Ion Pumps Research Articles

Sarcoglycans and integrins in human thyrocytes: an immunofluorescence study

The sarcoglycan sub-complex is a protein system which plays a key role in sarcolemma stabilization during muscle activity consisting of six glycosylated transmembrane proteins. Integrins play a key role in the process of cell adhesion, linking the extracellular matrix to the actin cytoskeleton. Here we have analysed the receptor for thyroid hormone, identified on αvβ3-integrin that has an important role in the activation of non-genomic actions of the hormone. Many non-genomic actions of the thyroid hormone appear to contribute to basal levels of activity of a variety of proteins, including ion pumps, intracellular protein trafficking and protein turnover. The purpose of our research was to study the presence and behaviour of sarcoglycans and integrins on the thyroid gland, in both normal and pathological conditions, for the first time. Our results show a normal fluorescence pattern in patients without pathology, and a reduced fluorescence pattern in patients with thyroid disease. Moreover, colocalization in healthy patients was found in double localization reactions, whereas in patients with Hashimoto’s thyroiditis sarcoglycans did not colocalize with tested integrin. These data could confirm the hypothesis of a close association between sarcoglycans and integrins, which, in pathological condition, are not found contemporarily hypothesizing that each single protein system could have a role in maintaining cell vitality.

Electromechanical model for object roughness perception during finger sliding

Touch allows us to gather abundant information in the world around us. However, how sensory cells embedded in the fingers convey texture information into their firing patterns is still poorly understood. Here, we develop an electromechanical model for roughness perception by incorporating main ingredients such as voltage-gated ion channels, active ion pumps, mechanosensitive channels, and cell deformation. The model reveals that sensory cells can convey texture wavelengths into the period of their firing patterns as the finger slides across object surfaces, but they can only convey a limited range of texture wavelengths. We also show that an increase in sliding speed broadens the decoding wavelength range at the cost of reduction of lower perception limits. Thus, a smaller sliding speed and a bigger contact force may be needed to successfully discern a smooth surface, consistent with previous psychophysical observations. Moreover, we show that cells with slowly adapting mechanosensitive channels can still fire action potentials under static loadings, indicating that slowly adapting mechanosensitive channels may contribute to the perception of coarse textures under static touch. Our work thus provides a new theoretical framework to study roughness perception and may have important implications for the design of electronic skin, artificial touch, and haptic interfaces.

Loss of fiber cell communication may contribute to the development of cataracts of many different etiologies.

The lens is an avascular organ that is supported by an internal circulation of water and solutes. This circulation is driven by ion pumps, channels and transporters in epithelial cells and by ion channels in fiber cells and is maintained by fiber-fiber and fiber-epithelial cell communication. Gap junctional intercellular channels formed of connexin46 and connexin50 are critical components of this circulation as demonstrated by studies of connexin null mice and connexin mutant mice. Moreover, connexin mutants are one of the most common causes of autosomal dominant congenital cataracts. However, alterations of the lens circulation and coupling between lens fiber cells are much more prevalent, beyond the connexin mutant lenses. Intercellular coupling and levels of connexins are decreased with aging. Gap junction-mediated intercellular communication decreases in mice expressing mutant forms of several different lens proteins and in some mouse models of lens protein damage. These observations suggest that disruption of ionic homeostasis due to reduction of the lens circulation is a common component of the development of many different types of cataracts. The decrease in the lens circulation often reflects low levels of lens fiber cell connexins and/or functional gap junction channels.

P10.03.B Insights into the development of tunable brain implants for local chemotherapy

