Phospho-Glucocorticoid Receptor (Ser134) Recombinant Rabbit mAb (S-5295)

Phospho-Glucocorticoid receptor (Ser134), namely the phosphorylation modification of the glucocorticoid receptor (GR) at serine residue 134, is a critical and unique post-translational modification in the regulation of GR function. Unlike most GR phosphorylation events that are hormone-dependent, phosphorylation at Ser134 is mediated by p38 mitogen-activated protein kinase (p38 MAPK) and serves as a direct response to various cellular stress signals. This modification occurs independently of hormonal stimulation and can be induced by stressors such as glucose deprivation, ultraviolet irradiation, osmotic shock, and oxidative stress. Upon phosphorylation at this site, the binding affinity of GR for 14-3-3ζ protein is significantly enhanced. This association alters the chromatin-binding pattern of GR and attenuates its transcriptional activity, ultimately "blunting" hormone-dependent transcriptional responses in a gene-specific manner. The significance of this modification is particularly prominent under pathological conditions. For instance, in triple-negative breast cancer, factors such as transforming growth factor β (TGFβ) and hepatocyte growth factor (HGF) in the tumor microenvironment can induce p38 MAPK-mediated phosphorylation of GR at Ser134, allowing the phosphorylated GR to form complexes with molecules like 14-3-3ζ, which in turn regulates gene expression programs that promote tumor progression, including tumor cell survival, metabolic reprogramming, and migration/invasion. Therefore, the Ser134-phosphorylated GR acts as a "molecular sensor" that integrates intracellular and extracellular stress signals, converting various stress cues into finely tuned transcriptional outputs through a hormone-independent pathway.