scholarly journals TMC1 Confers a Leak Conductance to Modulate Excitability of Auditory Hair Cells in Mammals

2019 ◽  
Author(s):  
Shuang Liu ◽  
Shufeng Wang ◽  
Linzhi Zou ◽  
Jie Li ◽  
Chenmeng Song ◽  
...  
Keyword(s):  
Hair Cells ◽  
Biological Processes ◽  
Membrane Excitability ◽  
Action Potential Firing ◽  
Cochlear Hair Cells ◽  
Auditory Hair Cells ◽  
Transmembrane Channel ◽  
Electrical Transducer ◽  
Potential Firing ◽  
Open Question

ABSTRACTHearing sensation relies on the mechano-electrical transducer (MET) channel of cochlear hair cells, in which Transmembrane channel-like 1 (TMC1) and TMC2 have been proposed to be the pore-forming subunits. Meanwhile it has been reported that TMCs regulate other biological processes in a variety of lower organisms ranging from sensations to motor functions. However, it is still an open question whether TMCs play roles other than their function in MET in mammals. In this study, we report that in mouse hair cells TMC1, but not TMC2, provides a background leak conductance, with properties distinct from those of the MET channels. By cysteine substitution, 4 amino acids of TMC1 are characterized critical for the leak conductance. The leak conductance is essential for action potential firing and tonotopic along the cochlear coil. Taken together, our results suggest that TMC1 confers a background leak conductance that modulates membrane excitability in cochlear hair cells.

scholarly journals TMC1 is an essential component of a leak channel that modulates tonotopy and excitability of auditory hair cells in mice

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Shuang Liu ◽  
Shufeng Wang ◽  
Linzhi Zou ◽  
Jie Li ◽  
Chenmeng Song ◽  
...  
Keyword(s):  
Hair Cells ◽  
Dependent Manner ◽  
Biological Processes ◽  
Action Potential Firing ◽  
Cochlear Hair Cells ◽  
Auditory Hair Cells ◽  
Leak Channel ◽  
Transmembrane Channel ◽  
Electrical Transducer ◽  
Potential Firing

Hearing sensation relies on the mechano-electrical transducer (MET) channel of cochlear hair cells, in which transmembrane channel-like 1 (TMC1) and transmembrane channel-like 2 (TMC2) have been proposed to be the pore-forming subunits in mammals. TMCs were also found to regulate biological processes other than MET in invertebrates, ranging from sensations to motor function. However, whether TMCs have a non-MET role remains elusive in mammals. Here, we report that in mouse hair cells, TMC1, but not TMC2, provides a background leak conductance, with properties distinct from those of the MET channels. By cysteine substitutions in TMC1, we characterized four amino acids that are required for the leak conductance. The leak conductance is graded in a frequency-dependent manner along the length of the cochlea and is indispensable for action potential firing. Taken together, our results show that TMC1 confers a background leak conductance in cochlear hair cells, which may be critical for the acquisition of sound-frequency and -intensity.

scholarly journals The effects of Tmc1 Beethoven mutation on mechanotransducer channel function in cochlear hair cells

2015 ◽  
Vol 146 (3) ◽  
pp. 233-243 ◽  
Author(s):  
Maryline Beurg ◽  
Adam C. Goldring ◽  
Robert Fettiplace
Keyword(s):  
Hair Cell ◽  
Hair Cells ◽  
Outer Hair Cells ◽  
Wild Type ◽  
Cochlear Hair Cells ◽  
Transmembrane Channel ◽  
Adaptive Shift ◽  
Electrical Transducer ◽  
Protein Isoform ◽  
The Relationship

Sound stimuli are converted into electrical signals via gating of mechano-electrical transducer (MT) channels in the hair cell stereociliary bundle. The molecular composition of the MT channel is still not fully established, although transmembrane channel–like protein isoform 1 (TMC1) may be one component. We found that in outer hair cells of Beethoven mice containing a M412K point mutation in TMC1, MT channels had a similar unitary conductance to that of wild-type channels but a reduced selectivity for Ca2+. The Ca2+-dependent adaptation that adjusts the operating range of the channel was also impaired in Beethoven mutants, with reduced shifts in the relationship between MT current and hair bundle displacement for adapting steps or after lowering extracellular Ca2+; these effects may be attributed to the channel’s reduced Ca2+ permeability. Moreover, the density of stereociliary CaATPase pumps for Ca2+ extrusion was decreased in the mutant. The results suggest that a major component of channel adaptation is regulated by changes in intracellular Ca2+. Consistent with this idea, the adaptive shift in the current–displacement relationship when hair bundles were bathed in endolymph-like Ca2+ saline was usually abolished by raising the intracellular Ca2+ concentration.

