*Laboratory of Metabolic Medicine, Singapore Bioimaging Consortium, #02-02 Helios, 11 Biopolis Way, 138667 Singapore.
‡Singapore Institute for Clinical Sciences, 30 Medical Drive, 117609 Singapore.
Biochem J. 2014 Dec 1;464(2):179-92. doi: 10.1042/BJ20140805.
Extensive actin cytoskeleton remodelling occurs during adipocyte development. We have previously shown that disruption of stress fibres by the actin-severing protein cofilin is a requisite step in adipogenesis. However, it remains unclear whether actin nucleation and assembly into the cortical structure are essential for adipocyte development. In the present study we investigated the role of cortical actin assembly and of actin nucleation by the actin-related protein 2/3 (Arp2/3) complex in adipogenesis. Cortical actin structure formation started with accumulation of filamentous actin (F-actin) patches near the plasma membrane during adipogenesis. Depletion of Arp2/3 by knockdown of its subunits Arp3 or ARPC3 strongly impaired adipocyte differentiation, although adipogenesis-initiating factors were unaffected. Moreover, the assembly of F-actin-rich structures at the plasma membrane was suppressed and the cortical actin structure poorly developed after adipogenic induction in Arp2/3-deficient cells. Finally, we provide evidence that the cortical actin cytoskeleton is essential for efficient glucose transporter 4 (GLUT4) vesicle exocytosis and insulin signal transduction. These results show that the Arp2/3 complex is an essential regulator of adipocyte development through control of the formation of cortical actin structures, which may facilitate nutrient uptake and signalling events.
在脂肪细胞发育过程中，细胞骨架发生广泛的重塑。我们之前已经表明，肌动蛋白丝的断裂蛋白丝切蛋白（cofilin）对脂肪生成是必需的。然而，目前尚不清楚肌动蛋白成核和组装到皮质结构对于脂肪细胞发育是否至关重要。在本研究中，我们研究了皮质肌动蛋白组装和肌动蛋白相关蛋白 2/3（Arp2/3）复合物在脂肪生成中的成核作用。皮质肌动蛋白结构的形成始于脂肪生成过程中靠近质膜的丝状肌动蛋白（F-actin）斑块的积累。通过敲低其亚基 Arp3 或 ARPC3 来耗尽 Arp2/3，强烈抑制了脂肪细胞分化，尽管脂肪生成起始因子不受影响。此外，在 Arp2/3 缺陷细胞中诱导脂肪生成后，富含 F-actin 的结构在质膜上的组装被抑制，皮质肌动蛋白结构的发育不良。最后，我们提供了证据表明，皮质肌动蛋白细胞骨架对于葡萄糖转运蛋白 4（GLUT4）囊泡胞吐和胰岛素信号转导是必需的。这些结果表明，Arp2/3 复合物通过控制皮质肌动蛋白结构的形成，是脂肪细胞发育的必需调节剂，这可能有助于营养物质的摄取和信号事件。
