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Liu Y, Shuai K, Sun Y, Zhu L, Wu XM. Advances in the study of axon-associated vesicles. Front Mol Neurosci 2022; 15:1045778. [PMID: 36545123 PMCID: PMC9760877 DOI: 10.3389/fnmol.2022.1045778] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Accepted: 11/17/2022] [Indexed: 12/12/2022] Open
Abstract
The central nervous system is the most important and difficult to study system in the human body and is known for its complex functions, components, and mechanisms. Neurons are the basic cellular units realizing neural functions. In neurons, vesicles are one of the critical pathways for intracellular material transport, linking information exchanges inside and outside cells. The axon is a vital part of neuron since electrical and molecular signals must be conducted through axons. Here, we describe and explore the formation, trafficking, and sorting of cellular vesicles within axons, as well as related-diseases and practical implications. Furthermore, with deepening of understanding and the development of new approaches, accumulating evidence proves that besides signal transmission between synapses, the material exchange and vesicular transmission between axons and extracellular environment are involved in physiological processes, and consequently to neural pathology. Recent studies have also paid attention to axonal vesicles and their physiological roles and pathological effects on axons themselves. Therefore, this review mainly focuses on these two key nodes to explain the role of intracellular vesicles and extracellular vesicles migrated from cells on axons and neurons, providing innovative strategy for future researches.
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Affiliation(s)
- Yanling Liu
- Institute of Special Environmental Medicine, Nantong University, Nantong, Jiangsu, China
| | - Ke Shuai
- Institute of Special Environmental Medicine, Nantong University, Nantong, Jiangsu, China
| | - Yiyan Sun
- Institute of Special Environmental Medicine, Nantong University, Nantong, Jiangsu, China
| | - Li Zhu
- Institute of Special Environmental Medicine, Nantong University, Nantong, Jiangsu, China,Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China
| | - Xiao-Mei Wu
- Institute of Special Environmental Medicine, Nantong University, Nantong, Jiangsu, China,Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China,*Correspondence: Xiao-Mei Wu,
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2
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Downs ME, Lee SA, Yang G, Kim S, Wang Q, Konofagou EE. Non-invasive peripheral nerve stimulation via focused ultrasound in vivo. Phys Med Biol 2018; 63:035011. [PMID: 29214985 DOI: 10.1088/1361-6560/aa9fc2] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Focused ultrasound (FUS) has been employed on a wide range of clinical applications to safely and non-invasively achieve desired effects that have previously required invasive and lengthy procedures with conventional methods. Conventional electrical neuromodulation therapies that are applied to the peripheral nervous system (PNS) are invasive and/or non-specific. Recently, focused ultrasound has demonstrated the ability to modulate the central nervous system and ex vivo peripheral neurons. Here, for the first time, noninvasive stimulation of the sciatic nerve eliciting a physiological response in vivo is demonstrated with FUS. FUS was applied on the sciatic nerve in mice with simultaneous electromyography (EMG) on the tibialis anterior muscle. EMG signals were detected during or directly after ultrasound stimulation along with observable muscle contraction of the hind limb. Transecting the sciatic nerve downstream of FUS stimulation eliminated EMG activity during FUS stimulation. Peak-to-peak EMG response amplitudes and latency were found to be comparable to conventional electrical stimulation methods. Histology along with behavioral and thermal testing did not indicate damage to the nerve or surrounding regions. The findings presented herein demonstrate that FUS can serve as a targeted, safe and non-invasive alternative to conventional peripheral nervous system stimulation to treat peripheral neuropathic diseases in the clinic.
