Yi Kexi, Wang Xu, Emmett Mark R, Marshall Alan G, Stewart Murray, Roberts Thomas M
Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA.
Mol Biol Cell. 2009 Jul;20(14):3200-8. doi: 10.1091/mbc.e09-03-0240. Epub 2009 May 20.
The crawling movement of nematode sperm requires coordination of leading edge protrusion with cell body retraction, both of which are powered by modulation of a cytoskeleton based on major sperm protein (MSP) filaments. We used a cell-free in vitro motility system in which both protrusion and retraction can be reconstituted, to identify two proteins involved in cell body retraction. Pharmacological and depletion-add back assays showed that retraction was triggered by a putative protein phosphatase 2A (PP2A, a Ser/Thr phosphatase activated by tyrosine dephosphorylation). Immunofluorescence showed that PP2A was present in the cell body and was concentrated at the base of the lamellipod where the force for retraction is generated. PP2A targeted MSP fiber protein 3 (MFP3), a protein unique to nematode sperm that binds to the MSP filaments in the motility apparatus. Dephosphorylation of MFP3 caused its release from the cytoskeleton and generated filament disassembly. Our results suggest that interaction between PP2A and MFP3 leads to local disassembly of the MSP cytoskeleton at the base of the lamellipod in sperm that in turn pulls the trailing cell body forward.
线虫精子的爬行运动需要前沿突出与细胞体收缩相协调，这两者均由基于主要精子蛋白（MSP）细丝的细胞骨架调节提供动力。我们使用了一种无细胞体外运动系统，在该系统中可以重建突出和收缩过程，以鉴定参与细胞体收缩的两种蛋白质。药理学和缺失-补充实验表明，收缩是由一种假定的蛋白磷酸酶2A（PP2A，一种由酪氨酸去磷酸化激活的丝氨酸/苏氨酸磷酸酶）触发的。免疫荧光显示，PP2A存在于细胞体中，并集中在片状伪足的基部，此处产生收缩力。PP2A作用于MSP纤维蛋白3（MFP3），这是一种线虫精子特有的蛋白质，它与运动装置中的MSP细丝结合。MFP3的去磷酸化导致其从细胞骨架中释放，并引起细丝解体。我们的结果表明，PP2A与MFP3之间的相互作用导致精子片状伪足基部的MSP细胞骨架局部解体，进而将后方的细胞体向前拉动。
