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Kang H, Choi SW, Kim JY, Oh SJ, Kim SJ, Lee MS. ER-to-lysosome Ca 2+ refilling followed by K + efflux-coupled store-operated Ca 2+ entry in inflammasome activation and metabolic inflammation. eLife 2024; 12:RP87561. [PMID: 38953285 PMCID: PMC11219040 DOI: 10.7554/elife.87561] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/03/2024] Open
Abstract
We studied lysosomal Ca2+ in inflammasome. Lipopolysaccharide (LPS) + palmitic acid (PA) decreased lysosomal Ca2+ ([Ca2+]Lys) and increased [Ca2+]i through mitochondrial ROS, which was suppressed in Trpm2-KO macrophages. Inflammasome activation and metabolic inflammation in adipose tissue of high-fat diet (HFD)-fed mice were ameliorated by Trpm2 KO. ER→lysosome Ca2+ refilling occurred after lysosomal Ca2+ release whose blockade attenuated LPS + PA-induced inflammasome. Subsequently, store-operated Ca2+entry (SOCE) was activated whose inhibition suppressed inflammasome. SOCE was coupled with K+ efflux whose inhibition reduced ER Ca2+ content ([Ca2+]ER) and impaired [Ca2+]Lys recovery. LPS + PA activated KCa3.1 channel, a Ca2+-activated K+ channel. Inhibitors of KCa3.1 channel or Kcnn4 KO reduced [Ca2+]ER, attenuated increase of [Ca2+]i or inflammasome activation by LPS + PA, and ameliorated HFD-induced inflammasome or metabolic inflammation. Lysosomal Ca2+ release induced delayed JNK and ASC phosphorylation through CAMKII-ASK1. These results suggest a novel role of lysosomal Ca2+ release sustained by ER→lysosome Ca2+ refilling and K+ efflux through KCa3.1 channel in inflammasome activation and metabolic inflammation.
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Affiliation(s)
- Hyereen Kang
- Severance Biomedical Science Institute, Yonsei University College of MedicineSeoulRepublic of Korea
| | - Seong Woo Choi
- Department of Physiology and Ion Channel Disease Research Center, Dongguk University College of MedicineGyeongjuRepublic of Korea
| | - Joo Young Kim
- Department of Pharmacology and Brain Korea 21 Project for Medical Sciences, Yonsei University College of MedicineSeoulRepublic of Korea
| | - Soo-Jin Oh
- Soonchunhyang Institute of Medi-bio Science and Division of Endocrinology, Department of Internal Medicine, Soonchunhyang University College of MedicineCheonanRepublic of Korea
| | - Sung Joon Kim
- Department of Physiology, Ischemic/Hypoxic Disease Institute, Seoul National University College of MedicineSeoulRepublic of Korea
| | - Myung-Shik Lee
- Severance Biomedical Science Institute, Yonsei University College of MedicineSeoulRepublic of Korea
- Soonchunhyang Institute of Medi-bio Science and Division of Endocrinology, Department of Internal Medicine, Soonchunhyang University College of MedicineCheonanRepublic of Korea
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Mlayah-Bellalouna S, Aissaoui-Zid D, Chantome A, Jebali J, Souid S, Ayedi E, Mejdoub H, Belghazi M, Marrakchi N, Essafi-Benkhadir K, Vandier C, Srairi-Abid N. Insights into the mechanisms governing P01 scorpion toxin effect against U87 glioblastoma cells oncogenesis. Front Pharmacol 2023; 14:1203247. [PMID: 37426811 PMCID: PMC10326281 DOI: 10.3389/fphar.2023.1203247] [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: 04/10/2023] [Accepted: 06/12/2023] [Indexed: 07/11/2023] Open
Abstract
The emerging concept of small conductance Ca2+-activated potassium channels (SKCa) as pharmacological target for cancer treatment has significantly increased in recent years. In this study, we isolated the P01 toxin from Androctonus australis (Aa) scorpion venom and investigated its effect on biological properties of glioblastoma U87, breast MDA-MB231 and colon adenocarcinoma LS174 cancer cell lines. Our results showed that P01 was active only on U87 glioblastoma cells. It inhibited their proliferation, adhesion and migration with IC50 values in the micromolar range. We have also shown that P01 reduced the amplitude of the currents recorded in HEK293 cells expressing SK2 channels with an IC50 value of 3 pM, while it had no effect on those expressing SK3 channels. The investigation of the SKCa channels expression pattern showed that SK2 transcripts were expressed differently in the three cancer cell lines. Particularly, we highlighted the presence of SK2 isoforms in U87 cells, which could explain and rely on the specific activity of P01 on this cell line. These experimental data highlighted the usefulness of scorpion peptides to decipher the role of SKCa channels in the tumorigenesis process, and develop potential therapeutic molecules targeting glioblastoma with high selectivity.
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Affiliation(s)
- Saoussen Mlayah-Bellalouna
- LR20IPT01 Biomolécules, Venins et Application Théranostique, Institut Pasteur de Tunis, Université de Tunis El Manar, Tunis, Tunisia
| | - Dorra Aissaoui-Zid
- LR20IPT01 Biomolécules, Venins et Application Théranostique, Institut Pasteur de Tunis, Université de Tunis El Manar, Tunis, Tunisia
| | - Aurelie Chantome
- N2C UMR 1069, Institut national de la santé et de la recherche médicale, University of Tours, Tours, France
| | - Jed Jebali
- LR20IPT01 Biomolécules, Venins et Application Théranostique, Institut Pasteur de Tunis, Université de Tunis El Manar, Tunis, Tunisia
| | - Soumaya Souid
- LR16IPT04 Laboratoire d’Epidémiologie Moléculaire et Pathologie Expérimentale, Institut Pasteur de Tunis, Université de Tunis El Manar, Tunis, Tunisia
| | - Emna Ayedi
- LR20IPT01 Biomolécules, Venins et Application Théranostique, Institut Pasteur de Tunis, Université de Tunis El Manar, Tunis, Tunisia
| | - Hafedh Mejdoub
- USCR Séquenceur de Protéines, Faculté des Sciences de Sfax, Route de Soukra, Sfax, Tunisia
| | - Maya Belghazi
- Aix Marseille Université, CNRS, Plateforme Protéomique, IMM FR3479, Marseille Protéomique (MaP), Marseille, France
| | - Naziha Marrakchi
- LR20IPT01 Biomolécules, Venins et Application Théranostique, Institut Pasteur de Tunis, Université de Tunis El Manar, Tunis, Tunisia
| | - Khadija Essafi-Benkhadir
- LR16IPT04 Laboratoire d’Epidémiologie Moléculaire et Pathologie Expérimentale, Institut Pasteur de Tunis, Université de Tunis El Manar, Tunis, Tunisia
| | - Christophe Vandier
- N2C UMR 1069, Institut national de la santé et de la recherche médicale, University of Tours, Tours, France
| | - Najet Srairi-Abid
- LR20IPT01 Biomolécules, Venins et Application Théranostique, Institut Pasteur de Tunis, Université de Tunis El Manar, Tunis, Tunisia
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Venom composition and pain-causing toxins of the Australian great carpenter bee Xylocopa aruana. Sci Rep 2022; 12:22168. [PMID: 36550366 PMCID: PMC9780326 DOI: 10.1038/s41598-022-26867-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Accepted: 12/21/2022] [Indexed: 12/24/2022] Open
Abstract
Most species of bee are capable of delivering a defensive sting which is often painful. A solitary lifestyle is the ancestral state of bees and most extant species are solitary, but information on bee venoms comes predominantly from studies on eusocial species. In this study we investigated the venom composition of the Australian great carpenter bee, Xylocopa aruana Ritsema, 1876. We show that the venom is relatively simple, composed mainly of one small amphipathic peptide (XYTX1-Xa1a), with lesser amounts of an apamin homologue (XYTX2-Xa2a) and a venom phospholipase-A2 (PLA2). XYTX1-Xa1a is homologous to, and shares a similar mode-of-action to melittin and the bombilitins, the major components of the venoms of the eusocial Apis mellifera (Western honeybee) and Bombus spp. (bumblebee), respectively. XYTX1-Xa1a and melittin directly activate mammalian sensory neurons and cause spontaneous pain behaviours in vivo, effects which are potentiated in the presence of venom PLA2. The apamin-like peptide XYTX2-Xa2a was a relatively weak blocker of small conductance calcium-activated potassium (KCa) channels and, like A. mellifera apamin and mast cell-degranulating peptide, did not contribute to pain behaviours in mice. While the composition and mode-of-action of the venom of X. aruana are similar to that of A. mellifera, the greater potency, on mammalian sensory neurons, of the major pain-causing component in A. mellifera venom may represent an adaptation to the distinct defensive pressures on eusocial Apidae.
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Butler AS, Hancox JC, Marrion NV. Preferential formation of human heteromeric SK2:SK3 channels limits homomeric SK channel assembly and function. J Biol Chem 2022; 299:102783. [PMID: 36502918 PMCID: PMC9841042 DOI: 10.1016/j.jbc.2022.102783] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 11/29/2022] [Accepted: 12/04/2022] [Indexed: 12/13/2022] Open
Abstract
Three isoforms of small conductance, calcium-activated potassium (SK) channel subunits have been identified (SK1-3) that exhibit a broad and overlapping tissue distribution. SK channels have been implicated in several disease states including hypertension and atrial fibrillation, but therapeutic targeting of SK channels is hampered by a lack of subtype-selective inhibitors. This is further complicated by studies showing that SK1 and SK2 preferentially form heteromeric channels during co-expression, likely limiting the function of homomeric channels in vivo. Here, we utilized a simplified expression system to investigate functional current produced when human (h) SK2 and hSK3 subunits are co-expressed. When expressed alone, hSK3 subunits were more clearly expressed on the cell surface than hSK2 subunits. hSK3 surface expression was reduced by co-transfection with hSK2. Whole-cell recording showed homomeric hSK3 currents were larger than homomeric hSK2 currents or heteromeric hSK2:hSK3 currents. The smaller amplitude of hSK2:hSK3-mediated current when compared with homomeric hSK3-mediated current suggests hSK2 subunits regulate surface expression of heteromers. Co-expression of hSK2 and hSK3 subunits produced a current that arose from a single population of heteromeric channels as exhibited by an intermediate sensitivity to the inhibitors apamin and UCL1684. Co-expression of the apamin-sensitive hSK2 subunit and a mutant, apamin-insensitive hSK3 subunit [hSK3(H485N)], produced an apamin-sensitive current. Concentration-inhibition relationships were best fit by a monophasic Hill equation, confirming preferential formation of heteromers. These data show that co-expressed hSK2 and hSK3 preferentially form heteromeric channels and suggest that the hSK2 subunit acts as a chaperone, limiting membrane expression of hSK2:hSK3 heteromeric channels.
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Affiliation(s)
- Andrew S Butler
- School of Physiology, Pharmacology and Neuroscience, Medical Sciences Building, University of Bristol, University Walk, Bristol, United Kingdom
| | - Jules C Hancox
- School of Physiology, Pharmacology and Neuroscience, Medical Sciences Building, University of Bristol, University Walk, Bristol, United Kingdom.
| | - Neil V Marrion
- School of Physiology, Pharmacology and Neuroscience, Medical Sciences Building, University of Bristol, University Walk, Bristol, United Kingdom.
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Kuzmenkov AI, Peigneur S, Nasburg JA, Mineev KS, Nikolaev MV, Pinheiro-Junior EL, Arseniev AS, Wulff H, Tytgat J, Vassilevski AA. Apamin structure and pharmacology revisited. Front Pharmacol 2022; 13:977440. [PMID: 36188602 PMCID: PMC9523135 DOI: 10.3389/fphar.2022.977440] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 08/05/2022] [Indexed: 12/02/2022] Open
Abstract
Apamin is often cited as one of the few substances selectively acting on small-conductance Ca2+-activated potassium channels (KCa2). However, published pharmacological and structural data remain controversial. Here, we investigated the molecular pharmacology of apamin by two-electrode voltage-clamp in Xenopus laevis oocytes and patch-clamp in HEK293, COS7, and CHO cells expressing the studied ion channels, as well as in isolated rat brain neurons. The microtitre broth dilution method was used for antimicrobial activity screening. The spatial structure of apamin in aqueous solution was determined by NMR spectroscopy. We tested apamin against 42 ion channels (KCa, KV, NaV, nAChR, ASIC, and others) and confirmed its unique selectivity to KCa2 channels. No antimicrobial activity was detected for apamin against Gram-positive or Gram-negative bacteria. The NMR solution structure of apamin was deposited in the Protein Data Bank. The results presented here demonstrate that apamin is a selective nanomolar or even subnanomolar-affinity KCa2 inhibitor with no significant effects on other molecular targets. The spatial structure as well as ample functional data provided here support the use of apamin as a KCa2-selective pharmacological tool and as a template for drug design.