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Affiliation(s)
- Matthew E Downs
- Departments of Biomedical Engineering, Columbia University, New York, NY 10032, United States of America
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3
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Liebert AD, Chow RT, Bicknell BT, Varigos E. Neuroprotective Effects Against POCD by Photobiomodulation: Evidence from Assembly/Disassembly of the Cytoskeleton. J Exp Neurosci 2016; 10:1-19. [PMID: 26848276 PMCID: PMC4737522 DOI: 10.4137/jen.s33444] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Revised: 12/09/2015] [Accepted: 12/15/2015] [Indexed: 02/07/2023] Open
Abstract
Postoperative cognitive dysfunction (POCD) is a decline in memory following anaesthesia and surgery in elderly patients. While often reversible, it consumes medical resources, compromises patient well-being, and possibly accelerates progression into Alzheimer's disease. Anesthetics have been implicated in POCD, as has neuroinflammation, as indicated by cytokine inflammatory markers. Photobiomodulation (PBM) is an effective treatment for a number of conditions, including inflammation. PBM also has a direct effect on microtubule disassembly in neurons with the formation of small, reversible varicosities, which cause neural blockade and alleviation of pain symptoms. This mimics endogenously formed varicosities that are neuroprotective against damage, toxins, and the formation of larger, destructive varicosities and focal swellings. It is proposed that PBM may be effective as a preconditioning treatment against POCD; similar to the PBM treatment, protective and abscopal effects that have been demonstrated in experimental models of macular degeneration, neurological, and cardiac conditions.
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Affiliation(s)
| | - Roberta T. Chow
- Brain and Mind Institute, University of Sydney, Sydney, NSW, Australia
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4
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Opening paths to novel analgesics: the role of potassium channels in chronic pain. Trends Neurosci 2014; 37:146-58. [PMID: 24461875 PMCID: PMC3945816 DOI: 10.1016/j.tins.2013.12.002] [Citation(s) in RCA: 183] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Revised: 12/13/2013] [Accepted: 12/17/2013] [Indexed: 01/02/2023]
Abstract
Potassium (K+) channels are crucial determinants of neuronal excitability. Nerve injury or inflammation alters K+ channel activity in neurons of the pain pathway. These changes can render neurons hyperexcitable and cause chronic pain. Therapies targeting K+ channels may provide improved pain relief in these states.
Chronic pain is associated with abnormal excitability of the somatosensory system and remains poorly treated in the clinic. Potassium (K+) channels are crucial determinants of neuronal activity throughout the nervous system. Opening of these channels facilitates a hyperpolarizing K+ efflux across the plasma membrane that counteracts inward ion conductance and therefore limits neuronal excitability. Accumulating research has highlighted a prominent involvement of K+ channels in nociceptive processing, particularly in determining peripheral hyperexcitability. We review salient findings from expression, pharmacological, and genetic studies that have untangled a hitherto undervalued contribution of K+ channels in maladaptive pain signaling. These emerging data provide a framework to explain enigmatic pain syndromes and to design novel pharmacological treatments for these debilitating states.
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5
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Schneider ER, Anderson EO, Gracheva EO, Bagriantsev SN. Temperature sensitivity of two-pore (K2P) potassium channels. CURRENT TOPICS IN MEMBRANES 2014; 74:113-33. [PMID: 25366235 DOI: 10.1016/b978-0-12-800181-3.00005-1] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
At normal body temperature, the two-pore potassium channels TREK-1 (K2P2.1/KCNK2), TREK-2 (K2P10.1/KCNK10), and TRAAK (K2P4.1/KCNK2) regulate cellular excitability by providing voltage-independent leak of potassium. Heat dramatically potentiates K2P channel activity and further affects excitation. This review focuses on the current understanding of the physiological role of heat-activated K2P current, and discusses the molecular mechanism of temperature gating in TREK-1, TREK-2, and TRAAK.
