-
Molecules (Basel, Switzerland) Dec 2023Lipid membrane nanodomains or lipid rafts are 10-200 nm diameter size cholesterol- and sphingolipid-enriched domains of the plasma membrane, gathering many proteins with... (Review)
Review
Lipid membrane nanodomains or lipid rafts are 10-200 nm diameter size cholesterol- and sphingolipid-enriched domains of the plasma membrane, gathering many proteins with different roles. Isolation and characterization of plasma membrane proteins by differential centrifugation and proteomic studies have revealed a remarkable diversity of proteins in these domains. The limited size of the lipid membrane nanodomain challenges the simple possibility that all of them can coexist within the same lipid membrane domain. As caveolin-1, flotillin isoforms and gangliosides are currently used as neuronal lipid membrane nanodomain markers, we first analyzed the structural features of these components forming nanodomains at the plasma membrane since they are relevant for building supramolecular complexes constituted by these molecular signatures. Among the proteins associated with neuronal lipid membrane nanodomains, there are a large number of proteins that play major roles in calcium signaling, such as ionotropic and metabotropic receptors for neurotransmitters, calcium channels, and calcium pumps. This review highlights a large variation between the calcium signaling proteins that have been reported to be associated with isolated caveolin-1 and flotillin-lipid membrane nanodomains. Since these calcium signaling proteins are scattered in different locations of the neuronal plasma membrane, i.e., in presynapses, postsynapses, axonal or dendritic trees, or in the neuronal soma, our analysis suggests that different lipid membrane-domain subtypes should exist in neurons. Furthermore, we conclude that classification of lipid membrane domains by their content in calcium signaling proteins sheds light on the roles of these domains for neuronal activities that are dependent upon the intracellular calcium concentration. Some examples described in this review include the synaptic and metabolic activity, secretion of neurotransmitters and neuromodulators, neuronal excitability (long-term potentiation and long-term depression), axonal and dendritic growth but also neuronal cell survival and death.
Topics: Caveolin 1; Calcium Signaling; Calcium; Proteomics; Membrane Microdomains; Neurons; Gangliosides; Neurotransmitter Agents
PubMed: 38067638
DOI: 10.3390/molecules28237909 -
European Journal of Pharmacology Sep 2023Capsaicin and allyl isothiocyanate (AITC) activate transient receptor potential (TRP) vanilloid-1 (TRPV1) and TRP ankyrin-1 (TRPA1), respectively. TRPV1 and TRPA1...
Capsaicin and allyl isothiocyanate (AITC) activate transient receptor potential (TRP) vanilloid-1 (TRPV1) and TRP ankyrin-1 (TRPA1), respectively. TRPV1 and TRPA1 expression have been identified in the gastrointestinal (GI) tract. GI mucosal functions remain largely undefined for TRPV1 and TRPA1 with side-dependence and regional differences in signalling unclear. Here we investigated TRPV1- and TRPA1-induced vectorial ion transport as changes in short-circuit current (ΔI), in defined segments of mouse colon mucosa (ascending, transverse and descending) under voltage-clamp conditions in Ussing chambers. Drugs were applied basolaterally (bl) or apically (ap). Capsaicin responses were biphasic, with primary secretory and secondary anti-secretory phases, observed with bl application only, which predominated in descending colon. AITC responses were monophasic and secretory, with ΔI dependent on colonic region (ascending vs. descending) and sidedness (bl vs. ap). Aprepitant (neurokinin-1 (NK1) antagonist, bl) and tetrodotoxin (Na channel blocker, bl) significantly inhibited capsaicin primary responses in descending colon, while GW627368 (EP4 receptor antagonist, bl) and piroxicam (cyclooxygenase inhibitor, bl) inhibited AITC responses in ascending and descending colonic mucosae. Antagonism of the calcitonin gene-related peptide (CGRP) receptor had no effect on mucosal TRPV1 signalling, while tetrodotoxin and antagonists of the 5-hydroxytryptamine-3 and 4 receptors, CGRP receptor, and EP1/2/3 receptors had no effect on mucosal TRPA1 signalling. Our data demonstrates the regional-specificity and side-dependence of colonic TRPV1 and TRPA1 signalling, with involvement of submucosal neurons and mediation by epithelial NK1 receptor activation for TRPV1, and endogenous prostaglandins and EP4 receptor activation for TRPA1 mucosal responses.
