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Alfred L Nuttall - One of the best experts on this subject based on the ideXlab platform.
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non uniform distribution of Outer Hair Cell transmembrane potential induced by extraCellular electric field
Biophysical Journal, 2013Co-Authors: Sripriya Ramamoorthy, Alfred L Nuttall, Teresa WilsonAbstract:Intracochlear electric fields arising out of sound-induced receptor currents, silent currents, or electrical current injected into the cochlea induce transmembrane potential along the Outer Hair Cell (OHC) but its distribution along the Cells is unknown. In this study, we investigated the distribution of OHC transmembrane potential induced along the Cell perimeter and its sensitivity to the direction of the extraCellular electric field (EEF) on isolated OHCs at a low frequency using the fast voltage-sensitive dye ANNINE-6plus. We calibrated the potentiometric sensitivity of the dye by applying known voltage steps to Cells by simultaneous whole-Cell voltage clamp. The OHC transmembrane potential induced by the EEF is shown to be highly nonuniform along the Cell perimeter and strongly dependent on the direction of the electrical field. Unlike in many other Cells, the EEF induces a field-direction-dependent intraCellular potential in the cylindrical OHC. We predict that without this induced intraCellular potential, EEF would not generate somatic electromotility in OHCs. In conjunction with the known heterogeneity of OHC membrane microdomains, voltage-gated ion channels, charge, and capacitance, the EEF-induced nonuniform transmembrane potential measured in this study suggests that the EEF would impact the cochlear amplification and electropermeability of molecules across the Cell.
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in vivo Outer Hair Cell length changes expose the active process in the cochlea
PLOS ONE, 2012Co-Authors: Anders Fridberger, Fangyi Chen, Dingjun Zha, Niloy Choudhury, Steven L Jacques, Ruikang K Wang, Sripriya Ramamoorthy, Alfred L NuttallAbstract:Background Mammalian hearing is refined by amplification of the sound-evoked vibration of the cochlear partition. This amplification is at least partly due to forces produced by protein motors residing in the cylindrical body of the Outer Hair Cell. To transmit power to the cochlear partition, it is required that the Outer Hair Cells dynamically change their length, in addition to generating force. These length changes, which have not previously been measured in vivo, must be correctly timed with the acoustic stimulus to produce amplification.
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Outer Hair Cell somatic electromotility in vivo and power transfer to the organ of corti
Biophysical Journal, 2012Co-Authors: Sripriya Ramamoorthy, Alfred L NuttallAbstract:The active amplification of sound-induced vibrations in the cochlea, known to be crucial for auditory sensitivity and frequency selectivity, is not well understood. The Outer Hair Cell (OHC) somatic electromotility is a potential mechanism for such amplification. Its effectiveness in vivo is putatively limited by the electrical low-pass filtering of the Cell's transmembrane potential. However, the transmembrane potential is an incomplete metric. We propose and estimate two metrics to evaluate the effectiveness of OHC electromotility in vivo. One metric is the OHC electromechanical ratio defined as the amplitude of the ratio of OHC displacement to the change in its transmembrane potential. The in vivo electromechanical ratio is derived from the recently measured in vivo displacements of the reticular lamina and the basilar membrane at the 19 kHz characteristic place in guinea pigs and using a model. The ratio, after accounting for the differences in OHC vibration in situ due to the impedances from the adjacent structures, is in agreement with the literature values of the in vitro electromechanical ratio measured by others. The second and more insightful metric is the OHC somatic power. Our analysis demonstrates that the organ of Corti is nearly optimized to receive maximum somatic power in vivo and that the estimated somatic power could account for the active amplification.
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effect of salicylate on kcnq4 of the guinea pig Outer Hair Cell
Journal of Neurophysiology, 2010Co-Authors: Hyo Jeong Kim, Alfred L Nuttall, Ebenezer N YamoahAbstract:Salicylate causes a moderate hearing loss and tinnitus in humans at high-dose levels. Salicylate-induced hearing loss has been attributed to impaired sound amplification by Outer Hair Cells (OHCs) ...
