爬行细胞的推拉不对称
An asymmetry between pushing and pulling for crawling cells
摘要：
真核细胞具有运动机制，使它们不仅能够自我推进，而且能够对障碍物施加力（推动）和携带货物（拉动）。为了研究主动推拉之间的固有不对称性，我们将爬行的肌动球蛋白细胞提取物建模为受到外力的活性凝胶的1D层。我们表明，推动是由突起控制的，突起占主导地位的运动机制的宏观签名是力-速度关系的平方。相反，仅在较小的拉力值下通过突出来驱动拉动，并且当拉力足够大时通过收缩来代替。这导致力速关系的凹凸结构更加复杂，特别是，突出和收缩之间的竞争可以在生物学相关范围内产生负迁移率。该模型说明了积极的重新调整的力产生机制，以响应外力的偶极子结构的变化。在互补的主动机制之间切换的可能性意味着，如果必要的话，“推动器”可以取代“拉动器”，反之亦然。
英文摘要：
Eukaryotic cells possess motility mechanisms allowing them not only to self-propel but also to exert forces on obstacles (to push) and to carry cargoes (to pull). To study the inherent asymmetry between active pushing and pulling we model a crawling acto-myosin cell extract as a 1D layer of active gel subjected to external forces. We show that pushing is controlled by protrusion and that the macroscopic signature of the protrusion dominated motility mechanism is concavity of the force velocity relation. Instead, pulling is driven by protrusion only at small values of the pulling force and it is replaced by contraction when the pulling force is sufficiently large. This leads to more complex convex-concave structure of the force velocity relation, in particular, competition between protrusion and contraction can produce negative mobility in a biologically relevant range. The model illustrates active readjustment of the force generating machinery in response to changes in the dipole structure of external forces. The possibility of switching between complementary active mechanisms implies that if necessary 'pushers' can replace 'pullers' and visa versa.
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