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Affiliation(s)
- Eve R Schneider
- Department of Cellular & Molecular Physiology, Yale School of Medicine, New Haven, CT, USA
| | - Evan O Anderson
- Department of Cellular & Molecular Physiology, Yale School of Medicine, New Haven, CT, USA
| | - Elena O Gracheva
- Department of Cellular & Molecular Physiology, Yale School of Medicine, New Haven, CT, USA; Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale School of Medicine, New Haven, CT, USA
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6
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Franssen H, Straver DC. Pathophysiology of immune-mediated demyelinating neuropathies-part I: Neuroscience. Muscle Nerve 2013; 48:851-64. [DOI: 10.1002/mus.24070] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/26/2013] [Indexed: 11/09/2022]
Affiliation(s)
- Hessel Franssen
- Department of Neurology, Section Neuromuscular Disorders, F02.230, Rudolf Magnus Institute for Neuroscience; University Medical Center Utrecht; Heidelberglaan 100, 3584 CX Utrecht The Netherlands
| | - Dirk C.G. Straver
- Department of Neurology, Section Neuromuscular Disorders, F02.230, Rudolf Magnus Institute for Neuroscience; University Medical Center Utrecht; Heidelberglaan 100, 3584 CX Utrecht The Netherlands
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7
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Patel SK, Jackson L, Warren AY, Arya P, Shaw RW, Khan RN. A role for two-pore potassium (K2P) channels in endometrial epithelial function. J Cell Mol Med 2013; 17:134-46. [PMID: 23305490 PMCID: PMC3823143 DOI: 10.1111/j.1582-4934.2012.01656.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Accepted: 10/15/2012] [Indexed: 11/20/2022] Open
Abstract
The human endometrial epithelium is pivotal to menstrual cycle progression, implantation and early pregnancy. Endometrial function is directly regulated by local factors that include pH, oxygen tension and ion concentrations to generate an environment conducive to fertilization. A superfamily of potassium channels characterized by two-pore domains (K2P) and encoded by KCNK genes is implicated in the control of the cell resting membrane potential through the generation of leak currents and modulation by various physicochemical stimuli. The aims of the study were to determine the expression and function of K2P channel subtypes in proliferative and secretory phase endometrium obtained from normo-ovulatory women and in an endometrial cancer cell line. Using immunochemical methods, real-time qRT-PCR proliferation assays and electrophysiology. Our results demonstrate mRNA for several K2P channel subtypes in human endometrium with molecular expression of TREK-1 shown to be higher in proliferative than secretory phase endometrium (P < 0.001). The K2P channel blockers methanandamide, lidocaine, zinc and curcumin had antiproliferative effects (P < 0.01) in an endometrial epithelial cancer cell line indicating a role for TASK and TREK-1 channels in proliferation. Tetraethylammonium- and 4-aminopyridine-insensitive outwards currents were inhibited at all voltages by reducing extracellular pH from 7.4 to 6.6. Higher expression of TREK-1 expression in proliferative phase endometrium may, in part, underlie linked to increased cell division. The effects of pH and a lack of effect of non-specific channel blockers of voltage-gated potassium channels imply a role for K2P channels in the regulation of human endometrial function.
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Affiliation(s)
- Suraj K Patel
- Academic Division of Obstetrics & Gynaecology, University of Nottingham, Derby, UK
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8
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Plant LD. A Role for K2P Channels in the Operation of Somatosensory Nociceptors. Front Mol Neurosci 2012; 5:21. [PMID: 22403526 PMCID: PMC3293133 DOI: 10.3389/fnmol.2012.00021] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Accepted: 02/09/2012] [Indexed: 12/20/2022] Open
Abstract
The ability to sense mechanical, thermal, and chemical stimuli is critical to normal physiology and the perception of pain. Contact with noxious stimuli triggers a complex series of events that initiate innate protective mechanisms designed to minimize or avoid injury. Extreme temperatures, mechanical stress, and chemical irritants are detected by specific ion channels and receptors clustered on the terminals of nociceptive sensory nerve fibers and transduced into electrical information. Propagation of these signals, from distant sites in the body to the spinal cord and the higher processing centers of the brain, is also orchestrated by distinct groups of ion channels. Since their identification in 1995, evidence has emerged to support roles for K2P channels at each step along this pathway, as receptors for physiological and noxious stimuli, and as determinants of nociceptor excitability and conductivity. In addition, the many subtypes of K2P channels expressed in somatosensory neurons are also implicated in mediating the effects of volatile, general anesthetics on the central and peripheral nervous systems. Here, I offer a critical review of the existing data supporting these attributes of K2P channel function and discuss how diverse regulatory mechanisms that control the activity of K2P channels act to govern the operation of nociceptors.
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Affiliation(s)
- Leigh D Plant
- Department of Biochemistry, Brandeis University Waltham, MA, USA
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9
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Enyedi P, Czirják G. Molecular background of leak K+ currents: two-pore domain potassium channels. Physiol Rev 2010; 90:559-605. [PMID: 20393194 DOI: 10.1152/physrev.00029.2009] [Citation(s) in RCA: 620] [Impact Index Per Article: 44.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Two-pore domain K(+) (K(2P)) channels give rise to leak (also called background) K(+) currents. The well-known role of background K(+) currents is to stabilize the negative resting membrane potential and counterbalance depolarization. However, it has become apparent in the past decade (during the detailed examination of the cloned and corresponding native K(2P) channel types) that this primary hyperpolarizing action is not performed passively. The K(2P) channels are regulated by a wide variety of voltage-independent factors. Basic physicochemical parameters (e.g., pH, temperature, membrane stretch) and also several intracellular signaling pathways substantially and specifically modulate the different members of the six K(2P) channel subfamilies (TWIK, TREK, TASK, TALK, THIK, and TRESK). The deep implication in diverse physiological processes, the circumscribed expression pattern of the different channels, and the interesting pharmacological profile brought the K(2P) channel family into the spotlight. In this review, we focus on the physiological roles of K(2P) channels in the most extensively investigated cell types, with special emphasis on the molecular mechanisms of channel regulation.
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Affiliation(s)
- Péter Enyedi
- Department of Physiology, Semmelweis University, Budapest, Hungary.
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10
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Molecular Biology of Background K Channels: Insights from K2P Knockout Mice. J Mol Biol 2009; 385:1331-44. [DOI: 10.1016/j.jmb.2008.11.048] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2008] [Revised: 11/07/2008] [Accepted: 11/19/2008] [Indexed: 12/18/2022]
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Abstract
Acidosis is a noxious condition associated with inflammation, ischaemia or defective acid containment. As a consequence, acid sensing has evolved as an important property of afferent neurons with unmyelinated and thinly myelinated nerve fibres. Protons evoke multiple currents in primary afferent neurons, which are carried by several acid-sensitive ion channels. Among these, acid-sensing ion channels (ASICs) and transient receptor potential (TRP) vanilloid-1 (TRPV1) ion channels have been most thoroughly studied. ASICs survey moderate decreases in extracellular pH, whereas TRPV1 is activated only by severe acidosis resulting in pH values below 6. Two-pore-domain K(+) (K(2P)) channels are differentially regulated by small deviations of extra- or intracellular pH from physiological levels. Other acid-sensitive channels include TRPV4, TRPC4, TRPC5, TRPP2 (PKD2L1), ionotropic purinoceptors (P2X), inward rectifier K(+) channels, voltage-activated K(+) channels, L-type Ca(2+) channels, hyperpolarization-activated cyclic nucleotide gated channels, gap junction channels, and Cl(-) channels. In addition, acid-sensitive G protein coupled receptors have also been identified. Most of these molecular acid sensors are expressed by primary sensory neurons, although to different degrees and in various combinations. Emerging evidence indicates that many of the acid-sensitive ion channels and receptors play a role in acid sensing, acid-induced pain and acid-evoked feedback regulation of homeostatic reactions. The existence and apparent redundancy of multiple pH surveillance systems attests to the concept that acid-base regulation is a vital issue for cell and tissue homeostasis. Since upregulation and overactivity of acid sensors appear to contribute to various forms of chronic pain, acid-sensitive ion channels and receptors are considered as targets for novel analgesic drugs. This approach will only be successful if the pathological implications of acid sensors can be differentiated pharmacologically from their physiological function.
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Affiliation(s)
- Peter Holzer
- Research Unit of Translational Neurogastroenterology, Institute of Experimental and Clinical Pharmacology, Medical University of Graz, Universitätsplatz 4, 8010, Graz, Austria.
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12
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Mtap2 is a constituent of the protein network that regulates twik-related K+ channel expression and trafficking. J Neurosci 2008; 28:8545-52. [PMID: 18716213 DOI: 10.1523/jneurosci.1962-08.2008] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Twik-related K+ (TREK) channels produce background currents that regulate cell excitability. In vivo, TREK-1 is involved in neuronal processes including neuroprotection against ischemia, general anesthesia, pain perception, and mood. Recently, we demonstrated that A-kinase anchoring protein AKAP150 binds to a major regulatory domain of TREK-1, promoting drastic changes in channel regulation by polyunsaturated fatty acids, pH, and stretch, and by G-protein-coupled receptors to neurotransmitters and hormones. Here, we show that the microtubule-associated protein Mtap2 is another constituent of native TREK channels in the brain. Mtap2 binding to TREK-1 and TREK-2 does not affect directly channel properties but enhances channel surface expression and current density. This effect relies on Mtap2 binding to microtubules. Mtap2 and AKAP150 interacting sites in TREK-1 are distinct and both proteins can dock simultaneously. Their effects on TREK-1 surface expression and activation are cumulative. In neurons, the three proteins are simultaneously detected in postsynaptic dense bodies. AKAP150 and Mtap2 put TREK channels at the center of a complex protein network that finely tunes channel trafficking, addressing, and regulation.
