Phosphatidylethanolamine‐Binding Protein Promotes Opioid Anti‐Nociception in the Brain and Spinal Cord by Reducing βarrestin2 Recruitment to the Mu Opioid Receptor

Abstract

Opioids have been widely accepted as an effective treatment for chronic pain at a cost of serious side effects, including tolerance and addiction. Side effects are caused in part by desensitization and downregulation of mu opioid receptors (MOR) through recruitment of βarrestin2. Phosphatidylethanolamine‐Binding Protein (PEBP) is known to regulate either Raf Kinase or G Protein Receptor Kinase‐2 (GRK2) through phosphorylation by Protein Kinase C (PKC), and GRK2 is a major player in the recruitment of βarrestin2. However, PEBP has not been investigated for its role in MOR signaling and opioid response. We first tested this using an in vitro model of βarrestin2 recruitment in MOR expressing U2OS cells. We found that by inhibiting PEBP through siRNA knockdown or the small molecule inhibitor locostatin, we could increase the recruitment of βarrestin2 to the MOR in 2 separate assays. Conversely, we found that activating PKC via phorbol myristate acetate (PMA) led to PEBP phosphorylation/activation, and a reduction in βarrestin2 recruitment to the MOR, which could be blocked by PEBP knockdown. We then tested the role of PEBP in vivo by injection of locostatin into the brain or spinal cord, or CRISPR editing of PEBP in the spinal cord. We found that blocking PEBP in vivo led to a strong reduction in morphine‐induced tail flick anti‐nociception in both the brain and spinal cord. Together, these results support the hypothesis that PEBP acts to sequester GRK2 and block βarrestin2 recruitment downstream of the MOR both in vivo and in vitro. These results also suggest that enhanced PKC/PEBP activation by opioid drugs could further reduce opioid side effects and enhance analgesic efficacy.Support or Funding InformationThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.