Vimentin interacts with the 5'-untranslated region of mouse mu opioid receptor (MOR) and is required for post-transcriptional regulation

The opioid receptors are among the most highly studied members of the superfamily of G-protein coupled receptors. Morphine and endogenous mu opioid peptides exert their pharmacological actions mainly through the mu opioid receptor (MOR). Expression of opioid receptor proteins is controlled by extensive transcriptional and post-transcriptional processing. Previously, the 5'-untranslated region (UTR) of the mouse MOR was found to be important for post-transcriptional regulation of the MOR gene in neuronal cells. Here, we demonstrate for the first time, the role of vimentin as a post-transcriptional repressor in MOR gene regulation. To identify potential regulators of the mouse MOR gene, we performed affinity column chromatography using 5'-UTR-specific RNA oligonucleotides using neuroblastoma NS20Y cells. Chromatography was followed by two-dimensional gel electrophoresis and MALDI-TOF mass spectrometry. We identified an intermediate filament protein, vimentin, which bound specifically to the region between -175 and -150 (175-150) of the MOR 5'-UTR. Binding was confirmed by western blot analysis and RNA supershift assay. Furthermore, a co-transfection study demonstrated that the presence of vimentin resulted in reduced expression of the mouse MOR. Our data suggest that vimentin functions as a repressor of MOR translation, dependent on 175-150 of the MOR 5'-UTR.