Abstract Background Glioblastomas (GBMs) remain an unmastered medical challenge. Poor delivery and systemic toxicity of many chemotherapeutic agents limit their therapeutic success in GBM treatment. Bioelectronic implants for local chemo drug delivery can optimize drug concentrations at the tumor site, duration of treatment and tumor suppression, while systemic effects remain at an acceptable low level. We present miniature bioelectronic devices for drug delivery able to administer chemotherapeutics via electric control with high spatiotemporal precision.1 The drug delivery is based on the electro migration of drug molecules in an ion selective matrix towards a target of choice. These bioelectronic devices, called chemotherapeutic ion pumps (chemoIPs), can be used for triggered drug release of chemotherapeutics that are usually shielded by the blood brain barrier. Material and Methods The performance of chemoIPs is studied in different brain tumor models with increasing complexity (cell culture and different in vivo models). With chemoIPs it is possible to constantly administer drugs with highest precision (delivery rates at pmol*min-1 precision) towards cell culture spheroids, ex ovo-grown tumors and in vivo brain tumors Results The treatment efficiency was analyzed via flow cytometry quantifying apoptosis and cell cycle arrest, as well as immune-histochemical analysis for apoptosis. ChemoIP treatment is able to trigger the disintegration of targeted tumor spheroids, and is able to inhibit the tumor growth of ex ovo-grown glioblastomas significantly. Furthermore, the proteomes of neurons and glioblastoma cells were recorded via proteomics, which showed that only GBM cells are harmed by the chemotherapeutic treatment, but not neurons. In parallel, can follow the pharmacokinetics of the chemoIP-mediated drug administration via drug quantification using mass spectrometry and compare it to computer simulations in different tumor models. Conclusion The here exemplified electrically-driven drug delivery via chemoIPs is a drug administration method that can serve as basis for further implant development, which has the potential to increase the efficacy of chemotherapy due to highly-targeted and locally-controlled drug delivery.

Regulation of Potassium and Chloride Concentrations in Nervous Tissue as a Method of Anticonvulsant Therapy

Under some pathological conditions, such as pharmacoresistantepilepsy, status epilepticus or certain forms of genetic abnormalities,spiking activity of GABAergic interneurons may enhance excitationprocesses in neuronal circuits and provoke the generation of ictaldischarges. As a result, anticonvulsants acting on the GABAergicsystem may be ineffective or even increase seizure activity. Thisparadoxical effect of the inhibitory system is due to ionic imbalancesin nervous tissue. This review addresses the mechanisms of ictaldischarge initiation in neuronal networks due to the imbalance ofchloride and potassium ions, as well as possible ways to regulateionic concentrations. Both the enhancement (or attenuation) of theactivity of certain neuronal ion transporters and ion pumps andtheir additional expression via gene therapy can be effective insuppressing seizure activity caused by ionic imbalances. The Na+–K+-pump,NKCC1 and KCC2 cotransporters are important for maintaining properK+ and Cl– concentrationsin nervous tissue, having been repeatedly considered as pharmacologicaltargets for antiepileptic exposures. Further progress in this directionis hampered by the lack of sufficiently selective pharmacologicaltools and methods for providing effective drug delivery to the epilepticfocus. The use of the gene therapy techniques, such as overexpressingof the KCC2 transporter in the epileptic focus, seems to be a more promisingapproach. Another possible direction could be the use of optogenetictools, namely specially designed light-activated ion pumps or ionchannels. In this case, photon energy can be used to create therequired gradients of chloride and potassium ions, although thesemethods also have significant limitations which complicate theirrapid introduction into medicine.

Fluorometric setup and method for studying the functional activity of corneal endotheliocytes

Subject of study. Experimental methods for investigating the state of preservation and functionality of the corneal endothelium, which is determined by the water permeability of the cells and activity of ion pumps, mainly by sodium–potassium adenosine triphosphatase, were considered. Aim of study. The aim of this study was to identify significant measurable parameters such as the fluorescence intensity integrated over the entire cornea preparation and the temporal dynamic of this fluorescence. Additionally, a specialized experimental fluorometric setup was designed based on fiber optics. Method. Modifications were introduced to the composition and design of a universal experimental setup for the measurement of cell functions that enabled implementation of a fluorescence-based method for determination of the intracellular sodium concentration without processing the digital image of the cornea preparation. Main results. The specialized experimental setup and method were developed for investigating functions of the corneal endothelial cells and the intracellular signaling mechanisms whose activation or disfunction under conditions of a traumatic inflammation and after a hypothermic preservation can be related to the development of a corneal edema and a corneal graft disease. Practical significance. The specialized experimental setup and methods for functional testing of the corneal endothelial cells developed in this study can be applied to determine the degree of suitability of the cornea as a transplantation material. They can also be used as a system of tests for determining the effectiveness of the cornea preservation methods.

Bioinspired Artificial Ion Pumps.

Ion pumps are important membrane-spanning transporters that pump ions against the electrochemical gradient across the cell membrane. In biological systems, ion pumping is essential to maintain intracellular osmotic pressure, to respond to external stimuli, and to regulate physiological activities by consuming adenosine triphosphate. In recent decades, artificial ion pumping systems with diverse geometric structures and functions have been developing rapidly with the progress of advanced materials and nanotechnology. In this Review, bioinspired artificial ion pumps, including four categories: asymmetric structure-driven ion pumps, pH gradient-driven ion pumps, light-driven ion pumps, and electron-driven ion pumps, are summarized. The working mechanisms, functions, and applications of those artificial ion pumping systems are discussed. Finally, a brief conclusion of underpinning challenges and outlook for future research are tentatively discussed.

Bidirectional Photochemistry of Antarctic Microbial Rhodopsin: Emerging Trend of Ballistic Photoisomerization from the 13-cis Resting State.

The decades-long ultrafast examination of nearly a dozen microbial retinal proteins, ion pumps, and sensory photoreceptors has not identified structure–function indicators which predict photoisomerization dynamics, whether it will be sub-picosecond and ballistic or drawn out with complex curve-crossing kinetics. Herein, we report the emergence of such an indicator. Using pH control over retinal isomer ratios, photoinduced transient absorption is recorded in an inward proton pumping Antarctic microbial rhodopsin (AntR) for 13-cis and all-trans retinal resting states. The all-trans fluorescent state decays with 1 ps exponential kinetics. In contrast, in 13-cis it decays within ∼300 fs accompanied by continuous spectral evolution, indicating ballistic internal conversion. The coherent wave packet nature of 13-cis isomerization in AntR matches published results for bacteriorhodopsin (BR) and Anabaena sensory rhodopsin (ASR), which also accommodate both all-trans and 13-cis retinal resting states, marking the emergence of a first structure–photodynamics indicator which holds for all three tested pigments.

The Mechanism of Energy Coupling in H+/Na+-Pumping Membrane Pyrophosphatase-Possibilities and Probabilities.

Membrane pyrophosphatases (mPPases) found in plant vacuoles and some prokaryotes and protists are ancient cation pumps that couple pyrophosphate hydrolysis with the H+ and/or Na+ transport out of the cytoplasm. Because this function is reversible, mPPases play a role in maintaining the level of cytoplasmic pyrophosphate, a known regulator of numerous metabolic reactions. mPPases arouse interest because they are among the simplest membrane transporters and have no homologs among known ion pumps. Detailed phylogenetic studies have revealed various subtypes of mPPases and suggested their roles in the evolution of the “sodium” and “proton” bioenergetics. This treatise focuses on the mechanistic aspects of the transport reaction, namely, the coupling step, the role of the chemically produced proton, subunit cooperation, and the relationship between the proton and sodium ion transport. The available data identify H+-PPases as the first non-oxidoreductase pump with a “direct-coupling” mechanism, i.e., the transported proton is produced in the coupled chemical reaction. They also support a “billiard” hypothesis, which unifies the H+ and Na+ transport mechanisms in mPPase and, probably, other transporters.

Precision Medicine in Chinese Medicine

This article attempts to demonstrate the scientificity and clinical practicability of the meridian and acupoint system in Chinese medicine by explaining the analogy of the meridian and acupoint system, in addition to some experimental results of the biomedical engineering of Western medicine. Precision medicine in Chinese medicine is accomplished through the coordinated operation of the neurohumoral regulation system, the cell transduction system and the meridian system. Appropriate stimulation of acupoints on the human body can trigger certain targets in the body and produce the desired response, such as anti-inflammatory reactions or pro-inflammatory reactions. It can also change the homeostasis of the human body's internal environment, including endocrine, physiological, pathological, psychological and cellular states by controlling body temperature regulation within a certain range. There are many functions of meridians. In fact, the meridian system can not only respond to acupuncture stimuli, but also transmit the effects of drugs to the target. Different acupoints on the surface of the human body have the same or different functions, and through the transduction of the meridian system, the local targets or all of the body will produce the same or different responses. Several experiments with acupuncture and other mechanical stimuli have confirmed the existence of this fact. But the experiment can only show a small part of the full function of acupuncture. The functions of various acupoints are equivalent to the functions of receptors, channels, ion pumps and other structures on the cell membrane. It is just that there are macro and micro differences in the form of expression. Intracellular and extracellular signal transduction, cascade reactions, and neurohumoral regulation are closely related to the meridian system.

Design of a vacuum system for space active hydrogen maser

With the high precision and stability of its frequency signal outputs, active hydrogen maser plays an important role in such fields as timing, satellite navigation, and communication. However, it needs to be lighter so as to be applied in space. We made a research, based on the calculation of the hydrogen flow and the adsorption efficiency of the adsorption unit, on the parameters of the vacuum system and the structural requirements, and designed a combined vacuum pump for the Space Active Hydrogen Maser (SAHM). This vacuum pump consists of a getter pump and a small ion pump, the total mass of which is about 5 kg. The pumping speed will be about 474 L/s by computation, when an amount, 2.5 MPa L, of hydrogen has been adsorbed by getters. Theoretically, the total source hydrogen inflow in lifetime is not higher than 20% of the total capacity getter pump, thus the design should amply meet the requirements of the SAHM vacuum system, and is of great significance for future SAHM applications.

Cryo-EM structures of the channelrhodopsin ChRmine in lipid nanodiscs

Microbial channelrhodopsins are light-gated ion channels widely used for optogenetic manipulation of neuronal activity. ChRmine is a bacteriorhodopsin-like cation channelrhodopsin (BCCR) more closely related to ion pump rhodopsins than other channelrhodopsins. ChRmine displays unique properties favorable for optogenetics including high light sensitivity, a broad, red-shifted activation spectrum, cation selectivity, and large photocurrents, while its slow closing kinetics impedes some applications. The structural basis for ChRmine function, or that of any other BCCR, is unknown. Here, we present cryo-EM structures of ChRmine in lipid nanodiscs in apo (opsin) and retinal-bound (rhodopsin) forms. The structures reveal an unprecedented trimeric architecture with a lipid filled central pore. Large electronegative cavities on either side of the membrane facilitate high conductance and selectivity for cations over protons. The retinal binding pocket structure suggests channel properties could be tuned with mutations and we identify ChRmine variants with ten-fold decreased and two-fold increased closing rates. A T119A mutant shows favorable properties relative to wild-type and previously reported ChRmine variants for optogenetics. These results provide insight into structural features that generate an ultra-potent microbial opsin and provide a platform for rational engineering of channelrhodopsins with improved properties that could expand the scale, depth, and precision of optogenetic experiments.

The change of the electrophysiological parameters using human intestinal tissues from ulcerative colitis and Crohn's disease

The purpose of this study was to investigate how disease state of the UC and CD patients affect tissue function determined from electrophysiology viewpoint the electrophysiological parameters on normal, ulcerative colitis (UC) and Crohn's disease (CD) patients. Potential differences (PD), short circuit current (Isc) and resistance (R) as electrophysiological parameters were determined using human large intestinal tissues.The measure of autoptical abnormality was quantified on an arbitrary scale of 0–2. A severe effect of ulcer and thickened mucosa by fibrosis was scored as Grade 2. The larger number of autopsy grade on both UC and CD tissues, the lower values of PD and R than those of normal tissues were observed, although Isc values were not statistically changed irrespective of autopsy grade. This electrophysiological observation of reduced PD indicated functional impairment of active ion transport via ion pumps. Additionally, the R values of CD tissues on each autopsy grade tended to be lower than those of UC tissues. These results suggest that the effect of inflammatory bowel disease on barrier function is different between UC and CD tissues. Therefore, the fibrosis on CD patients might affect the electrophysiological parameters than that of UC patients.

White Paper: An Integrated Perspective on the Causes of Hypometric Metabolic Scaling in Animals.

Larger animals studied during ontogeny, across populations, or across species, usually have lower mass-specific metabolic rates than smaller animals (hypometric scaling). This pattern is usually observed regardless of physiological state (e.g. basal, resting, field, maximally-active). The scaling of metabolism is usually highly correlated with the scaling of many life history traits, behaviors, physiological variables, and cellular/molecular properties, making determination of the causation of this pattern challenging. For across-species comparisons of resting and locomoting animals (but less so for across populations or during ontogeny), the mechanisms at the physiological and cellular level are becoming clear. Lower mass-specific metabolic rates of larger species at rest are due to a) lower contents of expensive tissues (brains, liver, kidneys), and b) slower ion leak across membranes at least partially due to membrane composition, with lower ion pump ATPase activities. Lower mass-specific costs of larger species during locomotion are due to lower costs for lower-frequency muscle activity, with slower myosin and Ca++ ATPase activities, and likely more elastic energy storage. The evolutionary explanation(s) for hypometric scaling remain(s) highly controversial. One subset of evolutionary hypotheses relies on constraints on larger animals due to changes in geometry with size; for example, lower surface-to-volume ratios of exchange surfaces may constrain nutrient or heat exchange, or lower cross-sectional areas of muscles and tendons relative to body mass ratios would make larger animals more fragile without compensation. Another subset of hypotheses suggests that hypometric scaling arises from biotic interactions and correlated selection, with larger animals experiencing less selection for mass-specific growth or neurolocomotor performance. A additional third type of explanation comes from population genetics. Larger animals with their lower effective population sizes and subsequent less effective selection relative to drift may have more deleterious mutations, reducing maximal performance and metabolic rates. Resolving the evolutionary explanation for the hypometric scaling of metabolism and associated variables is a major challenge for organismal and evolutionary biology. To aid progress, we identify some variation in terminology use that has impeded cross-field conversations on scaling. We also suggest that promising directions for the field to move forward include: 1) studies examining the linkages between ontogenetic, population-level, and cross-species allometries, 2) studies linking scaling to ecological or phylogenetic context, 3) studies that consider multiple, possibly interacting hypotheses, and 4) obtaining better field data for metabolic rates and the life history correlates of metabolic rate such as lifespan, growth rate and reproduction.

Cation-Selective Oxide Semiconductor Mesoporous Membranes for Biomimetic Ion Rectification and Light-Powered Ion Pumping.

Artificial membranes precisely imitating the biological functions of ion channels and ion pumps have attracted significant attention to explore nanofluidic energy conversion. Herein, inspired by the cyclic ion transport for the photosynthesis in purple bacteria, a bilayer inorganic membrane (TiO2 /AAO) composed of oxide semiconductor (TiO2 ) mesopores on anodic alumina (AAO) macropores is wedeveloped. This inorganic membrane achieves the functions of ion channels and ion pumps, including the ion rectification and light-powered ion pumping. The asymmetric charge distribution across the bilayer membrane contributes to the cationic selectivity and ion rectification characteristics. The electrons induced by ultraviolet irradiation introduce a built-in electric field across TiO2 /AAO membrane, which pumps the active ion transport from a low to a high concentration. This work integrates the functions of biological ion channels and ion pumps within an artificial membrane for the first time, which paves the way to explore multifunctional membranes analogous to its biological counterpart.

Focus on software, data acquisition, and instrumentation

Focus on software, data acquisition, and instrumentation

Intracellular sodium concentration and membrane potential oscillation in axonal conduction block induced by high-frequency biphasic stimulation

Objective. A new axonal conduction model was used to analyze the interaction between intracellular sodium concentration and membrane potential oscillation in axonal conduction block induced by high-frequency (kHz) biphasic stimulation (HFBS). Approach. The model includes intracellular and extracellular sodium and potassium concentrations and ion pumps. First, the HFBS (1 kHz, 5.4 mA) was applied for a duration (59.4 s) long enough to produce an axonal conduction block after terminating the stimulation, i.e. a post-stimulation block. Then, the intensity of HFBS was reduced to a lower level for 4 s to determine if the axonal conduction block could be maintained. Main results. The block duration was shortened from 1363 ms to 5 ms as the reduced HFBS intensity was increased from 0 mA to 4.1 mA. The block was maintained for the entire tested period (4000 ms) if the reduced intensity was above 4.2 mA. At the low intensity (<4.2 mA) the membrane potential oscillation disrupted the post-stimulation block caused by the increased intracellular sodium concentration, while at the high intensity (>4.2 mA) the membrane potential oscillation was strong enough to maintain the block and further increased the intracellular sodium concentration. Significance. This study indicates a possibility to develop a new nerve block method to reduce the HFBS intensity, which can extend the battery life for an implantable nerve stimulator in clinical applications to block pain of peripheral origin.

Cardiac glycosides from the roots of Streblus asper Lour. with activity against Epstein-Barr virus lytic replication

Cardiac glycosides (CGs) show potential broad-spectrum antiviral activity by targeting cellular host proteins. Herein are reported the isolation of five new (1–5) and eight known (7–13) CGs from the roots of Streblus asper Lour. Of these compounds 1 and 7 exhibited inhibitory action against EBV early antigen (EA) expression, with half-maximal effective concentration values (EC50) being less than 60 nM, and they also showed selectivity, with selectivity index (SI) values being 56.80 and 103.17, respectively. Preliminary structure activity relationships indicated that the C-10 substituent, C-5 hydroxy groups, and C-3 sugar unit play essential roles in the mediation of the inhibitory activity of CGs against EBV. Further enzyme experiments demonstrated that these compounds might inhibit ion pump function and thereby change the intracellular signal transduction pathway by binding to Na+/K+-ATPase, as validated by simulated molecular docking. This study is the first report that CGs can effectively limit EBV lytic replication, and the observations made in this study may be of value for lead compound development.

Cryo-EM structures of recombinant human sodium-potassium pump determined in three different states

Sodium-Potassium Pump (Na+/K+-ATPase, NKA) is an ion pump that generates an electrochemical gradient of sodium and potassium ions across the plasma membrane by hydrolyzing ATP. During each Post-Albers cycle, NKA exchanges three cytoplasmic sodium ions for two extracellular potassium ions through alternating changes between the E1 and E2 states. Hitherto, several steps remained unknown during the complete working cycle of NKA. Here, we report cryo-electron microscopy (cryo-EM) structures of recombinant human NKA (hNKA) in three distinct states at 2.7–3.2 Å resolution, representing the E1·3Na and E1·3Na·ATP states with cytosolic gates open and the basic E2·[2K] state, respectively. This work provides the insights into the cytoplasmic Na+ entrance pathway and the mechanism of cytoplasmic gate closure coupled with ATP hydrolysis, filling crucial gaps in the structural elucidation of the Post-Albers cycle of NKA.

Mitochondrial Ion Channels in Aging and Related Diseases

Transport of materials and information across cellular boundaries, such as plasma, mitochondrial and nuclear membranes, happens mainly through varieties of ion channels and pumps. Various biophysical and biochemical processes play vital roles. The underlying mechanisms and associated phenomenological lipid membrane transports are linked directly or indirectly to the cell health condition. Mitochondrial membranes (mitochondrial outer membrane (MOM) and mitochondrial inner membrane (MIM)) host crucial cellular processes. Their malfunction is often found responsible for the rise of cell-originated diseases, including cancer, Alzheimer's, neurodegenerative disease, etc. A large number of ion channels active across MOM and MIM are known to belong to vital cell-based structures found to be linked directly to cellular signaling. Hence, their malfunctions are often found to contribute to abnormalities in intracellular communication, which may even be associated with the rise of various diseases. This article aims to pinpoint ion channels that are directly or indirectly linked to especially aging and related abnormalities in health conditions. An attempt has been made to address the natural structures of these channels, their mutated conditions, and the ways we may cause interventions in their malfunctioning. The malfunction of ion channel subunits, especially various proteins, involved directly in channel formation and/or indirectly in channel stabilization leads to the rise of various channel-specific diseases, which are known as channelopathies. Channelopathies in aging will be discussed briefly. This mini-review may be found as an important reference for drug discovery scientists dealing with aging-related diseases.