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Affiliation(s)
- Alexey I. Kuzmenkov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | | | - Joshua A. Nasburg
- Department of Pharmacology, University of California, Davis, Davis, CA, United States
| | - Konstantin S. Mineev
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
- Moscow Institute of Physics and Technology, Moscow Region, Dolgoprudny, Russia
| | - Maxim V. Nikolaev
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, Saint Petersburg, Russia
| | | | - Alexander S. Arseniev
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
- Moscow Institute of Physics and Technology, Moscow Region, Dolgoprudny, Russia
| | - Heike Wulff
- Department of Pharmacology, University of California, Davis, Davis, CA, United States
| | - Jan Tytgat
- Toxicology and Pharmacology, KU Leuven, Leuven, Belgium
| | - Alexander A. Vassilevski
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
- Moscow Institute of Physics and Technology, Moscow Region, Dolgoprudny, Russia
- *Correspondence: Alexander A. Vassilevski,
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Plazas PV, Elgoyhen AB. The Cholinergic Lateral Line Efferent Synapse: Structural, Functional and Molecular Similarities With Those of the Cochlea. Front Cell Neurosci 2021; 15:765083. [PMID: 34712122 PMCID: PMC8545859 DOI: 10.3389/fncel.2021.765083] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Accepted: 09/21/2021] [Indexed: 11/25/2022] Open
Abstract
Vertebrate hair cell (HC) systems are innervated by efferent fibers that modulate their response to external stimuli. In mammals, the best studied efferent-HC synapse, the cholinergic medial olivocochlear (MOC) efferent system, makes direct synaptic contacts with HCs. The net effect of MOC activity is to hyperpolarize HCs through the activation of α9α10 nicotinic cholinergic receptors (nAChRs) and the subsequent activation of Ca2+-dependent SK2 potassium channels. A serious obstacle in research on many mammalian sensory systems in their native context is that their constituent neurons are difficult to access even in newborn animals, hampering circuit observation, mapping, or controlled manipulation. By contrast, fishes and amphibians have a superficial and accessible mechanosensory system, the lateral line (LL), which circumvents many of these problems. LL responsiveness is modulated by efferent neurons which aid to distinguish between external and self-generated stimuli. One component of the LL efferent system is cholinergic and its activation inhibits LL afferent activity, similar to what has been described for MOC efferents. The zebrafish (Danio rerio) has emerged as a powerful model system for studying human hearing and balance disorders, since LL HC are structurally and functionally analogous to cochlear HCs, but are optically and pharmacologically accessible within an intact specimen. Complementing mammalian studies, zebrafish have been used to gain significant insights into many facets of HC biology, including mechanotransduction and synaptic physiology as well as mechanisms of both hereditary and acquired HC dysfunction. With the rise of the zebrafish LL as a model in which to study auditory system function and disease, there has been an increased interest in studying its efferent system and evaluate the similarity between mammalian and piscine efferent synapses. Advances derived from studies in zebrafish include understanding the effect of the LL efferent system on HC and afferent activity, and revealing that an α9-containing nAChR, functionally coupled to SK channels, operates at the LL efferent synapse. In this review, we discuss the tools and findings of these recent investigations into zebrafish efferent-HC synapse, their commonalities with the mammalian counterpart and discuss several emerging areas for future studies.
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Affiliation(s)
- Paola V Plazas
- Instituto de Farmacología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Ana Belén Elgoyhen
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina
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Gamma-Aminobutyric Acid (GABA) Inhibits α-Melanocyte-Stimulating Hormone-Induced Melanogenesis through GABA A and GABA B Receptors. Int J Mol Sci 2021; 22:ijms22158257. [PMID: 34361022 PMCID: PMC8347673 DOI: 10.3390/ijms22158257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 07/26/2021] [Accepted: 07/28/2021] [Indexed: 11/25/2022] Open
Abstract
Gamma-aminobutyric acid (GABA) is considered the primary inhibitory neurotransmitter in the human cortex. However, whether GABA regulates melanogenesis has not been comprehensively elucidated. In this study, we reveal that GABA (20 mM) significantly inhibited α-melanocyte-stimulating hormone (α-MSH)-induced extracellular (from 354.9% ± 28.4% to 126.5% ± 16.0%) and intracellular melanin contents (from 236.7% ± 11.1% to 102.7% ± 23.1%) in B16F10 melanoma cells, without inducing cytotoxicity. In addition, α-MSH-induced hyperpigmentation in zebrafish larvae was inhibited from 246.3% ± 5.4% to 116.3% ± 3.1% at 40 mM GABA, displaying no apparent cardiotoxicity. We also clarify that the GABA-mediated antimelanogenic properties were related to the direct inhibition of microphthalmia-associated transcription factor (MITF) and tyrosinase expression by inhibiting cyclic adenosine monophosphate (cAMP) and cAMP response element-binding protein (CREB). Furthermore, under α-MSH stimulation, GABA-related antimelanogenic effects were mediated through the GABAA and GABAB receptors, with subsequent inhibition of Ca2+ accumulation. In B16F10 melanoma cells and zebrafish larvae, pretreatment with bicuculline, a GABAA receptor antagonist, and CGP 46381, a GABAB receptor antagonist, reversed the antimelanogenic effect of GABA following α-MSH treatment by upregulating Ca2+ accumulation. In conclusion, our results indicate that GABA inhibits α-MSH-induced melanogenesis. Hence, in addition to the health benefits of GABA in the central nervous system, it could ameliorate hyperpigmentation disorders.
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Abstract
K+ channels enable potassium to flow across the membrane with great selectivity. There are four K+ channel families: voltage-gated K (Kv), calcium-activated (KCa), inwardly rectifying K (Kir), and two-pore domain potassium (K2P) channels. All four K+ channels are formed by subunits assembling into a classic tetrameric (4x1P = 4P for the Kv, KCa, and Kir channels) or tetramer-like (2x2P = 4P for the K2P channels) architecture. These subunits can either be the same (homomers) or different (heteromers), conferring great diversity to these channels. They share a highly conserved selectivity filter within the pore but show different gating mechanisms adapted for their function. K+ channels play essential roles in controlling neuronal excitability by shaping action potentials, influencing the resting membrane potential, and responding to diverse physicochemical stimuli, such as a voltage change (Kv), intracellular calcium oscillations (KCa), cellular mediators (Kir), or temperature (K2P).
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9
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Kamata S, Kimura M, Ohyama S, Yamashita S, Shibukawa Y. Large-Conductance Calcium-Activated Potassium Channels and Voltage-Dependent Sodium Channels in Human Cementoblasts. Front Physiol 2021; 12:634846. [PMID: 33959036 PMCID: PMC8093401 DOI: 10.3389/fphys.2021.634846] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Accepted: 03/17/2021] [Indexed: 12/02/2022] Open
Abstract
Cementum, which is excreted by cementoblasts, provides an attachment site for collagen fibers that connect to the alveolar bone and fix the teeth into the alveolar sockets. Transmembrane ionic signaling, associated with ionic transporters, regulate various physiological processes in a wide variety of cells. However, the properties of the signals generated by plasma membrane ionic channels in cementoblasts have not yet been described in detail. We investigated the biophysical and pharmacological properties of ion channels expressed in human cementoblast (HCEM) cell lines by measuring ionic currents using conventional whole-cell patch-clamp recording. The application of depolarizing voltage steps in 10 mV increments from a holding potential (Vh) of −70 mV evoked outwardly rectifying currents at positive potentials. When intracellular K+ was substituted with an equimolar concentration of Cs+, the outward currents almost disappeared. Using tail current analysis, the contributions of both K+ and background Na+ permeabilities were estimated for the outward currents. Extracellular application of tetraethylammonium chloride (TEA) and iberiotoxin (IbTX) reduced the densities of the outward currents significantly and reversibly, whereas apamin and TRAM-34 had no effect. When the Vh was changed to −100 mV, we observed voltage-dependent inward currents in 30% of the recorded cells. These results suggest that HCEM express TEA- and IbTX-sensitive large-conductance Ca2+-activated K+ channels and voltage-dependent Na+ channels.
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Affiliation(s)
- Satomi Kamata
- Department of Removable Partial Prosthodontics, Tokyo Dental College, Tokyo, Japan.,Department of Physiology, Tokyo Dental College, Tokyo, Japan
| | - Maki Kimura
- Department of Physiology, Tokyo Dental College, Tokyo, Japan
| | - Sadao Ohyama
- Department of Physiology, Tokyo Dental College, Tokyo, Japan
| | - Shuichiro Yamashita
- Department of Removable Partial Prosthodontics, Tokyo Dental College, Tokyo, Japan
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Sevrain CM, Fontaine D, Bauduin A, Guéguinou M, Zhang BL, Chantôme A, Mahéo K, Pasqualin C, Maupoil V, Couthon H, Vandier C, Jaffrès PA. Thio-ether functionalized glycolipid amphiphilic compounds reveal a potent activator of SK3 channel with vasorelaxation effect. Org Biomol Chem 2021; 19:2753-2766. [PMID: 33687423 DOI: 10.1039/d1ob00021g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The modulation of SK3 ion channels can be efficiently and selectively achieved by using the amphiphilic compound Ohmline (a glyco-glycero-ether-lipid). We report herein a series of Ohmline analogues featuring the replacement of one ether function by a thioether function located at the same position or shifted close to its initial position. The variation of the lipid chain length and the preparation of two analogues featuring either one sulfoxide or one sulfone moiety complete this series. Patch clamp measurements indicate that the presence of the thioether function (compounds 7 and 17a) produces strong activators of SK3 channels, whereas the introduction of a sulfoxide or a sulfone function at the same place produces amphiphiles devoid of an effect on SK3 channels. Compounds 7 and 17a are the first amphiphilic compounds featuring strong activation of SK3 channels (close to 200% activation). The cytosolic calcium concentration determined from fluorescence at 3 different times for compound 7b (13 min, 1 h, 24 h) revealed that the effect is different suggesting that the compound could be metabolized over time. This compound could be used as a strong SK3 activator for a short time. The capacity of 7b to activate SK3 was then used to induce vasorelaxation via an endothelium-derived hyperpolarization (EDH) pathway. For the first time, we report that an amphiphilic compound can affect the endothelium dependent vasorelaxation.
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Affiliation(s)
- Charlotte M Sevrain
- Univ. Brest, CNRS, CEMCA UMR 6521, 6 Avenue Victor Le Gorgeu, Brest, F-29238 Brest, France.
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11
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Unraveling the Molecular Players at the Cholinergic Efferent Synapse of the Zebrafish Lateral Line. J Neurosci 2020; 41:47-60. [PMID: 33203744 DOI: 10.1523/jneurosci.1772-20.2020] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 09/25/2020] [Accepted: 10/30/2020] [Indexed: 12/26/2022] Open
Abstract
The lateral line (LL) is a sensory system that allows fish and amphibians to detect water currents. LL responsiveness is modulated by efferent neurons that aid in distinguishing between external and self-generated stimuli, maintaining sensitivity to relevant cues. One component of the efferent system is cholinergic, the activation of which inhibits afferent activity. LL hair cells (HCs) share structural, functional, and molecular similarities with those of the cochlea, making them a popular model for studying human hearing and balance disorders. Because of these commonalities, one could propose that the receptor at the LL efferent synapse is a α9α10 nicotinic acetylcholine receptor (nAChR). However, the identities of the molecular players underlying ACh-mediated inhibition in the LL remain unknown. Surprisingly, through the analysis of single-cell expression studies and in situ hybridization, we describe that α9, but not the α10, subunits are enriched in zebrafish HCs. Moreover, the heterologous expression of zebrafish α9 subunits indicates that homomeric receptors are functional and exhibit robust ACh-gated currents blocked by α-bungarotoxin and strychnine. In addition, in vivo Ca2+ imaging on mechanically stimulated zebrafish LL HCs show that ACh elicits a decrease in evoked Ca2+ signals, regardless of HC polarity. This effect is blocked by both α-bungarotoxin and apamin, indicating coupling of ACh-mediated effects to small-conductance Ca2+-activated potassium (SKs) channels. Our results indicate that an α9-containing (α9*) nAChR operates at the zebrafish LL efferent synapse. Moreover, the activation of α9* nAChRs most likely leads to LL HC hyperpolarization served by SK channels.SIGNIFICANCE STATEMENT The fish lateral line (LL) mechanosensory system shares structural, functional, and molecular similarities with those of the mammalian cochlea. Thus, it has become an accessible model for studying human hearing and balance disorders. However, the molecular players serving efferent control of LL hair cell (HC) activity have not been identified. Here we demonstrate that, different from the hearing organ of vertebrate species, a nicotinic acetylcholine receptor composed only of α9 subunits operates at the LL efferent synapse. Activation of α9-containing receptors leads to LL HC hyperpolarization because of the opening of small-conductance Ca2+-activated potassium channels. These results will further aid in the interpretation of data obtained from LL HCs as a model for cochlear HCs.
