PDF(Pubmed)
Abstract：
The Rho family of GTPases plays a crucial role in cellular mechanics by regulating actomyosin contractility through the parallel induction of actin and myosin assembly and function. Using exocytosis of large vesicles in the Drosophila larval salivary gland as a model, we followed the spatiotemporal regulation of Rho1, which in turn creates distinct organization patterns of actin and myosin. After vesicle fusion, low levels of activated Rho1 reach the vesicle membrane and drive actin nucleation in an uneven, spread-out pattern. Subsequently, the Rho1 activator RhoGEF2 distributes as an irregular meshwork on the vesicle membrane, activating Rho1 in a corresponding punctate pattern and driving local myosin II recruitment, resulting in vesicle constriction. Vesicle membrane buckling and subsequent crumpling occur at local sites of high myosin II concentrations. These findings indicate that distinct thresholds for activated Rho1 create a biphasic mode of actomyosin assembly, inducing anisotropic membrane crumpling during exocrine secretion.
摘要：
GTPases的Rho家族通过平行诱导肌动蛋白和肌球蛋白的组装和功能来调节肌动球蛋白的收缩性，在细胞力学中起着至关重要的作用。利用果蝇幼虫唾液腺中的大囊泡的胞吐作用作为模型，我们遵循Rho1的时空调节，这反过来又产生了肌动蛋白和肌球蛋白的不同组织模式。囊泡融合后,低水平的活化Rho1扩散到囊泡膜，驱动肌动蛋白成核在一个不均匀的，展开模式。随后，Rho1激活剂RhoGEF2在囊泡膜上分布为不规则的网状结构，以相应的点状模式激活Rho1，并驱动局部肌球蛋白II募集，导致囊泡收缩。在高肌球蛋白II浓度的局部部位发生囊泡膜屈曲和随后的褶皱。这些发现表明，激活的Rho1的不同阈值会产生肌动球蛋白组装的双相模式，在外分泌过程中诱导各向异性膜皱缩。
