Ye Fan, Breslow David K, Koslover Elena F, Spakowitz Andrew J, Nelson W James, Nachury Maxence V
Department of Molecular and Cellular Physiology , Stanford University School of Medicine , Stanford , United States ; Department of Biology , Stanford University , Stanford , United States.
Elife. 2013 Aug 6;2:e00654. doi: 10.7554/eLife.00654.
The dynamic organization of signaling cascades inside primary cilia is key to signal propagation. Yet little is known about the dynamics of ciliary membrane proteins besides a possible role for motor-driven Intraflagellar Transport (IFT). To characterize these dynamics, we imaged single molecules of Somatostatin Receptor 3 (SSTR3, a GPCR) and Smoothened (Smo, a Hedgehog signal transducer) in the ciliary membrane. While IFT trains moved processively from one end of the cilium to the other, single SSTR3 and Smo underwent mostly diffusive behavior interspersed with short periods of directional movements. Statistical subtraction of instant velocities revealed that SSTR3 and Smo spent less than a third of their time undergoing active transport. Finally, SSTR3 and IFT movements could be uncoupled by perturbing either membrane protein diffusion or active transport. Thus ciliary membrane proteins move predominantly by diffusion, and attachment to IFT trains is transient and stochastic rather than processive or spatially determined. DOI:http://dx.doi.org/10.7554/eLife.00654.001.
初级纤毛内部信号级联的动态组织是信号传播的关键。然而，除了动力驱动的鞭毛内运输（IFT）可能发挥的作用外，人们对纤毛膜蛋白的动态了解甚少。为了表征这些动态，我们对纤毛膜中的生长抑素受体3（SSTR3，一种G蛋白偶联受体）和 smoothened（Smo，一种刺猬信号转导蛋白）的单分子进行了成像。当IFT列车从纤毛的一端向另一端连续移动时，单个SSTR3和Smo大多表现出扩散行为，其间穿插着短时间的定向运动。对瞬时速度进行统计减法显示，SSTR3和Smo进行主动运输的时间不到三分之一。最后，通过干扰膜蛋白扩散或主动运输，可以使SSTR3和IFT运动解偶联。因此，纤毛膜蛋白主要通过扩散移动，与IFT列车的附着是短暂且随机的，而不是连续的或由空间决定的。DOI:http://dx.doi.org/10.7554/eLife.00654.001 。