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12
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Gunawan MG, Sangha SS, Shafaattalab S, Lin E, Heims-Waldron DA, Bezzerides VJ, Laksman Z, Tibbits GF. Drug screening platform using human induced pluripotent stem cell-derived atrial cardiomyocytes and optical mapping. Stem Cells Transl Med 2020; 10:68-82. [PMID: 32927497 PMCID: PMC7780813 DOI: 10.1002/sctm.19-0440] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 07/13/2020] [Accepted: 08/03/2020] [Indexed: 12/17/2022] Open
Abstract
Current drug development efforts for the treatment of atrial fibrillation are hampered by the fact that many preclinical models have been unsuccessful in reproducing human cardiac physiology and its response to medications. In this study, we demonstrated an approach using human induced pluripotent stem cell-derived atrial and ventricular cardiomyocytes (hiPSC-aCMs and hiPSC-vCMs, respectively) coupled with a sophisticated optical mapping system for drug screening of atrial-selective compounds in vitro. We optimized differentiation of hiPSC-aCMs by modulating the WNT and retinoid signaling pathways. Characterization of the transcriptome and proteome revealed that retinoic acid pushes the differentiation process into the atrial lineage and generated hiPSC-aCMs. Functional characterization using optical mapping showed that hiPSC-aCMs have shorter action potential durations and faster Ca2+ handling dynamics compared with hiPSC-vCMs. Furthermore, pharmacological investigation of hiPSC-aCMs captured atrial-selective effects by displaying greater sensitivity to atrial-selective compounds 4-aminopyridine, AVE0118, UCL1684, and vernakalant when compared with hiPSC-vCMs. These results established that a model system incorporating hiPSC-aCMs combined with optical mapping is well-suited for preclinical drug screening of novel and targeted atrial selective compounds.
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Affiliation(s)
- Marvin G Gunawan
- Molecular Cardiac Physiology Group, Departments of Biomedical Physiology and Kinesiology and Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada.,Tibbits Research Team, British Columbia Children's Hospital Research Institute, Vancouver, British Columbia, Canada
| | - Sarabjit S Sangha
- Molecular Cardiac Physiology Group, Departments of Biomedical Physiology and Kinesiology and Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada.,Tibbits Research Team, British Columbia Children's Hospital Research Institute, Vancouver, British Columbia, Canada
| | - Sanam Shafaattalab
- Molecular Cardiac Physiology Group, Departments of Biomedical Physiology and Kinesiology and Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada.,Tibbits Research Team, British Columbia Children's Hospital Research Institute, Vancouver, British Columbia, Canada.,Department of Cardiology, Boston Children's Hospital, Boston, Massachusetts, USA
| | - Eric Lin
- Molecular Cardiac Physiology Group, Departments of Biomedical Physiology and Kinesiology and Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | | | | | - Zachary Laksman
- Division of Cardiology, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada.,Centre for Heart and Lung Innovation, St. Paul's Hospital, Vancouver, British Columbia, Canada
| | - Glen F Tibbits
- Molecular Cardiac Physiology Group, Departments of Biomedical Physiology and Kinesiology and Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada.,Tibbits Research Team, British Columbia Children's Hospital Research Institute, Vancouver, British Columbia, Canada
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13
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Saljic A, Muthukumarasamy KM, la Cour JM, Boddum K, Grunnet M, Berchtold MW, Jespersen T. Impact of arrhythmogenic calmodulin variants on small conductance Ca 2+ -activated K + (SK3) channels. Physiol Rep 2020; 7:e14210. [PMID: 31587513 PMCID: PMC6778599 DOI: 10.14814/phy2.14210] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Accepted: 07/31/2019] [Indexed: 02/07/2023] Open
Abstract
Calmodulin (CaM) is a ubiquitous Ca2+‐sensing protein regulating many important cellular processes. Several CaM‐associated variants have been identified in a small group of patients with cardiac arrhythmias. The mechanism remains largely unknown, even though a number of ion channels, including the ryanodine receptors and the L‐type calcium channels have been shown to be functionally affected by the presence of mutant CaM. CaM is constitutively bound to the SK channel, which underlies the calcium‐gated ISK contributing to cardiac repolarization. The CaM binding to SK channels is essential for gating, correct assembly, and membrane expression. To elucidate the effect of nine different arrhythmogenic CaM variants on SK3 channel function, HEK293 cells stably expressing SK3 were transiently co‐transfected with CaMWT or variant and whole‐cell patch‐clamp recordings were performed with a calculated free Ca2+ concentration of 400 nmol/L. MDCK cells were transiently transfected with SK3 and/or CaMWT or variant to address SK3 and CaM localization by immunocytochemistry. The LQTS‐associated variants CaMD96V, CaMD130G, and CaMF142L reduced ISK,Ca compared with CaMWT (P < 0.01, P < 0.001, and P < 0.05, respectively). The CPVT associated variant CaMN54I also reduced the ISK,Ca (P < 0.05), which was linked to an accumulation of SK3/CaMN54I channel complexes in intracellular compartments (P < 0.05). The CPVT associated variants, CaMA103V and CaMD132E only revealed a tendency toward reduced current, while the variants CaMF90L and CaMN98S, causing LQTS syndrome, did not have any impact on ISK,Ca. In conclusion, we found that the arrhythmogenic CaM variants CaMN54I, CaMD96V, CaMD130G, and CaMF142L significantly down‐regulate the SK3 channel current, but with distinct mechanism.
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Affiliation(s)
- Arnela Saljic
- Laboratory of Cardiac Physiology, Faculty of Health and Medical Sciences, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Kalai Mangai Muthukumarasamy
- Laboratory of Cardiac Physiology, Faculty of Health and Medical Sciences, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jonas Marstrand la Cour
- Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Kim Boddum
- Laboratory of Cardiac Physiology, Faculty of Health and Medical Sciences, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | | | - Martin Werner Berchtold
- Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Thomas Jespersen
- Laboratory of Cardiac Physiology, Faculty of Health and Medical Sciences, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
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14
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Gamal-Eltrabily M, Espinosa de Los Monteros-Zúñiga A, Manzano-García A, Martínez-Lorenzana G, Condés-Lara M, González-Hernández A. The Rostral Agranular Insular Cortex, a New Site of Oxytocin to Induce Antinociception. J Neurosci 2020; 40:5669-5680. [PMID: 32571836 PMCID: PMC7363465 DOI: 10.1523/jneurosci.0962-20.2020] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 06/03/2020] [Accepted: 06/11/2020] [Indexed: 12/23/2022] Open
Abstract
The rostral agranular insular cortex (RAIC) is a relevant structure in nociception. Indeed, recruitment of GABAergic activity in RAIC promotes the disinhibition of the locus ceruleus, which in turn inhibits (by noradrenergic action) the peripheral nociceptive input at the spinal cord level. In this regard, at the cortical level, oxytocin can modulate the GABAergic transmission; consequently, an interaction modulating nociception could exist between oxytocin and GABA at RAIC. Here, we tested in male Wistar rats the effect of oxytocin microinjection into RAIC during an inflammatory (by subcutaneous peripheral injection of formalin) nociceptive input. Oxytocin microinjection produces a diminution of (1) flinches induced by formalin and (2) spontaneous firing of spinal wide dynamic range cells. The above antinociceptive effect was abolished by microinjection (at RAIC) of the following: (1) L-368899 (an oxytocin receptor [OTR] antagonist) or by (2) bicuculline (a preferent GABAA receptor blocker), suggesting a GABAergic activation induced by OTR. Since intrathecal injection of an α2A-adrenoceptor antagonist (BRL 44408) partially reversed the oxytocin effect, a descending noradrenergic antinociception is suggested. Further, injection of L-368899 per se induces a pronociceptive behavioral effect, suggesting a tonic endogenous oxytocin release during inflammatory nociceptive input. Accordingly, we found bilateral projections from the paraventricular nucleus of the hypothalamus (PVN) to RAIC. Some of the PVN-projecting cells are oxytocinergic and destinate GABAergic and OTR-expressing cells inside RAIC. Aside from the direct anatomic link between PVN and RAIC, our findings provide evidence about the role of oxytocinergic mechanisms modulating the pain process at the RAIC level.SIGNIFICANCE STATEMENT Oxytocin is a neuropeptide involved in several functions ranging from lactation to social attachment. Over the years, the role of this molecule in pain processing has emerged, showing that, at the spinal level, oxytocin blocks pain transmission. The present work suggests that oxytocin also modulates pain at the cortical insular level by favoring cortical GABAergic transmission and activating descending spinal noradrenergic mechanisms. Indeed, we show that the paraventricular hypothalamicnucleus sends direct oxytocinergic projections to the rostral agranular insular cortex on GABAergic and oxytocin receptor-expressing neurons. Together, our data support the notion that the oxytocinergic system could act as an orchestrator of pain modulation.
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Affiliation(s)
- Mohammed Gamal-Eltrabily
- Instituto de Neurobiología, Universidad Nacional Autónoma de México, Campus UNAM-Juriquilla, Juriquilla, CP 76230, Mexico
| | | | - Alfredo Manzano-García
- Instituto de Neurobiología, Universidad Nacional Autónoma de México, Campus UNAM-Juriquilla, Juriquilla, CP 76230, Mexico
| | - Guadalupe Martínez-Lorenzana
- Instituto de Neurobiología, Universidad Nacional Autónoma de México, Campus UNAM-Juriquilla, Juriquilla, CP 76230, Mexico
| | - Miguel Condés-Lara
- Instituto de Neurobiología, Universidad Nacional Autónoma de México, Campus UNAM-Juriquilla, Juriquilla, CP 76230, Mexico
| | - Abimael González-Hernández
- Instituto de Neurobiología, Universidad Nacional Autónoma de México, Campus UNAM-Juriquilla, Juriquilla, CP 76230, Mexico
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15
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Jones MJ, Dawson A, Hales TG, Hunter WN. A Structural Rationale for N-Methylbicuculline Acting as a Promiscuous Competitive Antagonist of Inhibitory Pentameric Ligand-Gated Ion Channels. Chembiochem 2020; 21:1526-1533. [PMID: 31859406 DOI: 10.1002/cbic.201900680] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Indexed: 11/07/2022]
Abstract
Bicuculline, a valued chemical tool in neurosciences research, is a competitive antagonist of specific GABAA receptors and affects other pentameric ligand-gated ion channels including the glycine, nicotinic acetylcholine and 5-hydroxytryptamine type 3 receptors. We used a fluorescence-quenching assay and isothermal titration calorimetry to record low-micromolar dissociation constants for N-methylbicuculline interacting with acetylcholine-binding protein and an engineered version called glycine-binding protein (GBP), which provides a surrogate for the heteromeric interface of the extracellular domain of the glycine receptor (GlyR). The 2.4 Å resolution crystal structure of the GBP:N-methylbicuculline complex, sequence and structural alignments reveal similarities and differences between GlyR and the GABAA receptor-bicuculline interactions. N-methylbicuculline displays a similar conformation in different structures, but adopts distinct orientations enforced by interactions and steric blocks with key residues and plasticity in the binding sites. These features explain the promiscuous activity of bicuculline against the principal inhibitory pentameric ligand-gated ion channels in the CNS.
