PXR (Pregnane Xenobiotic Receptor) belongs to the class II family of nuclear receptor (NR). PXR is considered as a master regulator of xenobiotic metabolism. PXR gets activated in a ligand-dependent manner and then heterodimerizes with RXR. PXR can also get activated via post-translational modifications and leads to crosstalk between signaling pathways. PXR is shown to be acetylated in vivo and this acetylation regulates its selective functions independent of ligands. However, the molecular players behind this acetylation and the impact of this acetylation in intracellular dynamics of PXR is not known. TIP60 is a lysine acetyltransferase which acetylates histones as well as non-histone proteins like ATM/ATR kinases and p53, and plays a role in DNA damage and repair pathway and in apoptosis. TIP60 is shown to interact with class I of NR. Thus, it might be interesting to reveal the role of TIP60 in acetylation of class II NR PXR.
We performed in vitro and in vivo co-immunoprecipitation assay and live cell imaging to show interaction as well as domain mapping. We found the site of acetylation in PXR by in silico and in vitro assay. To examine whether TIP60-PXR complex has any influence on these cellular processes, we performed cell migration, cell adhesion, cell proliferation and cell invasion assays.
In this study, we are trying to dissect the mechanism of PXR activation and functional dynamics by TIP60 dependent acetylation. We found the sites of interaction as LBD of PXR with NR box of TIP60 and thus TIP60 mediated subcellular dynamics of PXR. Also, we have found TIP60 mediated the acetylation site of PXR at lysine 170. This novel complex is independent of ligand and does not form a complex with RXR. Also, this complex does not activate ligand dependent PXR target genes. Interestingly, PXR augments TIP60 acetylation on histones. We further discovered TIP60-PXR complex promotes cell migration and adhesion, which might lead to their involvement in physiological or pathophysiological conditions.
This is the first report demonstrating the exclusive interaction of TIP60 with unliganded PXR and uncovers a potential role for the TIP60-PXR complex in cell migration and cell adhesion.
Clinical trial identification
Legal entity responsible for the study
ICMR and Shiv Nadar University.
The author has declared no conflicts of interest.