目的：探讨水杨酸对prestin正常表达小鼠耳蜗声损伤作用。方法：以出生18～30d的雄性C57BL／6小鼠为研究对象，分为3组（水杨酸＋噪声；0．9％氯化钠＋噪声；单纯水杨酸）。给予中心频率为8kHz强度为110 dB SPL的1／3倍频程噪声暴露3h...目的：探讨水杨酸对prestin正常表达小鼠耳蜗声损伤作用。方法：以出生18～30d的雄性C57BL／6小鼠为研究对象，分为3组（水杨酸＋噪声；0．9％氯化钠＋噪声；单纯水杨酸）。给予中心频率为8kHz强度为110 dB SPL的1／3倍频程噪声暴露3h。以听诱发脑干反应、扫描和透射电镜方法比较有、无水杨酸干预情况下小鼠耳蜗听力及形态损伤程度。用荧光定量PCR方法比较两组小鼠耳蜗prestinmRNA总量的变化情况。结果：噪声暴露后第1天，水杨酸干预组的ABR闽移较0．9％氯化钠组减少27dBSPL；第10天减少17dBSPL。水杨酸提前干预使耳蜗的噪声损伤后扫描电镜和透射电镜上外毛细胞及支持细胞损伤减轻。在噪声暴露后第10天，水杨酸组prestinmRNA总量较0．9％氯化钠组及噪声暴露前均升高。结论：水杨酸提前干预可以显著减轻prestin正常表达小鼠耳蜗的噪声损伤；水杨酸干预可能会导致外毛细胞马达蛋白prestin表达上升。展开更多
The electrically evoked somatic motility of outer hair cells （OHC）, briefly termed OHC electromotility, plays a crucial role in cochlear amplification that underlies the remarkably high sensitivity and frequency sel...The electrically evoked somatic motility of outer hair cells （OHC）, briefly termed OHC electromotility, plays a crucial role in cochlear amplification that underlies the remarkably high sensitivity and frequency selectivity of the mammalian hearing. Accompanying OHC electromotility is a voltage-dependent gating charge movement within the cell lateral membrane, manifested as a measurable nonlinear capacitance （NLC） in OHCs. The electromotility and NLC of OHCs are highly correlated by sharing a common molecular substrate, the motor protein prestin. In this study, we systematically characterized the quantitative relationship between OHC electromotility and NLC in their voltage dependences for the purpose of further understanding the electromechanical transduction in OHCs. The results demonstrated that the two possess differing voltage dependences with the V^2 of electromotility consistently being -20 mV depolarized in comparison with that of NLC although their slope factors a are statistically identical. Further investigations showed that the initial state of OHCs influences the voltage dependence of electromotility but not that of NLC, indicating that some biophysical factors other than the motor protein per se are involved in the process of OHC length changes. We proposed that the cytoskeletal spectrin-actin framework underneath the OHC plasma membrane and the cell＇ s turgor are the two most probable factors that cause the voltage-dependence discrepancy between OHC electromotility and NLC.展开更多
Prestin is the motor protein of cochlear outer hair cells （OHCs）. It is able to perform rapid and reciprocal electromechanical conversion that underlies OHC electromotility. Due to the inadequate size of a single pr...Prestin is the motor protein of cochlear outer hair cells （OHCs）. It is able to perform rapid and reciprocal electromechanical conversion that underlies OHC electromotility. Due to the inadequate size of a single prestin molecule to form the2 nm intramembraneous protein particles （IMPs） in the OHC lateral membrane （LM）, the possibility of prestin oligomerization has been proposed. It has been suggested that prestin molecules form highorder oligomers, most likely as the tetramer, in heterologous systems. In OHCs, however, the oligomeric structure of prestin remains unclear. Here we calculated the prestin-related charge density in both gerbil and guinea pig OHCs through measuring their nonlinear capacitance （NLC） and LM surface area, showing that the average charge density （22, 608 μm-2 in gerbils; 19, 460 μm-2 in guinea pigs） is statistically 4 times the average density of IMPs （5,686 μm-2 in gerbils; 5, 000 μm-2 in guinea pigs）. This suggests that each IMP contains four prestin molecules based upon the notion that each prestin transfers a single elementary charge, implying that prestin forms tetramers in OHCs. To determine whether the prestin tetramer functions as a mechanical unit, we subsequently compared the slope factors （α） of electromotility and NLC simultaneously measured from the same OHC, showing that the α values of the two are statistically the same. This suggests that each prestin molecule in the tetramer is mechanically independent and equally contributes to OHC electromotility.展开更多