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13
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Jiang YQ, Xing GG, Wang SL, Tu HY, Chi YN, Li J, Liu FY, Han JS, Wan Y. Axonal accumulation of hyperpolarization-activated cyclic nucleotide-gated cation channels contributes to mechanical allodynia after peripheral nerve injury in rat. Pain 2008; 137:495-506. [PMID: 18179873 DOI: 10.1016/j.pain.2007.10.011] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2007] [Revised: 09/02/2007] [Accepted: 10/08/2007] [Indexed: 12/27/2022]
Abstract
Peripheral nerve injury causes neuropathic pain including mechanical allodynia and thermal hyperalgesia due to central and peripheral sensitization. Spontaneous ectopic discharges derived from dorsal root ganglion (DRG) neurons and from the sites of injury are a key factor in the initiation of this sensitization. Numerous studies have focused primarily on DRG neurons; however, the injured axons themselves likely play an equally important role. Previous studies of neuropathic pain rats with spinal nerve ligation (SNL) showed that the hyperpolarization-activated cyclic nucleotide-gated cation (HCN) channel in DRG neuronal bodies is important for the development of neuropathic pain. Here, we investigate the role of the axonal HCN channel in neuropathic pain rats. Using the chronic constriction injury (CCI) model, we found abundant axonal accumulation of HCN channel protein at the injured sites accompanied by a slight decrease in DRG neuronal bodies. The function of these accumulated channels was verified by local application of ZD7288, a specific HCN blocker, which significantly suppressed the ectopic discharges from injured nerve fibers with no effect on impulse conduction. Moreover, mechanical allodynia, but not thermal hyperalgesia, was relieved significantly by ZD7288. These results suggest that axonal HCN channel accumulation plays an important role in ectopic discharges from injured spinal nerves and contributes to the development of mechanical allodynia in neuropathic pain rats.
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Affiliation(s)
- Yu-Qiu Jiang
- Neuroscience Research Institute, Peking University, Beijing 100083, China Department of Neurobiology, Peking University, Beijing 100083, China Key Laboratory for Neuroscience, Peking University, Beijing 100083, China Department of Pathology, Peking University, Beijing 100083, China
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14
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Alloui A, Zimmermann K, Mamet J, Duprat F, Noël J, Chemin J, Guy N, Blondeau N, Voilley N, Rubat-Coudert C, Borsotto M, Romey G, Heurteaux C, Reeh P, Eschalier A, Lazdunski M. TREK-1, a K+ channel involved in polymodal pain perception. EMBO J 2006; 25:2368-76. [PMID: 16675954 PMCID: PMC1478167 DOI: 10.1038/sj.emboj.7601116] [Citation(s) in RCA: 303] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2006] [Accepted: 04/04/2006] [Indexed: 12/14/2022] Open
Abstract
The TREK-1 channel is a temperature-sensitive, osmosensitive and mechano-gated K+ channel with a regulation by Gs and Gq coupled receptors. This paper demonstrates that TREK-1 qualifies as one of the molecular sensors involved in pain perception. TREK-1 is highly expressed in small sensory neurons, is present in both peptidergic and nonpeptidergic neurons and is extensively colocalized with TRPV1, the capsaicin-activated nonselective ion channel. Mice with a disrupted TREK-1 gene are more sensitive to painful heat sensations near the threshold between anoxious warmth and painful heat. This phenotype is associated with the primary sensory neuron, as polymodal C-fibers were found to be more sensitive to heat in single fiber experiments. Knockout animals are more sensitive to low threshold mechanical stimuli and display an increased thermal and mechanical hyperalgesia in conditions of inflammation. They display a largely decreased pain response induced by osmotic changes particularly in prostaglandin E2-sensitized animals. TREK-1 appears as an important ion channel for polymodal pain perception and as an attractive target for the development of new analgesics.