scholarly journals Generation of Cochlear Hair Cells from Sox2 Positive Supporting Cells via DNA Demethylation

2020 ◽  
Vol 21 (22) ◽  
pp. 8649
Author(s):  
Xin Deng ◽  
Zhengqing Hu
Keyword(s):  
Transgenic Mice ◽  
Inner Ear ◽  
Hair Cells ◽  
Dna Methyltransferase ◽  
Dna Demethylation ◽  
Egfp Expression ◽  
Supporting Cells ◽  
Cochlear Hair Cells ◽  
Auditory Hair Cells ◽  
Adult Mice

Regeneration of auditory hair cells in adult mammals is challenging. It is also difficult to track the sources of regenerated hair cells, especially in vivo. Previous paper found newly generated hair cells in deafened mouse by injecting a DNA methyltransferase inhibitor 5-azacytidine into the inner ear. This paper aims to investigate the cell sources of new hair cells. Transgenic mice with enhanced green fluorescent protein (EGFP) expression controlled by the Sox2 gene were used in the study. A combination of kanamycin and furosemide was applied to deafen adult mice, which received 4 mM 5-azacytidine injection into the inner ear three days later. Mice were followed for 3, 5, 7 and 14 days after surgery to track hair cell regeneration. Immunostaining of Myosin VIIa and EGFP signals were used to track the fate of Sox2-expressing supporting cells. The results show that (i) expression of EGFP in the transgenic mice colocalized the supporting cells in the organ of Corti, and (ii) the cell source of regenerated hair cells following 5-azacytidine treatment may be supporting cells during 5–7 days post 5-azacytidine injection. In conclusion, 5-azacytidine may promote the conversion of supporting cells to hair cells in chemically deafened adult mice.

The temporal characteristics of Ca2+ entry through L-type and T-type Ca2+ channels shape exocytosis efficiency in chick auditory hair cells during development

2012 ◽  
Vol 108 (11) ◽  
pp. 3116-3123 ◽  
Author(s):  
Snezana Levic ◽  
Didier Dulon
Keyword(s):  
Hair Cells ◽  
Low Voltage ◽  
Domestic Chick ◽  
Cochlear Hair Cells ◽  
Auditory Hair Cells ◽  
Temporal Characteristics ◽  
Cochlear Development ◽  
Synaptic Exocytosis ◽  
Fast Release ◽  
Ca2 Channels

During development, synaptic exocytosis by cochlear hair cells is first initiated by patterned spontaneous Ca2+ spikes and, at the onset of hearing, by sound-driven graded depolarizing potentials. The molecular reorganization occurring in the hair cell synaptic machinery during this developmental transition still remains elusive. We characterized the changes in biophysical properties of voltage-gated Ca2+ currents and exocytosis in developing auditory hair cells of a precocial animal, the domestic chick. We found that immature chick hair cells (embryonic days 10–12) use two types of Ca2+ currents to control exocytosis: low-voltage-activating, rapidly inactivating (mibefradil sensitive) T-type Ca2+ currents and high-voltage-activating, noninactivating (nifedipine sensitive) L-type currents. Exocytosis evoked by T-type Ca2+ current displayed a fast release component (RRP) but lacked the slow sustained release component (SRP), suggesting an inefficient recruitment of distant synaptic vesicles by this transient Ca2+ current. With maturation, the participation of L-type Ca2+ currents to exocytosis largely increased, inducing a highly Ca2+ efficient recruitment of an RRP and an SRP component. Notably, L-type-driven exocytosis in immature hair cells displayed higher Ca2+ efficiency when triggered by prerecorded native action potentials than by voltage steps, whereas similar efficiency for both protocols was found in mature hair cells. This difference likely reflects a tighter coupling between release sites and Ca2+ channels in mature hair cells. Overall, our results suggest that the temporal characteristics of Ca2+ entry through T-type and L-type Ca2+ channels greatly influence synaptic release by hair cells during cochlear development.

