Department of Cell Biology, University of Connecticut Health Center, Farmington, CT 06030, USA.
Mol Biol Cell. 2011 Apr 15;22(8):1321-9. doi: 10.1091/mbc.E10-09-0741. Epub 2011 Feb 9.
Microtubule (MT)-based organelle transport is driven by MT motor proteins that move cargoes toward MT minus-ends clustered in the cell center (dyneins) or plus-ends extended to the periphery (kinesins). Cells are able to rapidly switch the direction of transport in response to external cues, but the signaling events that control switching remain poorly understood. Here, we examined the signaling mechanism responsible for the rapid activation of dynein-dependent MT minus-end-directed pigment granule movement in Xenopus melanophores (pigment aggregation). We found that, along with the previously identified protein phosphatase 2A (PP2A), pigment aggregation signaling also involved casein kinase 1ε (CK1ε), that both enzymes were bound to pigment granules, and that their activities were increased during pigment aggregation. Furthermore we found that CK1ε functioned downstream of PP2A in the pigment aggregation signaling pathway. Finally, we discovered that stimulation of pigment aggregation increased phosphorylation of dynein intermediate chain (DIC) and that this increase was partially suppressed by CK1ε inhibition. We propose that signal transduction during pigment aggregation involves successive activation of PP2A and CK1ε and CK1ε-dependent phosphorylation of DIC, which stimulates dynein motor activity and increases minus-end-directed runs of pigment granules.
微管（MT）- 基于细胞器的运输是由 MT 马达蛋白驱动的，这些蛋白将货物向细胞中心聚集的 MT 负端（动力蛋白）或延伸到外围的 MT 正端（驱动蛋白）移动。细胞能够快速响应外部信号改变运输方向，但控制转换的信号事件仍知之甚少。在这里，我们研究了负责快速激活 Xenopus melanophores（色素聚集）中依赖于动力蛋白的 MT 负端定向色素颗粒运动的信号转导机制。我们发现，除了先前鉴定的蛋白磷酸酶 2A（PP2A）外，色素聚集信号还涉及酪蛋白激酶 1ε（CK1ε），这两种酶都与色素颗粒结合，并且在色素聚集过程中它们的活性增加。此外，我们发现 CK1ε 在色素聚集信号通路中位于 PP2A 的下游。最后，我们发现刺激色素聚集会增加中间链动力蛋白（DIC）的磷酸化，而 CK1ε 的抑制部分抑制了这种增加。我们提出，色素聚集过程中的信号转导涉及 PP2A 和 CK1ε 的连续激活以及 CK1ε 依赖性 DIC 的磷酸化，这刺激了动力蛋白的活性并增加了色素颗粒的负端定向运行。