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Affiliation(s)
- Abdelkrim Alloui
- Laboratoire de Pharmacologie Médicale EA 3848 INSERM/Faculté de Médecine/CHU, Clermont-Ferrand, France
| | - Katharina Zimmermann
- Department of Physiology and Pathophysiology, University Erlangen-Nuremberg, Erlangen, Germany
| | - Julien Mamet
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS-Université de Nice, Institut Paul Hamel, Sophia Antipolis, Valbonne, France
| | - Fabrice Duprat
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS-Université de Nice, Institut Paul Hamel, Sophia Antipolis, Valbonne, France
| | - Jacques Noël
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS-Université de Nice, Institut Paul Hamel, Sophia Antipolis, Valbonne, France
| | - Jean Chemin
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS-Université de Nice, Institut Paul Hamel, Sophia Antipolis, Valbonne, France
| | - Nicolas Guy
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS-Université de Nice, Institut Paul Hamel, Sophia Antipolis, Valbonne, France
| | - Nicolas Blondeau
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS-Université de Nice, Institut Paul Hamel, Sophia Antipolis, Valbonne, France
| | - Nicolas Voilley
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS-Université de Nice, Institut Paul Hamel, Sophia Antipolis, Valbonne, France
| | - Catherine Rubat-Coudert
- Laboratoire de Pharmacologie Médicale EA 3848 INSERM/Faculté de Médecine/CHU, Clermont-Ferrand, France
| | - Marc Borsotto
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS-Université de Nice, Institut Paul Hamel, Sophia Antipolis, Valbonne, France
| | - Georges Romey
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS-Université de Nice, Institut Paul Hamel, Sophia Antipolis, Valbonne, France
| | - Catherine Heurteaux
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS-Université de Nice, Institut Paul Hamel, Sophia Antipolis, Valbonne, France
| | - Peter Reeh
- Department of Physiology and Pathophysiology, University Erlangen-Nuremberg, Erlangen, Germany
| | - Alain Eschalier
- Laboratoire de Pharmacologie Médicale EA 3848 INSERM/Faculté de Médecine/CHU, Clermont-Ferrand, France
| | - Michel Lazdunski
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS-Université de Nice, Institut Paul Hamel, Sophia Antipolis, Valbonne, France
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS-Université de Nice, Institut Paul Hamel, 660, Route des Lucioles, Sophia Antipolis, 06560 Valbonne, France. Tel.: +33 493 957702; Fax: +33 493 957704; E-mail:
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15
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Kalapesi FB, Tan JCH, Coroneo MT. Stretch-activated channels: a mini-review. Are stretch-activated channels an ocular barometer? Clin Exp Ophthalmol 2005; 33:210-7. [PMID: 15807835 DOI: 10.1111/j.1442-9071.2005.00981.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
All cells are subject to physical forces by virtue of their position in a dynamically changing environment. This review outlines the various putative 'mechanosensors', or sensors of pressure cells possess, and discusses in particular the role stretch-activated membrane channels play in pressure recognition and transduction. The widespread occurrence of these channels is discussed and these 'mechanosensors' are related to pressure-related diseases, in particular, glaucoma.
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Affiliation(s)
- Freny B Kalapesi
- Department of Ophthalmology, Prince of Wales Hospital, University of New South Wales, Sydney, New South Wales, Australia
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16
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Nicolas MT, Lesage F, Reyes R, Barhanin J, Demêmes D. Localization of TREK-1, a two-pore-domain K+ channel in the peripheral vestibular system of mouse and rat. Brain Res 2004; 1017:46-52. [PMID: 15261098 DOI: 10.1016/j.brainres.2004.05.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/01/2004] [Indexed: 10/26/2022]
Abstract
The distribution of two-pore-domain (2P-domain) K(+) channels of the TREK subfamily was studied using immunocytochemistry in the peripheral vestibular system of mouse and rat. Using RT-PCR, the mRNA for TREK-1, but not for TREK-2 or TRAAK, were detected in mouse vestibular endorgans and ganglia. The TREK-1 channel protein was immunodetected in both nerve fibers and nerve cell bodies in the vestibular ganglion, both afferent fibers and nerve calyces innervating type I hair cells in the utricle and cristae. The post-synaptic localization in afferent calyces may suggest a neuroprotective role in glutamatergic excitotoxicity during ischemic conditions. In non-neuronal cells, TREK-1 was immunodetected in the apical membrane of dark cells and transitional cells, both of which are involved in endolymph K(+) secretion and recycling. TREK-1 may subserve some neuroprotective function in afferent nerve fibers as well as play a role in endolymph potassium homeostasis.
