An Outer Arm Dynein Conformational Switch Is Required for Metachronal Synchrony of Motile Cilia in Planaria

Here we use the motile ventral cilia of the planarian S. mediterranea to examine the role of outer arm dynein in the generation and maintenance of metachronal synchrony. We demonstrate that a single dynein light chain plays a mechanosensory role necessary to entrain and maintain the metachronal synchrony of motile cilia

Mode of Ca2+ action on ciliary beat frequency in single ovine airway epithelial cells

We analysed the kinetics of coupling between cytoplasmic calcium ([Ca2+]i) and ciliary beat frequency (CBF) using simultaneous single cilium recording and single cell [Ca2+]i measurements from cultured ovine tracheal epithelial cells.CBF and [Ca2+]i (indicated by fura-2) were measured at rest and in response to activation of the G-protein coupled M3 muscarinic receptor by 10 μM acetylcholine (ACh).Fourier transform analysis of 3 s data segments of light intensity from phase-contrast microscopy showed no significant delay between changes in [Ca2+]i and CBF during a 2 min exposure to ACh and subsequent washout.CBF time resolution was improved by computing instantaneous beat frequency. This revealed that CBF lagged the rapid increase in [Ca2+]i in response to ACh with a delay of less than 1 beat cycle (143 ms at 7 Hz). When CBF was estimated by an improved Fourier method, this delay was observed to be 70 ± 30 ms (mean ± s.e.m.; n = 20 cilia). During the slower return to baseline, a lag of 8 ± 3.2 s was observed, indicative of hysteresis.While calmodulin inhibitors (calmidazolium and W-7; each n = 5) decreased baseline CBF by an average of 1.1 ± 0.1 Hz, they did not alter the kinetic relationship between [Ca2+]i and CBF. Similarly, phosphatase inhibitors (okadaic acid and cyclosporin A; each n = 5), changed neither baseline CBF nor the kinetic coupling between [Ca2+]i and CBF.These data suggest that the timing of Ca2+ action on CBF in ovine airway epithelial cells, is unlikely to be determined by phosphorylation reactions involving calmodulin or kinase/phosphatase reactions.A simple model for Ca2+ stimulation of CBF is presented. Fits of the model to the data suggest four or more Ca2+ ions bind cooperatively to speed up CBF