Upregulated WDR26 serves as a scaffold to coordinate PI3K/ AKT pathway-driven breast cancer cell growth, migration, and invasion
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Yuanchao Ye1, Xiaoyun Tang1,3, Zhizeng Sun1,4, Songhai Chen1,2
1Department of Pharmacology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA, USA
2Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA, USA
3Current address: Department of Biochemistry, University of Alberta, Edmonton, AB, Canada
4Current address: Department of Pharmacology, Baylor College of Medicine, Houston, TX, USA
Songhai Chen, e-mail: firstname.lastname@example.org
Keywords: WDR26, G protein-coupled receptors, PI3K, AKT, breast cancer growth and metastasis
Received: January 27, 2016 Accepted: January 30, 2016 Published: February 17, 2016
The phosphatidylinositol 3-kinase (PI3K)/AKT pathway transmits signals downstream of receptor tyrosine kinases and G protein-coupled receptors (GPCRs), and is one of the most dysregulated pathways in breast cancer. PI3Ks and AKTs consist of multiple isoforms that play distinct and even opposite roles in breast cancer cell growth and metastasis. However, it remains unknown how the activities of various PI3K and AKT isoforms are coordinated during breast cancer progression. Previously, we showed WDR26 is a novel WD40 protein that binds Gβγ and promotes Gβγ signaling. Here, we demonstrate that WDR26 is overexpressed in highly malignant breast tumor cell lines and human breast cancer samples, and that WDR26 overexpression correlates with shortened survival of breast cancer patients. In highly malignant cell lines (MDA-MB231, DU4475 and BT549), downregulation of WDR26 expression selectively alleviated GPCR- but not EGF receptor-stimulated PI3K/AKT signaling and tumor cell growth, migration and invasion. In contrast, in a less malignant cell line (MCF7), WDR26 overexpression had the opposite effect. Additional studies indicate that downstream of GPCR stimulation, WDR26 serves as a scaffold that fosters assembly of a specific signaling complex consisting of Gβγ, PI3Kβ and AKT2. In an orthotopic xenograft mouse model of breast cancer, disrupting formation of this complex, by overexpressing WDR26 mutants in MDA-MB231 cells, abrogated PI3K/AKT activation and tumor cell growth and metastasis. Together, our results identify a novel mechanism regulating GPCR-dependent activation of the PI3K/AKT signaling axis in breast tumor cells, and pinpoint WDR26 as a potential therapeutic target for breast cancer.
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