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chlorpromazine alters cochlear mechanics and amplification in vivo evidence for a role of stiffness modulation in the organ of corti
Journal of Neurophysiology, 2007Co-Authors: Jiefu Zheng, Niranjan Deo, Yuan Zou, Karl Grosh, Alfred L NuttallAbstract:Although prestin-mediated Outer Hair Cell (OHC) electromotility provides mechanical force for sound amplification in the mammalian cochlea, proper OHC stiffness is required to maintain normal elect...
William E Brownell - One of the best experts on this subject based on the ideXlab platform.
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The potential and electric field in the cochlear Outer Hair Cell membrane
Medical & Biological Engineering & Computing, 2015Co-Authors: Ben Harland, William E Brownell, Wen-han Lee, Sean X. Sun, Alexander A SpectorAbstract:Outer Hair Cell electromechanics, critically important to mammalian active hearing, is driven by the Cell membrane potential. The membrane protein prestin is a crucial component of the active Outer Hair Cell’s motor. The focus of the paper is the analysis of the local membrane potential and electric field resulting from the interaction of electric charges involved. Here the relevant charges are the ions inside and outside the Cell, lipid bilayer charges, and prestin-associated charges (mobile—transferred by the protein under the action of the applied field, and stationary—relatively unmoved by the field). The electric potentials across and along the membrane are computed for the case of an applied DC-field. The local amplitudes and phases of the potential under different frequencies are analyzed for the case of a DC + AC-field. We found that the effect of the system of charges alters the electric potential and internal field, which deviate significantly from their traditional linear and constant distributions. Under DC + AC conditions, the strong frequency dependence of the prestin mobile charge has a relatively small effect on the amplitude and phase of the resulting potential. The obtained results can help in a better understanding and experimental verification of the mechanism of prestin performance.
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High-Frequency Force Generation in the Constrained Cochlear Outer Hair Cell: A Model Study
2015Co-Authors: Zhijie Liao, William E Brownell, Aleksander S Popel, Alexander A SpectorAbstract:Cochlear Outer Hair Cell (OHC) electromotility is be-lieved to be responsible for the sensitivity and fre-quency selectivity of the mammalian hearing process. Its contribution to hearing is better understood by examining the force generated by the OHC as a feedback to vibration of the basilar membrane (BM). In this study, we examine the effects of the con-straints imposed on the OHC and of the surrounding fluids on the Cell’s high-frequency active force generated under in vitro and in vivo conditions. The OHC is modeled as a viscoelastic and piezoelectric cylindrical shell coupled with viscous intraCellular and extraCellular fluids, and the constraint is repre-sented by a spring with adjustable stiffness. The so-lution is obtained in the form of a Fourier series. The model results are consistent with previously reported experiments under both low- and high-frequency conditions. We find that constrained OHCs achieve a much higher corner frequency than free OHCs, depending on the stiffness of the constraint. We an-alyze cases in which the stiffness of the constraint is similar to that of the BM, reticular lamina, and tectorial membrane, and find that the force per unit transmembrane potential generated by the OHC can be constant up to several tens of kHz. This model, describing the OHC as a local amplifier, can be incorporated into a global cochlear model that considers cochlear hydrodynamics and frequency modulation of the receptor potential, as well as the graded BM stiffness and OHC length
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Sound-induced length changes in Outer Hair Cell stereocilia
Nature communications, 2012Co-Authors: Pierre Hakizimana, William E Brownell, Stefan Jacob, Anders FridbergerAbstract:Hearing relies on mechanical stimulation of stereocilia bundles on the sensory Cells of the inner ear. When sound hits the ear, each stereocilium pivots about a neck-like taper near their base. More than three decades of research have established that sideways deflection of stereocilia is essential for converting mechanical stimuli into electrical signals. Here we show that mammalian Outer Hair Cell stereocilia not only move sideways but also change length during sound stimulation. Currents that enter stereocilia through mechanically sensitive ion channels control the magnitude of both length changes and bundle deflections in a reciprocal manner: the smaller the length change, the larger is the bundle deflection. Thus, the transduction current is important for maintaining the resting mechanical properties of stereocilia. Hair Cell stimulation is most effective when bundles are in a state that ensures minimal length change.