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Affiliation(s)
- Mathew J Jones
- Division of Biological Chemistry and Drug Discovery School of Life Sciences, University of Dundee, Dow St, Dundee, DD1 5EH, UK
| | - Alice Dawson
- Division of Biological Chemistry and Drug Discovery School of Life Sciences, University of Dundee, Dow St, Dundee, DD1 5EH, UK
| | - Tim G Hales
- Division of Systems Medicine, School of Medicine, Ninewells Hospital, University of Dundee, Dundee, DD1 9SY, UK
| | - William N Hunter
- Division of Biological Chemistry and Drug Discovery School of Life Sciences, University of Dundee, Dow St, Dundee, DD1 5EH, UK
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16
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Castañeda MS, Tonini R, Richards CD, Stocker M, Pedarzani P. Benzamil inhibits neuronal and heterologously expressed small conductance Ca2+-activated K+ channels. Neuropharmacology 2019; 158:107738. [DOI: 10.1016/j.neuropharm.2019.107738] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 07/10/2019] [Accepted: 08/07/2019] [Indexed: 10/26/2022]
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17
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Bock T, Honnuraiah S, Stuart GJ. Paradoxical Excitatory Impact of SK Channels on Dendritic Excitability. J Neurosci 2019; 39:7826-7839. [PMID: 31420457 PMCID: PMC6774406 DOI: 10.1523/jneurosci.0105-19.2019] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2019] [Revised: 08/07/2019] [Accepted: 08/12/2019] [Indexed: 11/21/2022] Open
Abstract
Dendritic excitability regulates how neurons integrate synaptic inputs and thereby influences neuronal output. As active dendritic events are associated with significant calcium influx they are likely to be modulated by calcium-dependent processes, such as calcium-activated potassium channels. Here we investigate the impact of small conductance calcium-activated potassium channels (SK channels) on dendritic excitability in male and female rat cortical pyramidal neurons in vitro and in vivo Using local applications of the SK channel antagonist apamin in vitro, we show that blocking somatic SK channels enhances action potential output, whereas blocking dendritic SK channels paradoxically reduces the generation of dendritic calcium spikes and associated somatic burst firing. Opposite effects were observed using the SK channel enhancer NS309. The effect of apamin on dendritic SK channels was occluded when R-type calcium channels were blocked, indicating that the inhibitory impact of apamin on dendritic calcium spikes involved R-type calcium channels. Comparable effects were observed in vivo Intracellular application of apamin via the somatic whole-cell recording pipette reduced the medium afterhyperpolarization and increased action potential output during UP states. In contrast, extracellular application of apamin to the cortical surface to block dendritic SK channels shifted the distribution of action potentials within UP states from an initial burst to a more distributed firing pattern, while having no impact on overall action potential firing frequency or UP and DOWN states. These data indicate that somatic and dendritic SK channels have opposite effects on neuronal excitability, with dendritic SK channels counter-intuitively promoting rather than suppressing neuronal output.SIGNIFICANCE STATEMENT Neurons typically receive input from other neurons onto processes called dendrites, and use electrical events such as action potentials for signaling. As electrical events in neurons are usually associated with calcium influx they can be regulated by calcium-dependent processes. One such process is through the activation of calcium-dependent potassium channels, which usually act to reduce action potential signaling. Although this is the case for calcium-dependent potassium channels found at the cell body, we show here that calcium-dependent potassium channels in dendrites of cortical pyramidal neurons counter-intuitively promote rather than suppress action potential output.
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Affiliation(s)
- Tobias Bock
- Eccles Institute of Neuroscience and Australian Research Council Centre of Excellence for Integrative Brain Function, John Curtin School of Medical Research, Australian National University, Canberra, 2601 Australia
| | - Suraj Honnuraiah
- Eccles Institute of Neuroscience and Australian Research Council Centre of Excellence for Integrative Brain Function, John Curtin School of Medical Research, Australian National University, Canberra, 2601 Australia
| | - Greg J Stuart
- Eccles Institute of Neuroscience and Australian Research Council Centre of Excellence for Integrative Brain Function, John Curtin School of Medical Research, Australian National University, Canberra, 2601 Australia
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18
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In Vivo Analysis of Potassium Channelopathies: Loose Patch Recording of Purkinje Cell Firing in Living, Awake Zebrafish. Methods Mol Biol 2018; 1684:237-252. [PMID: 29058196 DOI: 10.1007/978-1-4939-7362-0_18] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/26/2023]
Abstract
Zebrafish is a lower vertebrate model organism that facilitates integrative analysis of the in vivo effects of potassium and other ion channel mutations at the molecular, cellular, developmental, circuit, systems, and behavioral levels of analysis. Here, we describe a method for extracellular, loose patch electrophysiological recording of electrical activity in cerebellar Purkinje cells in living, awake zebrafish, with the goal of investigating pathological mechanisms underlying channelopathies or other diseases that disrupt cerebellar function. Purkinje cell excitability and a functional cerebellar circuit develop rapidly in zebrafish and show strong conservation with the mammalian cerebellum.
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19
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Lee H, Koh BH, Peri LE, Corrigan RD, Lee HT, George NE, Bhetwal BP, Xie Y, Perrino BA, Chai TC, Sanders KM, Koh SD. Premature contractions of the bladder are suppressed by interactions between TRPV4 and SK3 channels in murine detrusor PDGFRα + cells. Sci Rep 2017; 7:12245. [PMID: 28947806 PMCID: PMC5613012 DOI: 10.1038/s41598-017-12561-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Accepted: 09/11/2017] [Indexed: 11/09/2022] Open
Abstract
During filling, urinary bladder volume increases dramatically with little change in pressure. This is accomplished by suppressing contractions of the detrusor muscle that lines the bladder wall. Mechanisms responsible for regulating detrusor contraction during filling are poorly understood. Here we describe a novel pathway to stabilize detrusor excitability involving platelet-derived growth factor receptor-α positive (PDGFRα+) interstitial cells. PDGFRα+ cells express small conductance Ca2+-activated K+ (SK) and TRPV4 channels. We found that Ca2+ entry through mechanosensitive TRPV4 channels during bladder filling stabilizes detrusor excitability. GSK1016790A (GSK), a TRPV4 channel agonist, activated a non-selective cation conductance that coupled to activation of SK channels. GSK induced hyperpolarization of PDGFRα+ cells and decreased detrusor contractions. Contractions were also inhibited by activation of SK channels. Blockers of TRPV4 or SK channels inhibited currents activated by GSK and increased detrusor contractions. TRPV4 and SK channel blockers also increased contractions of intact bladders during filling. Similar enhancement of contractions occurred in bladders of Trpv4 -/- mice during filling. An SK channel activator (SKA-31) decreased contractions during filling, and rescued the overactivity of Trpv4 -/- bladders. Our findings demonstrate how Ca2+ influx through TRPV4 channels can activate SK channels in PDGFRα+ cells and prevent bladder overactivity during filling.
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Affiliation(s)
- Haeyeong Lee
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, 89557, USA.
| | - Byoung H Koh
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, 89557, USA
| | - Lauren E Peri
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, 89557, USA
| | - Robert D Corrigan
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, 89557, USA
| | - Hyun-Tai Lee
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, 89557, USA
| | - Nikita E George
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, 89557, USA
| | - Bhupal P Bhetwal
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, 89557, USA
| | - Yeming Xie
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, 89557, USA
| | - Brian A Perrino
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, 89557, USA
| | - Toby C Chai
- Department of Urology, Yale University School of Medicine, New Haven, CT, 06519, USA
| | - Kenton M Sanders
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, 89557, USA
| | - Sang Don Koh
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, 89557, USA
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20
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Honrath B, Krabbendam IE, Culmsee C, Dolga AM. Small conductance Ca 2+-activated K + channels in the plasma membrane, mitochondria and the ER: Pharmacology and implications in neuronal diseases. Neurochem Int 2017; 109:13-23. [PMID: 28511953 DOI: 10.1016/j.neuint.2017.05.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Revised: 04/24/2017] [Accepted: 05/08/2017] [Indexed: 12/14/2022]
Abstract
Ca2+-activated K+ (KCa) channels regulate after-hyperpolarization in many types of neurons in the central and peripheral nervous system. Small conductance Ca2+-activated K+ (KCa2/SK) channels, a subfamily of KCa channels, are widely expressed in the nervous system, and in the cardiovascular system. Voltage-independent SK channels are activated by alterations in intracellular Ca2+ ([Ca2+]i) which facilitates the opening of these channels through binding of Ca2+ to calmodulin that is constitutively bound to the SK2 C-terminus. In neurons, SK channels regulate synaptic plasticity and [Ca2+]i homeostasis, and a number of recent studies elaborated on the emerging neuroprotective potential of SK channel activation in conditions of excitotoxicity and cerebral ischemia, as well as endoplasmic reticulum (ER) stress and oxidative cell death. Recently, SK channels were discovered in the inner mitochondrial membrane and in the membrane of the endoplasmic reticulum which sheds new light on the underlying molecular mechanisms and pathways involved in SK channel-mediated protective effects. In this review, we will discuss the protective properties of pharmacological SK channel modulation with particular emphasis on intracellularly located SK channels as potential therapeutic targets in paradigms of neuronal dysfunction.
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Affiliation(s)
- Birgit Honrath
- Institute of Pharmacology and Clinical Pharmacy, University of Marburg, 35043 Marburg, Germany; Faculty of Science and Engineering, Groningen Research Institute of Pharmacy, Department of Molecular Pharmacology, University of Groningen, 9713 AV Groningen, The Netherlands
| | - Inge E Krabbendam
- Faculty of Science and Engineering, Groningen Research Institute of Pharmacy, Department of Molecular Pharmacology, University of Groningen, 9713 AV Groningen, The Netherlands
| | - Carsten Culmsee
- Institute of Pharmacology and Clinical Pharmacy, University of Marburg, 35043 Marburg, Germany
| | - Amalia M Dolga
- Institute of Pharmacology and Clinical Pharmacy, University of Marburg, 35043 Marburg, Germany; Faculty of Science and Engineering, Groningen Research Institute of Pharmacy, Department of Molecular Pharmacology, University of Groningen, 9713 AV Groningen, The Netherlands.
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21
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Yang T, Zhang HL, Liang Q, Shi Y, Mei YA, Barrett PQ, Hu C. Small-Conductance Ca2+-Activated Potassium Channels Negatively Regulate Aldosterone Secretion in Human Adrenocortical Cells. Hypertension 2016; 68:785-95. [PMID: 27432863 DOI: 10.1161/hypertensionaha.116.07094] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Accepted: 05/05/2016] [Indexed: 01/23/2023]
Abstract
Aldosterone, which plays a key role in maintaining water and electrolyte balance, is produced by zona glomerulosa cells of the adrenal cortex. Autonomous overproduction of aldosterone from zona glomerulosa cells causes primary hyperaldosteronism. Recent clinical studies have highlighted the pathological role of the KCNJ5 potassium channel in primary hyperaldosteronism. Our objective was to determine whether small-conductance Ca(2+)-activated potassium (SK) channels may also regulate aldosterone secretion in human adrenocortical cells. We found that apamin, the prototypic inhibitor of SK channels, decreased membrane voltage, raised intracellular Ca(2+) and dose dependently increased aldosterone secretion from human adrenocortical H295R cells. By contrast, 1-Ethyl-2-benzimidazolinone, an agonist of SK channels, antagonized apamin's action and decreased aldosterone secretion. Commensurate with an increase in aldosterone production, apamin increased mRNA expression of steroidogenic acute regulatory protein and aldosterone synthase that control the early and late rate-limiting steps in aldosterone biosynthesis, respectively. In addition, apamin increased angiotensin II-stimulated aldosterone secretion, whereas 1-Ethyl-2-benzimidazolinone suppressed both angiotensin II- and high K(+)-stimulated production of aldosterone in H295R cells. These findings were supported by apamin-modulation of basal and angiotensin II-stimulated aldosterone secretion from acutely prepared slices of human adrenals. We conclude that SK channel activity negatively regulates aldosterone secretion in human adrenocortical cells. Genetic association studies are necessary to determine whether mutations in SK channel subtype 2 genes may also drive aldosterone excess in primary hyperaldosteronism.
