Retinoid X receptor α (RXRA) is the founding RXR family member and is predominantly expressed in the liver, kidney, epidermis, intestine, and a variety of tissues. Knockout of the murine rxrα gene results in embryonic lethality tentatively due to myocardial hypoplasia, which demonstrates the importance of RXRA in retinoid signaling in vivo. Biochemical evidence suggests that RXRA transcriptional activity is post-translationally regulated through the Ras-Raf-MAPK signaling cascade. MAPK-dependent phosphorylation of RXRα directly abrogates the ability of RXRA to associate with nuclear receptor coactivators.