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Effect of Outer Hair Cell membrane piezoelectric properties on the receptor potential under high-frequency conditions
Proceedings of the Second Joint 24th Annual Conference and the Annual Fall Meeting of the Biomedical Engineering Society] [Engineering in Medicine and, 2002Co-Authors: A.a. Spector, William E Brownell, Aleksander S PopelAbstract:We have found that the band pass characteristics of the cochlear Outer Hair Cell can be improved by introducing the piezoelectric properties of the Cell membrane. In contrast to the conventional analysis, the Cell membrane receptor potential does not tend to zero and at any frequency is greater than a limiting value. The piezoelectric properties cause an additional, strain-dependent, displacement current in the Cell wall. In short Cells, we have found that for the low-frequency value about 2-3 mV and the strain level 0.1% the receptor potential can reach 0.4 mV throughout the whole frequency range. In long Cells, we have found that the effect of the piezoelectric properties is negligible.
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micro and nanomechanics of the cochlear Outer Hair Cell
Annual Review of Biomedical Engineering, 2001Co-Authors: William E Brownell, Robert M Raphael, Alexander A Spector, Aleksander S PopelAbstract:▪ Abstract Outer Hair Cell electromotility is crucial for the amplification, sharp frequency selectivity, and nonlinearities of the mammalian cochlea. Current modeling efforts based on morphological, physiological, and biophysical observations reveal transmembrane potential gradients and membrane tension as key independent variables controlling the passive and active mechanics of the Cell. The Cell's mechanics has been modeled on the microscale using a continuum approach formulated in terms of effective (Cellular level) mechanical and electric properties. Another modeling approach is nanostructural and is based on the molecular organization of the Cell's membranes and cytoskeleton. It considers interactions between the components of the composite Cell wall and the molecular elements within each of its components. The methods and techniques utilized to increase our understanding of the central role Outer Hair Cell mechanics plays in hearing are also relevant to broader research questions in Cell mechanics,...
Joseph Santossacchi - One of the best experts on this subject based on the ideXlab platform.
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single particle cryo em structure of the Outer Hair Cell motor protein prestin
bioRxiv, 2021Co-Authors: Carmen Butan, Jun-ping Bai, Dhasakumar Navaratnam, Qiang Song, Winston Tan, Joseph SantossacchiAbstract:The mammalian Outer Hair Cell (OHC) protein prestin (Slc26a5), a member of the solute carrier 26 (Slc26) family of membrane proteins, differs from other members of the family owing to its unique piezoelectric-like property that drives OHC electromotility. Prestin is required by OHCs for cochlear amplification, a process that enhances mammalian hearing. Despite substantial biophysical characterization, the mechanistic basis for the prestins electro-mechanical behavior is not fully understood. To gain insight into such behavior, we have used cryo-electron microscopy at subnanometer resolution (overall resolution of 4.0 A) to investigate the three-dimensional structure of prestin from gerbil (Meriones unguiculatus). Our studies show that prestin dimerizes with a 3D architecture strikingly similar to the dimeric conformation observed in the Slc26a9 anion transporter in an inside open/intermediate state, which we infer, based on patch clamp recordings, to reflect the contracted state of prestin. The structure shows two well separated transmembrane (TM) subunits and two cytoplasmic sulfate transporter and anti-sigma factor antagonist (STAS) domains forming a swapped dimer. The dimerization interface is defined by interactions between the domain-swapped STAS dimer and the transmembrane domains of the opposing half unit, further strengthened by an antiparallel beta strand at its N terminus. The structure also shows that each one of its two transmembrane subunits consists of 14 transmembrane segments organized in two inverted 7-segment repeats with a topology that was first observed in the structure of the bacterial symporter UraA (Lu F, et al., Nature 472, 2011). Finally, the solved anion binding site structural features of prestin are quite similar to that of Slc26a9 and other family members. Despite this similarity, we find that Slc26a9 lacks the characteristic displacement currents (or NonLinear Capacitance(NLC)) found with prestin, and we show that mutation of prestins Cl- binding site removes salicylate competition with anions in the face of normal NLC, thus refuting the yet accepted extrinsic voltage sensor hypothesis and any associated transport-like requirements for voltage-driven electromotility.
