Golub Tamara, Caroni Pico
Friedrich Miescher Institut, Basel, 4058 Switzerland.
J Cell Biol. 2005 Apr 11;169(1):151-65. doi: 10.1083/jcb.200407058. Epub 2005 Apr 4.
The lipid second messenger PI(4,5)P(2) modulates actin dynamics, and its local accumulation at plasmalemmal microdomains (rafts) might mediate regulation of protrusive motility. However, how PI(4,5)P(2)-rich rafts regulate surface motility is not well understood. Here, we show that upon signals promoting cell surface motility, PI(4,5)P(2) directs the assembly of dynamic raft-rich plasmalemmal patches, which promote and sustain protrusive motility. The accumulation of PI(4,5)P(2) at rafts, together with Cdc42, promotes patch assembly through N-WASP. The patches exhibit locally regulated PI(4,5)P(2) turnover and reduced diffusion-mediated exchange with their environment. Patches capture microtubules (MTs) through patch IQGAP1, to stabilize MTs at the leading edge. Captured MTs in turn deliver PKA to patches to promote patch clustering through further PI(4,5)P(2) accumulation in response to cAMP. Patch clustering restricts, spatially confines, and polarizes protrusive motility. Thus, PI(4,5)P(2)-dependent raft-rich patches enhance local signaling for motility, and their assembly into clusters is regulated through captured MTs and PKA, coupling local regulation of motility to cell polarity, and organization.
脂质第二信使磷脂酰肌醇-4,5-二磷酸(PI(4,5)P(2))可调节肌动蛋白动力学,其在质膜微结构域(脂筏)中的局部积累可能介导对突出性运动的调节。然而,富含PI(4,5)P(2)的脂筏如何调节表面运动尚不清楚。在此,我们表明,在促进细胞表面运动的信号作用下,PI(4,5)P(2)引导富含脂筏的动态质膜斑块的组装,这些斑块促进并维持突出性运动。PI(4,5)P(2)在脂筏处的积累与Cdc42一起,通过N-WASP促进斑块组装。这些斑块表现出局部调节的PI(4,5)P(2)周转,并减少了与其周围环境的扩散介导交换。斑块通过斑块IQGAP1捕获微管(MTs),以在前缘稳定MTs。捕获的MTs进而将蛋白激酶A(PKA)递送至斑块,以通过响应环磷酸腺苷(cAMP)进一步积累PI(4,5)P(2)来促进斑块聚集。斑块聚集限制、在空间上限制并使突出性运动极化。因此,依赖PI(4,5)P(2)的富含脂筏的斑块增强了运动的局部信号传导,并且它们聚集成簇的过程通过捕获的MTs和PKA进行调节,将运动的局部调节与细胞极性和组织联系起来。