Plasma membrane Ca2+-ATPase isoform 2a is the PMCA of hair bundles
Plasma membrane Ca2+-ATPase isoform 2a is the PMCA of hair bundles
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DOI：
10.1523/jneurosci.21-14-05066.2001
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发表时间：
2001-07-15
影响因子：
5.3
通讯作者：
Gillespie, PG
中科院分区：
文献类型：
--
作者：
Dumont, RA;Lins, U;Gillespie, PG
毛细胞的机电转导通道允许相当数量的Ca2+进入，Ca2+调节适应并触发毛束的机械活动。大多数进入转导通道的Ca2+是由质膜Ca2+- atp酶（PMCA）挤出的，PMCA是一种Ca2+泵，高度集中在毛束中，可能是正常毛细胞功能所必需的。由于PMCA同工酶和剪接形式的调节不同，具有不同的生化特性，我们确定了青蛙和大鼠毛细胞中毛束PMCA的同一性。通过筛选牛蛙囊性cDNA文库，鉴定出丰富的PMCA1b和PMCA2a克隆，以及罕见的PMCA2b和PMCA2c克隆。通过免疫细胞化学和免疫沉淀实验，我们在牛蛙小囊中发现PMCA1b是毛细胞和支持细胞基底外膜的主要同工酶，PMCA2a是唯一存在于毛束中的PMCA。这种PMCA1和PMCA2同工酶的完全分离适用于大鼠听觉和前庭毛细胞；PMCA2a是外毛细胞和前庭毛细胞毛束中唯一的PMCA亚型，是内毛细胞毛束中主要的PMCA亚型。我们的数据表明，毛细胞通过靶向特定的PMCA同工酶到不同的亚细胞位置来控制质膜Ca2+泵送活性。因为PMCA2a是唯一的Ca2+泵存在于相当水平的毛束，该泵的生化特性必须充分说明跨膜Ca2+泵在束的生理特征。
Mechanoelectrical transduction channels of hair cells allow for the entry of appreciable amounts of Ca2+, which regulates adaptation and triggers the mechanical activity of hair bundles. Most Ca2+ that enters transduction channels is extruded by the plasma membrane Ca2+-ATPase (PMCA), a Ca2+ pump that is highly concentrated in hair bundles and may be essential for normal hair cell function. Because PMCA isozymes and splice forms are regulated differentially and have distinct biochemical properties, we determined the identity of hair bundle PMCA in frog and rat hair cells. By screening a bullfrog saccular cDNA library, we identified abundant PMCA1b and PMCA2a clones as well as rare PMCA2b and PMCA2c clones. Using immunocytochemistry and immunoprecipitation experiments, we showed in bullfrog sacculus that PMCA1b is the major isozyme of hair cell and supporting cell basolateral membranes and that PMCA2a is the only PMCA present in hair bundles. This complete segregation of PMCA1 and PMCA2 isozymes holds for rat auditory and vestibular hair cells; PMCA2a is the only PMCA isoform in hair bundles of outer hair cells and vestibular hair cells and is the predominant PMCA of hair bundles of inner hair cells. Our data suggest that hair cells control plasma membrane Ca2+-pumping activity by targeting specific PMCA isozymes to distinct subcellular locations. Because PMCA2a is the only Ca2+ pump present at appreciable levels in hair bundles, the biochemical properties of this pump must account fully for the physiological features of transmembrane Ca2+ pumping in bundles.