Kelley Joshua B, Dixit Gauri, Sheetz Joshua B, Venkatapurapu Sai Phanindra, Elston Timothy C, Dohlman Henrik G
Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, 120 Mason Farm Road, 3046 Genetic Medicine Building, Campus Box 7260, Chapel Hill, NC 27599, USA; Department of Pharmacology, University of North Carolina at Chapel Hill, 120 Mason Farm Road, 4009 Genetic Medicine Building, Campus Box 7365, Chapel Hill, NC 27599, USA.
Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, 120 Mason Farm Road, 3046 Genetic Medicine Building, Campus Box 7260, Chapel Hill, NC 27599, USA.
Curr Biol. 2015 Feb 2;25(3):275-285. doi: 10.1016/j.cub.2014.11.047. Epub 2015 Jan 15.
Septins are well known to form a boundary between mother and daughter cells in mitosis, but their role in other morphogenic states is poorly understood.
Using microfluidics and live-cell microscopy, coupled with new computational methods for image analysis, we investigated septin function during pheromone-dependent chemotropic growth in yeast. We show that septins colocalize with the regulator of G protein signaling (RGS) Sst2, a GTPase-activating protein that dampens pheromone receptor signaling. We show further that the septin structure surrounds the polar cap, ensuring that cell growth is directed toward the source of pheromone. When RGS activity is abrogated, septins are partially disorganized. Under these circumstances, the polar cap travels toward septin structures and away from sites of exocytosis, resulting in a loss of gradient tracking.
Septin organization is dependent on RGS protein activity. When assembled correctly, septins promote turning of the polar cap and proper tracking of a pheromone gradient.
众所周知，在有丝分裂过程中，Septin蛋白在母细胞和子细胞之间形成边界，但它们在其他形态发生状态中的作用却鲜为人知。
我们利用微流控技术和活细胞显微镜技术，并结合新的图像分析计算方法，研究了酵母中信息素依赖性趋化生长过程中Septin蛋白的功能。我们发现Septin蛋白与G蛋白信号调节因子（RGS）Sst2共定位，Sst2是一种GTP酶激活蛋白，可抑制信息素受体信号传导。我们进一步表明，Septin蛋白结构围绕着极性帽，确保细胞生长朝向信息素来源。当RGS活性被消除时，Septin蛋白会部分紊乱。在这种情况下，极性帽会朝着Septin蛋白结构移动并远离胞吐位点，导致梯度追踪丧失。
Septin蛋白的组织依赖于RGS蛋白活性。当正确组装时，Septin蛋白促进极性帽的转向和对信息素梯度的正确追踪。
