Garcia Miguel, Ray Sibnath, Brown Isaiah, Irom Jon, Brazill Derrick
Department of Biological Sciences, Center for the Study of Gene Structure and Function, Hunter College and the Graduate Center of the City University of New York, New York, New York, USA.
Eukaryot Cell. 2014 Jan;13(1):119-26. doi: 10.1128/EC.00216-13. Epub 2013 Nov 15.
Proper regulation of the actin cytoskeleton is essential for cell function and ultimately for survival. Tight control of actin dynamics is required for many cellular processes, including differentiation, proliferation, adhesion, chemotaxis, endocytosis, exocytosis, and multicellular development. Here we describe a putative p21-activated protein kinase, PakD, that regulates the actin cytoskeleton in Dictyostelium discoideum. We found that cells lacking pakD are unable to aggregate and thus unable to develop. Compared to the wild type, cells lacking PakD have decreased membrane extensions, suggesting defective regulation of the actin cytoskeleton. pakD(-) cells show poor chemotaxis toward cyclic AMP (cAMP) but normal chemotaxis toward folate, suggesting that PakD mediates some but not all chemotaxis responses. pakD(-) cells have decreased polarity when placed in a cAMP gradient, indicating that the chemotactic defects of the pakD(-) cells may be due to an impaired cytoskeletal response to cAMP. In addition, while wild-type cells polymerize actin in response to global stimulation by cAMP, pakD(-) cells exhibit F-actin depolymerization under the same conditions. Taken together, the results suggest that PakD is part of a pathway coordinating F-actin organization during development.
肌动蛋白细胞骨架的适当调控对于细胞功能乃至最终的生存至关重要。许多细胞过程，包括分化、增殖、黏附、趋化性、内吞作用、外排作用和多细胞发育，都需要对肌动蛋白动力学进行严格控制。在这里，我们描述了一种假定的p21激活蛋白激酶PakD，它在盘基网柄菌中调节肌动蛋白细胞骨架。我们发现缺乏pakD的细胞无法聚集，因此无法发育。与野生型相比，缺乏PakD的细胞的膜延伸减少，这表明肌动蛋白细胞骨架的调节存在缺陷。pakD(-)细胞对环磷酸腺苷（cAMP）的趋化性较差，但对叶酸的趋化性正常，这表明PakD介导了部分而非全部的趋化反应。当置于cAMP梯度中时，pakD(-)细胞的极性降低，这表明pakD(-)细胞的趋化缺陷可能是由于细胞骨架对cAMP的反应受损。此外，虽然野生型细胞在受到cAMP的全局刺激时会聚合肌动蛋白，但pakD(-)细胞在相同条件下表现出F-肌动蛋白解聚。综上所述，这些结果表明PakD是发育过程中协调F-肌动蛋白组织的途径的一部分。