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the frequency response of Outer Hair Cell voltage dependent motility is limited by kinetics of prestin
The Journal of Neuroscience, 2018Co-Authors: Joseph Santossacchi, Winston TanAbstract:The voltage-dependent protein SLC26a5 (prestin) underlies Outer Hair Cell electromotility (eM), which is responsible for cochlear amplification in mammals. The electrical signature of eM is a bell-shaped nonlinear capacitance (NLC), deriving from prestin sensor-charge (Qp) movements, which peaks at the membrane voltage, Vh, where charge is distributed equally on either side of the membrane. Voltage dependencies of NLC and eM differ depending on interrogation frequency and intraCellular chloride, revealing slow intermediate conformational transitions between anion binding and voltage-driven Qp movements. Consequently, NLC exhibits low-pass characteristics, substantially below prevailing estimates of eM frequency response. Here we study in guinea pig and mouse of either sex synchronous prestin electrical (NLC, Qp) and mechanical (eM) activity across frequencies under voltage clamp (whole Cell and microchamber). We find that eM and Qp magnitude and phase correspond, indicating tight piezoelectric coupling. Electromechanical measures (both NLC and eM) show dual-Lorentzian, low-pass behavior, with a limiting (τ2) time constant at Vh of 32.6 and 24.8 μs, respectively. As expected for voltage-dependent kinetics, voltage excitation away from Vh has a faster, flatter frequency response, with our fastest measured τ2 for eM of 18.2 μs. Previous observations of ultrafast eM (τ ≈ 2 μs) were obtained at offsets far removed from Vh We hypothesize that trade-offs in eM gain-bandwith arising from voltage excitation at membrane potentials offset from Vh influence the effectiveness of cochlear amplification across frequencies.SIGNIFICANCE STATEMENT Of two types of Hair Cells within the organ of Corti, inner Hair Cells and Outer Hair Cells, the latter evolved to boost sensitivity to sounds. Damage results in hearing loss of 40-60 dB, revealing amplification gains of 100-1000× that arise from voltage-dependent mechanical responses [electromotility (eM)]. eM, driven by the membrane protein prestin, may work beyond 70 kHz. However, this speed exceeds, by over an order of magnitude, kinetics of typical voltage-dependent membrane proteins. We find eM is actually low pass in nature, indicating that prestin bears kinetics typical of other membrane proteins. These observations highlight potential difficulties in providing sufficient amplification beyond a cutoff frequency near 20 kHz. Nevertheless, observed trade-offs in eM gain-bandwith may sustain cochlear amplification across frequency.
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prestin molecular mechanisms underlying Outer Hair Cell electromotility
2017Co-Authors: Joseph Santossacchi, Dhasakumar Navaratnam, Rob Raphael, Dominik OliverAbstract:Prestin is a member of the SLC26 family of anion transporters that has evolved to serve as a molecular motor in Outer Hair Cells (OHCs) of the mammalian inner ear. The protein is piezoelectric-like, exhibiting voltage and tension sensitivity, with significant modulation by anions, chiefly intraCellular chloride. Receptor potentials of OHCs drive molecular conformational changes in prestin, as evidenced by voltage sensor charge movements, that evoke robust length changes in OHCs, thereby contributing to a mechanical feedback mechanism and, therefore, to cochlear amplification, which enhances our auditory sensitivity. Current research has been focused on tertiary structural determinations, prestin interactions with other proteins and membrane lipids, trafficking, and the mechanism of anion effects. One of the key remaining questions is the determination of structural changes induced by membrane voltage perturbations and how those changes result in forces exerted by the OHCs. Indeed, much remains to be understood about this extraordinary molecule.