文摘目的：探讨水杨酸对prestin正常表达小鼠耳蜗声损伤作用。方法：以出生18～30d的雄性C57BL／6小鼠为研究对象，分为3组（水杨酸＋噪声；0．9％氯化钠＋噪声；单纯水杨酸）。给予中心频率为8kHz强度为110 dB SPL的1／3倍频程噪声暴露3h。以听诱发脑干反应、扫描和透射电镜方法比较有、无水杨酸干预情况下小鼠耳蜗听力及形态损伤程度。用荧光定量PCR方法比较两组小鼠耳蜗prestinmRNA总量的变化情况。结果：噪声暴露后第1天，水杨酸干预组的ABR闽移较0．9％氯化钠组减少27dBSPL；第10天减少17dBSPL。水杨酸提前干预使耳蜗的噪声损伤后扫描电镜和透射电镜上外毛细胞及支持细胞损伤减轻。在噪声暴露后第10天，水杨酸组prestinmRNA总量较0．9％氯化钠组及噪声暴露前均升高。结论：水杨酸提前干预可以显著减轻prestin正常表达小鼠耳蜗的噪声损伤；水杨酸干预可能会导致外毛细胞马达蛋白prestin表达上升。
文摘The electrically evoked somatic motility of outer hair cells （OHC）, briefly termed OHC electromotility, plays a crucial role in cochlear amplification that underlies the remarkably high sensitivity and frequency selectivity of the mammalian hearing. Accompanying OHC electromotility is a voltage-dependent gating charge movement within the cell lateral membrane, manifested as a measurable nonlinear capacitance （NLC） in OHCs. The electromotility and NLC of OHCs are highly correlated by sharing a common molecular substrate, the motor protein prestin. In this study, we systematically characterized the quantitative relationship between OHC electromotility and NLC in their voltage dependences for the purpose of further understanding the electromechanical transduction in OHCs. The results demonstrated that the two possess differing voltage dependences with the V^2 of electromotility consistently being -20 mV depolarized in comparison with that of NLC although their slope factors a are statistically identical. Further investigations showed that the initial state of OHCs influences the voltage dependence of electromotility but not that of NLC, indicating that some biophysical factors other than the motor protein per se are involved in the process of OHC length changes. We proposed that the cytoskeletal spectrin-actin framework underneath the OHC plasma membrane and the cell＇ s turgor are the two most probable factors that cause the voltage-dependence discrepancy between OHC electromotility and NLC.
基金supported by an NIDCD grant (R01DC004696) to DHby National Natural Science Foundation of China grants 30871398, 30730040 and 30628030 to SY and DHsupported bygrant number G20RR024001 from the National Center for Research Resources
文摘Prestin is the motor protein of cochlear outer hair cells （OHCs）. It is able to perform rapid and reciprocal electromechanical conversion that underlies OHC electromotility. Due to the inadequate size of a single prestin molecule to form the2 nm intramembraneous protein particles （IMPs） in the OHC lateral membrane （LM）, the possibility of prestin oligomerization has been proposed. It has been suggested that prestin molecules form highorder oligomers, most likely as the tetramer, in heterologous systems. In OHCs, however, the oligomeric structure of prestin remains unclear. Here we calculated the prestin-related charge density in both gerbil and guinea pig OHCs through measuring their nonlinear capacitance （NLC） and LM surface area, showing that the average charge density （22, 608 μm-2 in gerbils; 19, 460 μm-2 in guinea pigs） is statistically 4 times the average density of IMPs （5,686 μm-2 in gerbils; 5, 000 μm-2 in guinea pigs）. This suggests that each IMP contains four prestin molecules based upon the notion that each prestin transfers a single elementary charge, implying that prestin forms tetramers in OHCs. To determine whether the prestin tetramer functions as a mechanical unit, we subsequently compared the slope factors （α） of electromotility and NLC simultaneously measured from the same OHC, showing that the α values of the two are statistically the same. This suggests that each prestin molecule in the tetramer is mechanically independent and equally contributes to OHC electromotility.
