Dataset Information

Tonotopic Differentiation of Coupling between Ca²⁺ and Kv1.1 Expression in Brainstem Auditory Circuit.

ABSTRACT: Tonotopic differentiations of ion channels ensure sound processing across frequencies. Afferent input plays a critical role in differentiations. We demonstrate here in organotypic culture of chicken cochlear nucleus that expression of Kv1.1 was coupled with Ca²⁺ to a different degree depending on tonotopic regions, thereby differentiating the level of expression within the nucleus. In the culture, Kv1.1 was down-regulated and not differentiated tonotopically. Chronic depolarization increased Kv1.1 expression in a level-dependent manner. Moreover, the dependence was steeper at higher-frequency regions, which restored the differentiation. The depolarization increased Kv1.1 via activation of Cav1 channels, whereas basal Ca²⁺ level elevated similarly irrespective of tonotopic regions. Thus, the efficiency of Ca²⁺-dependent Kv1.1 expression would be fine-tuned in a tonotopic-region-specific manner, emphasizing the importance of neuronal tonotopic identity as well as pattern of afferent input in the tonotopic differentiation of the channel in the auditory circuit.

SUBMITTER: Adachi R

PROVIDER: S-EPMC6411580 | biostudies-literature | 2019 Mar

REPOSITORIES: biostudies-literature

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Tonotopic Differentiation of Coupling between Ca<sup>2+</sup> and Kv1.1 Expression in Brainstem Auditory Circuit.

Adachi Ryota R Yamada Rei R Kuba Hiroshi H

iScience 20190227

Tonotopic differentiations of ion channels ensure sound processing across frequencies. Afferent input plays a critical role in differentiations. We demonstrate here in organotypic culture of chicken cochlear nucleus that expression of Kv1.1 was coupled with Ca<sup>2+</sup> to a different degree depending on tonotopic regions, thereby differentiating the level of expression within the nucleus. In the culture, Kv1.1 was down-regulated and not differentiated tonotopically. Chronic depolarization in ...[more]

PMID: 30856389

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Project description:The cochlea processes auditory signals over a wide range of frequencies and intensities. However, the transfer characteristics at hair cell ribbon synapses are still poorly understood at different frequency locations along the cochlea. Using recordings from mature gerbils, we report here a surprisingly strong block of exocytosis by the slow Ca2+ buffer EGTA (10 mM) in basal hair cells tuned to high frequencies (∼30 kHz). In addition, using recordings from gerbil, mouse, and bullfrog auditory organs, we find that the spatial coupling between Ca2+ influx and exocytosis changes from nanodomain in low-frequency tuned hair cells (∼<2 kHz) to progressively more microdomain in high-frequency cells (∼>2 kHz). Hair cell synapses have thus developed remarkable frequency-dependent tuning of exocytosis: accurate low-latency encoding of onset and offset of sound intensity in the cochlea's base and submillisecond encoding of membrane receptor potential fluctuations in the apex for precise phase-locking to sound signals. We also found that synaptic vesicle pool recovery from depletion was sensitive to high concentrations of EGTA, suggesting that intracellular Ca2+ buffers play an important role in vesicle recruitment in both low- and high-frequency hair cells. In conclusion, our results indicate that microdomain coupling is important for exocytosis in high-frequency hair cells, suggesting a novel hypothesis for why these cells are more susceptible to sound-induced damage than low-frequency cells; high-frequency inner hair cells must have a low Ca2+ buffer capacity to sustain exocytosis, thus making them more prone to Ca2+-induced cytotoxicity.SIGNIFICANCE STATEMENT In the inner ear, sensory hair cells signal reception of sound. They do this by converting the sound-induced movement of their hair bundles present at the top of these cells, into an electrical current. This current depolarizes the hair cell and triggers the calcium-induced release of the neurotransmitter glutamate that activates the postsynaptic auditory fibers. The speed and precision of this process enables the brain to perceive the vital components of sound, such as frequency and intensity. We show that the coupling strength between calcium channels and the exocytosis calcium sensor at inner hair cell synapses changes along the mammalian cochlea such that the timing and/or intensity of sound is encoded with high precision.

Dataset Information

Tonotopic Differentiation of Coupling between Ca²⁺ and Kv1.1 Expression in Brainstem Auditory Circuit.

Publications

Tonotopic Differentiation of Coupling between Ca<sup>2+</sup> and Kv1.1 Expression in Brainstem Auditory Circuit.

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Dataset Information

Tonotopic Differentiation of Coupling between Ca2+ and Kv1.1 Expression in Brainstem Auditory Circuit.

Publications

Tonotopic Differentiation of Coupling between Ca<sup>2+</sup> and Kv1.1 Expression in Brainstem Auditory Circuit.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets

Tonotopic Differentiation of Coupling between Ca²⁺ and Kv1.1 Expression in Brainstem Auditory Circuit.