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Affiliation(s)
- Tingting Yang
- From the Department of Physiology and Biophysics, School of Life Sciences, Institutes of Brain Science (T.Y., Q.L., Y.-A.M., C.H.) and Department of Oncology, Shanghai Medical College (H.-L.Z.), Fudan University, China; Department of Urology, Fudan University Shanghai Cancer Center, China (H.-L.Z.); and Department of Pharmacology, University of Virginia, Charlottesville (Y.S., P.Q.B.)
| | - Hai-Liang Zhang
- From the Department of Physiology and Biophysics, School of Life Sciences, Institutes of Brain Science (T.Y., Q.L., Y.-A.M., C.H.) and Department of Oncology, Shanghai Medical College (H.-L.Z.), Fudan University, China; Department of Urology, Fudan University Shanghai Cancer Center, China (H.-L.Z.); and Department of Pharmacology, University of Virginia, Charlottesville (Y.S., P.Q.B.)
| | - Qingnan Liang
- From the Department of Physiology and Biophysics, School of Life Sciences, Institutes of Brain Science (T.Y., Q.L., Y.-A.M., C.H.) and Department of Oncology, Shanghai Medical College (H.-L.Z.), Fudan University, China; Department of Urology, Fudan University Shanghai Cancer Center, China (H.-L.Z.); and Department of Pharmacology, University of Virginia, Charlottesville (Y.S., P.Q.B.)
| | - Yingtang Shi
- From the Department of Physiology and Biophysics, School of Life Sciences, Institutes of Brain Science (T.Y., Q.L., Y.-A.M., C.H.) and Department of Oncology, Shanghai Medical College (H.-L.Z.), Fudan University, China; Department of Urology, Fudan University Shanghai Cancer Center, China (H.-L.Z.); and Department of Pharmacology, University of Virginia, Charlottesville (Y.S., P.Q.B.)
| | - Yan-Ai Mei
- From the Department of Physiology and Biophysics, School of Life Sciences, Institutes of Brain Science (T.Y., Q.L., Y.-A.M., C.H.) and Department of Oncology, Shanghai Medical College (H.-L.Z.), Fudan University, China; Department of Urology, Fudan University Shanghai Cancer Center, China (H.-L.Z.); and Department of Pharmacology, University of Virginia, Charlottesville (Y.S., P.Q.B.)
| | - Paula Q Barrett
- From the Department of Physiology and Biophysics, School of Life Sciences, Institutes of Brain Science (T.Y., Q.L., Y.-A.M., C.H.) and Department of Oncology, Shanghai Medical College (H.-L.Z.), Fudan University, China; Department of Urology, Fudan University Shanghai Cancer Center, China (H.-L.Z.); and Department of Pharmacology, University of Virginia, Charlottesville (Y.S., P.Q.B.)
| | - Changlong Hu
- From the Department of Physiology and Biophysics, School of Life Sciences, Institutes of Brain Science (T.Y., Q.L., Y.-A.M., C.H.) and Department of Oncology, Shanghai Medical College (H.-L.Z.), Fudan University, China; Department of Urology, Fudan University Shanghai Cancer Center, China (H.-L.Z.); and Department of Pharmacology, University of Virginia, Charlottesville (Y.S., P.Q.B.).
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23
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Lu L, Sirish P, Zhang Z, Woltz RL, Li N, Timofeyev V, Knowlton AA, Zhang XD, Yamoah EN, Chiamvimonvat N. Regulation of gene transcription by voltage-gated L-type calcium channel, Cav1.3. J Biol Chem 2014; 290:4663-4676. [PMID: 25538241 DOI: 10.1074/jbc.m114.586883] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Cav1.3 L-type Ca(2+) channel is known to be highly expressed in neurons and neuroendocrine cells. However, we have previously demonstrated that the Cav1.3 channel is also expressed in atria and pacemaking cells in the heart. The significance of the tissue-specific expression of the channel is underpinned by our previous demonstration of atrial fibrillation in a Cav1.3 null mutant mouse model. Indeed, a recent study has confirmed the critical roles of Cav1.3 in the human heart (Baig, S. M., Koschak, A., Lieb, A., Gebhart, M., Dafinger, C., Nürnberg, G., Ali, A., Ahmad, I., Sinnegger-Brauns, M. J., Brandt, N., Engel, J., Mangoni, M. E., Farooq, M., Khan, H. U., Nürnberg, P., Striessnig, J., and Bolz, H. J. (2011) Nat. Neurosci. 14, 77-84). These studies suggest that detailed knowledge of Cav1.3 may have broad therapeutic ramifications in the treatment of cardiac arrhythmias. Here, we tested the hypothesis that there is a functional cross-talk between the Cav1.3 channel and a small conductance Ca(2+)-activated K(+) channel (SK2), which we have documented to be highly expressed in human and mouse atrial myocytes. Specifically, we tested the hypothesis that the C terminus of Cav1.3 may translocate to the nucleus where it functions as a transcriptional factor. Here, we reported for the first time that the C terminus of Cav1.3 translocates to the nucleus where it functions as a transcriptional regulator to modulate the function of Ca(2+)-activated K(+) channels in atrial myocytes. Nuclear translocation of the C-terminal domain of Cav1.3 is directly regulated by intracellular Ca(2+). Utilizing a Cav1.3 null mutant mouse model, we demonstrate that ablation of Cav1.3 results in a decrease in the protein expression of myosin light chain 2, which interacts and increases the membrane localization of SK2 channels.
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Affiliation(s)
- Ling Lu
- From the Department of Internal Medicine, Division of Cardiovascular Medicine, University of California, Davis, California 95616,; the College of Life Sciences, Nanjing Normal University, Nanjing 210046, China.
| | - Padmini Sirish
- From the Department of Internal Medicine, Division of Cardiovascular Medicine, University of California, Davis, California 95616
| | - Zheng Zhang
- From the Department of Internal Medicine, Division of Cardiovascular Medicine, University of California, Davis, California 95616
| | - Ryan L Woltz
- From the Department of Internal Medicine, Division of Cardiovascular Medicine, University of California, Davis, California 95616
| | - Ning Li
- From the Department of Internal Medicine, Division of Cardiovascular Medicine, University of California, Davis, California 95616
| | - Valeriy Timofeyev
- From the Department of Internal Medicine, Division of Cardiovascular Medicine, University of California, Davis, California 95616
| | - Anne A Knowlton
- From the Department of Internal Medicine, Division of Cardiovascular Medicine, University of California, Davis, California 95616,; the Department of Veterans Affairs, Northern California Health Care System, Mather, California 95655
| | - Xiao-Dong Zhang
- From the Department of Internal Medicine, Division of Cardiovascular Medicine, University of California, Davis, California 95616
| | - Ebenezer N Yamoah
- the Department of Physiology, School of Medicine, University of Nevada, Reno, Nevada 89557, and.
| | - Nipavan Chiamvimonvat
- From the Department of Internal Medicine, Division of Cardiovascular Medicine, University of California, Davis, California 95616,; the Department of Veterans Affairs, Northern California Health Care System, Mather, California 95655,.
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Church TW, Weatherall KL, Corrêa SAL, Prole DL, Brown JT, Marrion NV. Preferential assembly of heteromeric small conductance calcium-activated potassium channels. Eur J Neurosci 2014; 41:305-15. [PMID: 25421315 DOI: 10.1111/ejn.12789] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Revised: 10/16/2014] [Accepted: 10/20/2014] [Indexed: 11/27/2022]
Abstract
The activation of small conductance calcium-dependent (SK) channels regulates membrane excitability by causing membrane hyperpolarization. Three subtypes (SK1-3) have been cloned, with each subtype expressed within the nervous system. The locations of channel subunits overlap, with SK1 and SK2 subunits often expressed in the same brain region. We showed that expressed homomeric rat SK1 subunits did not form functional channels, because subunits accumulated in the Golgi. This raised the question of whether heteromeric channels could form with SK1 subunits. The co-expression of SK1 and SK2 subunits in HEK293 cells preferentially co-assembled to produce heteromeric channels with a fixed stoichiometry of alternating subunits. The expression in hippocampal CA1 neurons of mutant rat SK1 subunits [rat SK1(LV213/4YA)] that produced an apamin-sensitive current changed the amplitude and pharmacology of the medium afterhyperpolarization. The overexpression of rat SK1(LV213/4YA) subunits reduced the sensitivity of the medium afterhyperpolarization to apamin, substantiating the preferential co-assembly of SK1 and SK2 subunits to form heteromeric channels. Species-specific channel assembly occurred as the co-expression of human SK1 with rat SK2 did not form functional heteromeric channels. The replacement of two amino acids within the C-terminus of rat SK2 with those from human SK2 permitted the assembly of heteromeric channels when co-expressed with human SK1. These data showed that species-specific co-assembly was mediated by interaction between the C-termini of SK channel subunits. The finding that SK channels preferentially co-assembled to form heteromeric channels suggested that native heteromeric channels will predominate in cells expressing multiple SK channel subunits.
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Affiliation(s)
- Timothy W Church
- School of Physiology and Pharmacology, University of Bristol, Bristol, UK
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25
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Schmitt N, Grunnet M, Olesen SP. Cardiac potassium channel subtypes: new roles in repolarization and arrhythmia. Physiol Rev 2014; 94:609-53. [PMID: 24692356 DOI: 10.1152/physrev.00022.2013] [Citation(s) in RCA: 160] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
About 10 distinct potassium channels in the heart are involved in shaping the action potential. Some of the K+ channels are primarily responsible for early repolarization, whereas others drive late repolarization and still others are open throughout the cardiac cycle. Three main K+ channels drive the late repolarization of the ventricle with some redundancy, and in atria this repolarization reserve is supplemented by the fairly atrial-specific KV1.5, Kir3, KCa, and K2P channels. The role of the latter two subtypes in atria is currently being clarified, and several findings indicate that they could constitute targets for new pharmacological treatment of atrial fibrillation. The interplay between the different K+ channel subtypes in both atria and ventricle is dynamic, and a significant up- and downregulation occurs in disease states such as atrial fibrillation or heart failure. The underlying posttranscriptional and posttranslational remodeling of the individual K+ channels changes their activity and significance relative to each other, and they must be viewed together to understand their role in keeping a stable heart rhythm, also under menacing conditions like attacks of reentry arrhythmia.
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Yu CC, Ai T, Weiss JN, Chen PS. Apamin does not inhibit human cardiac Na+ current, L-type Ca2+ current or other major K+ currents. PLoS One 2014; 9:e96691. [PMID: 24798465 PMCID: PMC4010514 DOI: 10.1371/journal.pone.0096691] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Accepted: 04/10/2014] [Indexed: 12/03/2022] Open
Abstract
Background Apamin is commonly used as a small-conductance Ca2+-activated K+ (SK) current inhibitor. However, the specificity of apamin in cardiac tissues remains unclear. Objective To test the hypothesis that apamin does not inhibit any major cardiac ion currents. Methods We studied human embryonic kidney (HEK) 293 cells that expressed human voltage-gated Na+, K+ and Ca2+ currents and isolated rabbit ventricular myocytes. Whole-cell patch clamp techniques were used to determine ionic current densities before and after apamin administration. Results Ca2+ currents (CACNA1c+CACNB2b) were not affected by apamin (500 nM) (data are presented as median [25th percentile;75th percentile] (from –16 [–20;–10] to –17 [–19;–13] pA/pF, P = NS), but were reduced by nifedipine to –1.6 [–3.2;–1.3] pA/pF (p = 0.008). Na+ currents (SCN5A) were not affected by apamin (from –261 [–282;–145] to –268 [–379;–132] pA/pF, P = NS), but were reduced by flecainide to –57 [–70;–47] pA/pF (p = 0.018). None of the major K+ currents (IKs, IKr, IK1 and Ito) were inhibited by 500 nM of apamin (KCNQ1+KCNE1, from 28 [20]; [37] to 23 [18]; [32] pA/pF; KCNH2+KCNE2, from 28 [24]; [30] to 27 [24]; [29] pA/pF; KCNJ2, from –46 [–48;–40] to –46 [–51;–35] pA/pF; KCND3, from 608 [505;748] to 606 [454;684]). Apamin did not inhibit the INa or ICaL in isolated rabbit ventricular myocytes (INa, from –67 [–75;–59] to –68 [–71;–59] pA/pF; ICaL, from –16 [–17;–14] to –14 [–15;–13] pA/pF, P = NS for both). Conclusions Apamin does not inhibit human cardiac Na+ currents, L-type Ca2+ currents or other major K+ currents. These findings indicate that apamin is a specific SK current inhibitor in hearts as well as in other organs.
