Allosteric Regulation in the Ligand Binding Domain of Retinoic Acid Receptor?.

ABSTRACT: Retinoic acid (RA) plays key roles in cell differentiation and growth arrest through nuclear retinoic acid receptors (RARs), which are ligand-dependent transcription factors. While the main trigger of RAR activation is the binding of RA, phosphorylation of the receptors has also emerged as an important regulatory signal. Phosphorylation of the RAR? N-terminal domain (NTD) is known to play a functional role in neuronal differentiation. In this work, we investigated the phosphorylation of RAR? ligand binding domain (LBD), and present evidence that the phosphorylation status of the LBD affects the phosphorylation of the NTD region. We solved the X-ray structure of a phospho-mimetic mutant of the LBD (RAR? S371E), which we used in molecular dynamics simulations to characterize the consequences of the S371E mutation on the RAR? structural dynamics. Combined with simulations of the wild-type LBD, we show that the conformational equilibria of LBD salt bridges (notably R387-D340) are affected by the S371E mutation, which likely affects the recruitment of the kinase complex that phosphorylates the NTD. The molecular dynamics simulations also showed that a conservative mutation in this salt bridge (R387K) affects the dynamics of the LBD without inducing large conformational changes. Finally, cellular assays showed that the phosphorylation of the NTD of RAR? is differentially regulated by retinoic acid in RAR?WT and in the S371N, S371E and R387K mutants. This multidisciplinary work highlights an allosteric coupling between phosphorylations of the LBD and the NTD of RAR? and supports the importance of structural dynamics involving electrostatic interactions in the regulation of RARs activity.

SUBMITTER: Chebaro Y 

PROVIDER: S-EPMC5268703 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature