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EMBO Reports May 2023Vesicular transport is a means of communication. While cells can communicate with each other via secretion of extracellular vesicles, less is known regarding...
Vesicular transport is a means of communication. While cells can communicate with each other via secretion of extracellular vesicles, less is known regarding organelle-to organelle communication, particularly in the case of mitochondria. Mitochondria are responsible for the production of energy and for essential metabolic pathways in the cell, as well as fundamental processes such as apoptosis and aging. Here, we show that functional mitochondria isolated from Saccharomyces cerevisiae release vesicles, independent of the fission machinery. We isolate these mitochondrial-derived vesicles (MDVs) and find that they are relatively uniform in size, of about 100 nm, and carry selective protein cargo enriched for ATP synthase subunits. Remarkably, we further find that these MDVs harbor a functional ATP synthase complex. We demonstrate that these vesicles have a membrane potential, produce ATP, and seem to fuse with naive mitochondria. Our findings reveal a possible delivery mechanism of ATP-producing vesicles, which can potentially regenerate ATP-deficient mitochondria and may participate in organelle-to-organelle communication.
Topics: Membrane Potentials; Mitochondria; Biological Transport; Saccharomyces cerevisiae; Adenosine Triphosphate
PubMed: 36929726
DOI: 10.15252/embr.202256114 -
International Journal of Molecular... Nov 2022G protein-coupled receptors (GPCRs) are involved in a vast majority of signal transduction processes. Although they span the cell membrane, they have not been considered... (Review)
Review
G protein-coupled receptors (GPCRs) are involved in a vast majority of signal transduction processes. Although they span the cell membrane, they have not been considered to be regulated by the membrane potential. Numerous studies over the last two decades have demonstrated that several GPCRs, including muscarinic, adrenergic, dopaminergic, and glutamatergic receptors, are voltage regulated. Following these observations, an effort was made to elucidate the molecular basis for this regulatory effect. In this review, we will describe the advances in understanding the voltage dependence of GPCRs, the suggested molecular mechanisms that underlie this phenomenon, and the possible physiological roles that it may play.
Topics: Membrane Potentials; Signal Transduction; Receptors, G-Protein-Coupled; Cell Membrane
PubMed: 36430466
DOI: 10.3390/ijms232213988 -
Current Opinion in Chemical Biology Dec 2022Plasma membrane potential is a key driver of the physiology of excitable cells like neurons and cardiomyocytes. Voltage-sensitive fluorescent indicators offer a powerful... (Review)
Review
Plasma membrane potential is a key driver of the physiology of excitable cells like neurons and cardiomyocytes. Voltage-sensitive fluorescent indicators offer a powerful complement to traditional electrode-based approaches to measuring and monitoring membrane potential. Intracellular organelles can also generate membrane potential, yet the electrode- and fluorescent indicator-based approaches used for plasma membrane potential imaging are difficult to implement on intact organelles in their native environment. Here, we survey recent advances in developing and deploying voltage-sensitive fluorescent indicators to interrogate organelle membrane potential in intact cells.
Topics: Membrane Potentials; Fluorescent Dyes; Organelles; Neurons; Diagnostic Imaging
PubMed: 36084425
DOI: 10.1016/j.cbpa.2022.102203 -
Pflugers Archiv : European Journal of... Dec 2023In the early 2000s, the field of neuroscience experienced a groundbreaking transformation with the advent of optogenetics. This innovative technique harnesses the... (Review)
Review
In the early 2000s, the field of neuroscience experienced a groundbreaking transformation with the advent of optogenetics. This innovative technique harnesses the properties of naturally occurring and genetically engineered rhodopsins to confer light sensitivity upon target cells. The remarkable spatiotemporal precision offered by optogenetics has provided researchers with unprecedented opportunities to dissect cellular physiology, leading to an entirely new level of investigation. Initially revolutionizing neuroscience, optogenetics quickly piqued the interest of the wider scientific community, and optogenetic applications were expanded to cardiovascular research. Over the past decade, researchers have employed various optical tools to observe, regulate, and steer the membrane potential of excitable cells in the heart. Despite these advancements, achieving control over specific signaling pathways within the heart has remained an elusive goal. Here, we review the optogenetic tools suitable to control cardiac signaling pathways with a focus on GPCR signaling, and delineate potential applications for studying these pathways, both in healthy and diseased hearts. By shedding light on these exciting developments, we hope to contribute to the ongoing progress in basic cardiac research to facilitate the discovery of novel therapeutic possibilities for treating cardiovascular pathologies.
