Farahbakhsh Nasser A, Narins Peter M
Department of Physiological Science, 621 Charles E. Young Drive S., University of California, Los Angeles, CA 90095-1606, USA.
Hear Res. 2008 Jul;241(1-2):7-17. doi: 10.1016/j.heares.2008.04.007. Epub 2008 Apr 29.
Using video, fluorescence and confocal microscopy, quantitative analysis and modeling, we investigated intracellular processes mediating the calcium/calmodulin (Ca(2+)/CaM)-dependent slow motility in hair cells dissociated from the rostral region of amphibian papilla, one of the two auditory organs in frogs. The time course of shape changes in these hair cells during the period of pretreatment with several specific inhibitors, as well as their response to the calcium ionophore, ionomycin, were recorded and compared. These cells respond to ionomycin with a tri-phasic shape change: an initial phase of iso-volumetric length decrease; a period of concurrent shortening and swelling; and the final phase of increase in both length and volume. We found that both the myosin light chain kinase inhibitor, ML-7, and antagonists of the multifunctional Ca(2+)/CaM-dependent kinases, KN-62 and KN-93, inhibit the iso-volumetric shortening phase of the response to ionomycin. The type 1 protein phosphatase inhibitors, calyculin A and okadaic acid induce minor shortening on their own, but do not significantly alter phase 1 response. However, they appear to counter effects of the inhibitors of Ca(2+)/CaM-dependent kinases. We hypothesize that an active actomyosin-based process mediates the iso-volumetric shortening in the frog rostral amphibian papillar hair cells.
我们利用视频、荧光和共聚焦显微镜、定量分析和建模，研究了介导钙/钙调蛋白（Ca(2+)/CaM）依赖性缓慢运动的细胞内过程，该过程存在于从蛙类两个听觉器官之一的两栖乳头吻端区域解离的毛细胞中。记录并比较了这些毛细胞在用几种特异性抑制剂预处理期间的形状变化时间进程，以及它们对钙离子载体离子霉素的反应。这些细胞对离子霉素的反应呈现三相形状变化：等容长度减少的初始阶段；同时缩短和肿胀的时期；以及长度和体积均增加的最终阶段。我们发现，肌球蛋白轻链激酶抑制剂ML-7以及多功能Ca(2+)/CaM依赖性激酶的拮抗剂KN-62和KN-93，均抑制了对离子霉素反应的等容缩短阶段。1型蛋白磷酸酶抑制剂，如毛喉素A和冈田酸，自身会诱导轻微缩短，但不会显著改变第一阶段的反应。然而，它们似乎能抵消Ca(2+)/CaM依赖性激酶抑制剂的作用。我们推测，基于肌动球蛋白的活跃过程介导了蛙类吻端两栖乳头毛细胞的等容缩短。
