Department of Life Sciences, University of Seoul, Seoul, Korea.
PLoS One. 2010 Jun 8;5(6):e11012. doi: 10.1371/journal.pone.0011012.
A TRPN channel protein is essential for sensory transduction in insect mechanosensory neurons and in vertebrate hair cells. The Drosophila TRPN homolog, NOMPC, is required to generate mechanoreceptor potentials and currents in tactile bristles. NOMPC is also required, together with a TRPV channel, for transduction by chordotonal neurons of the fly's antennal ear, but the TRPN or TRPV channels have distinct roles in transduction and in regulating active antennal mechanics. The evidence suggests that NOMPC is a primary mechanotransducer channel, but its subcellular location-key for understanding its exact role in transduction-has not yet been established.
METHODOLOGY/PRINCIPAL FINDINGS: Here, by immunostaining, we locate NOMPC at the tips of mechanosensory cilia in both external and chordotonal sensory neurons, as predicted for a mechanotransducer channel. In chordotonal neurons, the TRPN and TRPV channels are respectively segregated into distal and proximal ciliary zones. This zonal separation is demarcated by and requires the ciliary dilation, an intraciliary assembly of intraflagellar transport (IFT) proteins.
Our results provide a strong evidence for NOMPC as a primary transduction channel in Drosophila mechansensory organs. The data also reveals a structural basis for the model of auditory chordotonal transduction in which the TRPN and TRPV channels play sequential roles in generating and amplifying the receptor potential, but have opposing roles in regulating active ciliary motility.
TRPN 通道蛋白对于昆虫机械感觉神经元和脊椎动物毛细胞中的感觉转导至关重要。果蝇的 TRPN 同源物，NOMPC，对于在触须刚毛中产生机械感受器电位和电流是必需的。NOMPC 还与 TRPV 通道一起，对于蝇触角的听弦神经元的转导是必需的，但是 TRPN 或 TRPV 通道在转导和调节活跃的触角力学方面具有不同的作用。有证据表明，NOMPC 是一种主要的机械感受器通道，但其亚细胞位置——对于理解其在转导中的确切作用至关重要——尚未确定。
方法/主要发现：在这里，通过免疫染色，我们将 NOMPC 定位在外部和听弦感觉神经元的机械感受器纤毛的尖端，这与机械感受器通道的预测相符。在听弦神经元中，TRPN 和 TRPV 通道分别分离到纤毛的远端和近端区域。这种区域分离由纤毛扩张来划定，纤毛扩张是内鞭毛运输（IFT）蛋白的细胞内组装。
我们的结果为 NOMPC 作为果蝇机械感觉器官中的主要转导通道提供了强有力的证据。该数据还揭示了听觉听弦转导模型的结构基础，其中 TRPN 和 TRPV 通道在产生和放大感受器电位方面发挥顺序作用，但在调节活跃的纤毛运动方面具有相反的作用。