Topics: Mice; Animals; Transient Receptor Potential Channels; TRPA1 Cation Channel; Capsaicin; Tetrodotoxin; Colon; Mucous Membrane; TRPV Cation Channels
PubMed: 37394028
DOI: 10.1016/j.ejphar.2023.175897 -
ELife Dec 2023Changes in the intracellular concentration of free calcium (Ca) underpin egg activation and initiation of development in animals and plants. In mammals, the Ca release...
Changes in the intracellular concentration of free calcium (Ca) underpin egg activation and initiation of development in animals and plants. In mammals, the Ca release is periodical, known as Ca oscillations, and mediated by the type 1 inositol 1,4,5-trisphosphate receptor (IPR1). Another divalent cation, zinc (Zn), increases exponentially during oocyte maturation and is vital for meiotic transitions, arrests, and polyspermy prevention. It is unknown if these pivotal cations interplay during fertilization. Here, using mouse eggs, we showed that basal concentrations of labile Zn are indispensable for sperm-initiated Ca oscillations because Zn-deficient conditions induced by cell-permeable chelators abrogated Ca responses evoked by fertilization and other physiological and pharmacological agonists. We also found that chemically or genetically generated eggs with lower levels of labile Zn displayed reduced IPR1 sensitivity and diminished ER Ca leak despite the stable content of the stores and IPR1 mass. Resupplying Zn restarted Ca oscillations, but excessive Zn prevented and terminated them, hindering IPR1 responsiveness. The findings suggest that a window of Zn concentrations is required for Ca responses and IPR1 function in eggs, ensuring optimal response to fertilization and egg activation.
Topics: Male; Animals; Mice; Oocytes; Semen; Oogenesis; Fertilization; Spermatozoa; Calcium; Calcium Signaling; Mammals
PubMed: 38099643
DOI: 10.7554/eLife.88082 -
Proceedings of the National Academy of... Aug 2023The deficit in cerebral blood flow (CBF) seen in patients with hypertension-induced vascular dementia is increasingly viewed as a therapeutic target for...
The deficit in cerebral blood flow (CBF) seen in patients with hypertension-induced vascular dementia is increasingly viewed as a therapeutic target for disease-modifying therapy. Progress is limited, however, due to uncertainty surrounding the mechanisms through which elevated blood pressure reduces CBF. To investigate this, we used the BPH/2 mouse, a polygenic model of hypertension. At 8 mo of age, hypertensive mice exhibited reduced CBF and cognitive impairment, mimicking the human presentation of vascular dementia. Small cerebral resistance arteries that run across the surface of the brain (pial arteries) showed enhanced pressure-induced constriction due to diminished activity of large-conductance Ca-activated K (BK) channels-key vasodilatory ion channels of cerebral vascular smooth muscle cells. Activation of BK channels by transient intracellular Ca signals from the sarcoplasmic reticulum (SR), termed Ca sparks, leads to hyperpolarization and vasodilation. Combining patch-clamp electrophysiology, high-speed confocal imaging, and proximity ligation assays, we demonstrated that this vasodilatory mechanism is uncoupled in hypertensive mice, an effect attributable to physical separation of the plasma membrane from the SR rather than altered properties of BK channels or Ca sparks, which remained intact. This pathogenic mechanism is responsible for the observed increase in constriction and can now be targeted as a possible avenue for restoring healthy CBF in vascular dementia.
Topics: Mice; Humans; Animals; Large-Conductance Calcium-Activated Potassium Channels; Dementia, Vascular; Muscle, Smooth, Vascular; Cerebral Arteries; Hypertension; Calcium Signaling; Calcium
PubMed: 37549299
DOI: 10.1073/pnas.2307513120 -
The Journal of Biological Chemistry Nov 2023T-cell receptor stimulation triggers cytosolic Ca signaling by inositol-1,4,5-trisphosphate (IP)-mediated Ca release from the endoplasmic reticulum (ER) and Ca entry...
T-cell receptor stimulation triggers cytosolic Ca signaling by inositol-1,4,5-trisphosphate (IP)-mediated Ca release from the endoplasmic reticulum (ER) and Ca entry through Ca release-activated Ca (CRAC) channels gated by ER-located stromal-interacting molecules (STIM1/2). Physiologically, cytosolic Ca signaling manifests as regenerative Ca oscillations, which are critical for nuclear factor of activated T-cells-mediated transcription. In most cells, Ca oscillations are thought to originate from IP receptor-mediated Ca release, with CRAC channels indirectly sustaining them through ER refilling. Here, experimental and computational evidence support a multiple-oscillator mechanism in Jurkat T-cells whereby both IP receptor and CRAC channel activities oscillate and directly fuel antigen-evoked Ca oscillations, with the CRAC channel being the major contributor. KO of either STIM1 or STIM2 significantly reduces CRAC channel activity. As such, STIM1 and STIM2 synergize for optimal Ca oscillations and activation of nuclear factor of activated T-cells 1 and are essential for ER refilling. The loss of both STIM proteins abrogates CRAC channel activity, drastically reduces ER Ca content, severely hampers cell proliferation and enhances cell death. These results clarify the mechanism and the contribution of STIM proteins to Ca oscillations in T-cells.
