Membrane tension directly shifts voltage dependence of outer hair cell motility and associated gating charge

Kakehata, Seiji; Santos‐Sacchi, Joseph

doi:10.1016/s0006-3495(95)80401-7

Cited by 184 publications

(227 citation statements)

References 43 publications

(74 reference statements)

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“…In addition, a positional shift of the voltage peak value (V pk C m ) indicates the existence of indirect effects (i.e. changes in cell turgor) that modify the operating point of the motors (27)(28)(29)(30). In a first series of experiments, we found that up to 30 min of incubation of isolated OHCs with Y-27632 did not induce significant changes in either C m or V pk C m (data not shown).…”

Section: Expression Of Rock and Adducin In The Guineamentioning

confidence: 99%

ROCK-dependent and ROCK-independent Control of Cochlear Outer Hair Cell Electromotility

Zhang

Kalinec

Urrutia

et al. 2003

Journal of Biological Chemistry

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Outer hair cell electromotility is crucial for the proper function of the cochlear amplifier, the active process that enhances sensitivity and frequency discrimination of the mammalian ear. Previous work (Kalinec, F., Zhang, M., Urrutia, R., and Kalinec, G. (2000) J. Biol. Chem. 275, 28000 -28005) has suggested a role for Rho GTPases in the regulation of outer hair cell electromotility, although the signaling pathways mediated by these enzymes remain to be established. Here we have investigated the cellular and molecular mechanisms underlying the homeostatic regulation of the electromotile response of guinea pig outer hair cells. Our findings defined a ROCK-mediated signaling cascade that continuously modulates outer hair cell electromotility by selectively targeting the cytoskeleton. A distinct ROCKindependent pathway functions as a fast resetting mechanism for this system. Neither pathway affects the function of prestin, the unique molecular motor of outer hair cells. These results extend our understanding of a basic mechanism of both normal human hearing and deafness, revealing the key role of the cytoskeleton in the regulation of outer hair cell electromotility and suggesting ROCK as a molecular target for modulating the function of the cochlear amplifier. Cochlear outer hair cells (OHCs)1 undergo reversible changes in length when electrically stimulated. This electromotile response results from a membrane-based force generator mechanism associated with conformational changes and rearrangement of a voltage-sensitive integral membrane protein (1). The OHC motor protein has been recently identified as a novel anion transporter (SLC26A5-prestin) (2), with voltage sensitivity conferred by the intracellular anions chloride and bicarbonate (Ref. 3; reviewed in Ref. 4). The vectorial component to the forces generated in the OHC plasma membrane is provided by the cortical cytoskeleton, an actin-spectrin meshwork placed immediately underneath the plasma membrane and connected to it through thousands of 25-nm-long rod-like structures (pillars) (5, 6).It has been recently demonstrated that OHC electromotility is necessary for the correct work of the cochlear amplifier, the active process that enhances sensitivity and frequency discrimination of the mammalian ear (7). Cochlear amplification is maximal at low signal levels (ϳ0 -5-db sound pressure level), decreases proportionally to increases in signal intensity, and becomes inhibited at sounds of ϳ80 db (4, 8). This "automatic gain control" is crucial for extending the dynamic range of the auditory system because it provides the cochlea with the ability to amplify very faint sounds and to process the loudest without suffering permanent damage (9). The direct association between cochlear amplification and OHC electromotility suggests that this gain control may be provided by the modulation of the OHC electromotile response.OHCs must undergo continuous mechanical changes to optimize the sensitivity and frequency selectivity of the cochlea (10 -13). We used the term "mecha...

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Section: Expression Of Rock and Adducin In The Guineamentioning

confidence: 99%

ROCK-dependent and ROCK-independent Control of Cochlear Outer Hair Cell Electromotility

Zhang

Kalinec

Urrutia

et al. 2003

Journal of Biological Chemistry

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“…The effects of MβCD application on capacitance are quite similar to those of increasing the membrane tension [17]. This similarity suggests that depleting cholesterol may decrease the rigidity of both plasma membrane and cortical lattice, resulting in increase of tension in the less rigid plasma membrane.…”

Section: Discussionmentioning

confidence: 62%

“…Huang et al indicated that cell shape change caused by intracellular trypsin treatment itself did not affect the NLC [15]. Kakehata et al also demonstrated that the OHCs treated by trypsin showed no change of C mpeak and V cmpeak in constant pressure [17]. However, based on these results, the dramatic effects of MβCD on OHCs are difficult to explain only by the membrane tension change.…”

Section: Discussionmentioning

confidence: 99%

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Effects of cholesterol alterations are mediated via G-protein-related pathways in outer hair cells

