Glucocorticoid Receptor {beta} Stimulates Akt1 Growth Pathway by Attenuation of PTEN [Cell Biology]

May 9th, 2014 by Stechschulte, L. A., Wuescher, L., Marino, J. S., Hill, J. W., Eng, C., Hinds, T. D.

Glucocorticoids (GCs) are known inhibitors of proliferation and are commonly prescribed to cancer patients to inhibit tumor growth and induce apoptosis via the glucocorticoid receptor (GR). Due to alternative splicing, the GR exists as two isoforms, GRα and GRβ. The growth inhibitory actions of GCs are mediated via GRα, a hormone induced transcription factor. The GRβ isoform, however, lacks helix 12 of the ligand-binding domain and cannot bind GCs. While we have previously shown that GRβ mRNA is responsive to insulin, the role of GRβ in insulin signaling and growth pathways is unknown. In the present study, we show that GRβ suppresses PTEN expression, leading to enhanced insulin stimulated growth. These characteristics were independent of the inhibitory qualities that have been reported for GRβ on GRα. Additionally, we found that GRβ increased phosphorylation of Akt basally, which was further amplified following insulin treatment. In particular, GRβ specifically targets Akt1 in growth pathways. Our results demonstrate that the GRβ/Akt1 axis is a major player in insulin-stimulated growth.