TMEM16B induces chloride currents activated by calcium in mammalian cells

Pifferi, Simone; Dibattista, Michele; Menini, Anna

doi:10.1007/s00424-009-0684-9

Cited by 209 publications

(275 citation statements)

References 54 publications

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“…5d,f), but not at 13 µM free Ca 2+ (Fig. 5g,i) similar to data reported for Ca 2+ -activated Cl -currents for heterologously expressed Ano1 and Ano2 [20][21][22]33,34 and for frog OSNs 7 . We could not detect these Cl -currents in Ano2 -/-OSNs (Fig.…”

supporting

confidence: 87%

“…The superfusate could be switched to a solution containing niflumic acid (NFA). NFA has been widely used to block Ca 2+ -activated Cl -channels in OSNs and other 6 cells 4,6,9,11,16,34,36,37 and inhibits both Ano1 and Ano2 18,20,21,33,34 . The response to odorants was reduced by roughly 40% in Ano2 -/-EOGs compared to the wild type (Fig.…”

Section: Disruption Of Ano2 Moderately Reduces Eogsmentioning

confidence: 99%

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Ca2+-activated Cl− currents are dispensable for olfaction

et al. 2011

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Graduate student at the Freie Universität Berlin Olfaction in mammals involves the binding of odorants to a subset of the large number of different G protein-coupled receptors that are present in the cilia of olfactory sensory neurons (OSNs) 1 . These neurons are predominantly found in the MOE, which senses and discriminates myriad volatile compounds. In the mouse, the nose contains additional, apparently more specialized olfactory organs, such the septal organ of Masera and the VNO 2 . Sensory neurons in the VNO are morphologically distinct and use odorant receptors and signal transduction cascades that differ from those found in the MOE.In the canonical OSN signal transduction pathway, odorant binding to the receptor locally increases cytosolic cAMP through activation of the olfactory G protein G olf and adenylate cyclase type III 1,2 . cAMP then opens heteromeric cyclic nucleotide-gated (CNG) cation channels 3 . The resulting influx of Na + and Ca 2+ depolarizes the plasma membrane and raises the cytosolic Ca 2+ concentration ([Ca 2+ ] i ), thereby activating Ca 2+ -activated Cl -channels 1,4-10 . All these components of the signal transduction cascade are localized to sensory cilia, which are embedded in the mucus covering the MOE. These cilia provide a large interaction surface for odorants, and the cilia's small diameters facilitate large local increases in cytosolic cAMP and [Ca 2+ ].There has been broad consensus that Ca 2+ -activated Cl -channels powerfully amplify olfactory signal transduction 1,4-10 . These channels are thought to mediate an outward flow of Cl -, which generates a depolarizing current that, in rodents, is five-to tenfold larger than currents through CNG channels 8,11,12 . A prerequisite for Cl -efflux 3 is an inside-out electrochemical Cl --gradient. It is believed that cytosolic chloride concentration of OSNs is raised by the Na + K + 2Cl -co-transporter Nkcc1 9,10,13 and that [Cl -] is low in the mucus surrounding the cilia 14,15 . However, mucosal ion concentrations are difficult to measure in vivo, and Nkcc1 knockout mice display attenuated electro-olfactograms (EOGs) 11,16 , but normal olfactory sensitivity 17 .To investigate the role of Ca 2+ -activated Cl -channels in olfaction, we disrupted Ano2 in mice. Ano2 is a member of the Anoctamin (Tmem16) gene family, which encodes several Ca 2+ -activated Cl -channels [18][19][20] . Agreeing with recent results 13,21-23 , our knockout-controlled immunolabeling showed Ano2 expression in cilia of OSNs in the MOE, in microvilli of VNO sensory neurons and in synapses of photoreceptors. Additionally, we found Ano2 in the olfactory bulb. Ano1 expression overlapped with Ano2 in the VNO and the retina, but not in the MOE. Patch-clamp analysis showed that Ca 2+ -activated Cl -currents were undetectable in Ano2 -/-OSNs.Unexpectedly, however, EOGs of Ano2 -/-mice were reduced by only up to ~40%, and Ano2 -/-mice were able to smell normally. Our work calls for a revision of the current view that Ca 2+ -activated Cl -channels have a crucial role...