scholarly journals Conductance and block of hair-cell mechanotransducer channels in transmembrane channel–like protein mutants

2014 ◽  
Vol 144 (1) ◽  
pp. 55-69 ◽  
Author(s):  
Maryline Beurg ◽  
Kyunghee X. Kim ◽  
Robert Fettiplace
Keyword(s):  
Hair Cells ◽  
Outer Hair Cells ◽  
Incomplete Block ◽  
Wild Type ◽  
Pharmacological Profile ◽  
Cochlear Hair Cells ◽  
Transmembrane Channel ◽  
Protein Mutants ◽  
Tip Link ◽  
Peptide Toxin

Transmembrane channel–like (TMC) proteins TMC1 and TMC2 are crucial to the function of the mechanotransducer (MT) channel of inner ear hair cells, but their precise function has been controversial. To provide more insight, we characterized single MT channels in cochlear hair cells from wild-type mice and mice with mutations in Tmc1, Tmc2, or both. Channels were recorded in whole-cell mode after tip link destruction with BAPTA or after attenuating the MT current with GsMTx-4, a peptide toxin we found to block the channels with high affinity. In both cases, the MT channels in outer hair cells (OHCs) of wild-type mice displayed a tonotopic gradient in conductance, with channels from the cochlear base having a conductance (110 pS) nearly twice that of those at the apex (62 pS). This gradient was absent, with channels at both cochlear locations having similar small conductances, with two different Tmc1 mutations. The conductance of MT channels in inner hair cells was invariant with cochlear location but, as in OHCs, was reduced in either Tmc1 mutant. The gradient of OHC conductance also disappeared in Tmc1/Tmc2 double mutants, in which a mechanically sensitive current could be activated by anomalous negative displacements of the hair bundle. This “reversed stimulus–polarity” current was seen with two different Tmc1/Tmc2 double mutants, and with Tmc1/Tmc2/Tmc3 triple mutants, and had a pharmacological sensitivity comparable to that of native MT currents for most antagonists, except dihydrostreptomycin, for which the affinity was less, and for curare, which exhibited incomplete block. The existence in the Tmc1/Tmc2 double mutants of MT channels with most properties resembling those of wild-type channels indicates that proteins other than TMCs must be part of the channel pore. We suggest that an external vestibule of the MT channel may partly account for the channel’s large unitary conductance, high Ca2+ permeability, and pharmacological profile, and that this vestibule is disrupted in Tmc mutants.

scholarly journals Calcium-Induced Calcium Release during Action Potential Firing in Developing Inner Hair Cells

2015 ◽  
Vol 108 (5) ◽  
pp. 1003-1012 ◽  
Author(s):  
Radu Iosub ◽  
Daniele Avitabile ◽  
Lisa Grant ◽  
Krasimira Tsaneva-Atanasova ◽  
Helen J. Kennedy
Keyword(s):  
Action Potential ◽  
Hair Cells ◽  
Calcium Release ◽  
Action Potential Firing ◽  
Inner Hair Cells ◽  
Potential Firing ◽  
Calcium Induced Calcium Release

scholarly journals The acquisition of mechano‐electrical transducer current adaptation in auditory hair cells requires myosin VI

2016 ◽  
Vol 594 (13) ◽  
pp. 3667-3681 ◽  
Author(s):  
Walter Marcotti ◽  
Laura F. Corns ◽  
Richard J. Goodyear ◽  
Agnieszka K. Rzadzinska ◽  
Karen B. Avraham ◽  
...  
Keyword(s):  
Hair Cells ◽  
Myosin Vi ◽  
Auditory Hair Cells ◽  
Electrical Transducer

scholarly journals The role of transmembrane channel–like proteins in the operation of hair cell mechanotransducer channels

