Hydrostatic pressure shows that lamellipodial motility in Ascaris sperm requires membrane-associated major sperm protein filament nucleation and elongation.
Hydrostatic pressure shows that lamellipodial motility in Ascaris sperm requires membrane-associated major sperm protein filament nucleation and elongation.
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DOI：
10.1083/jcb.140.2.367
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发表时间：
1998-01-26
期刊：
影响因子：
--
通讯作者：
Stewart M
中科院分区：
文献类型：
--
作者：
Roberts TM;Salmon ED;Stewart M
线虫的精子使用主要精子蛋白（MSP）细胞骨架代替肌动蛋白细胞骨架来驱动其阿米巴运动。运动性与伪足质膜前缘附近的 MSP 纤维的组装耦合。这种独特的运动系统已在猪蛔虫精子的无细胞提取物中在体外重建：源自质膜的由内而外的囊泡触发 MSP 细丝网状结构的组装，称为纤维，在囊泡生长时推动囊泡前进（Italiano, J.E., Jr., T.M. Roberts, M. Stewart, and C.A. Fontana. 1996. Cell. 84:105–114）。我们利用显微镜光学室内静水压力的变化来研究运动装置的组装机制。体内和体外压力对 MSP 细胞骨架的影响相似：压力 >50 atm 会减慢纤维生长，>300 atm 则会停止纤维生长。我们专注于体外系统，以表明丝组装发生在囊泡附近。在 300 个大气压下，纤维是稳定的，但囊泡经常从纤维末端脱落。当压力下降时，脱离的囊泡发生正常的纤维生长，但没有囊泡的纤维末端不生长。低于 300 atm，压力调节囊泡处组装的细丝数量（与纤维光密度和细丝成核率成正比）及其组装速率（与纤维生长和细丝伸长率成正比）。因此，纤维生长不仅仅是因为在现有细丝末端添加了亚基，而是受到囊泡表面或附近的压力敏感因素的调节。一旦细丝并入纤维中，其亚基的添加和损失速率非常慢，并且通过与组装不同的途径发生分解。压力对纤维组装的影响对提取物的稀释敏感，但很大程度上与 MSP 浓度无关，表明囊泡缔合丝成核和伸长需要除 MSP 之外的胞质成分。基于这些数据，我们提出了与运动相关的 MSP 聚合机制的模型，其原理通常适用于细胞局部组装细丝以驱动前缘突出的方式。
Sperm from nematodes use a major sperm protein (MSP) cytoskeleton in place of an actin cytoskeleton to drive their ameboid locomotion. Motility is coupled to the assembly of MSP fibers near the leading edge of the pseudopod plasma membrane. This unique motility system has been reconstituted in vitro in cell-free extracts of sperm from Ascaris suum: inside-out vesicles derived from the plasma membrane trigger assembly of meshworks of MSP filaments, called fibers, that push the vesicle forward as they grow (Italiano, J.E., Jr., T.M. Roberts, M. Stewart, and C.A. Fontana. 1996. Cell. 84:105–114). We used changes in hydrostatic pressure within a microscope optical chamber to investigate the mechanism of assembly of the motile apparatus. The effects of pressure on the MSP cytoskeleton in vivo and in vitro were similar: pressures >50 atm slowed and >300 atm stopped fiber growth. We focused on the in vitro system to show that filament assembly occurs in the immediate vicinity of the vesicle. At 300 atm, fibers were stable, but vesicles often detached from the ends of fibers. When the pressure was dropped, normal fiber growth occurred from detached vesicles but the ends of fibers without vesicles did not grow. Below 300 atm, pressure modulates both the number of filaments assembled at the vesicle (proportional to fiber optical density and filament nucleation rate), and their rate of assembly (proportional to the rates of fiber growth and filament elongation). Thus, fiber growth is not simply because of the addition of subunits onto the ends of existing filaments, but rather is regulated by pressure-sensitive factors at or near the vesicle surface. Once a filament is incorporated into a fiber, its rates of addition and loss of subunits are very slow and disassembly occurs by pathways distinct from assembly. The effects of pressure on fiber assembly are sensitive to dilution of the extract but largely independent of MSP concentration, indicating that a cytosolic component other than MSP is required for vesicle-association filament nucleation and elongation. Based on these data we present a model for the mechanism of locomotion-associated MSP polymerization the principles of which may apply generally to the way cells assemble filaments locally to drive protrusion of the leading edge.
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影响因子：
--
作者：
BOURNS, B;FRANKLIN, S;SALMON, ED
通讯作者：
SALMON, ED
影响因子：
7.5
作者：
ROBERTS, TM;STEWART, M
通讯作者：
STEWART, M
DOI：
10.1083/jcb.118.6.1421
发表时间：
1992-09
期刊：
The Journal of cell biology
影响因子：
--
作者：
Hartwig JH
通讯作者：
Hartwig JH
影响因子：
--
作者：
KING, KL;ESSIG, J;MOERLAND, TS
通讯作者：
MOERLAND, TS
影响因子：
--
作者：
ROBERTS, TM;KING, KL
通讯作者：
KING, KL