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Affiliation(s)
- Chih-Chieh Yu
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
- Department of Integrated Diagnostic & Therapeutics, National Taiwan University, Taipei, Taiwan
| | - Tomohiko Ai
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
- Department of Molecular Pathogenesis, Division of Pathophysiology, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - James N. Weiss
- Cardiovascular Research Laboratory, Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Peng-Sheng Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
- * E-mail:
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Nishiyama K, Azuma YT, Shintaku K, Yoshida N, Nakajima H, Takeuchi T. Evidence that Nitric Oxide Is a Non-Adrenergic Non-Cholinergic Inhibitory Neurotransmitter in the Circular Muscle of the Mouse Distal Colon: A Study on the Mechanism of Nitric Oxide-Induced Relaxation. Pharmacology 2014; 94:99-108. [DOI: 10.1159/000363191] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Accepted: 04/25/2014] [Indexed: 11/19/2022]
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Benton DCH, Garbarg M, Moss GWJ. The relationship between functional inhibition and binding for K(Ca)2 channel blockers. PLoS One 2013; 8:e73328. [PMID: 24039913 PMCID: PMC3769273 DOI: 10.1371/journal.pone.0073328] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Accepted: 07/30/2013] [Indexed: 11/25/2022] Open
Abstract
Small conductance calcium-activated potassium channels (KCa2.1,2.2,2.3) are blocked with high affinity by both peptide toxins (e.g. apamin) and small molecule blockers (e.g. UCL 1848). In electrophysiological experiments, apamin shows subtype selectivity with IC50s of ∼100 pM and ∼1 nM for block KCa2.2 and KCa2.3 respectively. In binding studies, however, apamin appears not to discriminate between KCa2.2 and 2.3 and is reported to have a significantly higher (∼20–200-fold) affinity (∼5 pM). This discrepancy between binding and block has been suggested to reflect an unusual mode of action of apamin. However, these binding and electrophysiological block experiments have not been conducted in the same ionic conditions, so it is also possible that the discrepancy arises simply because of differences in experimental conditions. We have now examined this latter possibility. Thus, we measured 125I-apamin binding to intact HEK 293 cells expressing KCa2 channels under the same ionic conditions (i.e. normal physiological conditions) that we also used for current block measurements. We find that binding and block experiments agree well if the same ionic conditions are used. Further, the binding of apamin and other blockers showed subtype selectivity when measured in normal physiological solutions (e.g.125I-apamin bound to KCa2.2 with KL 91±40 pM and to KCa2.3 with KL 711±126 pM, while inhibiting KCa2.2 current at IC50 103±2 pM). We also examined KCa2 channel block in Ca2+ and Mg2+ free solutions that mimic conditions reported in the literature for binding experiments. Under these (non-physiological) conditions the IC50 for apamin block of KCa2.2 was reduced to 20±3 pM. Our results therefore suggest that the apparent discrepancy between blocking and binding reported in the literature can be largely accounted for by the use of non-physiological ionic conditions in binding experiments.
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Affiliation(s)
- David Charles Hammond Benton
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
- * E-mail:
| | - Monique Garbarg
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
| | - Guy William John Moss
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
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29
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Yang D, Arifhodzic L, Ganellin CR, Jenkinson DH. Further studies on bis-charged tetraazacyclophanes as potent inhibitors of small conductance Ca(2+)-activated K+ channels. Eur J Med Chem 2013; 63:907-23. [PMID: 23685886 DOI: 10.1016/j.ejmech.2013.02.029] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2013] [Revised: 02/21/2013] [Accepted: 02/22/2013] [Indexed: 11/20/2022]
Abstract
Previously, quinolinium-based tetraazacyclophanes, such as UCL 1684 and UCL 1848, have been shown to be extraordinarily sensitive to changes in chemical structure (especially to the size of the cyclophane system) with respect to activity as potent non-peptidic blockers of the small conductance Ca(2+)-activated K(+) ion channels (SKCa). The present work has sought to optimize the structure of the linking chains in UCL 1848. We report the synthesis and SKCa channel-blocking activity of 29 analogues of UCL 1848 in which the central CH2 of UCL 1848 is replaced by other groups X or Y = O, S, CF2, CO, CHOH, CC, CHCH, CHMe to explore whether subtle changes in bond length or flexibility can improve potency still further. The possibility of improving potency by introducing ring substituents has also been explored by synthesizing and testing 25 analogues of UCL 1684 and UCL 1848 with substituents (NO2, NH2, CF3, F, Cl, CH3, OCH3, OCF3, OH) in the 5, 6 or 7 positions of the aminoquinolinium rings. As in our earlier work, each compound was assayed for inhibition of the afterhyperpolarization (AHP) in rat sympathetic neurons, an action mediated by the SK3 subtype of the SKCa channel. One of the new compounds (39, R(7) = Cl, UCL 2053) is twice as potent as UCL 1848 and UCL 1684: seven are comparable in activity.
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Affiliation(s)
- Donglai Yang
- Department of Chemistry, University College London, Gower Street, London WC1E 6BT, UK
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30
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Benton MD, Lewis AH, Bant JS, Raman IM. Iberiotoxin-sensitive and -insensitive BK currents in Purkinje neuron somata. J Neurophysiol 2013; 109:2528-41. [PMID: 23446695 DOI: 10.1152/jn.00127.2012] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Purkinje cells have specialized intrinsic ionic conductances that generate high-frequency action potentials. Disruptions of their Ca or Ca-activated K (KCa) currents correlate with altered firing patterns in vitro and impaired motor behavior in vivo. To examine the properties of somatic KCa currents, we recorded voltage-clamped KCa currents in Purkinje cell bodies isolated from postnatal day 17-21 mouse cerebellum. Currents were evoked by endogenous Ca influx with approximately physiological Ca buffering. Purkinje somata expressed voltage-activated, Cd-sensitive KCa currents with iberiotoxin (IBTX)-sensitive (>100 nS) and IBTX-insensitive (>75 nS) components. IBTX-sensitive currents activated and partially inactivated within milliseconds. Rapid, incomplete macroscopic inactivation was also evident during 50- or 100-Hz trains of 1-ms depolarizations. In contrast, IBTX-insensitive currents activated more slowly and did not inactivate. These currents were insensitive to the small- and intermediate-conductance KCa channel blockers apamin, scyllatoxin, UCL1684, bicuculline methiodide, and TRAM-34, but were largely blocked by 1 mM tetraethylammonium. The underlying channels had single-channel conductances of ∼150 pS, suggesting that the currents are carried by IBTX-resistant (β4-containing) large-conductance KCa (BK) channels. IBTX-insensitive currents were nevertheless increased by small-conductance KCa channel agonists EBIO, chlorzoxazone, and CyPPA. During trains of brief depolarizations, IBTX-insensitive currents flowed during interstep intervals, and the accumulation of interstep outward current was enhanced by EBIO. In current clamp, EBIO slowed spiking, especially during depolarizing current injections. The two components of BK current in Purkinje somata likely contribute differently to spike repolarization and firing rate. Moreover, augmentation of BK current may partially underlie the action of EBIO and chlorzoxazone to alleviate disrupted Purkinje cell firing associated with genetic ataxias.
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Affiliation(s)
- Mark D Benton
- Interdepartmental Neuroscience Program, Northwestern University, Evanston, Illinois, USA
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31
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Deardorff AS, Romer SH, Deng Z, Bullinger KL, Nardelli P, Cope TC, Fyffe REW. Expression of postsynaptic Ca2+-activated K+ (SK) channels at C-bouton synapses in mammalian lumbar -motoneurons. J Physiol 2013; 591:875-97. [PMID: 23129791 PMCID: PMC3591704 DOI: 10.1113/jphysiol.2012.240879] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Accepted: 10/31/2012] [Indexed: 01/27/2023] Open
Abstract
Small-conductance calcium-activated potassium (SK) channels mediate medium after-hyperpolarization (AHP) conductances in neurons throughout the central nervous system. However, the expression profile and subcellular localization of different SK channel isoforms in lumbar spinal α-motoneurons (α-MNs) is unknown. Using immunohistochemical labelling of rat, mouse and cat spinal cord, we reveal a differential and overlapping expression of SK2 and SK3 isoforms across specific types of α-MNs. In rodents, SK2 is expressed in all α-MNs, whereas SK3 is expressed preferentially in small-diameter α-MNs; in cats, SK3 is expressed in all α-MNs. Function-specific expression of SK3 was explored using post hoc immunostaining of electrophysiologically characterized rat α-MNs in vivo. These studies revealed strong relationships between SK3 expression and medium AHP properties. Motoneurons with SK3-immunoreactivity exhibit significantly longer AHP half-decay times (24.67 vs. 11.02 ms) and greater AHP amplitudes (3.27 vs. 1.56 mV) than MNs lacking SK3-immunoreactivity. We conclude that the differential expression of SK isoforms in rat and mouse spinal cord may contribute to the range of medium AHP durations across specific MN functional types and may be a molecular factor distinguishing between slow- and fast-type α-MNs in rodents. Furthermore, our results show that SK2- and SK3-immunoreactivity is enriched in distinct postsynaptic domains that contain Kv2.1 channel clusters associated with cholinergic C-boutons on the soma and proximal dendrites of α-MNs. We suggest that this remarkably specific subcellular membrane localization of SK channels is likely to represent the basis for a cholinergic mechanism for effective regulation of channel function and cell excitability.
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Affiliation(s)
- Adam S Deardorff
- Department of Neuroscience, Cell Biology & Physiology, Wright State University, Boonshoft School of Medicine, Dayton, OH 45435, USA
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Affiliation(s)
| | - Sergey M. Bezrukov
- Program in Physical Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, U.S.A
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Abstract
Over the past decade, compelling evidence has emerged from population-based studies to suggest that AF is a heritable disease. More recently, we have begun to elucidate the genetic substrate underlying AF. Genome-wide association studies (GWAS) have led to the identification of multiple risk loci that confer increased susceptibility to the arrhythmia. These loci harbor intriguing candidate genes including those encoding ion channels, transcription factors, and signaling molecules. Current efforts are ongoing to functionally validate the role of these genes in disease pathogenesis. In the future, novel genotyping technologies such as exome sequencing and whole-genome sequencing promise to uncover a greater proportion of the heritability underlying AF. In this article we review recent advances in AF genetics research and discuss future developments in the field.
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Affiliation(s)
- Saagar Mahida
- Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, MA, USA
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34
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The contribution of d-tubocurarine-sensitive and apamin-sensitive K-channels to EDHF-mediated relaxation of mesenteric arteries from eNOS-/- mice. J Cardiovasc Pharmacol 2012; 59:413-25. [PMID: 22217882 DOI: 10.1097/fjc.0b013e318248acd9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The nature of the potassium channels involved in determining endothelium-derived hyperpolarizing factor-mediated relaxation was investigated in first-order small mesenteric arteries from male endothelial nitric oxide synthase (eNOS-/-)-knockout and control (+/+) mice. Acetylcholine-induced endothelium-dependent relaxation of small mesenteric arteries of eNOS-/- was resistant to N-nitro-L-arginine and indomethacin and the guanylyl cyclase inhibitor, 1H-(1,2,4) oxadiazolo (4,3-a) quinoxalin-1-one. Apamin and the combination of apamin and iberiotoxin or apamin and charybdotoxin induced a transient endothelium-dependent contraction of small mesenteric arteries from both eNOS-/- and +/+ mice. Acetylcholine-induced relaxation in eNOS-/- mice was unaffected by charybdotoxin or apamin alone but significantly inhibited by the combination of these agents. However, the combination of scyllatoxin and iberiotoxin did not mimic the inhibitory effect of the apamin/charybdotoxin combination. Tubocurarine alone completely blocked acetylcholine-induced relaxation in eNOS-/- mice. Single channel analysis of myocytes from small mesenteric arterioles revealed a large conductance calcium-activated potassium channel that was sensitive to iberiotoxin, charybdotoxin, and tetraethylammonium. Tubocurarine blocked this channel from the cytosolic side but not when applied extracellularly. Solutions of nitric oxide (NO) gas also relaxed small mesenteric arteries that had been contracted with cirazoline in a concentration-dependent manner, and the sensitivity to NO was reduced by iberiotoxin and the combination of apamin, scyllatoxin, or tubocurarine with charybdotoxin but not by apamin, charybdotoxin, scyllatoxin, or tubocurarine alone. These data indicate that acetylcholine-induced endothelium-derived hyperpolarizing factor-mediated relaxation in small mesenteric arteries from eNOS-/- involved the activation of tubocurarine and apamin-/charybdotoxin-sensitive K-channels. In eNOS+/+ mice, the acetylcholine-induced response was primarily mediated by NO and was sensitive to iberiotoxin and the combination of apamin and charybdotoxin.
