Human cytomegalovirus encoded chemokine receptor US28 activates the HIF-1α/PKM2 axis in glioblastoma cells
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Raymond H. de Wit1,*, Azra Mujić-Delić1,*, Jeffrey R. van Senten1, Alberto Fraile-Ramos2, Marco Siderius1 and Martine J. Smit1
1 Division of Medicinal Chemistry, Amsterdam Institute for Molecules Medicines and Systems, Vrije Universiteit Amsterdam, De Boelelaan, Amsterdam, The Netherlands
2 Division of Cell Biology, Faculty of Medicine, Universidad Complutense de Madrid, Madrid, Spain
* These authors have contributed equally to this work
Martine J. Smit, email:
Keywords: G protein-coupled receptor (GPCR), human cytomegalovirus (HCMV), hypoxia-inducible factor (HIF), chemokine, glioblastoma
Received: June 09, 2016 Accepted: August 25, 2016 Published: September 01, 2016
The human cytomegalovirus (HCMV) encoded chemokine receptor US28 promotes tumorigenesis through activation of various proliferative and angiogenic signaling pathways. Upon infection, US28 displays constitutive activity and signals in a G protein-dependent manner, hijacking the host’s cellular machinery. In tumor cells, the hypoxia inducible factor-1α/pyruvate kinase M2 (HIF-1α/PKM2) axis plays an important role by supporting proliferation, angiogenesis and reprogramming of energy metabolism. In this study we show that US28 signaling results in activation of the HIF-1α/PKM2 feedforward loop in fibroblasts and glioblastoma cells. The constitutive activity of US28 increases HIF-1 protein stability through a Gαq-, CaMKII- and Akt/mTOR-dependent mechanism. Furthermore, we found that VEGF and lactate secretion are increased and HIF-1 target genes, glucose transporter type 1 (GLUT1) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), involved in glucose metabolism, are upregulated in US28 expressing cells. In addition, PKM2 is phosphorylated and found to be in a tumor-associated dimeric state upon US28 expression. Also in HCMV-infected cells HIF-1 activity is enhanced, which in part is US28-dependent. Finally, increased proliferation of cells expressing US28 is abolished upon inhibition of the HIF-1α/PKM2 cascade. These data highlight the importance of HIF-1α and PKM2 in US28-induced proliferation, angiogenesis and metabolic reprogramming.
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