Nociceptors are a subset of small primary afferent neurons that respond to noxious chemical, thermal and mechanical stimuli. Ion channels in nociceptors respond differently to noxious stimuli and ...generate electrical signals in different ways. Anoctamin 1 (ANO1 also known as TMEM16A) is a Ca(2+)-activated chloride channel that is essential for numerous physiological functions. We found that ANO1 was activated by temperatures over 44 °C with steep heat sensitivity. ANO1 was expressed in small sensory neurons and was highly colocalized with nociceptor markers, which suggests that it may be involved in nociception. Application of heat ramps to dorsal root ganglion (DRG) neurons elicited robust ANO1-dependent depolarization. Furthermore, knockdown or deletion of ANO1 in DRG neurons substantially reduced nociceptive behavior in thermal pain models. These results indicate that ANO1 is a heat sensor that detects nociceptive thermal stimuli in sensory neurons and possibly mediates nociception.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Calcium (Ca(2+))-activated chloride channels are fundamental mediators in numerous physiological processes including transepithelial secretion, cardiac and neuronal excitation, sensory transduction, ...smooth muscle contraction and fertilization. Despite their physiological importance, their molecular identity has remained largely unknown. Here we show that transmembrane protein 16A (TMEM16A, which we also call anoctamin 1 (ANO1)) is a bona fide Ca(2+)-activated chloride channel that is activated by intracellular Ca(2+) and Ca(2+)-mobilizing stimuli. With eight putative transmembrane domains and no apparent similarity to previously characterized channels, ANO1 defines a new family of ionic channels. The biophysical properties as well as the pharmacological profile of ANO1 are in full agreement with native Ca(2+)-activated chloride currents. ANO1 is expressed in various secretory epithelia, the retina and sensory neurons. Furthermore, knockdown of mouse Ano1 markedly reduced native Ca(2+)-activated chloride currents as well as saliva production in mice. We conclude that ANO1 is a candidate Ca(2+)-activated chloride channel that mediates receptor-activated chloride currents in diverse physiological processes.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Anoctamin 1 (ANO1)/transmembrane protein 16A (TMEM16A) is a calcium-activated anion channel that may play a role in HCO ₃⁻ secretion in epithelial cells. Here, we report that the anion selectivity of ...ANO1 is dynamically regulated by the Ca ²⁺/calmodulin complex. Whole-cell current measurements in HEK 293T cells indicated that ANO1 becomes highly permeable to HCO ₃⁻ at high Ca ²⁺ ᵢ. Interestingly, this result was not observed in excised patches, indicating the involvement of cytosolic factors in this process. Further studies revealed that the direct association between ANO1 and calmodulin at high Ca ²⁺ ᵢ is responsible for changes in anion permeability. Calmodulin physically interacted with ANO1 in a Ca ²⁺ ᵢ-dependent manner, and addition of recombinant calmodulin to the cytosolic side of excised patches reversibly increased P HCO₃/P Cₗ. In addition, the high Ca ²⁺ ᵢ-induced increase in HCO ₃⁻ permeability was reproduced in mouse submandibular gland acinar cells, in which ANO1 plays a critical role in fluid secretion. These results indicate that the HCO ₃⁻ permeability of ANO1 can be dynamically modulated and that ANO1 may play an important role in cellular HCO ₃⁻ transport, especially in transepithelial HCO ₃⁻ secretion.
