LGR5 receptor promotes cell-cell adhesion in stem cells and colon cancer cells via the IQGAP1-Rac1 pathway.
LGR5 receptor promotes cell-cell adhesion in stem cells and colon cancer cells via the IQGAP1-Rac1 pathway.
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DOI：
10.1074/jbc.m117.786798
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发表时间：
2017-09-08
期刊：
影响因子：
--
通讯作者：
Liu QJ
中科院分区：
文献类型：
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作者：
Carmon KS;Gong X;Yi J;Wu L;Thomas A;Moore CM;Masuho I;Timson DJ;Martemyanov KA;Liu QJ
富含亮氨酸重复序列的G蛋白偶联受体5(LGR5)是几种上皮组织中的成体干细胞的真正标志物，在许多结直肠癌、肝细胞癌和卵巢癌中高度上调。在体外，R-响应素配体激活LGR5可增强WNT/β-连环蛋白信号转导；然而，干细胞中LGR5的缺失对WNT/β-连环蛋白信号转导或体内细胞增殖几乎没有影响。值得注意的是，在没有RSPO刺激的情况下，LGR5的表达调控对肌动蛋白的细胞骨架结构和细胞黏附有重要影响，但其分子机制尚不清楚。在这里，我们发现LGR5与含有IQ基序的GTPase激活蛋白1(IQGAP1)相互作用，IQGAP1是rac1/CDC42 GTP酶的效应器，在肌动蛋白细胞骨架动力学和细胞间黏附的调节中发挥作用。具体地说，LGR5降低了Ser-1441/1443处IQGAP1的磷酸化水平，导致rac1与IQGAP1结合增加，从而增加了皮质F-肌动蛋白的水平，并增强了细胞与细胞的黏附。切除结肠癌细胞和隐窝干细胞中的LGR5导致皮质F-肌动蛋白丢失，细胞-细胞黏附减少，黏附相关蛋白的定位中断。没有发现LGR5与四种主要的异三聚体G蛋白亚型中的任何一种偶联的证据。这些发现表明，LGR5主要通过IQGAP1-rac1途径增强正常成人隐窝干细胞和结肠癌细胞的细胞-细胞黏附。
Leucine-rich repeat-containing G protein–coupled receptor 5 (LGR5) is a bona fide marker of adult stem cells in several epithelial tissues, most notably in the intestinal crypts, and is highly up-regulated in many colorectal, hepatocellular, and ovarian cancers. LGR5 activation by R-spondin (RSPO) ligands potentiates Wnt/β-catenin signaling in vitro; however, deletion of LGR5 in stem cells has little or no effect on Wnt/β-catenin signaling or cell proliferation in vivo. Remarkably, modulation of LGR5 expression has a major impact on the actin cytoskeletal structure and cell adhesion in the absence of RSPO stimulation, but the molecular mechanism is unclear. Here, we show that LGR5 interacts with IQ motif-containing GTPase-activating protein 1 (IQGAP1), an effector of Rac1/CDC42 GTPases, in the regulation of actin cytoskeleton dynamics and cell–cell adhesion. Specifically, LGR5 decreased levels of IQGAP1 phosphorylation at Ser-1441/1443, leading to increased binding of Rac1 to IQGAP1 and thus higher levels of cortical F-actin and enhanced cell–cell adhesion. LGR5 ablation in colon cancer cells and crypt stem cells resulted in loss of cortical F-actin, reduced cell–cell adhesion, and disrupted localization of adhesion-associated proteins. No evidence of LGR5 coupling to any of the four major subtypes of heterotrimeric G proteins was found. These findings suggest that LGR5 primarily functions via the IQGAP1–Rac1 pathway to strengthen cell–cell adhesion in normal adult crypt stem cells and colon cancer cells.