Max Planck Institute of Biochemistry, Martinsried, Germany.
Biophys J. 2012 Sep 19;103(6):1170-8. doi: 10.1016/j.bpj.2012.08.004.
In a motile eukaryotic cell, front protrusion and tail retraction are superimposed on each other. To single out mechanisms that result in front to tail or in tail to front transition, we separated the two processes in time using cells that oscillate between a full front and a full tail state. State transitions were visualized by total internal reflection fluorescence microscopy using as a front marker PIP3 (phosphatidylinositol [3,4,5] tris-phosphate), and as a tail marker the tumor-suppressor PTEN (phosphatase tensin homolog) that degrades PIP3. Negative fluctuations in the PTEN layer of the membrane gated a local increase in PIP3. In a subset of areas lacking PTEN (PTEN holes), PIP3 was amplified until a propagated wave was initiated. Wave propagation implies that a PIP3 signal is transmitted by a self-sustained process, such that the temporal and spatial profiles of the signal are maintained during passage of the wave across the entire expanse of the cell membrane. Actin clusters were remodeled into a ring along the perimeter of the expanding PIP3 wave. The reverse transition of PIP3 to PTEN was linked to the previous site of wave initiation: where PIP3 decayed first, the entry of PTEN was primed.
在一个能动的真核细胞中，前端突出和后端缩回相互叠加。为了单独分离导致前端到后端或后端到前端转变的机制，我们使用在完全前端和完全后端状态之间振荡的细胞在时间上分离这两个过程。使用 PIP3（磷脂酰肌醇 [3,4,5] 三磷酸）作为前端标记物和肿瘤抑制因子 PTEN（磷酸酶张力蛋白同源物）作为后端标记物，通过全内反射荧光显微镜可视化状态转换，PTEN 降解 PIP3。膜中的 PTEN 层的负波动门控 PIP3 的局部增加。在缺乏 PTEN（PTEN 孔）的一小部分区域中，PIP3 被放大，直到引发传播波。波传播意味着 PIP3 信号通过自维持过程进行传输，使得信号的时间和空间分布在波穿过整个细胞膜的整个过程中得以维持。肌动蛋白簇在扩展的 PIP3 波的周边重塑成一个环。PIP3 向 PTEN 的反向转变与波起始的先前位点相关联：PIP3 首先衰减的地方，PTEN 的进入被引发。