Myenteric plexus interstitial cells of Cajal (ICC-MY) in the small intestine are Kit+ electrical pacemakers that express the Ano1/TMEM16A Ca2+-activated Cl- channel, whose functions in the ...gastrointestinal tract remain incompletely understood. In this study, an inducible Cre-LoxP-based approach was used to advance the understanding of Ano1 in ICC-MY of adult mouse small intestine. KitCreERT2/+;Ano1Fl/Fl mice were treated with tamoxifen or vehicle, and small intestines (mucosa free) were examined. Quantitative RT-PCR demonstrated ~50% reduction in Ano1 mRNA in intestines of conditional knockouts (cKOs) compared with vehicle-treated controls. Whole mount immunohistochemistry showed a mosaic/patchy pattern loss of Ano1 protein in ICC networks. Ca2+ transients in ICC-MY network of cKOs displayed reduced duration compared with highly synchronized controls and showed synchronized and desynchronized profiles. When matched, the rank order for Ano1 expression in Ca2+ signal imaged fields of view was as follows: vehicle controls>>>cKO(synchronized)>cKO(desynchronized). Maintenance of Ca2+ transients' synchronicity despite high loss of Ano1 indicates a large functional reserve of Ano1 in the ICC-MY network. Slow waves in cKOs displayed reduced duration and increased inter-slow-wave interval and occurred in regular- and irregular-amplitude oscillating patterns. The latter activity suggested ongoing interaction by independent interacting oscillators. Lack of slow waves and depolarization, previously reported for neonatal constitutive knockouts, were also seen. In summary, Ano1 in adults regulates gastrointestinal function by determining Ca2+ transients and electrical activity depending on the level of Ano1 expression. Partial Ano1 loss results in Ca2+ transients and slow waves displaying reduced duration, while complete and widespread absence of Ano1 in ICC-MY causes lack of slow wave and desynchronized Ca2+ transients.NEW & NOTEWORTHY The Ca2+-activated Cl- channel, Ano1, in interstitial cells of Cajal (ICC) is necessary for normal gastrointestinal motility. We knocked out Ano1 to varying degrees in ICC of adult mice. Partial knockout of Ano1 shortened the widths of electrical slow waves and Ca2+ transients in myenteric ICC but Ca2+ transient synchronicity was preserved. Near-complete knockout was necessary for transient desynchronization and loss of slow waves, indicating a large functional reserve of Ano1 in ICC.
Ca
2+
-activated Cl
−
channels (CaCCs) are a class of Cl
−
channels activated by intracellular Ca
2+
that are known to mediate numerous physiological functions. In 2008, the molecular identity of ...CaCCs was found to be anoctamin 1 (ANO1/TMEM16A). Its roles have been studied in electrophysiological, histological, and genetic aspects. ANO1 is known to mediate Cl
−
secretion in secretory epithelia such as airways, salivary glands, intestines, renal tubules, and sweat glands. ANO1 is a heat sensor activated by noxious heat in somatosensory neurons and mediates acute pain sensation as well as chronic pain. ANO1 is also observed in vascular as well as airway smooth muscles, controlling vascular tone as well as airway hypersensitivity. ANO1 is upregulated in numerous types of cancers and thus thought to be involved in tumorigenesis. ANO1 is also found in proliferating cells. In addition to ANO1, involvement of its paralogs in pathophysiological conditions was also reported. ANO2 is involved in olfaction, whereas ANO6 works as a scramblase whose mutation causes a rare bleeding disorder, the Scott syndrome. ANO5 is associated with muscle and bone diseases. Recently, an X-ray crystal structure of a fungal TMEM16 was reported, which explains a precise molecular gating mechanism as well as ion conduction or phospholipid transport across the plasma membrane.
Itch is one of the major complications of skin diseases. Although there are various substances that induce itch or pruritus, it is evident that histamine is the best known endogenous agent that ...evokes itch. Even though histamine-induced itch has been studied for some time, the underlying mechanism of itch is just beginning to emerge. Although various downstream signaling pathways of histamine receptors have been revealed, more studies are required to determine the cause of histamine-induced itch. It appears that itch and pain involve different neuronal pathways. Pain generally inhibits itch, which indicates an inter-communication between the two. Complex interactions between itch and pain may be expected based on reports on disease states and opioids. In this review, we discuss the molecular mechanism and the pharmacological aspects of histamine-induced itch. Especially, the underlying mechanism of TRPV1 (an anti-pruritus target) has been determined to some extent.
Background:
Various pathological conditions such as inflammation or injury can evoke pain hypersensitivity. That represents the response to innocuous stimuli or exaggerated response to noxious ...stimuli. The molecular mechanism based on the pain hypersensitivity is associated with changes in many of ion channels in dorsal-root ganglion (DRG) neurons. Anoctamin 1 (ANO1/TMEM16A), a Ca2+ activated chloride channel is highly visible in small DRG neurons and responds to heat. Mice with an abolished function of ANO1 in DRG neurons demonstrated attenuated pain-like behaviors when exposed to noxious heat, suggesting a role in acute thermal nociception. In this study, we further examined the function of ANO1 in mediating inflammation- or injury-induced hyperalgesia or allodynia.
