scholarly journals Regulation of membrane homeostasis by TMC1 mechanoelectrical transduction channels is essential for hearing

2021 ◽  
Author(s):  
Angela Ballesteros ◽  
Kenton J Swartz
Keyword(s):  
Hearing Loss ◽  
Intracellular Calcium ◽  
Hair Cells ◽  
Calcium Concentration ◽  
Membrane Remodeling ◽  
Auditory Hair Cells ◽  
Membrane Blebbing ◽  
Mechanoelectrical Transduction ◽  
Phosphatidylserine Externalization ◽  
Calcium Lead

The mechanoelectrical transduction (MET) channel complex of auditory hair cells converts sound into electrical signals, allowing us to hear. After decades of research, the transmembrane-like channel 1 and 2 (TMC1 and TMC2) have been recently identified as pore-forming subunits of the MET channels, but the molecular peculiarity that differentiates these two proteins and makes TMC1 essential for hearing remains elusive. Here, we show that TMC1, but not TMC2, is essential for membrane remodeling triggered by a decrease in intracellular calcium concentration. We demonstrate that inhibition of MET channels or buffering of intracellular calcium lead to pronounced phosphatidylserine externalization, membrane blebbing and ectosome release at the hair cell sensory organelle, culminating in the loss of TMC1 protein. Moreover, three TMC1 deafness-causing mutations cause constitutive phosphatidylserine externalization that correlates with the deafness phenotype, suggesting that the mechanisms of hearing loss involve alterations in membrane homeostasis.

scholarly journals Caffeine Induces Autophagy and Apoptosis in Auditory Hair Cells via the SGK1/HIF-1α Pathway

2021 ◽  
Vol 9 ◽  
Author(s):  
Xiaomin Tang ◽  
Yuxuan Sun ◽  
Chenyu Xu ◽  
Xiaotao Guo ◽  
Jiaqiang Sun ◽  
...  
Keyword(s):  
Hearing Loss ◽  
Hair Cells ◽  
Stria Vascularis ◽  
Spiral Ganglion ◽  
Organ Of Corti ◽  
Spiral Ganglion Neurons ◽  
Auditory Hair Cells ◽  
Qrt Pcr ◽  
Ganglion Neurons

Caffeine is being increasingly used in daily life, such as in drinks, cosmetics, and medicine. Caffeine is known as a mild stimulant of the central nervous system, which is also closely related to neurologic disease. However, it is unknown whether caffeine causes hearing loss, and there is great interest in determining the effect of caffeine in cochlear hair cells. First, we explored the difference in auditory brainstem response (ABR), organ of Corti, stria vascularis, and spiral ganglion neurons between the control and caffeine-treated groups of C57BL/6 mice. RNA sequencing was conducted to profile mRNA expression differences in the cochlea of control and caffeine-treated mice. A CCK-8 assay was used to evaluate the approximate concentration of caffeine. Flow cytometry, TUNEL assay, immunocytochemistry, qRT-PCR, and Western blotting were performed to detect the effects of SGK1 in HEI-OC1 cells and basilar membranes. In vivo research showed that 120 mg/ kg caffeine injection caused hearing loss by damaging the organ of Corti, stria vascularis, and spiral ganglion neurons. RNA-seq results suggested that SGK1 might play a vital role in ototoxicity. To confirm our observations in vitro, we used the HEI-OC1 cell line, a cochlear hair cell-like cell line, to investigate the role of caffeine in hearing loss. The results of flow cytometry, TUNEL assay, immunocytochemistry, qRT-PCR, and Western blotting showed that caffeine caused autophagy and apoptosis via SGK1 pathway. We verified the interaction between SGK1 and HIF-1α by co-IP. To confirm the role of SGK1 and HIF-1α, GSK650394 was used as an inhibitor of SGK1 and CoCl2 was used as an inducer of HIF-1α. Western blot analysis suggested that GSK650394 and CoCl2 relieved the caffeine-induced apoptosis and autophagy. Together, these results indicated that caffeine induces autophagy and apoptosis in auditory hair cells via the SGK1/HIF-1α pathway, suggesting that caffeine may cause hearing loss. Additionally, our findings provided new insights into ototoxic drugs, demonstrating that SGK1 and its downstream pathways may be potential therapeutic targets for hearing research at the molecular level.

scholarly journals Research Progress on the Mechanism of Cochlear Hair Cell Regeneration

2021 ◽  
Vol 15 ◽  
Author(s):  
Shan Xu ◽  
Ning Yang
Keyword(s):  
Hearing Loss ◽  
Hair Cell ◽  
Sensorineural Hearing Loss ◽  
Hair Cells ◽  
Molecular Mechanisms ◽  
Sensorineural Hearing ◽  
Research Progress ◽  
Cell Regeneration ◽  
Hair Cell Regeneration ◽  
Auditory Hair Cells

Mammalian inner ear hair cells do not have the ability to spontaneously regenerate, so their irreversible damage is the main cause of sensorineural hearing loss. The damage and loss of hair cells are mainly caused by factors such as aging, infection, genetic factors, hypoxia, autoimmune diseases, ototoxic drugs, or noise exposure. In recent years, research on the regeneration and functional recovery of mammalian auditory hair cells has attracted more and more attention in the field of auditory research. How to regenerate and protect hair cells or auditory neurons through biological methods and rebuild auditory circuits and functions are key scientific issues that need to be resolved in this field. This review mainly summarizes and discusses the recent research progress in gene therapy and molecular mechanisms related to hair cell regeneration in the field of sensorineural hearing loss.

scholarly journals Expression of a membrane-targeted fluorescent reporter disrupts auditory hair cell mechanoelectrical transduction and causes profound deafness

