Human cytomegalovirus activates glucose transporter 4 expression to increase glucose uptake during infection.

ABSTRACT

Glucose transport into mammalian cells is mediated by a group of glucose transporters (GLUTs) on the plasma membrane. Human cytomegalovirus (HCMV)-infected human fibroblasts (HFs) demonstrate significantly increased glucose consumption compared to mock-infected cells, suggesting a possible alteration in glucose transport during infection. Inhibition of GLUTs by using cytochalasin B indicated that infected cells utilize GLUT4, whereas normal HFs use GLUT1. Quantitative reverse transcription-PCR and Western analysis confirmed that GLUT4 levels are greatly increased in infected cells. In contrast, GLUT1 was eliminated by a mechanism involving the HCMV major immediate-early protein IE72. The HCMV-mediated induction of GLUT4 circumvents characterized controls of GLUT4 expression that involve serum stimulation, glucose concentration, and nuclear functions of ATP-citrate lyase (ACL). In infected cells the well-characterized Akt-mediated translocation of GLUT4 to the cell surface is also circumvented; GLUT4 localized on the surface of infected cells that were serum starved and had Akt activity inhibited. The significance of GLUT4 induction for the success of HCMV infection was indicated using indinavir, a drug that specifically inhibits glucose uptake by GLUT4. The addition of the drug inhibited glucose uptake in infected cells as well as viral production. Our data show that HCMV-specific mechanisms are used to replace GLUT1, the normal HF GLUT, with GLUT4, the major glucose transporter in adipose tissue, which has a 3-fold-higher glucose transport capacity.