Topics: Heart; Signal Transduction; Membrane Potentials; Optogenetics
PubMed: 38097805
DOI: 10.1007/s00424-023-02892-y -
Proceedings of the National Academy of... May 2023Voltage-dependent ion channels underlie the propagation of action potentials and other forms of electrical activity in cells. In these proteins, voltage sensor domains...
Voltage-dependent ion channels underlie the propagation of action potentials and other forms of electrical activity in cells. In these proteins, voltage sensor domains (VSDs) regulate opening and closing of the pore through the displacement of their positive-charged S4 helix in response to the membrane voltage. The movement of S4 at hyperpolarizing membrane voltages in some channels is thought to directly clamp the pore shut through the S4-S5 linker helix. The KCNQ1 channel (also known as K7.1), which is important for heart rhythm, is regulated not only by membrane voltage but also by the signaling lipid phosphatidylinositol 4,5-bisphosphate (PIP). KCNQ1 requires PIP to open and to couple the movement of S4 in the VSD to the pore. To understand the mechanism of this voltage regulation, we use cryogenic electron microscopy to visualize the movement of S4 in the human KCNQ1 channel in lipid membrane vesicles with a voltage difference across the membrane, i.e., an applied electric field in the membrane. Hyperpolarizing voltages displace S4 in such a manner as to sterically occlude the PIP-binding site. Thus, in KCNQ1, the voltage sensor acts primarily as a regulator of PIP binding. The voltage sensors' influence on the channel's gate is indirect through the reaction sequence: voltage sensor movement → alter PIP ligand affinity → alter pore opening.
Topics: Humans; KCNQ1 Potassium Channel; Protein Domains; Binding Sites; Action Potentials; Lipids
PubMed: 37192161
DOI: 10.1073/pnas.2301985120 -
Annual Review of Biophysics May 2021Membrane potential (V) is a fundamental biophysical signal present in all cells. V signals range in time from milliseconds to days, and they span lengths from microns to... (Review)
Review
Membrane potential (V) is a fundamental biophysical signal present in all cells. V signals range in time from milliseconds to days, and they span lengths from microns to centimeters. V affects many cellular processes, ranging from neurotransmitter release to cell cycle control to tissue patterning. However, existing tools are not suitable for V quantification in many of these areas. In this review, we outline the diverse biology of V, drafting a wish list of features for a V sensing platform. We then use these guidelines to discuss electrode-based and optical platforms for interrogating V. On the one hand, electrode-based strategies exhibit excellent quantification but are most effective in short-term, cellular recordings. On the other hand, optical strategies provide easier access to diverse samples but generally only detect relative changes in V. By combining the respective strengths of these technologies, recent advances in optical quantification of absolute V enable new inquiries into V biology.
Topics: Animals; Humans; Intracellular Space; Membrane Potentials; Time Factors
PubMed: 33651949
DOI: 10.1146/annurev-biophys-062920-063555 -
International Journal of Molecular... Jul 2023Sperm cells must undergo a complex maturation process after ejaculation to be able to fertilize an egg. One component of this maturation is hyperpolarization of the... (Review)
Review
Sperm cells must undergo a complex maturation process after ejaculation to be able to fertilize an egg. One component of this maturation is hyperpolarization of the membrane potential to a more negative value. The ion channel responsible for this hyperpolarization, SLO3, was first cloned in 1998, and since then much progress has been made to determine how the channel is regulated and how its function intertwines with various signaling pathways involved in sperm maturation. Although was originally thought to be present only in the sperm of mammals, recent evidence suggests that a primordial form of the gene is more widely expressed in some fish species. , like many reproductive genes, is rapidly evolving with low conservation between closely related species and different regulatory and pharmacological profiles. Despite these differences, SLO3 appears to have a conserved role in regulating sperm membrane potential and driving large changes in response to stimuli. The effect of this hyperpolarization of the membrane potential may vary among mammalian species just as the regulation of the channel does. Recent discoveries have elucidated the role of SLO3 in these processes in human sperm and provided tools to target the channel to affect human fertility.
Topics: Animals; Male; Humans; Membrane Potentials; Large-Conductance Calcium-Activated Potassium Channels; Semen; Spermatozoa; Signal Transduction; Mammals
PubMed: 37446382
DOI: 10.3390/ijms241311205 -
Advanced Science (Weinheim,... Mar 2023Recent studies have shown that bacterial membrane potential is dynamic and plays signaling roles. Yet, little is still known about the mechanisms of membrane potential...