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Affiliation(s)
- Marie-Thérèse Nicolas
- Université Montpellier 2, Place Eugène Bataillon, P.O. Box 089, 34095 Montpellier, cedex 05, France.
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17
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Magloire H, Lesage F, Couble ML, Lazdunski M, Bleicher F. Expression and localization of TREK-1 K+ channels in human odontoblasts. J Dent Res 2003; 82:542-5. [PMID: 12821716 DOI: 10.1177/154405910308200711] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
During tooth development, odontoblasts are the cells that form dentin and possibly mediate early stages of sensory processing in teeth. It is suggested that ion channels assist in these events. Indeed, mechanosensitive potassium currents, transducing mechanical stimuli into electrical cell signals, have been previously recorded in the human odontoblast cell membrane. Here, we show by RT-PCR that the mechanosensitive potassium channel TREK-1 (a member of the two-pore-domain potassium channel family) is overexpressed in these cultured cells compared with pulp cells in vitro. In situ hybridization showed that transcripts are detected in the odontoblast layer in vivo. The use of antibodies shows that TREK-1 is strongly expressed in the membrane of coronal odontoblasts and absent in the root. This distribution is related to the spatial distribution of nerve endings identified by labeling of the low-affinity nerve growth factor (NGF) receptor (p75(NTR)). These results demonstrate the expression of TREK-1 in human odontoblasts in vitro and in vivo.
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Affiliation(s)
- H Magloire
- Laboratoire du Développement des Tissus Dentaires, EA 1892, IFR 62, Faculté d'Odontologie, Rue G. Paradin, 69372, Lyon cedex 08, France.
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Ungless MA, Gasull X, Walters ET. Long-term alteration of S-type potassium current and passive membrane properties in aplysia sensory neurons following axotomy. J Neurophysiol 2002; 87:2408-20. [PMID: 11976378 DOI: 10.1152/jn.2002.87.5.2408] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In many neurons, axotomy triggers long-lasting alterations in excitability as well as regenerative growth. We have investigated mechanisms contributing to the expression of axotomy-induced, long-term hyperexcitability (LTH) of mechanosensory neurons in Aplysia californica. Electrophysiological tests were applied to pleural sensory neurons 5-10 days after unilateral crush of pedal nerves. Two-electrode current-clamp experiments revealed that compared with uninjured sensory neurons on the contralateral side of the body, axotomized sensory neurons consistently displayed alterations of passive membrane properties: notably, increases in input resistance (R(in)), membrane time constant (tau), and apparent input capacitance. In some cells, axotomy also depolarized the resting membrane potential (RMP). Axotomized sensory neurons showed a lower incidence of voltage relaxation ("sag") during prolonged hyperpolarizing pulses and greater depolarizations during long (2 s) but not brief (20 ms) pulses. In addition to a reduction in spike accommodation, axotomized sensory neurons displayed a dramatic decrease in current (rheobase) required to reach spike threshold during long depolarizations. The increase in tau was associated with prolongation of responses to brief current pulses and with a large increase in the latency to spike at rheobase. Two-electrode voltage-clamp revealed an axotomy-induced decrease in a current with two components: a leakage current component and a slowly activating, noninactivating outward current component. Neither component was blocked by agents known to block other K(+) currents in these neurons. In contrast to the instantaneous leakage current seen with hyperpolarizing and depolarizing steps, the late component of the axotomy-sensitive outward current showed a relatively steep voltage dependence with pulses to V(m) > -40 mV. These features match those of the S-type ("serotonin-sensitive") K(+) current, I(K,S). The close resemblance of I(K,S) to a background current mediated by TREK-1 (KCNK2) channels in mammals, raises interesting questions about alterations of this family of channels during axotomy-induced LTH in both Aplysia and mammals. The increase in apparent C(in) may be a consequence of the extensive sprouting that has been observed in axotomized sensory neurons near their somata, and the decrease in I(K,S) probably helps to compensate for the decrease in excitability that would otherwise occur as new growth causes both cell volume and C(in) to increase. In peripheral regions of the sensory neuron, a decrease in I(K,S) might enhance the safety factor for conduction across regenerating segments that are highly susceptible to conduction block.