Topics: Humans; Calcium; Calcium Release Activated Calcium Channels; Calcium Signaling; Jurkat Cells; Stromal Interaction Molecule 1; Stromal Interaction Molecule 2; Gene Knockout Techniques; Models, Biological; Protein Isoforms; Protein Transport; Cell Proliferation; Cell Survival
PubMed: 37778728
DOI: 10.1016/j.jbc.2023.105310 -
Science Advances Oct 2023ClC-6 is a late endosomal voltage-gated chloride-proton exchanger that is predominantly expressed in the nervous system. Mutated forms of ClC-6 are associated with...
ClC-6 is a late endosomal voltage-gated chloride-proton exchanger that is predominantly expressed in the nervous system. Mutated forms of ClC-6 are associated with severe neurological disease. However, the mechanistic role of ClC-6 in normal and pathological states remains largely unknown. Here, we present cryo-EM structures of ClC-6 that guided subsequent functional studies. Previously unrecognized ATP binding to cytosolic ClC-6 domains enhanced ion transport activity. Guided by a disease-causing mutation (p.Y553C), we identified an interaction network formed by Y553/F317/T520 as potential hotspot for disease-causing mutations. This was validated by the identification of a patient with a de novo pathogenic variant p.T520A. Extending these findings, we found contacts between intramembrane helices and connecting loops that modulate the voltage dependence of ClC-6 gating and constitute additional candidate regions for disease-associated gain-of-function mutations. Besides providing insights into the structure, function, and regulation of ClC-6, our work correctly predicts hotspots for mutations in neurodegenerative disorders.
Topics: Humans; Chloride Channels; Ion Transport; Mutation; Neurodegenerative Diseases; Structure-Activity Relationship
PubMed: 37831762
DOI: 10.1126/sciadv.adg4479 -
Cell Reports Dec 2023Store-operated Ca entry (SOCE) mediated by stromal interacting molecule (STIM)-gated ORAI channels at endoplasmic reticulum (ER) and plasma membrane (PM) contact sites...
Store-operated Ca entry (SOCE) mediated by stromal interacting molecule (STIM)-gated ORAI channels at endoplasmic reticulum (ER) and plasma membrane (PM) contact sites maintains adequate levels of Ca within the ER lumen during Ca signaling. Disruption of ER Ca homeostasis activates the unfolded protein response (UPR) to restore proteostasis. Here, we report that the UPR transducer inositol-requiring enzyme 1 (IRE1) interacts with STIM1, promotes ER-PM contact sites, and enhances SOCE. IRE1 deficiency reduces T cell activation and human myoblast differentiation. In turn, STIM1 deficiency reduces IRE1 signaling after store depletion. Using a CaMPARI2-based Ca genome-wide screen, we identify CAMKG2 and slc105a as SOCE enhancers during ER stress. Our findings unveil a direct crosstalk between SOCE and UPR via IRE1, acting as key regulator of ER Ca and proteostasis in T cells and muscles. Under ER stress, this IRE1-STIM1 axis boosts SOCE to preserve immune cell functions, a pathway that could be targeted for cancer immunotherapy.