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supporting

confidence: 87%

Section: Disruption Of Ano2 Moderately Reduces Eogsmentioning

confidence: 99%

Ca2+-activated Cl− currents are dispensable for olfaction

et al. 2011

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“…Third, the molecular identity of the ion channels that conduct the excitatory Cl − current is not definitely established. The best candidate protein is TMEM16B (alias ANO2) (7,8), but it is not clear whether this protein is expressed in the sensory cilia. Here we examine these questions, and we propose a solution to each of them.…”

mentioning

confidence: 99%

Molecular components of signal amplification in olfactory sensory cilia

Hengl

Kaneko

Dauner

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

102

100

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The mammalian olfactory system detects an unlimited variety of odorants with a limited set of odorant receptors. To cope with the complexity of the odor world, each odorant receptor must detect many different odorants. The demand for low odor selectivity creates problems for the transduction process: the initial transduction step, the synthesis of the second messenger cAMP, operates with low efficiency, mainly because odorants bind only briefly to their receptors. Sensory cilia of olfactory receptor neurons have developed an unusual solution to this problem. They accumulate chloride ions at rest and discharge a chloride current upon odor detection. This chloride current amplifies the receptor potential and promotes electrical excitation. We have studied this amplification process by examining identity, subcellular localization, and regulation of its molecular components. We found that the Na + /K + /2Cl − cotransporter NKCC1 is expressed in the ciliary membrane, where it mediates chloride accumulation into the ciliary lumen. Gene silencing experiments revealed that the activity of this transporter depends on the kinases SPAK and OSR1, which are enriched in the cilia together with their own activating kinases, WNK1 and WNK4. A second Cl − transporter, the Cl − /HCO 3 − exchanger SLC4A1, is expressed in the cilia and may support Cl − accumulation. The calcium-dependent chloride channel TMEM16B (ANO2) provides a ciliary pathway for the excitatory chloride current. These findings describe a specific set of ciliary proteins involved in anion-based signal amplification. They provide a molecular concept for the unique strategy that allows olfactory sensory neurons to operate as efficient transducers of weak sensory stimuli.chloride | olfaction | sensory transduction | transport | kinase M ammalian olfactory receptor neurons (ORNs) present to the air a tuft of sensory cilia equipped with odorant receptors. Upon contact with odorants, these receptors actuate a transduction cascade that leads to firing of action potentials. This cascade has an unusual, two-stage organization (1). First, the activated odorant receptors induce a rise of the second messengers cAMP and Ca 2+ in the cilia, a process that involves cAMP-gated, Ca 2+ -permeable ion channels. In the second stage, inflowing Ca 2+ opens Cl − channels. By conducting a depolarizing Cl − efflux from the cilia, these channels amplify the receptor potential approximately 10-fold, thus helping to excite the neuron even when stimulation is weak. ORNs accumulate chloride through the Na + /K + /2Cl − cotransporter NKCC1 and maintain an elevated intracellular Cl − concentration (2, 3) to support amplification. Accordingly, gene ablation of NKCC1, as well as the pharmacologic suppression of Cl − accumulation or Cl − efflux, strongly inhibits the sensory response of ORNs (3-5). Although these observations provide a robust concept for signal amplification, several points are still unclear. These concern both the Cl − accumulation process and the excitatory Cl − currents. First, ...

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“…The TMEM16/anoctamin family has nine more members named TMEM16B to -K, or anoctamin 2-10 (Galindo and Vacquier 2005 ). The biophysical characteristics among the members of this family of ion channels such as voltage dependence, selectivity, and conductance differ (Pifferi et al 2009 ;Scudieri et al 2012 ). Almost all show enzymatic properties in addition to the transport function, which has led to the speculation that they are multifunctional proteins, one of them being permeable to Cl − (Tian et al 2012 ).…”

Section: Ca 2+ -Activated CL − Channels (Caccs)mentioning

confidence: 99%

Cl− Channels and Transporters in Sperm Physiology

Treviño

Orta

Figueiras-Fierro

et al. 2014

Sexual Reproduction in Animals and Plants

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Spermatozoa must decode environmental and cellular cues to succeed in fertilization, and this process relies heavily on ion channels. New observations bring to light the relevant participation of Cl − channels and anion transporters in some of the main sperm functions. Here we review the evidence that indicates the participation of Cl − channels in motility, maturation, and the acrosome reaction (AR), and what is known about their molecular identity and regulation. Our better understanding of sperm anion transport will yield tools to handle some infertility problems, improve animal breeding and preserve biodiversity, and develop selective and secure male contraceptives.

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TMEM16B induces chloride currents activated by calcium in mammalian cells

Cited by 209 publications

References 54 publications

Ca2+-activated Cl− currents are dispensable for olfaction

Ca2+-activated Cl− currents are dispensable for olfaction

Molecular components of signal amplification in olfactory sensory cilia

Cl− Channels and Transporters in Sperm Physiology

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