Nagaki

Kakehata

Kitani

et al. 2013

Pflugers Arch - Eur J Physiol

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Cholesterol is an essential component of cell membranes, and determines their rigidity and fluidity. Alterations in membrane cholesterol by MβCD or water-soluble cholesterol affect the stiffness, capacitance, motility, and cell length of outer hair cells (OHCs). This suggests that reconstruction of the cytoskeleton may be induced by cholesterol alterations. In this study, we investigated intracellular signaling pathways involving G proteins to determine whether they modulate the changes in voltage-dependent capacitance caused by cholesterol alterations. Membrane capacitance of isolated guinea pig OHCs were assessed using a two-sine voltage stimulus protocol superimposed onto a voltage ramp (200 ms duration) from −150 to +140 mV. One group of OHCs was treated with 100 μM guanosine 5′-O-(3-thiotriphosphate) tetralithium salt (GTPγS), the GTP analog, administrated into individual cells via patch pipettes. Another group of OHCs was internally perfused with 600 μM guanosine 5′-(β-thio) diphosphate trilithium salt (GDPβS), the GDP analog. A third group was perfused with internal solution only as a control. Application of 1 mM MβCD shifted non-linear capacitance curves to the depolarized direction of the control group with reduction of the peak capacitance (C mpeak ). After the 10-min application of MβCD, shifts of voltage at C mpeak (V cmpeak ) and reduction of C mpeak were 73.32±11.09 mV and 9.09±2.10 pF, respectively (n=4). On the other hand, in the GTPγS-treated group, the shift of V cmpeak and reduction of C mpeak were attenuated remarkably. The shift of V cmpeak and reduction of C mpeak in the 10-min application of MβCD were 9.73± 10.92 mV and 3.08±1.91 pF, respectively (n=7). MβCD decreased the cell length by 16.53±4.27 % in the control group and by 6.45±6.22 % in the GTPγS group. In addition, we investigated the effects of GDPβS on cholesteroltreated OHCs. One millimolar cholesterol was externally applied after the 4-min application of 1 mM MβCD because the shift of V-C m function caused by cholesterol alone was small. Application of cholesterol shifted V-C m curves of the control group to the hyperpolarized direction with increase of the C mpeak . After the 10-min application of cholesterol, changes of V cmpeak and C mpeak were −9.19±6.68 mV and 2.14±0.44 pF, respectively (n=4). On the other hand, in the GDPβS-treated OHCs, the shift of V cmpeak and increase of C mpeak were attenuated markedly. The shift of V cmpeak and increase of C mpeak after 10 min were 5.13±10.46 mV and −0.55±1.39 pF, respectively (n=6). This study demonstrated that internally perfused GTPγS inhibited the MβCD effects and GDPβS inhibited the cholesterol effects, raising the possibility that G proteins may be involved in outer hair cell homeostasis as well as the possibility that cholesterol response may be G protein mediated. More study is required to clarify the detailed role of G proteins in the relation between cholesterol and the OHC cytoskeleton.

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“…For example, it is possible that HDAd-prestin-GFP alters cell turgor and shifts the voltage dependence of the nonlinear capacitance (Chertoff and Brownell 1994;Kakehata and Santos-Sacchi 1995;Oghalai et al 2000). Based on the transduction pattern, it is possible that trauma enhances the ability of HDAd to infect a cell.…”

Section: Discussionmentioning

confidence: 99%

Functional Prestin Transduction of Immature Outer Hair Cells from Normal and Prestin-Null Mice

Xia

Wooltorton

Palmer

et al. 2008

JARO

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Prestin is a membrane protein in the outer hair cell (OHC) that has been shown to be essential for electromotility. OHCs from prestin-null mice do not express prestin, do not have a nonlinear capacitance (the electrical signature of electromotility), and are smaller in size than wild-type OHCs. We sought to determine whether prestin-null OHCs can be transduced to incorporate functional prestin protein in a normal fashion. A recombinant helper-dependent adenovirus expressing prestin and green fluorescent protein (HDAd-prestin-GFP) was created and tested in human embryonic kidney cells (HEK cells). Transduced HEK cells demonstrated membrane expression of prestin and nonlinear capacitance. HDAd-prestin-GFP was then applied to cochlear sensory epithelium explants harvested from wild-type and prestin-null mice at postnatal days 2-3, the age at which native prestin is just beginning to become functional in wildtype mice. At postnatal days 4-5, we investigated transduced OHCs for (1) their prestin expression pattern as revealed by immunofluorescence; (2) their cell surface area as measured by linear capacitance; and (3) their prestin function as indicated by nonlinear capacitance. HDAd-prestin-GFP efficiently transduced OHCs of both genotypes and prestin protein localized to the plasma membrane. Whole-cell voltage clamp studies revealed a nonlinear capacitance in transduced wild-type and prestin-null OHCs, but not in non-transduced cells of either genotype. Prestin transduction did not increase the linear capacitance (cell surface area) for either genotype. In peak nonlinear capacitance, voltage at peak nonlinear capacitance, charge density of the nonlinear capacitance, and shape of the voltage-capacitance curves, the transduced cells of the two genotypes resembled each other and previously reported data from adult wildtype mouse OHCs. Thus, prestin introduced into prestin-deficient OHCs segregates normally to the cell membrane and generates a normal nonlinear capacitance, indicative of normal prestin function.

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Membrane tension directly shifts voltage dependence of outer hair cell motility and associated gating charge

Cited by 184 publications

References 43 publications

ROCK-dependent and ROCK-independent Control of Cochlear Outer Hair Cell Electromotility

ROCK-dependent and ROCK-independent Control of Cochlear Outer Hair Cell Electromotility

Effects of cholesterol alterations are mediated via G-protein-related pathways in outer hair cells

Functional Prestin Transduction of Immature Outer Hair Cells from Normal and Prestin-Null Mice

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