S4A-5 Screening ofμOpioid Receptor-Interacting Proteins and Effects of ABIN-1 on Receptor Function

Aim:To determine the proteins that interact with the carboxyl-terminal of theμopioid receptor(MOR-C)after chronic morphine exposure.Methods:The brain cDNA library of chronic morphine treatment rats was screened using rat MOR-C to investigate the regulator of opioids dependence in the present study.The brain cDNA library from chronic morphine-dependent rats was constructed using the SMART(Switching Mechanism At 5′end of RNA Transcript)technique.Bacterial two-hybrid system was used to screening the rat MOR-C interacting proteins from the cDNA library.RT-qPCR and immunoblotting were used to determine the variation of MOR-C interacting proteins in rat brain after chronic morphine treatment.Column overlay assays,immunocytochemistry and coimmunoprecipitation were used to demonstrate the interaction of MOR-C and p75NTR-associated cell death executor(NADE)or A20-binding inhibitor of nuclear factor kB(ABIN-1).Results:21 positive proteins,including 19 known proteins were screened to interact with rat MOR-C.Expression of several of these proteins was altered in specific rat brain regions after chronic morphine treatment.Among these proteins,ABIN-1 and NADE were confirmed to interact with rat MOR-C by in vitro proteinprotein binding and coimmunoprecipitation in Chinese hamster ovary(CHO)cells and rat brain with or without chronic morphine treatment.Saturation binding studies showed that ABIN-1 had no effect on MOR binding.However,the interaction of ABIN-1 and MOR inhibited the activation of G proteins induced by DAMGO([D-Ala2,N-Me-Phe4,Gly5-ol]-Enkephalin).MOR phosphorylation,ubiquitination,and internalization induced by DAMGO were decreased in Chinese hamster ovary cells that coexpressed MOR and ABIN-1.The suppression of forskolinstimulated adenylylcyclase by DAMGO was also inhibited by the interaction of ABIN-1with MOR.In addition,extracellular signal-regulated kinase activation was also negatively regulated by overexpression of ABIN-1.These data suggest that ABIN-1 is a negative coregulator of MOR activation,phosphorylation,and internalization in vitro.ABIN-1 also inhibited morphine-induced hyperlocomotion in zebrafish larvae(AB strain).By utilization of an antisense morpholino oligonucleotide(MO)gene knockdown technology,the ABIN-1MO-injected zebrafish larvae showed a significant increase(approximately 60%)in distance moved compared with control MO-injected larvae after acute morphine treatment(P≤0.01).Conclusion:Understanding the rat MOR-C interacting proteins and the proteins variation under chronic morphine treatment may be critical for determining the pathophysiological basis of opioid tolerance and addiction.Among these proteins,ABIN-1 negatively regulates MOR function in vitro and in vivo.Other MOR-C interacting proteins’influence on the opioid tolerance and addiction need further study.