Topics: Humans; Calcium; Calcium Channels; Calcium Signaling; Cell Membrane; Neoplasm Proteins; ORAI1 Protein; Protein Serine-Threonine Kinases; Stromal Interaction Molecule 1
PubMed: 38060449
DOI: 10.1016/j.celrep.2023.113540 -
The Journal of General Physiology Aug 2023We celebrate this year the 50th anniversary of the first electrophysiological recordings of the gating currents from voltage-dependent ion channels done in 1973. This... (Review)
Review
We celebrate this year the 50th anniversary of the first electrophysiological recordings of the gating currents from voltage-dependent ion channels done in 1973. This retrospective tries to illustrate the context knowledge on channel gating and the impact gating-current recording had then, and how it continued to clarify concepts, elaborate new ideas, and steer the scientific debate in these 50 years. The notion of gating particles and gating currents was first put forward by Hodgkin and Huxley in 1952 as a necessary assumption for interpreting the voltage dependence of the Na and K conductances of the action potential. 20 years later, gating currents were actually recorded, and over the following decades have represented the most direct means of tracing the movement of the gating charges and gaining insights into the mechanisms of channel gating. Most work in the early years was focused on the gating currents from the Na and K channels as found in the squid giant axon. With channel cloning and expression on heterologous systems, other channels as well as voltage-dependent enzymes were investigated. Other approaches were also introduced (cysteine mutagenesis and labeling, site-directed fluorometry, cryo-EM crystallography, and molecular dynamics [MD] modeling) to provide an integrated and coherent view of voltage-dependent gating in biological macromolecules. The layout of this retrospective reflects the past 50 years of investigations on gating currents, first addressing studies done on Na and K channels and then on other voltage-gated channels and non-channel structures. The review closes with a brief overview of how the gating-charge/voltage-sensor movements are translated into pore opening and the pathologies associated with mutations targeting the structures involved with the gating currents.
Topics: Ion Channel Gating; Ion Channels; Ion Transport; Mutation; Retrospective Studies
PubMed: 37410612
DOI: 10.1085/jgp.202313380 -
Annual Review of Entomology Jan 2024Water is essential to life. Terrestrial insects lose water by evaporation from the body surface and respiratory surfaces, as well as in the excretory products, posing a... (Review)
Review
Water is essential to life. Terrestrial insects lose water by evaporation from the body surface and respiratory surfaces, as well as in the excretory products, posing a challenge made more acute by their high surface-to-volume ratio. These losses must be kept to a minimum and be offset by water gained from other sources. By contrast, insects such as the blood-sucking bug consume up to 10 times their body weight in a single blood meal, necessitating rapid expulsion of excess water and ions. How do insects manage their ion and water budgets? A century of study has revealed a great deal about the organ systems that insects use to maintain their ion and water balance and their regulation. Traditionally, a taxonomically wide range of species were studied, whereas more recent research has focused on model organisms to leverage the power of the molecular genetic approach. Key advances in new technologies have become available for a wider range of species in the past decade. We document how these approaches have already begun to inform our understanding of the diversity and conservation of insect systemic osmoregulation. We advocate that these technologies be combined with traditional approaches to study a broader range of nonmodel species to gain a comprehensive overview of the mechanism underpinning systemic osmoregulation in the most species-rich group of animals on earth, the insects.
Topics: Animals; Osmoregulation; Earth, Planet; Insecta; Water
PubMed: 37758224
DOI: 10.1146/annurev-ento-040323-021222 -
Channels (Austin, Tex.) Dec 2024Voltage-gated calcium channels (VGCCs) are the major conduits for calcium ions (Ca) within excitable cells. Recent studies have highlighted the non-ionotropic... (Review)
Review
Voltage-gated calcium channels (VGCCs) are the major conduits for calcium ions (Ca) within excitable cells. Recent studies have highlighted the non-ionotropic functionality of VGCCs, revealing their capacity to activate intracellular pathways independently of ion flow. This non-ionotropic signaling mode plays a pivotal role in excitation-coupling processes, including gene transcription through excitation-transcription (ET), synaptic transmission via excitation-secretion (ES), and cardiac contraction through excitation-contraction (EC). However, it is noteworthy that these excitation-coupling processes require extracellular calcium (Ca) and Ca occupancy of the channel ion pore. Analogous to the "non-canonical" characterization of the non-ionotropic signaling exhibited by the N-methyl-D-aspartate receptor (NMDA), which requires extracellular Ca without the influx of ions, VGCC activation requires depolarization-triggered conformational change(s) concomitant with Ca binding to the open channel. Here, we discuss the contributions of VGCCs to ES, ET, and EC coupling as Ca binding macromolecules that transduces external stimuli to intracellular input prior to elevating intracellular Ca. We emphasize the recognition of calcium ion occupancy within the open ion-pore and its contribution to the excitation coupling processes that precede the influx of calcium. The non-ionotropic activation of VGCCs, triggered by the upstroke of an action potential, provides a conceptual framework to elucidate the mechanistic aspects underlying the microseconds nature of synaptic transmission, cardiac contractility, and the rapid induction of first-wave genes.
Topics: Calcium; Calcium Channels; Signal Transduction; Excitation Contraction Coupling; Ions; Calcium Signaling; Calcium Channels, L-Type
PubMed: 38601983
DOI: 10.1080/19336950.2024.2341077