Figure 1.

UL33 and US28 mediate constitutive activation of proliferative and proangiogenic signal transduction pathways in HEK293T cells. A, dose-dependent receptor expression in HEK293T cells transiently transfected with increasing amounts of DNA encoding UL33-HA or US28-HA (C-terminally epitope-tagged receptors), as assessed through anti-HA ELISA. B, HEK293T cells were transfected with 12 ng of UL33-HA or 40 ng of US28-HA/10⁶ cells in combination with the corresponding luciferase reporter genes. At similar expression levels, the constitutive activation of multiple signaling pathways was assessed. Mock cells (transfected with reporter gene plasmid) were stimulated with 8 pm TGFβ for 24 h as a positive control for SMAD3 activation. Constitutive NF-κB activation (C) or InsP production (D) was assessed in HEK293T cells transfected with a series of DNA encoding UL33-HA or US28-HA. AlF₃ was included as positive control in the InsP production assay. Graphs are representatives of at least three individual experiments performed in triplicate, and data are presented as mean ± S.D. (error bars). *, p < 0.05; **, p < 0.01; and ****, p < 0.0001.