2020 ◽  
Author(s):  
Angela Ballesteros ◽  
Tracy S. Fitzgerald ◽  
Kenton J. Swartz
Keyword(s):  
Hair Cells ◽  
Otoacoustic Emissions ◽  
Fluorescent Protein ◽  
Super Resolution ◽  
Auditory Brainstem ◽  
Auditory Brainstem Responses ◽  
Fluorescent Reporter ◽  
Auditory Hair Cells ◽  
Mechanoelectrical Transduction ◽  
Distortion Product

AbstractThe reporter mT/mG mice expressing a membrane-targeted fluorescent protein are becoming widely used to study the auditory and vestibular system due to its versatility. Here we show that high expression levels of the fluorescent mtdTomato reporter affect the function of the sensory hair cells and the auditory performance of mT/mG transgenic mice. Auditory brainstem responses and distortion product otoacoustic emissions revealed that adult mT/mG homozygous mice are profoundly deaf, whereas heterozygous mice present high frequency loss. We explore whether this line would be useful for studying and visualizing the membrane of auditory hair cells by airyscan super-resolution confocal microscopy. Membrane localization of the reporter was observed in hair cells of the cochlea, facilitating imaging of both cell bodies and stereocilia bundles without altering cellular architecture or the expression of the integral membrane motor protein prestin. Remarkably, hair cells from mT/mG homozygous mice failed to uptake the FM1-43 dye and to locate TMC1 at the stereocilia, indicating defective mechanoelectrical transduction machinery. Our work emphasizes that precautions must be considered when working with reporter mice and highlights the potential role of the cellular membrane in maintaining functional hair cells and ensuring proper hearing.

scholarly journals Avenanthramide-C prevents noise- and drug-induced hearing loss while protecting auditory hair cells from oxidative stress

2019 ◽  
Vol 5 (1) ◽  
Author(s):  
Alphonse Umugire ◽  
Sungsu Lee ◽  
Dami Kim ◽  
Munyoung Choi ◽  
Hyung-Seok Kim ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Hearing Loss ◽  
Hair Cells ◽  
Drug Induced ◽  
Auditory Hair Cells

Two Components of Transducer Adaptation in Auditory Hair Cells

1999 ◽  
Vol 82 (5) ◽  
pp. 2171-2181 ◽  
Author(s):  
Yuh-Cherng Wu ◽  
A. J. Ricci ◽  
R. Fettiplace
Keyword(s):  
Intracellular Calcium ◽  
Hair Cells ◽  
Time Course ◽  
Similar Time ◽  
Auditory Hair Cells ◽  
Calcium Buffer ◽  
Atpase Inhibitors ◽  
Butanedione Monoxime ◽  
Fast Adaptation ◽  
Dependent Mechanism

Mechanoelectrical transducer currents in turtle auditory hair cells adapted to maintained stimuli via a Ca2+-dependent mechanism characterized by two time constants of ∼1 and 15 ms. The time course of adaptation slowed as the stimulus intensity was raised because of an increased prominence of the second component. The fast component of adaptation had a similar time constant for both positive and negative displacements and was unaffected by the myosin ATPase inhibitors, vanadate and butanedione monoxime. Adaptation was modeled by a scheme in which Ca2+ ions, entering through open transducer channels, bind at two intracellular sites to trigger independent processes leading to channel closure. It was assumed that the second site activates a modulator with 10-fold slower kinetics than the first site. The model was implemented by computing Ca2+diffusion within a single stereocilium, incorporating intracellular calcium buffers and extrusion via a plasma membrane CaATPase. The theoretical results reproduced several features of the experimental responses, including sensitivity to the concentration of external Ca2+ and intracellular calcium buffer and a dependence on the onset speed of the stimulus. The model also generated damped oscillatory transducer responses at a frequency dependent on the rate constant for the fast adaptive process. The properties of fast adaptation make it unlikely to be mediated by a myosin motor, and we suggest that it may result from Ca2+ binding to the transducer channel or a nearby cytoskeletal element.

scholarly journals Alternative Splicing of Cdh23 Exon 68 Is Regulated by RBM24, RBM38, and PTBP1

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Nana Li ◽  
Haibo Du ◽  
Rui Ren ◽  
Yanfei Wang ◽  
Zhigang Xu
Keyword(s):  
Hearing Loss ◽  
Alternative Splicing ◽  
Inner Ear ◽  
Hair Cells ◽  
Cell Types ◽  
Splicing Factors ◽  
Mechanoelectrical Transduction ◽  
Eukaryotic Proteins ◽  
A Cell ◽  
Cadherin 23

Alternative splicing plays a pivotal role in modulating the function of eukaryotic proteins. In the inner ear, many genes undergo alternative splicing, and errors in this process lead to hearing loss. Cadherin 23 (CDH23) forms part of the so-called tip links, which are indispensable for mechanoelectrical transduction (MET) in the hair cells. Cdh23 gene contains 69 exons, and exon 68 is subjected to alternative splicing. Exon 68 of the Cdh23 gene is spliced into its mRNA only in a few cell types including hair cells. The mechanism responsible for the alternative splicing of Cdh23 exon 68 remains elusive. In the present work, we performed a cell-based screening to look for splicing factors that regulate the splicing of Cdh23 exon 68. RBM24 and RBM38 were identified to enhance the inclusion of Cdh23 exon 68. The splicing of Cdh23 exon 68 is affected in Rbm24 knockdown or knockout cells. Moreover, we also found that PTBP1 inhibits the inclusion of Cdh23 exon 68. Taken together, we show here that alternative splicing of Cdh23 exon 68 is regulated by RBM24, RBM38, and PTBP1.

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