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Affiliation(s)
- Mark A Ungless
- Department of Integrative Biology and Pharmacology, University of Texas-Houston Medical School, Houston, Texas 77030, USA
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19
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Abstract
Two-pore-domain potassium (K(+)) channels are substrates for resting K(+) currents in neurons. They are major targets for endogenous modulators, as well as for clinically important compounds such as volatile anesthetics. In the current study, we report on the CNS distribution in the rat and mouse of mRNA encoding seven two-pore-domain K(+) channel family members: TASK-1 (KCNK3), TASK-2 (KCNK5), TASK-3 (KCNK9), TREK-1 (KCNK2), TREK-2 (KCNK10), TRAAK (KCNK4), and TWIK-1 (KCNK1). All of these genes were expressed in dorsal root ganglia, and for all of the genes except TASK-2, there was a differential distribution in the CNS. For TASK-1, highest mRNA accumulation was seen in the cerebellum and somatic motoneurons. TASK-3 was much more widely distributed, with robust expression in all brain regions, with particularly high expression in somatic motoneurons, cerebellar granule neurons, the locus ceruleus, and raphe nuclei and in various nuclei of the hypothalamus. TREK-1 was highest in the striatum and in parts of the cortex (layer IV) and hippocampus (CA2 pyramidal neurons). mRNA for TRAAK also was highest in the cortex, whereas expression of TREK-2 was primarily restricted to the cerebellar granule cell layer. There was widespread distribution of TWIK-1, with highest levels in the cerebellar granule cell layer, thalamic reticular nucleus, and piriform cortex. The differential expression of each of these genes likely contributes to characteristic excitability properties in distinct populations of neurons, as well as to diversity in their susceptibility to modulation.
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Roncarati R, Di Chio M, Sava A, Terstappen GC, Fumagalli G. Presynaptic localization of the small conductance calcium-activated potassium channel SK3 at the neuromuscular junction. Neuroscience 2001; 104:253-62. [PMID: 11311547 DOI: 10.1016/s0306-4522(01)00066-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Small conductance, calcium-activated potassium channels (SK channels) are present in most neurons, in denervated muscles and in several non-excitable cell types. In excitable cells SK channels play a fundamental role in the generation of the afterhyperpolarization which follows an action potential, thereby modulating neuronal firing and regulating excitability. To date, three channel subunits (SK1-3) have been cloned from mammalian brain. Since SK3 only has been shown to be expressed in muscles upon denervation, this channel may be involved in hyperexcitability and afterhyperpolarization observed in muscle cells in the absence of the nerve. Using confocal microscopy and SK3 specific antibodies, we demonstrate that SK3 immunoreactivity is present at the rat neuromuscular junction in denervated but also in innervated muscles. In denervated muscle fibers, SK3 is localized in the extrajunctional as well as the junctional plasma membrane, where it appears to be less abundant in the acetylcholine receptor-rich domains, corresponding to the crests of the postsynaptic folds. In innervated muscles, SK3 is not detectable in the muscle fiber but is present at the neuromuscular junction and seems to be localized presynaptically in the motor nerve terminals. Axonal accumulation of SK3 immunoreactivity occurs above and below a ligature of rat sciatic nerve, indicating that the SK3 protein is transported in both directions along the axons of the motor neurons. During rat development SK3 immunoreactivity is not found at the neuromuscular junction until day 35 of postnatal development when SK3 first appears in the motor neuron terminals. These results indicate that SK3 channels are components of the presynaptic compartment in the mature neuromuscular junction, where they may play an important regulatory role in synaptic transmission.
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Affiliation(s)
- R Roncarati
- Department of Medicine and Public Health, Section of Pharmacology, University of Verona, 37134, Verona, Italy.
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