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chloride and salicylate influence prestin dependent specific membrane capacitance support for the area motor model
Journal of Biological Chemistry, 2014Co-Authors: Joseph Santossacchi, Lei SongAbstract:The Outer Hair Cell is electromotile, its membrane motor identified as the protein SLC26a5 (prestin). An area motor model, based on two-state Boltzmann statistics, was developed about two decades ago and derives from the observation that Outer Hair Cell surface area is voltage-dependent. Indeed, aside from the nonlinear capacitance imparted by the voltage sensor charge movement of prestin, linear capacitance (Clin) also displays voltage dependence as motors move between expanded and compact states. Naturally, motor surface area changes alter membrane capacitance. Unit linear motor capacitance fluctuation (δCsa) is on the order of 140 zeptofarads. A recent three-state model of prestin provides an alternative view, suggesting that voltage-dependent linear capacitance changes are not real but only apparent because the two component Boltzmann functions shift their midpoint voltages (Vh) in opposite directions during treatment with salicylate, a known competitor of required chloride binding. We show here using manipulations of nonlinear capacitance with both salicylate and chloride that an enhanced area motor model, including augmented δCsa by salicylate, can accurately account for our novel findings. We also show that although the three-state model implicitly avoids measuring voltage-dependent motor capacitance, it registers δCsa effects as a byproduct of its assessment of Clin, which increases during salicylate treatment as motors are locked in the expanded state. The area motor model, in contrast, captures the characteristics of the voltage dependence of δCsa, leading to a better understanding of prestin.
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n terminal mediated homomultimerization of prestin the Outer Hair Cell motor protein
Biophysical Journal, 2005Co-Authors: Dhasakumar Navaratnam, Jun-ping Bai, Haresha Samaranayake, Joseph SantossacchiAbstract:The Outer Hair Cell lateral membrane motor, prestin, drives the Cell's mechanical response that underpins mammalian cochlear amplification. Little is known about the protein's structure-function relations. Here we provide evidence that prestin is a 10-transmembrane domain protein whose membrane topology differs from that of previous models. We also present evidence that both intraCellular termini of prestin are required for normal voltage sensing, with short truncations of either terminal resulting in absent or modified activity despite quantitative findings of normal membrane targeting. Finally, we show with fluorescence resonance energy transfer that prestin-prestin interactions are dependent on an intact N-terminus, suggesting that this terminus is important for homo-oligomerization of prestin. These domains, which we have perturbed, likely contribute to allosteric modulation of prestin via interactions among prestin molecules or possibly between prestin and other proteins, as well.
Peter Dallos - One of the best experts on this subject based on the ideXlab platform.
