The Cav3.1 T-type Ca2+ channel contributes to voltage-dependent calcium currents in rat outer hair cells
The Cav3.1 T-type Ca2+ channel contributes to voltage-dependent calcium currents in rat outer hair cells
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DOI：
10.1016/j.brainres.2008.01.058
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发表时间：
2008-03-27
期刊：
影响因子：
2.9
通讯作者：
Shimada, Shoichi
中科院分区：
文献类型：
--
作者：
Inagaki, Akira;Ugawa, Shinya;Shimada, Shoichi
哺乳动物外毛细胞（OHCs）中通过电压依赖性Ca2+通道（VDCCs）的钙电流通常被认为具有l型（二氢吡啶敏感）电流的药理学特性。然而，OHCs的低静息电位及其在声音刺激下的轻微去极化表明，低电压激活通道可能有助于Ca（2+）调节。我们提出了在成熟大鼠OHCs中存在Ca(v)3.1 t型Ca（2+）通道的形态学和电生理证据，这是一种低压激活的Ca（2+）通道。PCR实验显示Ca(v)3.1在成熟大鼠耳蜗中表达，Ca(v)3.2和Ca(v)3.3在成熟大鼠耳蜗中不表达。原位杂交和免疫组化结果显示，Cav3.1在毛细胞的mRNA水平上均有表达，而在蛋白水平上仅在OHCs中表达。抗ca (v)3.1抗体的Western blot分析显示成熟大鼠耳蜗裂解液中存在242 kDa的条带。膜片钳记录听力开始后从大鼠耳蜗分离的OHCs显示，与-70 mV保持电位相比，在-100 mV保持电位下，全细胞电压依赖性Ca2+电流在去极化步骤中显着增加。只有-100 mV的电流表现出明显的瞬态内向Ca2+电流，并且该瞬态成分被1 μ M的t型特异性拮抗剂mibefradil有效阻断。我们的数据表明Ca(v)3.1参与成熟OHCs细胞内Ca（2+）的调节。(C) 2008 Elsevier B.V.版权所有
Calcium currents through voltage-dependent Ca2+ channels (VDCCs) in mammalian outer hair cells (OHCs) are generally considered to possess the pharmacological properties of L-type (dihydropyridine-sensitive) currents. However, the OHCs' low resting potentials and their slight depolarization upon sound stimuli suggest that the low voltage-activated channels may contribute to Ca(2+)regulation. We present morphological and electrophysiological evidence for the presence of the Ca(v)3.1 T-type Ca(2+)channels, one of the low voltage-activated Ca(2+)channels, in mature rat OHCs. PCR experiments revealed the expression of Ca(v)3.1, but not Ca(v)3.2 or Ca(v)3.3, in the mature rat cochlea. In situ hybridization and immunohistochemistry revealed expression of Cav3.1 in both inner and outer hair cells at the mRNA level, but only in the OHCs at the protein level. Western blot analysis of anti-Ca(v)3.1 antibody showed a 242 kDa band in mature rat cochlear lysates. Patch-clamp recordings of OHCs isolated from rat cochleae after the onset of hearing revealed that whole-cell voltage-dependent Ca2+ currents were significantly increased in depolarizing steps from a holding potential of -100 mV when compared with those from -70 mV. Only the currents from -100 mV manifested a distinct transient inward Ca2+ current, and this transient component was effectively blocked by 1 mu M of the T-type-specific antagonist, mibefradil. Our data suggest an involvement of Ca(v)3.1 in intracellular Ca(2+)regulation in mature OHCs. (C) 2008 Elsevier B.V. All rights reserved.