Results:
Using Advillin/Ano1fl/fl (Adv/Ano1fl/fl) mice that have a functional ablation of Ano1 mainly in DRG neurons, we were able to determine its role in mediating thermal hyperalgesia and mechanical allodynia induced by inflammation or nerve injury. The thermal hyperalgesia and mechanical allodynia induced by carrageenan injection and spared-nerve injury were significantly reduced in Adv/Ano1fl/fl mice. In addition, flinching or licking behavior after bradykinin or formalin injection was also significantly reduced in Adv/Ano1fl/fl mice. Since pathological conditions augment nociceptive behaviors, we expected ANO1's contribution to the excitability of DRG neurons. Indeed, the application of inflammatory mediators reduced the threshold for action potential (rheobase) or time for induction of the first action potential in DRG neurons isolated from control (Ano1fl/fl) mice. These parameters for neuronal excitability induced by inflammatory mediators were not changed in Adv/Ano1fl/fl mice, suggesting an active contribution of ANO1 in augmenting the neuronal excitability.
Conclusions:
In addition to ANO1's role in mediating acute thermal pain as a heat sensor, ANO1 is also capable of augmenting the excitability of DRG neurons under inflammatory or neuropathic conditions and thereby aggravates inflammation- or tissue injury-induced pathological pain.
Mechanically activating (MA) channels transduce numerous physiological functions. Tentonin 3/TMEM150C (TTN3) confers MA currents with slow inactivation kinetics in somato- and barosensory neurons. ...However, questions were raised about its role as a Piezo1 regulator and its potential as a channel pore. Here, we demonstrate that purified TTN3 proteins incorporated into the lipid bilayer displayed spontaneous and pressure-sensitive channel currents. These MA currents were conserved across vertebrates and differ from Piezo1 in activation threshold and pharmacological response. Deep neural network structure prediction programs coupled with mutagenetic analysis predicted a rectangular-shaped, tetrameric structure with six transmembrane helices and a pore at the inter-subunit center. The putative pore aligned with two helices of each subunit and had constriction sites whose mutations changed the MA currents. These findings suggest that TTN3 is a pore-forming subunit of a distinct slow inactivation MA channel, potentially possessing a tetrameric structure.
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•Mechanically gated currents of TTN3 are conserved throughout the vertebrate phyla•Bilayer-embedded TTN3 proteins exhibit spontaneous and stretch-sensitive channel currents•Activation threshold and pharmacological profile of TTN3 are separate from Piezo1•A rectangular-shaped tetrameric structure and a pore at the inter-subunit center are predicted
Pak et al. reveal Tentonin 3/TMEM150C (TTN3) as a slowly adapting mechanosensitive channel conserved within the vertebrate phyla eliciting stretch-sensitive currents. TTN3 activation requires high-threshold stimulation and is inhibited by NMB-1. Further on, structure-predicting algorithmic programs reveal TTN3 as a rectangular-shaped tetrameric structure forming a pore at the center.
Benign prostatic hyperplasia (BPH) is characterized by an enlargement of the prostate, causing lower urinary tract symptoms in elderly men worldwide. However, the molecular mechanism underlying the ...pathogenesis of BPH is unclear. Anoctamin1 (ANO1) encodes a Ca2+-activated chloride channel (CaCC) that mediates various physiological functions. Here, we demonstrate that it is essential for testosterone-induced BPH. ANO1 was highly amplified in dihydrotestosterone (DHT)-treated prostate epithelial cells, whereas the selective knockdown of ANO1 inhibited DHT-induced cell proliferation. Three androgen-response elements were found in the ANO1 promoter region, which is relevant for the DHT-dependent induction of ANO1. Administration of the ANO1 blocker orAno1small interfering RNA, inhibited prostate enlargement and reduced histological abnormalities in vivo. We therefore concluded that ANO1 is essential for the development of prostate hyperplasia and is a potential target for the treatment of BPH.
Neuroscience research has become a national priority for the Korean government. Korean scholars have dedicated interest in the societal ramifications of neurotechnologies; neuroethics is an integral ...component of the Korea Brain Initiative and to the formation of its growing neuroscience community.
Neuroscience research has become a national priority for the Korean government. Korean scholars have dedicated interest in the societal ramifications of neurotechnologies; neuroethics is an integral component of the Korea Brain Initiative and to the formation of its growing neuroscience community.
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