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35
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Balut CM, Hamilton KL, Devor DC. Trafficking of intermediate (KCa3.1) and small (KCa2.x) conductance, Ca(2+)-activated K(+) channels: a novel target for medicinal chemistry efforts? ChemMedChem 2012; 7:1741-55. [PMID: 22887933 DOI: 10.1002/cmdc.201200226] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2012] [Revised: 07/09/2012] [Indexed: 12/22/2022]
Abstract
Ca(2+)-activated K(+) (KCa) channels play a pivotal role in the physiology of a wide variety of tissues and disease states, including vascular endothelia, secretory epithelia, certain cancers, red blood cells (RBC), neurons, and immune cells. Such widespread involvement has generated an intense interest in elucidating the function and regulation of these channels, with the goal of developing pharmacological strategies aimed at selective modulation of KCa channels in various disease states. Herein we give an overview of the molecular and functional properties of these channels and their therapeutic importance. We discuss the achievements made in designing pharmacological tools that control the function of KCa channels by modulating their gating properties. Moreover, this review discusses the recent advances in our understanding of KCa channel assembly and anterograde trafficking toward the plasma membrane, the micro-domains in which these channels are expressed within the cell, and finally the retrograde trafficking routes these channels take following endocytosis. As the regulation of intracellular trafficking by agonists as well as the protein-protein interactions that modify these events continue to be explored, we anticipate this will open new therapeutic avenues for the targeting of these channels based on the pharmacological modulation of KCa channel density at the plasma membrane.
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Affiliation(s)
- Corina M Balut
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA
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36
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Kuiper EFE, Nelemans A, Luiten P, Nijholt I, Dolga A, Eisel U. K(Ca)2 and k(ca)3 channels in learning and memory processes, and neurodegeneration. Front Pharmacol 2012; 3:107. [PMID: 22701424 PMCID: PMC3372087 DOI: 10.3389/fphar.2012.00107] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2012] [Accepted: 05/19/2012] [Indexed: 11/13/2022] Open
Abstract
Calcium-activated potassium (KCa) channels are present throughout the central nervous system as well as many peripheral tissues. Activation of KCa channels contribute to maintenance of the neuronal membrane potential and was shown to underlie the afterhyperpolarization (AHP) that regulates action potential firing and limits the firing frequency of repetitive action potentials. Different subtypes of KCa channels were anticipated on the basis of their physiological and pharmacological profiles, and cloning revealed two well defined but phylogenetic distantly related groups of channels. The group subject of this review includes both the small conductance KCa2 channels (KCa2.1, KCa2.2, and KCa2.3) and the intermediate-conductance (KCa3.1) channel. These channels are activated by submicromolar intracellular Ca2+ concentrations and are voltage independent. Of all KCa channels only the KCa2 channels can be potently but differentially blocked by the bee-venom apamin. In the past few years modulation of KCa channel activation revealed new roles for KCa2 channels in controlling dendritic excitability, synaptic functioning, and synaptic plasticity. Furthermore, KCa2 channels appeared to be involved in neurodegeneration, and learning and memory processes. In this review, we focus on the role of KCa2 and KCa3 channels in these latter mechanisms with emphasis on learning and memory, Alzheimer’s disease and on the interplay between neuroinflammation and different neurotransmitters/neuromodulators, their signaling components and KCa channel activation.
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Affiliation(s)
- Els F E Kuiper
- Molecular Neurobiology, University of Groningen Groningen, Netherlands
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37
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Lin MT, Adelman JP, Maylie J. Modulation of endothelial SK3 channel activity by Ca²+dependent caveolar trafficking. Am J Physiol Cell Physiol 2012; 303:C318-27. [PMID: 22621787 DOI: 10.1152/ajpcell.00058.2012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Small- and intermediate-conductance Ca(2+)-activated K(+) channels (SK3/Kcnn3 and IK1/Kcnn4) are expressed in vascular endothelium. Their activities play important roles in regulating vascular tone through their modulation of intracellular concentration ([Ca(2+)](i)) required for the production of endothelium-derived vasoactive agents. Activation of endothelial IK1 or SK3 channels hyperpolarizes endothelial cell membrane potential, increases Ca(2+) influx, and leads to the release of vasoactive factors, thereby impacting blood pressure. To examine the distinct roles of IK1 and SK3 channels, we used electrophysiological recordings to investigate IK1 and SK3 channel trafficking in acutely dissociated endothelial cells from mouse aorta. The results show that SK3 channels undergo Ca(2+)-dependent cycling between the plasma membrane and intracellular organelles; disrupting Ca(2+)-dependent endothelial caveolae cycling abolishes SK3 channel trafficking. Moreover, transmitter-induced changes in SK3 channel activity and surface expression modulate endothelial membrane potential. In contrast, IK1 channels do not undergo rapid trafficking and their activity remains unchanged when either exo- or endocytosis is block. Thus modulation of SK3 surface expression may play an important role in regulating endothelial membrane potential in a Ca(2+)-dependent manner.
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Affiliation(s)
- Mike T Lin
- Vollum Institute, Oregon Health and Science University, Portland, Oregon, USA.
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38
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Zhang XH, Zhang YY, Sun HY, Jin MW, Li GR. Functional ion channels and cell proliferation in 3T3-L1 preadipocytes. J Cell Physiol 2012; 227:1972-9. [DOI: 10.1002/jcp.22925] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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39
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Kernig K, Kirschstein T, Würdemann T, Rohde M, Köhling R. The afterhyperpolarizing potential following a train of action potentials is suppressed in an acute epilepsy model in the rat Cornu Ammonis 1 area. Neuroscience 2012; 201:288-96. [PMID: 22100272 DOI: 10.1016/j.neuroscience.2011.11.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2011] [Revised: 10/11/2011] [Accepted: 11/02/2011] [Indexed: 11/18/2022]
Abstract
In hippocampal Cornu Ammonis 1 (CA1) neurons, a prolonged depolarization evokes a train of action potentials followed by a prominent afterhyperpolarizing potential (AHP), which critically dampens neuronal excitability. Because it is not known whether epileptiform activity alters the AHP and whether any alteration of the AHP is independent of inhibition, we acutely induced epileptiform activity by bath application of the GABA(A) receptor blocker gabazine (5 μM) in the rat hippocampal slice preparation and studied its impact on the AHP using intracellular recordings. Following 10 min of gabazine wash-in, slices started to develop spontaneous epileptiform discharges. This disinhibition was accompanied by a significant shift of the resting membrane potential of CA1 neurons to more depolarized values. Prolonged depolarizations (600 ms) elicited a train of action potentials, the number of which was not different between baseline and gabazine treatment. However, the AHP following the train of action potentials was significantly reduced after 20 min of gabazine treatment. When the induction of epileptiform activity was prevented by co-application of 6-cyano-7-nitroquinoxaline-2,3-dione disodium (CNQX, 10 μM) and D-(-)-2-amino-5-phosphonopentanoic acid (D-AP5, 50 μM) to block α-amino-3-hydroxy-5-methylisoxazolepropionate (AMPA) and N-methyl-d-aspartate (NMDA) receptors, respectively, the AHP was preserved despite of GABA(A) receptor inhibition suggesting that the epileptiform activity was required to suppress the AHP. Moreover, the AHP was also preserved when the slices were treated with the protein kinase blockers H-9 (100 μM) and H-89 (1 μM). These results demonstrate that the AHP following a train of action potentials is rapidly suppressed by acutely induced epileptiform activity due to a phosphorylation process-presumably involving protein kinase A.
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Affiliation(s)
- K Kernig
- Oscar Langendorff Institute of Physiology, University of Rostock, Gertrudenstrasse 9, 18057 Rostock, Germany
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Schulz R, Kirschstein T, Brehme H, Porath K, Mikkat U, Köhling R. Network excitability in a model of chronic temporal lobe epilepsy critically depends on SK channel-mediated AHP currents. Neurobiol Dis 2012; 45:337-47. [DOI: 10.1016/j.nbd.2011.08.019] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2011] [Revised: 08/13/2011] [Accepted: 08/18/2011] [Indexed: 11/29/2022] Open
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41
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Yu T, Deng C, Wu R, Guo H, Zheng S, Yu X, Shan Z, Kuang S, Lin Q. Decreased expression of small-conductance Ca2+-activated K+ channels SK1 and SK2 in human chronic atrial fibrillation. Life Sci 2011; 90:219-27. [PMID: 22154908 DOI: 10.1016/j.lfs.2011.11.008] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2011] [Revised: 10/19/2011] [Accepted: 11/12/2011] [Indexed: 01/13/2023]
Abstract
AIMS Small-conductance Ca2+-activated K+ (SK) channels are recognized as new ion channel candidates in atrial fibrillation (AF), with pivotal implications as novel drug targets due to their atrial-selective distribution in humans. The purpose of this study was to investigate whether SK channels and the Ca2+-activated K+ current (IK,Ca) are involved in electrical remodeling of human chronic AF (cAF) and whether they display the differential distribution between the right (RA) and left atria (LA). MAIN METHODS The right (RAA) and left atrial appendage (LAA) myocytes were obtained from 29 sinus rhythm (SR) and 22 cAF patients. The IK,Ca and action potential (AP) were recorded using the patch-clamp technique. Three SK channel subtypes (SK1-3) expressions were assayed by western blot and real-time quantitative PCR analysis. KEY FINDINGS The IK,Ca was decreased and its role in AP repolarization was attenuated in cAF, concomitant with a significant decrease in protein and mRNA levels of SK1 and SK2. In either SR or cAF, there was no difference in the IK,Ca density and protein and mRNA expression levels of SK1-3 between RAA and LAA myocytes. SIGNIFICANCE Our results demonstrated that SK1 and SK2 are involved in electrical remodeling of cAF. SK1-3 and IK,Ca do not display the inter-atrial differential distribution in SR or cAF. These findings provide a new insight into mechanisms of electrical remodeling of human cAF.
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Affiliation(s)
- Tao Yu
- Department of Cardiac surgery, Guangdong Cardiovascular Institute, 96 Dongchuan Road, Guangzhou 510080, China
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Patuzzi R. Ion flow in cochlear hair cells and the regulation of hearing sensitivity. Hear Res 2011; 280:3-20. [DOI: 10.1016/j.heares.2011.04.006] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2010] [Revised: 03/28/2011] [Accepted: 04/11/2011] [Indexed: 12/22/2022]
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Nunn N, Womack M, Dart C, Barrett-Jolley R. Function and pharmacology of spinally-projecting sympathetic pre-autonomic neurones in the paraventricular nucleus of the hypothalamus. Curr Neuropharmacol 2011; 9:262-77. [PMID: 22131936 PMCID: PMC3131718 DOI: 10.2174/157015911795596531] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2010] [Revised: 09/01/2010] [Accepted: 09/14/2010] [Indexed: 12/16/2022] Open
Abstract
The paraventricular nucleus (PVN) of the hypothalamus has been described as the "autonomic master controller". It co-ordinates critical physiological responses through control of the hypothalamic-pituitary-adrenal (HPA)-axis, and by modulation of the sympathetic and parasympathetic branches of the central nervous system. The PVN comprises several anatomical subdivisions, including the parvocellular/ mediocellular subdivision, which contains neurones projecting to the medulla and spinal cord. Consensus indicates that output from spinally-projecting sympathetic pre-autonomic neurones (SPANs) increases blood pressure and heart rate, and dysfunction of these neurones has been directly linked to elevated sympathetic activity during heart failure. The influence of spinally-projecting SPANs on cardiovascular function high-lights their potential as targets for future therapeutic drug development. Recent studies have demonstrated pharmacological control of these spinally-projecting SPANs with glutamate, GABA, nitric oxide, neuroactive steroids and a number of neuropeptides (including angiotensin, substance P, and corticotrophin-releasing factor). The underlying mechanism of control appears to be a state of tonic inhibition by GABA, which is then strengthened or relieved by the action of other modulators. The physiological function of spinally-projecting SPANs has been subject to some debate, and they may be involved in physiological stress responses, blood volume regulation, glucose regulation, thermoregulation and/or circadian rhythms. This review describes the pharmacology of PVN spinally-projecting SPANs and discusses their likely roles in cardiovascular control.
