four transmembrane segments. The fourth transmembrane segment (S4) of Hv channels contains three periodically aligned arginines (R1, R2, R3). It remains unknown where protons permeate or how voltage sensing is coupled to ion permeation in Hv channels. Here we report that Hv channels truncated just downstream of R2 in the S4 segment retain most channel properties. Two assays, site-directed cysteine-scanning using accessibility of maleimide-reagent as detected by Western blotting and insertion into dog pancreas microsomes, both showed that S4 inserts into the membrane, even if it is truncated between the R2 and R3 positions. These findings provide important clues to the molecular mechanism underlying voltage sensing and proton permeation in Hv channels.

scholarly journals Regulation of Neutrophil Functions by Hv1/VSOP Voltage-Gated Proton Channels

2021 ◽  
Vol 22 (5) ◽  
pp. 2620
Author(s):  
Yoshifumi Okochi ◽  
Yasushi Okamura
Keyword(s):  
Hypochlorous Acid ◽  
Proton Channel ◽  
Ros Generation ◽  
Ros Production ◽  
Proton Extrusion ◽  
Charge Imbalance ◽  
Proton Channels ◽  
Extracellular Signal Regulated Kinase ◽  
Voltage Gated ◽  
Extracellular Signal

The voltage-gated proton channel, Hv1, also termed VSOP, was discovered in 2006. It has long been suggested that proton transport through voltage-gated proton channels regulate reactive oxygen species (ROS) production in phagocytes by counteracting the charge imbalance caused by the activation of NADPH oxidase. Discovery of Hv1/VSOP not only confirmed this process in phagocytes, but also led to the elucidation of novel functions in phagocytes. The compensation of charge by Hv1/VSOP sustains ROS production and is also crucial for promoting Ca2+ influx at the plasma membrane. In addition, proton extrusion into neutrophil phagosomes by Hv1/VSOP is necessary to maintain neutral phagosomal pH for the effective killing of bacteria. Contrary to the function of Hv1/VSOP as a positive regulator for ROS generation, it has been revealed that Hv1/VSOP also acts to inhibit ROS production in neutrophils. Hv1/VSOP inhibits hypochlorous acid production by regulating degranulation, leading to reduced inflammation upon fungal infection, and suppresses the activation of extracellular signal-regulated kinase (ERK) signaling by inhibiting ROS production. Thus, Hv1/VSOP is a two-way player regulating ROS production. Here, we review the functions of Hv1/VSOP in neutrophils and discuss future perspectives.

scholarly journals Voltage-Gated Proton Channels Find Their Dream Job Managing the Respiratory Burst in Phagocytes

Physiology ◽  
2010 ◽  
Vol 25 (1) ◽  
pp. 27-40 ◽  
Author(s):  
Thomas E. DeCoursey
Keyword(s):  
Reactive Oxygen Species ◽  
Nadph Oxidase ◽  
Respiratory Burst ◽  
Proton Channel ◽  
Oxygen Species ◽  
Proton Extrusion ◽  
Proton Channels ◽  
Voltage Gated ◽  
Voltage Gated Ion Channels ◽  
Voltage Sensing Domain

The voltage-gated proton channel bears surprising resemblance to the voltage-sensing domain (S1–S4) of other voltage-gated ion channels but is a dimer with two conduction pathways. The proton channel seems designed for efficient proton extrusion from cells. In phagocytes, it facilitates the production of reactive oxygen species by NADPH oxidase.

scholarly journals Zinc modulation of proton currents in a new voltage‐gated proton channel suggests a mechanism of inhibition

FEBS Journal ◽  
2020 ◽  
Vol 287 (22) ◽  
pp. 4996-5018 ◽  
Author(s):  
Gustavo Chaves ◽  
Stefanie Bungert‐Plümke ◽  
Arne Franzen ◽  
Iryna Mahorivska ◽  
Boris Musset
Keyword(s):  
Proton Channel ◽  
Voltage Gated ◽  
Mechanism Of Inhibition ◽  
Proton Currents

scholarly journals Absence of Proton Channels in COS-7 Cells Expressing Functional NADPH Oxidase Components

2002 ◽  
Vol 119 (6) ◽  
pp. 571-580 ◽  
Author(s):  
Deri Morgan ◽  
Vladimir V. Cherny ◽  
Marianne O. Price ◽  
Mary C. Dinauer ◽  
Thomas E. DeCoursey
Keyword(s):  
Nadph Oxidase ◽  
Superoxide Anion ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Proton Channel ◽  
Charge Movement ◽  
Wild Type ◽  
Electrophysiological Properties ◽  
Proton Channels ◽  
Proton Currents ◽  
Gp91phox Subunit

Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase is an enzyme of phagocytes that produces bactericidal superoxide anion (O2−) via an electrogenic process. Proton efflux compensates for the charge movement across the cell membrane. The proton channel responsible for the H+ efflux was thought to be contained within the gp91phox subunit of NADPH oxidase, but recent data do not support this idea (DeCoursey, T.E., V.V. Cherny, D. Morgan, B.Z. Katz, and M.C. Dinauer. 2001. J. Biol. Chem. 276:36063–36066). In this study, we investigated electrophysiological properties and superoxide production of COS-7 cells transfected with all NADPH oxidase components required for enzyme function (COSphox). The 7D5 antibody, which detects an extracellular epitope of the gp91phox protein, labeled 96–98% of COSphox cells. NADPH oxidase was functional because COSphox (but not COSWT) cells stimulated by phorbol myristate acetate (PMA) or arachidonic acid (AA) produced superoxide anion. No proton currents were detected in either wild-type COS-7 cells (COSWT) or COSphox cells studied at pHo 7.0 and pHi 5.5 or 7.0. Anion currents that decayed at voltages positive to 40 mV were the only currents observed. PMA or AA did not elicit detectable H+ current in COSWT or COSphox cells. Therefore, gp91phox does not function as a proton channel in unstimulated cells or in activated cells with a demonstrably functional oxidase.

Embryotoxicity testing of IVF disposables: how do manufacturers test?

2020 ◽  
Vol 35 (2) ◽  
pp. 283-292 ◽  
Author(s):  
L Delaroche ◽  
P Oger ◽  
E Genauzeau ◽  
P Meicler ◽  
F Lamazou ◽  
...  
Keyword(s):  
Culture Media ◽  
Toxicity Testing ◽  
Human Sperm ◽  
Culture Conditions ◽  
Mouse Strains ◽  
Control Programs ◽  
Registration Number ◽  
Competing Interest ◽  
High Degree

Abstract STUDY QUESTION How do manufacturers perform embryotoxicity testing in their quality control programs when validating IVF consumables? SUMMARY ANSWER The Mouse Embryo Assay (MEA) and Human Sperm Survival Assay (HSSA) used for IVF disposables differed from one manufacturer to another. WHAT IS KNOWN ALREADY Many components used in IVF laboratories, such as culture media and disposable consumables, may negatively impact human embryonic development. STUDY DESIGN, SIZE, DURATION Through a questionnaire-based survey, the main manufacturers of IVF disposable devices were contacted during the period November to December 2018 to compare the methodology of the MEA and HSSA. We focused on catheters for embryo transfer, catheters for insemination, straws, serological pipettes, culture dishes and puncture needles used in the ART procedures. PARTICIPANTS/MATERIALS, SETTING, METHODS We approached the manufacturers of IVF disposables and asked for details about methodology of the MEA and HSSA performed for toxicity testing of their IVF disposable devices. All specific parameters like mouse strains, number of embryos used, culture conditions (media, temperature, atmosphere), extraction protocol, subcontracting, and thresholds were registered and compared between companies. MAIN RESULTS AND THE ROLE OF CHANCE Twenty-one companies were approached, of which only 11 answered the questionnaire. Significant differences existed in the methodologies and thresholds of the MEA and HSSA used for toxicity testing of IVF disposables. Importantly, some of these parameters could influence the sensitivity of the tests. LIMITATIONS, REASONS FOR CAUTION Although we approached the main IVF manufacturers, the response rate was relatively low. WIDER IMPLICATIONS OF THE FINDINGS Our study confirms the high degree of heterogeneity of the embryotoxicity tests performed by manufacturers when validating their IVF disposable devices. Currently, no regulations exist on this issue. Professionals should call for and request standardization and a future higher degree of transparency as regards embryotoxicity testing from supplying companies; moreover, companies should be urged to provide the users clear and precise information about the results of their tests and how testing was performed. Future recommendations are urgently awaited to improve the sensitivity and reproducibility of embryotoxicity assays over time. STUDY FUNDING/COMPETING INTEREST(S) This study did not receive any funding. L.D. declares a competing interest with Patrick Choay SAS. TRIAL REGISTRATION NUMBER N/A

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