Duncan R K, Fuchs P A
Department of Otolaryngology: Head and Neck Surgery, Johns Hopkins University, 521 Traylor Building, 720 Rutland Avenue, Baltimore, MD 21205, USA.
J Physiol. 2003 Mar 1;547(Pt 2):357-71. doi: 10.1113/jphysiol.2002.029785. Epub 2003 Jan 17.
The mechanism for electrical tuning in non-mammalian hair cells rests within the widely diverse kinetics of functionally distinct, large-conductance potassium channels (BK), thought to result from alternative splicing of the pore-forming alpha subunit and variable co-expression with an accessory beta subunit. Inside-out patches from hair cells along the chicken basilar papilla revealed 'tonotopic' gradations in calcium sensitivity and deactivation kinetics. The resonant frequency for the hair cell from which the patch was taken was estimated from deactivation rates, and this frequency reasonably matched that predicted from the originating cell's tonotopic location. The rates of deactivation for native BK channels were much faster than rates reported for cloned chicken BK channels including both alpha and beta subunits. This result was surprising since patches were pulled from hair cells in the apical half of the papilla where beta subunits are most highly expressed. Heterogeneity in the properties of native chicken BK channels implies a high degree of molecular variation and hinders our ability to identify those molecular constituents.
非哺乳动物毛细胞电调谐的机制在于功能各异的大电导钾通道（BK）具有广泛多样的动力学特性，这被认为是由孔形成α亚基的可变剪接以及与辅助β亚基的可变共表达所致。沿鸡基底乳头的毛细胞进行的内面向外膜片钳记录显示，钙敏感性和失活动力学存在“音频拓扑”梯度。根据失活速率估算了进行膜片钳记录的毛细胞的共振频率，该频率与根据起源细胞的音频拓扑位置预测的频率合理匹配。天然BK通道的失活速率比报道的包括α和β亚基的克隆鸡BK通道的失活速率快得多。这一结果令人惊讶，因为膜片是从乳头顶端一半的毛细胞中获取的，而此处β亚基表达最为丰富。天然鸡BK通道特性的异质性意味着分子变异程度很高，阻碍了我们识别这些分子成分的能力。