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prestin dependence of Outer Hair Cell survival and partial rescue of Outer Hair Cell loss in prestinv499g y501h knockin mice
PLOS ONE, 2015Co-Authors: Mary Ann Cheatham, Peter Dallos, Kazuaki Homma, Roxanne Edge, Emily L Leserman, Jing ZhengAbstract:A knockin (KI) mouse expressing mutated prestinV499G/Y501H (499 prestin) was created to study cochlear amplification. Recordings from isolated Outer Hair Cells (OHC) in this mutant showed vastly reduced electromotility and, as a consequence, reduced hearing sensitivity. Although 499 prestin OHCs were normal in stiffness and longer than OHCs lacking prestin, accelerated OHC death was unexpectedly observed relative to that documented in prestin knockout (KO) mice. These observations imply an additional role of prestin in OHC maintenance besides its known requirement for mammalian cochlear amplification. In order to gain mechanistic insights into prestin-associated OHC loss, we implemented several interventions to improve survival. First, 499 prestin KI’s were backcrossed to Bak KO mice, which lack the mitochondrial pro-apoptotic gene Bak. Because oxidative stress is implicated in OHC death, another group of 499 prestin KI mice was fed the antioxidant diet, Protandim. 499 KI mice were also backcrossed onto the FVB murine strain, which retains exCellent high-frequency hearing well into adulthood, to reduce the compounding effect of age-related hearing loss associated with the original 499 prestin KIs. Finally, a compound heterozygous (chet) mouse expressing one copy of 499 prestin and one copy of KO prestin was also created to reduce quantities of 499 prestin protein. Results show reduction in OHC death in chets, and in 499 prestin KIs on the FVB background, but only a slight improvement in OHC survival for mice receiving Protandim. We also report that improved OHC survival in 499 prestin KIs had little effect on hearing phenotype, reaffirming the original contention about the essential role of prestin’s motor function in cochlear amplification.
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prestin based Outer Hair Cell motility is necessary for mammalian cochlear amplification
Neuron, 2008Co-Authors: Peter Dallos, Jing Zheng, Xiang Wang, Shuping Jia, Mary Ann Cheatham, Jiangang Gao, Soma Sengupta, Charles T Anderson, Wendy H Y Cheng, Jian ZuoAbstract:Summary It is a central tenet of cochlear neurobiology that mammalian ears rely on a local, mechanical amplification process for their high sensitivity and sharp frequency selectivity. While it is generally agreed that Outer Hair Cells provide the amplification, two mechanisms have been proposed: stereociliary motility and somatic motility. The latter is driven by the motor protein prestin. Electrophysiological phenotyping of a prestin knockout mouse intimated that somatic motility is the amplifier. However, Outer Hair Cells of knockout mice have significantly altered mechanical properties, making this mouse model unsatisfactory. Here, we study a mouse model without alteration to Outer Hair Cell and organ of Corti mechanics or to mechanoelectric transduction, but with diminished prestin function. These animals have knockout-like behavior, demonstrating that prestin-based electromotility is required for cochlear amplification.
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intraCellular anions as the voltage sensor of prestin the Outer Hair Cell motor protein
Science, 2001Co-Authors: Dominik Oliver, Peter Dallos, Jost Ludwig, Nikolaj Klocker, Uwe Schulte, Siegfried Waldegger, J P Ruppersberg, Bernd FaklerAbstract:Outer Hair Cells (OHCs) of the mammalian cochlea actively change their Cell length in response to changes in membrane potential. This electromotility, thought to be the basis of cochlear amplification, is mediated by a voltage-sensitive motor molecule recently identified as the membrane protein prestin. Here, we show that voltage sensitivity is conferred to prestin by the intraCellular anions chloride and bicarbonate. Removal of these anions abolished fast voltage-dependent motility, as well as the characteristic nonlinear charge movement ("gating currents") driving the underlying structural rearrangements of the protein. The results support a model in which anions act as extrinsic voltage sensors, which bind to the prestin molecule and thus trigger the conformational changes required for motility of OHCs.
