Actin polymerization as a mechanochemical reaction -its role in cell shape change

研究目的：为了阐明细胞运动的机制，我们开发了一种将肌动蛋白单体掺入脂质体并聚合的系统。我们发现，脂质体变形后肌动蛋白聚合。因此，我们的目的是进一步研究伴随着肌动蛋白聚合在脂质体中的变化。计划：（1）研究ATP水解是否是脂质体变形所必需的。(2)to用针型电极尖端产生的电场使磷脂膜产生突起后，将肌动蛋白固定在脂质体中，然后通过向脂质体中引入离子并加入离子载体，研究预先形成的突起是否被聚合的肌动蛋白所支撑。这是因为从系统中完全除去ATP是非常困难的。除非能保证完全切除，否则很难获得完全切除的结果。(2)用离子载体缬氨霉素成功地将K离子引入含肌动蛋白的脂质体中：我们发现当将含肌动蛋白的脂质体加入含K离子的溶液中时，出现刚性和纺锤形的脂质体。然而，发现从脂质体中拉出突起难以再现。这部分是因为成功的膜变形所需的条件需要对电极形状、位置和电场强度进行精细的控制。需要进一步研究以优化这些条件。

Aim of the research : in order to elucidated the mechanism of cell locomotion, we have developed a system in which actin monomersare incorporated in liposomes and polymerized. We found that the liposomes deformed upon actin polymerization. We thus aimed to further investigate the change accompanying the actin polymerization in the liposomes.Plan : (1)to investigate if ATP hydrolysis is necessary for the liposome deformation. (2)to polymerize the actin in a liposome after making projections of phospholipid membrane with an electric field generated at the tip of a needle type electrode in order to sudy if the pre-formed projection is supported by polymerizing actin afterward by introducing ions into the liposome withthe addition of ionophore.Results : (1) this is still under investigation. the reason for this is beacuse it is extremely dificult to remove completely ATP from the system. Unless the complete removal is guaranteed, cnclusive result will be difficult to obtain. (2) introduction ofK ions into the actin containing liposome with the ionophore valinomycin was found to be successful : we found that rigid and spindle-shaped liposomes appeared when the actin-containingliposomes are added into solution containing K ions. However, pulling out the projections from the liposome was found to be difficult to reproduce. This was partly because the condition tobe achieved for successful membrane deformation requires subtle control of electrode shape, positioning, and electric field intensity. Further investigation is needed to optimize those conditions.