Watson G M, Roberts J
Department of Biology, University of Southwestern Louisiana, Lafayette 70504-2451, USA.
Cell Motil Cytoskeleton. 1995;30(3):208-20. doi: 10.1002/cm.970300305.
Hair bundles located on tentacles of sea anemones are morphodynamic mechanoreceptors employed to regulate discharge of nematocysts into swimming prey. Activation of chemoreceptors for N-acetylated sugars is known to induce anemone hair bundles to elongate while shifting discharge to lower frequencies matching those produced by calmly swimming prey. In the continued presence of N-acetylated sugars, activation of proline receptors is known to induce hair bundles to shorten while shifting nematocyst discharge to higher frequencies presumed to correspond to movements produced by wounded, struggling prey. In the present study, N-acetylneuraminic acid (NANA) causes stereocilia to become more intensely fluorescent in confocal optical sections of phalloidin-stained specimens, suggesting that receptors for N-acetylated sugars initiate processes to increase the density of F-actin within stereocilia. Computer analysis of electron micrographs is consistent with this interpretation for large diameter stereocilia but not for small diameter stereocilia. In the continued presence of NANA, proline causes fluorescence intensity of phalloidin to decrease to or below control levels. DNaseI uniformly stains large diameter stereocilia, suggesting that these stereocilia contain a pool of G-actin. Fluorescence intensity of DNaseI in stereocilia is significantly less bright in specimens exposed to NANA alone than in specimens exposed to proline in the continued presence of NANA. It appears that whereas activated receptors for NANA induce G-actin to polymerize in large diameter stereocilia, activated receptors for proline induce F-actin to depolymerize, restoring G-actin pools.
海葵触须上的毛束是形态动力学机械感受器，用于调节刺丝囊向游动猎物的释放。已知对N - 乙酰化糖的化学感受器激活会诱导海葵毛束伸长，同时将释放频率转移到与平静游动猎物产生的频率相匹配的较低频率。在持续存在N - 乙酰化糖的情况下，已知脯氨酸受体的激活会诱导毛束缩短，同时将刺丝囊释放频率转移到更高频率，推测这与受伤挣扎的猎物产生的运动相对应。在本研究中，N - 乙酰神经氨酸（NANA）在鬼笔环肽染色标本的共聚焦光学切片中使静纤毛发出更强的荧光，这表明N - 乙酰化糖的受体启动了增加静纤毛内F - 肌动蛋白密度的过程。对电子显微镜照片的计算机分析与对大直径静纤毛的这种解释一致，但对小直径静纤毛则不然。在持续存在NANA的情况下，脯氨酸会使鬼笔环肽的荧光强度降低到对照水平或以下。脱氧核糖核酸酶I均匀地染色大直径静纤毛，表明这些静纤毛含有G - 肌动蛋白池。单独暴露于NANA的标本中静纤毛内脱氧核糖核酸酶I的荧光强度明显低于在持续存在NANA的情况下暴露于脯氨酸的标本。似乎虽然激活的NANA受体诱导大直径静纤毛中的G - 肌动蛋白聚合，但激活的脯氨酸受体诱导F - 肌动蛋白解聚，恢复G - 肌动蛋白池。