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effects of membrane potential and tension on prestin the Outer Hair Cell lateral membrane motor protein
The Journal of Physiology, 2001Co-Authors: Joseph Santossacchi, Jing Zheng, Weixing Shen, Peter DallosAbstract:1. Under whole-Cell voltage clamp, the effects of initial voltage conditions and membrane tension on gating charge and voltage-dependent capacitance were studied in human embryonic kidney Cells (TSA201 Cell line) transiently transfected with the gene encoding the gerbil protein prestin. Conformational changes in this membrane-bound protein probably provide the molecular basis of the Outer Hair Cell (OHC) voltage-driven mechanical activity, which spans the audio spectrum. 2. Boltzmann characteristics of the charge movement in transfected Cells were similar to those reported for OHCs (Q(max) = 0.99 +/- 0.16 pC, z = 0.88 +/- 0.02; n = 5, means +/- S.E.M.). Unlike that of the adult OHC, the voltage at peak capacitance (V(pkcm)) was very negative (-74.7 +/- 3.8 mV). Linear capacitance in transfected Cells was 43.7 +/- 13.8 pF and membrane resistance was 458 +/- 123 Mohms. 3. Voltage steps from the holding potential preceding the measurement of capacitance-voltage functions caused a time- and voltage-dependent shift in V(pkcm). For a prepulse to -150 mV, from a holding potential of 0 mV, V(pkcm) shifted 6.4 mV, and was fitted by a single exponential time constant of 45 ms. A higher resolution analysis of this time course was made by measuring the change in capacitance during a fixed voltage step and indicated a double exponential shift (tau(0) = 51.6 ms, tau(1) = 8.5 s) similar to that of the native gerbil OHC. 4. Membrane tension, delivered by increasing pipette pressure, caused a positive shift in V(pkcm). A maximal shift of 7.5 mV was obtained with 2 kPa of pressure. The effect was reversible. 5. Our results show that the sensitivity of prestin to initial voltage and membrane tension, though present, is less than that observed in adult OHCs. It remains possible that some other interacting molecular species within the lateral plasma membrane of the native OHC amplifies the effect of tension and prior voltage on prestin's activity.
Jing Zheng - One of the best experts on this subject based on the ideXlab platform.
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the r130s mutation significantly affects the function of prestin the Outer Hair Cell motor protein
Journal of Molecular Medicine, 2016Co-Authors: Satoe Takahashi, Jing Zheng, Mary Ann Cheatham, Kazuaki HommaAbstract:A missense mutation, R130S, was recently found in the prestin gene, SLC26A5, of patients with moderate to severe hearing loss (DFNB61). In order to define the pathology of hearing loss associated with this missense mutation, a recombinant prestin construct harboring the R130S mutation (R130S-prestin) was generated, and its functional consequences examined in a heterologous expression system. We found that R130S-prestin targets the plasma membrane but less efficiently compared to wild-type. The voltage operating point and voltage sensitivity of the motor function of R130S-prestin were similar to wild-type prestin. However, the motor activity of R130S-prestin is greatly reduced at higher voltage stimulus frequencies, indicating a reduction in motor kinetics. Our study thus provides experimental evidence that supports a causal relationship between the R130S mutation in the prestin gene and hearing loss found in patients with this missense mutation.
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prestin dependence of Outer Hair Cell survival and partial rescue of Outer Hair Cell loss in prestinv499g y501h knockin mice
PLOS ONE, 2015Co-Authors: Mary Ann Cheatham, Peter Dallos, Kazuaki Homma, Roxanne Edge, Emily L Leserman, Jing ZhengAbstract:A knockin (KI) mouse expressing mutated prestinV499G/Y501H (499 prestin) was created to study cochlear amplification. Recordings from isolated Outer Hair Cells (OHC) in this mutant showed vastly reduced electromotility and, as a consequence, reduced hearing sensitivity. Although 499 prestin OHCs were normal in stiffness and longer than OHCs lacking prestin, accelerated OHC death was unexpectedly observed relative to that documented in prestin knockout (KO) mice. These observations imply an additional role of prestin in OHC maintenance besides its known requirement for mammalian cochlear amplification. In order to gain mechanistic insights into prestin-associated OHC loss, we implemented several interventions to improve survival. First, 499 prestin KI’s were backcrossed to Bak KO mice, which lack the mitochondrial pro-apoptotic gene Bak. Because oxidative stress is implicated in OHC death, another group of 499 prestin KI mice was fed the antioxidant diet, Protandim. 499 KI mice were also backcrossed onto the FVB murine strain, which retains exCellent high-frequency hearing well into adulthood, to reduce the compounding effect of age-related hearing loss associated with the original 499 prestin KIs. Finally, a compound heterozygous (chet) mouse expressing one copy of 499 prestin and one copy of KO prestin was also created to reduce quantities of 499 prestin protein. Results show reduction in OHC death in chets, and in 499 prestin KIs on the FVB background, but only a slight improvement in OHC survival for mice receiving Protandim. We also report that improved OHC survival in 499 prestin KIs had little effect on hearing phenotype, reaffirming the original contention about the essential role of prestin’s motor function in cochlear amplification.
