N-myc Downstream-regulated Gene 2, a Novel Estrogen-targeted Gene, Is Involved in the Regulation of Na+/K+-ATPase

Na(+)/K(+)-ATPase, a plasma membrane protein abundantly expressed in epithelial tissues, has been identified and linked to numerous biological events, including ion transport and reabsorption. In Na(+)/K(+)-ATPase, the β-subunit plays a fundamental role in the structural integrity and functional maturation of holoenzyme. Estrogens are important circulating hormones that can regulate Na(+)/K(+)-ATPase abundance and activity; however, the specific molecules participating in this process are largely unknown. Here, we characterize that N-myc downstream-regulated gene 2 (NDRG2) is an estrogen up-regulated gene. 17β-Estradiol binds with estrogen receptor β but not estrogen receptor α to up-regulate NDRG2 expression via transcriptional activation. We also find that NDRG2 interacts with the β1-subunit of Na(+)/K(+)-ATPase and stabilizes the β1-subunit by inhibiting its ubiquitination and degradation. NDRG2-induced prolongation of the β1-subunit protein half-life is accompanied by a similar increase in Na(+)/K(+)-ATPase-mediated Na(+) transport and Na(+) current in epithelial cells. In addition, NDRG2 silencing largely attenuates the accumulation of β1-subunit regulated by 17β-estradiol. Our results demonstrate that estrogen/NDRG2/Na(+)/K(+)-ATPase β1 pathway is important in promoting Na(+)/K(+)-ATPase activity and suggest this novel pathway might have substantial roles in ion transport, fluid balance, and homeostasis.