2013 ◽  
Vol 142 (5) ◽  
pp. 493-505 ◽  
Author(s):  
Kyunghee X. Kim ◽  
Maryline Beurg ◽  
Carole M. Hackney ◽  
David N. Furness ◽  
Shanthini Mahendrasingam ◽  
...  
Keyword(s):  
Hair Cells ◽  
Hair Bundle ◽  
Wild Type ◽  
Cochlear Hair Cells ◽  
Transmembrane Channel ◽  
Protein Partners ◽  
Tip Link ◽  
Lower Permeability ◽  
Precise Role

Sound stimuli elicit movement of the stereocilia that make up the hair bundle of cochlear hair cells, putting tension on the tip links connecting the stereocilia and thereby opening mechanotransducer (MT) channels. Tmc1 and Tmc2, two members of the transmembrane channel–like family, are necessary for mechanotransduction. To assess their precise role, we recorded MT currents elicited by hair bundle deflections in mice with null mutations of Tmc1, Tmc2, or both. During the first postnatal week, we observed a normal MT current in hair cells lacking Tmc1 or Tmc2; however, in the absence of both isoforms, we recorded a large MT current that was phase-shifted 180°, being evoked by displacements of the hair bundle away from its tallest edge rather than toward it as in wild-type hair cells. The anomalous MT current in hair cells lacking Tmc1 and Tmc2 was blocked by FM1-43, dihydrostreptomycin, and extracellular Ca2+ at concentrations similar to those that blocked wild type. MT channels in the double knockouts carried Ca2+ with a lower permeability than wild-type or single mutants. The MT current in double knockouts persisted during exposure to submicromolar Ca2+, even though this treatment destroyed the tip links. We conclude that the Tmc isoforms do not themselves constitute the MT channel but are essential for targeting and interaction with the tip link. Changes in the MT conductance and Ca2+ permeability observed in the absence of Tmc1 mutants may stem from loss of interaction with protein partners in the transduction complex.

scholarly journals The role of parvalbumin interneuron GIRK signaling in regulation of affect and cognition in male and female mice

2020 ◽  
Author(s):  
EM Anderson ◽  
S Demis ◽  
H D’Acquisto ◽  
A Engelhardt ◽  
M Hearing
Keyword(s):  
Action Potential ◽  
Pyramidal Neurons ◽  
Forced Swim Test ◽  
Membrane Excitability ◽  
Cellular Mechanisms ◽  
Action Potential Firing ◽  
Male And Female ◽  
Female Mice ◽  
Potential Firing ◽  
Affect And Cognition

ABSTRACTPathological impairments in the regulation of affect (i.e. emotion) and flexible decision-making are commonly observed across numerous neuropsychiatric disorders and are thought to reflect dysfunction of cortical and subcortical circuits that arise in part from imbalances in excitation and inhibition within these structures. Disruptions in GABA transmission, in particular that from parvalbumin-expressing interneurons (PVI), has been highlighted as a likely mechanism by which this imbalance arises, as they regulate excitation and synchronization of principle output neurons. G protein-gated inwardly rectifying potassium ion (GIRK/Kir3) channels are known to modulate excitability and output of pyramidal neurons in areas like the medial prefrontal cortex and hippocampus, however the role GIRK plays in PVI excitability and behavior is unknown. Male and female mice lacking GIRK1 in PVI (Girk1flox/flox:PVcre) and expressing td-tomato in PVI (Girk1flox/flox:PVCre:PVtdtom) exhibited increased open arm time in the elevated plus maze, while males showed an increase in immobile episodes during the forced swim test. Loss of GIRK1 did not alter motivated behavior for an appetitive reward or impair overall performance in an operant-based attention set-shifting model of cognitive flexibility, however it did alter types of errors committed during the visual cue test. Unexpectedly, baseline sex differences were also identified in these tasks, with females exhibiting overall poorer performance compared to males and distinct types of errors, highlighting potential differences in task-related problem solving. Interestingly, reductions in PVI GIRK signaling did not correspond to changes in membrane excitability but did increase action potential firing at higher current injections in PVI of males, but not females. This is the first investigation on the role that PVI GIRK-signaling has on membrane excitability, action potential firing, and their role on affect and cognition together increasing understanding of PVI cellular mechanisms and function.

Sign in / Sign up

Export Citation Format

Share Document