Recent studies have shown that bacterial membrane potential is dynamic and plays signaling roles. Yet, little is still known about the mechanisms of membrane potential dynamics regulation-owing to a scarcity of appropriate research tools. Optical modulation of bacterial membrane potential could fill this gap and provide a new approach for studying and controlling bacterial physiology and electrical signaling. Here, the authors show that a membrane-targeted azobenzene (Ziapin2) can be used to photo-modulate the membrane potential in cells of the Gram-positive bacterium Bacillus subtilis. It is found that upon exposure to blue-green light (λ = 470 nm), isomerization of Ziapin2 in the bacteria membrane induces hyperpolarization of the potential. To investigate the origin of this phenomenon, ion-channel-deletion strains and ion channel blockers are examined. The authors found that in presence of the chloride channel blocker idanyloxyacetic acid-94 (IAA-94) or in absence of KtrAB potassium transporter, the hyperpolarization response is attenuated. These results reveal that the Ziapin2 isomerization can induce ion channel opening in the bacterial membrane and suggest that Ziapin2 can be used for studying and controlling bacterial electrical signaling. This new optical tool could contribute to better understand various microbial phenomena, such as biofilm electric signaling and antimicrobial resistance.
Topics: Membrane Potentials; Azo Compounds; Potassium; Bacteria
PubMed: 36710255
DOI: 10.1002/advs.202205007 -
Clinical Neurophysiology : Official... Jul 2023To understand the pathophysiology of myopathies by using muscle velocity recovery cycles (MVRC) and frequency ramp (RAMP) methodologies.
OBJECTIVE
To understand the pathophysiology of myopathies by using muscle velocity recovery cycles (MVRC) and frequency ramp (RAMP) methodologies.
METHODS
42 patients with quantitative electromyography (qEMG) and biopsy or genetic verified myopathy and 42 healthy controls were examined with qEMG, MVRC and RAMP, all recorded from the anterior tibial muscle.
RESULTS
There were significant differences in the motor unit potential (MUP) duration, the early and late supernormalities of the MVRC and the RAMP latencies in myopathy patients compared to controls (p < 0.05 apart from muscle relatively refractory period (MRRP)). When dividing into subgroups, the above-mentioned changes in MVRC and RAMP parameters were increased for the patients with non-inflammatory myopathy, while there were no significant changes in the group of patients with inflammatory myopathy.
CONCLUSIONS
The MVRC and RAMP parameters can discriminate between healthy controls and myopathy patients, more significantly for non-inflammatory myopathy. MVRC differences with normal MRRP in myopathy differs from other conditions with membrane depolarisation.
SIGNIFICANCE
MVCR and RAMP may have a potential in understanding disease pathophysiology in myopathies. The pathogenesis in non-inflammatory myopathy does not seem to be caused by a depolarisation of the resting membrane potential but rather by the change in sodium channels of the muscle membrane.
Topics: Humans; Muscle, Skeletal; Electromyography; Membrane Potentials; Muscular Diseases; Muscle Contraction
PubMed: 37148747
DOI: 10.1016/j.clinph.2023.04.001 -
Cold Spring Harbor Perspectives in... Aug 2021Auxin regulates the transcription of auxin-responsive genes by the TIR1/AFBs-Aux/IAA-ARF signaling pathway, and in this way facilitates plant growth and development.... (Review)
Review
Auxin regulates the transcription of auxin-responsive genes by the TIR1/AFBs-Aux/IAA-ARF signaling pathway, and in this way facilitates plant growth and development. However, rapid, nontranscriptional responses to auxin that cannot be explained by this pathway have been reported. In this review, we focus on several examples of rapid auxin responses: (1) the triggering of changes in plasma membrane potential in various plant species and tissues, (2) inhibition of root growth, which also correlates with membrane potential changes, cytosolic Ca spikes, and a rise of apoplastic pH, (3) the influence on endomembrane trafficking of PIN proteins and other membrane cargoes, and (4) activation of ROPs (Rho of plants) and their downstream effectors such as the cytoskeleton or vesicle trafficking. In most cases, the signaling pathway triggering the response is poorly understood. A role for the TIR1/AFBs in rapid root growth regulation is emerging, as well as the involvement of transmembrane kinases (TMKs) in the activation of ROPs. We discuss similarities and differences among these rapid responses and focus on their physiological significance, which remains an enigma in most cases.
Topics: Calcium; Endocytosis; GTP-Binding Proteins; Indoleacetic Acids; Membrane Potentials; Plant Proteins; Plant Roots; Plants; Receptors, Cell Surface
PubMed: 33648988
DOI: 10.1101/cshperspect.a039891