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prestin based Outer Hair Cell motility is necessary for mammalian cochlear amplification
Neuron, 2008Co-Authors: Peter Dallos, Jing Zheng, Xiang Wang, Shuping Jia, Mary Ann Cheatham, Jiangang Gao, Soma Sengupta, Charles T Anderson, Wendy H Y Cheng, Jian ZuoAbstract:Summary It is a central tenet of cochlear neurobiology that mammalian ears rely on a local, mechanical amplification process for their high sensitivity and sharp frequency selectivity. While it is generally agreed that Outer Hair Cells provide the amplification, two mechanisms have been proposed: stereociliary motility and somatic motility. The latter is driven by the motor protein prestin. Electrophysiological phenotyping of a prestin knockout mouse intimated that somatic motility is the amplifier. However, Outer Hair Cells of knockout mice have significantly altered mechanical properties, making this mouse model unsatisfactory. Here, we study a mouse model without alteration to Outer Hair Cell and organ of Corti mechanics or to mechanoelectric transduction, but with diminished prestin function. These animals have knockout-like behavior, demonstrating that prestin-based electromotility is required for cochlear amplification.
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effects of membrane potential and tension on prestin the Outer Hair Cell lateral membrane motor protein
The Journal of Physiology, 2001Co-Authors: Joseph Santossacchi, Jing Zheng, Weixing Shen, Peter DallosAbstract:1. Under whole-Cell voltage clamp, the effects of initial voltage conditions and membrane tension on gating charge and voltage-dependent capacitance were studied in human embryonic kidney Cells (TSA201 Cell line) transiently transfected with the gene encoding the gerbil protein prestin. Conformational changes in this membrane-bound protein probably provide the molecular basis of the Outer Hair Cell (OHC) voltage-driven mechanical activity, which spans the audio spectrum. 2. Boltzmann characteristics of the charge movement in transfected Cells were similar to those reported for OHCs (Q(max) = 0.99 +/- 0.16 pC, z = 0.88 +/- 0.02; n = 5, means +/- S.E.M.). Unlike that of the adult OHC, the voltage at peak capacitance (V(pkcm)) was very negative (-74.7 +/- 3.8 mV). Linear capacitance in transfected Cells was 43.7 +/- 13.8 pF and membrane resistance was 458 +/- 123 Mohms. 3. Voltage steps from the holding potential preceding the measurement of capacitance-voltage functions caused a time- and voltage-dependent shift in V(pkcm). For a prepulse to -150 mV, from a holding potential of 0 mV, V(pkcm) shifted 6.4 mV, and was fitted by a single exponential time constant of 45 ms. A higher resolution analysis of this time course was made by measuring the change in capacitance during a fixed voltage step and indicated a double exponential shift (tau(0) = 51.6 ms, tau(1) = 8.5 s) similar to that of the native gerbil OHC. 4. Membrane tension, delivered by increasing pipette pressure, caused a positive shift in V(pkcm). A maximal shift of 7.5 mV was obtained with 2 kPa of pressure. The effect was reversible. 5. Our results show that the sensitivity of prestin to initial voltage and membrane tension, though present, is less than that observed in adult OHCs. It remains possible that some other interacting molecular species within the lateral plasma membrane of the native OHC amplifies the effect of tension and prior voltage on prestin's activity.
