Phosphorylation of Serine422 increases the stability and transactivation activities of human Osterix

Osterix (Osx) is an essential regulator for osteoblast differentiation and bone formation. Although phosphorylation has been reported to be involved in the regulation of Osx activity, the precise underlying mechanisms remain to be elucidated. Here we identified S422 as a novel phosphorylation site of Osx and demonstrated that GSK-3β interacted and co-localized with Osx. GSK-3β increased the stability and transactivation activity of Osx through phosphorylation of the newly identified site. These findings expanded our understanding of the mechanisms of posttranslational regulation of Osx and the role of GSK-3β in the control of Osx transactivation activity.