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Affiliation(s)
| | | | | | - Richard Barrett-Jolley
- Centre for Integrative Mammalian Biology, University of Liverpool, Brownlow Hill & Crown St. Liverpool, L69 7ZJ, UK
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Romero-Curiel A, López-Carpinteyro D, Gamboa C, De la cruz F, Zamudio S, Flores G. Apamin induces plastic changes in hippocampal neurons in senile Sprague-Dawley rats. Synapse 2011; 65:1062-72. [DOI: 10.1002/syn.20938] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Accepted: 03/24/2011] [Indexed: 12/13/2022]
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45
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Paracrine Role of GABA in Adrenal Chromaffin Cells. Cell Mol Neurobiol 2010; 30:1217-24. [DOI: 10.1007/s10571-010-9569-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2010] [Accepted: 09/02/2010] [Indexed: 10/18/2022]
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46
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Diness JG, Sørensen US, Nissen JD, Al-Shahib B, Jespersen T, Grunnet M, Hansen RS. Inhibition of Small-Conductance Ca
2+
-Activated K
+
Channels Terminates and Protects Against Atrial Fibrillation. Circ Arrhythm Electrophysiol 2010; 3:380-90. [DOI: 10.1161/circep.110.957407] [Citation(s) in RCA: 144] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background—
Recently, evidence has emerged that small-conductance Ca
2+
-activated K
+
(SK) channels are predominantly expressed in the atria in a number of species including human. In rat, guinea pig, and rabbit ex vivo and in vivo models of atrial fibrillation (AF), we used 3 different SK channel inhibitors, UCL1684,
N
-(pyridin-2-yl)-4-(pyridin-2-yl)thiazol-2-amine (ICA), and NS8593, to assess the hypothesis that pharmacological inhibition of SK channels is antiarrhythmic.
Methods and Results—
In isolated, perfused guinea pig hearts, AF could be induced in all control hearts (n=7) with a combination of 1 μmol/L acetylcholine combined with electric stimulation. Pretreatment with 3 μmol/L NS8593, which had no effect on QT interval, prolonged the atrial effective refractory period by 37.1±7.7% (
P
<0.001) and prevented acetylcholine-induced AF (
P
<0.001, n=7). After AF induction, perfusion with NS8593 (10 μmol/L), UCL1684 (1 μmol/L), or ICA (1 μmol/L) terminated AF in all hearts, comparable to 10 μmol/L amiodarone. In isolated, perfused rat hearts, AF was induced with electric stimulation; 10 μmol/L NS8593 terminated AF and prevented reinduction of AF in all hearts (n=6,
P
<0.001). In all hearts, AF could be reinduced after washing. In isolated, perfused rabbit hearts, AF was induced with 10 μmol/L acetylcholine and burst pacing; 10 μmol/L NS8593 terminated AF and prevented reinduction of AF in all hearts (n=6,
P
<0.001). After washing, AF could be reinduced in 75% of the hearts (n=4,
P
=0.06). In an in vivo rat model of acute AF induced by burst pacing, injection of 5 mg/kg of either NS8593 or amiodarone shortened AF duration significantly to (23.2±20.0%,
P
<0.001, n=5, and 26.2±17.9%,
P
<0.001, n=5, respectively) as compared with injection of vehicle (96.3±33.2%, n=5).
Conclusions—
Inhibition of SK channels prolongs atrial effective refractory period without affecting QT interval and prevents and terminates AF ex vivo and in vivo, thus offering a promising new therapeutic opportunity in the treatment of AF.
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Affiliation(s)
- Jonas Goldin Diness
- From NeuroSearch A/S (J.G.D., U.S.S., B.A.-S., M.G., R.S.H.), Ballerup, Denmark; and the Danish National Research Foundation Centre for Cardiac Arrhythmia (J.G.D., J.D.N., T.J., M.G.), Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Ulrik S. Sørensen
- From NeuroSearch A/S (J.G.D., U.S.S., B.A.-S., M.G., R.S.H.), Ballerup, Denmark; and the Danish National Research Foundation Centre for Cardiac Arrhythmia (J.G.D., J.D.N., T.J., M.G.), Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jakob Dahl Nissen
- From NeuroSearch A/S (J.G.D., U.S.S., B.A.-S., M.G., R.S.H.), Ballerup, Denmark; and the Danish National Research Foundation Centre for Cardiac Arrhythmia (J.G.D., J.D.N., T.J., M.G.), Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Baha Al-Shahib
- From NeuroSearch A/S (J.G.D., U.S.S., B.A.-S., M.G., R.S.H.), Ballerup, Denmark; and the Danish National Research Foundation Centre for Cardiac Arrhythmia (J.G.D., J.D.N., T.J., M.G.), Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Thomas Jespersen
- From NeuroSearch A/S (J.G.D., U.S.S., B.A.-S., M.G., R.S.H.), Ballerup, Denmark; and the Danish National Research Foundation Centre for Cardiac Arrhythmia (J.G.D., J.D.N., T.J., M.G.), Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Morten Grunnet
- From NeuroSearch A/S (J.G.D., U.S.S., B.A.-S., M.G., R.S.H.), Ballerup, Denmark; and the Danish National Research Foundation Centre for Cardiac Arrhythmia (J.G.D., J.D.N., T.J., M.G.), Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Rie Schultz Hansen
- From NeuroSearch A/S (J.G.D., U.S.S., B.A.-S., M.G., R.S.H.), Ballerup, Denmark; and the Danish National Research Foundation Centre for Cardiac Arrhythmia (J.G.D., J.D.N., T.J., M.G.), Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
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Weatherall KL, Goodchild SJ, Jane DE, Marrion NV. Small conductance calcium-activated potassium channels: From structure to function. Prog Neurobiol 2010; 91:242-55. [DOI: 10.1016/j.pneurobio.2010.03.002] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2009] [Revised: 03/05/2010] [Accepted: 03/24/2010] [Indexed: 10/19/2022]
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Oliveira MS, Skinner F, Arshadmansab MF, Garcia I, Mello CF, Knaus HG, Ermolinsky BS, Otalora LFP, Garrido-Sanabria ER. Altered expression and function of small-conductance (SK) Ca(2+)-activated K+ channels in pilocarpine-treated epileptic rats. Brain Res 2010; 1348:187-99. [PMID: 20553876 DOI: 10.1016/j.brainres.2010.05.095] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2009] [Revised: 05/28/2010] [Accepted: 05/30/2010] [Indexed: 01/09/2023]
Abstract
Small conductance calcium (Ca(2+)) activated SK channels are critical regulators of neuronal excitability in hippocampus. Accordingly, these channels are thought to play a key role in controlling neuronal activity in acute models of epilepsy. In this study, we investigate the expression and function of SK channels in the pilocarpine model of mesial temporal lobe epilepsy. For this purpose, protein expression was assessed using western blotting assays and gene expression was analyzed using TaqMan-based probes and the quantitative real-time polymerase chain reaction (qPCR) comparative method delta-delta cycle threshold ( big up tri, open big up tri, openCT) in samples extracted from control and epileptic rats. In addition, the effect of SK channel antagonist UCL1684 and agonist NS309 on CA1 evoked population spikes was studied in hippocampal slices. Western blotting analysis showed a significant reduction in the expression of SK1 and SK2 channels at 10days following status epilepticus (SE), but levels recovered at 1month and at more than 2months after SE. In contrast, a significant down-regulation of SK3 channels was detected after 10days of SE. Analysis of gene expression by qPCR revealed a significant reduction of transcripts for SK2 (Kcnn1) and SK3 (Kcnn3) channels as early as 10days following pilocarpine-induced SE and during the chronic phase of the pilocarpine model. Moreover, bath application of UCL1684 (100nM for 15min) induced a significant increase of the population spike amplitude and number of spikes in the hippocampal CA1 area of slices obtained control and chronic epileptic rats. This effect was obliterated by co-administration of UCL1684 with SK channel agonist NS309 (1microM). Application of NS309 failed to modify population spikes in the CA1 area of slices taken from control and epileptic rats. These data indicate an abnormal expression of SK channels and a possible dysfunction of these channels in experimental MTLE.
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Affiliation(s)
- Mauro S Oliveira
- Departamento de Fisiologia e Farmacologia, Centro de Ciências da Saúde, Universidade Federal de Santa Maria, RS, Brazil
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Klement G, Druzin M, Haage D, Malinina E, Arhem P, Johansson S. Spontaneous ryanodine-receptor-dependent Ca2+-activated K+ currents and hyperpolarizations in rat medial preoptic neurons. J Neurophysiol 2010; 103:2900-11. [PMID: 20457857 DOI: 10.1152/jn.00566.2009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The aim of the present study was to clarify the identity of slow spontaneous currents, the underlying mechanism and possible role for impulse generation in neurons of the rat medial preoptic nucleus (MPN). Acutely dissociated neurons were studied with the perforated patch-clamp technique. Spontaneous outward currents, at a frequency of approximately 0.5 Hz and with a decay time constant of approximately 200 ms, were frequently detected in neurons when voltage-clamped between approximately -70 and -30 mV. The dependence on extracellular K(+) concentration was consistent with K(+) as the main charge carrier. We concluded that the main characteristics were similar to those of spontaneous miniature outward currents (SMOCs), previously reported mainly for muscle fibers and peripheral nerve. From the dependence on voltage and from a pharmacological analysis, we concluded that the currents were carried through small-conductance Ca(2+)-activated (SK) channels, of the SK3 subtype. From experiments with ryanodine, xestospongin C, and caffeine, we concluded that the spontaneous currents were triggered by Ca(2+) release from intracellular stores via ryanodine receptor channels. An apparent voltage dependence was explained by masking of the spontaneous currents as a consequence of steady SK-channel activation at membrane potentials > -30 mV. Under current-clamp conditions, corresponding transient hyperpolarizations occasionally exceeded 10 mV in amplitude and reduced the frequency of spontaneous impulses. In conclusion, MPN neurons display spontaneous hyperpolarizations triggered by Ca(2+) release via ryanodine receptors and SK3-channel activation. Thus such events may affect impulse firing of MPN neurons.
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Affiliation(s)
- Göran Klement
- Department of Integrative Medical Biology, Section for Physiology, Umeå University, Umeå, Sweden
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50
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Dhaese I, Van Colen I, Lefebvre RA. Mechanisms of action of hydrogen sulfide in relaxation of mouse distal colonic smooth muscle. Eur J Pharmacol 2009; 628:179-86. [PMID: 19919833 DOI: 10.1016/j.ejphar.2009.11.024] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2009] [Revised: 10/29/2009] [Accepted: 11/10/2009] [Indexed: 12/24/2022]
Abstract
Hydrogen sulfide (H(2)S) has been suggested as a gaseous neuromodulator in mammals. The aim of this study was to examine the influence of H(2)S on contractility in mouse distal colon. The effect of sodium hydrogen sulfide (NaHS; H(2)S donor) on prostaglandin F(2alpha) (PGF(2alpha))-contracted circular muscle strips of mouse distal colon was investigated. In addition, tension and cytosolic calcium concentration ([Ca(2+)](cyt)) in the mouse distal colon strips were measured simultaneously in the presence of NaHS. NaHS caused concentration-dependent relaxation of the pre-contracted mouse distal colon strips. The NaHS-induced relaxation was not influenced by the K(+) channels blockers glibenclamide, apamin, charybdotoxin, barium chloride and 4-aminopyridine. The relaxation by NaHS was also not influenced by the nitric oxide inhibitor L-NAME, by the soluble guanylate cyclase respectively adenylate cyclase inhibitors ODQ and SQ 22536, by the nerve blockers capsazepine, omega-conotoxin and tetrodotoxin or by several channel and receptor blockers (ouabain, nifedipine, 2-aminoethyl diphenylborinate, ryanodine and thapsigargin). The initiation of the NaHS-induced relaxation was accompanied by an increase in [Ca(2+)](cyt), but once the relaxation was maximal and sustained, no change in [Ca(2+)](cyt) was measured. This calcium desensitization is not related to the best known calcium desensitizing mechanism as the myosin light chain phosphatase (MLCP) inhibitor calyculin-A and the Rho-kinase inhibitor Y-27632 had no influence. We conclude that NaHS caused concentration-dependent relaxations in mouse distal colon not involving the major known K(+) channels and without a change in [Ca(2+)](cyt). This calcium desensitization is not related to inhibition of Rho-kinase or activation of MLCP.
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Affiliation(s)
- Ingeborg Dhaese
- Heymans Institute of Pharmacology, Ghent University, Ghent, Belgium
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