Samson Edward B, Tsao David S, Zimak Jan, McLaughlin R Tyler, Trenton Nicholaus J, Mace Emily M, Orange Jordan S, Schweikhard Volker, Diehl Michael R
Department of Bioengineering, Rice University, Houston, TX 77030, USA.
Graduate Program in Systems, Synthetic and Physical Biology, Rice University, Houston, TX 77030, USA.
Biol Open. 2017 Jun 15;6(6):785-799. doi: 10.1242/bio.022624.
IQGAP1 is a large, multi-domain scaffold that helps orchestrate cell signaling and cytoskeletal mechanics by controlling interactions among a spectrum of receptors, signaling intermediates, and cytoskeletal proteins. While this coordination is known to impact cell morphology, motility, cell adhesion, and vesicular traffic, among other functions, the spatiotemporal properties and regulatory mechanisms of IQGAP1 have not been fully resolved. Herein, we describe a series of super-resolution and live-cell imaging analyses that identified a role for IQGAP1 in the regulation of an actin cytoskeletal shell surrounding a novel membranous compartment that localizes selectively to the basal cortex of polarized epithelial cells (MCF-10A). We also show that IQGAP1 appears to both stabilize the actin coating and constrain its growth. Loss of compartmental IQGAP1 initiates a disassembly mechanism involving rapid and unconstrained actin polymerization around the compartment and dispersal of its vesicle contents. Together, these findings suggest IQGAP1 achieves this control by harnessing both stabilizing and antagonistic interactions with actin. They also demonstrate the utility of these compartments for image-based investigations of the spatial and temporal dynamics of IQGAP1 within endosome-specific actin networks.
IQGAP1是一种大型的多结构域支架蛋白，它通过控制一系列受体、信号中间体和细胞骨架蛋白之间的相互作用，来协调细胞信号传导和细胞骨架力学。虽然已知这种协调作用会影响细胞形态、运动性、细胞粘附和囊泡运输等多种功能，但IQGAP1的时空特性和调控机制尚未完全明确。在此，我们描述了一系列超分辨率和活细胞成像分析，这些分析确定了IQGAP1在调节围绕一个新型膜性区室的肌动蛋白细胞骨架壳中的作用，该膜性区室选择性地定位于极化上皮细胞（MCF - 10A）的基底皮质。我们还表明，IQGAP1似乎既能稳定肌动蛋白涂层，又能限制其生长。区室化IQGAP1的缺失会引发一种拆解机制，该机制涉及区室周围肌动蛋白的快速且不受限制的聚合以及其囊泡内容物的分散。总之，这些发现表明IQGAP1通过利用与肌动蛋白的稳定和拮抗相互作用来实现这种控制。它们还证明了这些区室在基于图像研究IQGAP1在内体特异性肌动蛋白网络中的时空动态方面的实用性。
