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The Journal of Neuroscience, January 7, 2009, 29(1):222-233; doi:10.1523/JNEUROSCI.4315-08.2009

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Cellular/Molecular
Neurokinin 1 Receptors Regulate Morphine-Induced Endocytosis and Desensitization of µ-Opioid Receptors in CNS Neurons

Y. Joy Yu,¹ Seksiri Arttamangkul,³ Christopher J. Evans,⁴ John T. Williams,³ and Mark von Zastrow^1,2

¹Program in Neuroscience and ²Department of Psychiatry and Cellular and Molecular Pharmacology, University of California at San Francisco, San Francisco, California 94158, ³Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239, and ⁴Department of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, Los Angeles, California 90024

Correspondence should be addressed to Mark von Zastrow, Room N212 Genentech Hall, University of California at San Francisco Mission Bay Campus, 600 16th Street, San Francisco, CA 94158-2140. Email: mark.vonzastrow{at}ucsf.edu

µ-Opioid receptors (MORs) are G-protein-coupled receptors (GPCRs) that mediate the physiological effects of endogenous opioid neuropeptides and opiate drugs such as morphine. MORs are coexpressed with neurokinin 1 receptors (NK1Rs) in several regions of the CNS that control opioid dependence and reward. NK1R activation affects opioid reward specifically, however, and the cellular basis for this specificity is unknown. We found that ligand-induced activation of NK1Rs produces a cell-autonomous and nonreciprocal inhibition of MOR endocytosis induced by diverse opioids. Studies using epitope-tagged receptors expressed in cultured striatal neurons and a neuroblastoma cell model indicated that this heterologous regulation is mediated by NK1R-dependent sequestration of arrestins on endosome membranes. First, endocytic inhibition mediated by wild-type NK1Rs was overcome in cells overexpressing β-arrestin2, a major arrestin isoform expressed in striatum. Second, NK1R activation promoted sequestration of β-arrestin2 on endosomes, whereas MOR activation did not. Third, heterologous inhibition of MOR endocytosis was prevented by mutational disruption of β-arrestin2 sequestration by NK1Rs. NK1R-mediated regulation of MOR trafficking was associated with reduced opioid-induced desensitization of adenylyl cyclase signaling in striatal neurons. Furthermore, heterologous regulation of MOR trafficking was observed in both amygdala and locus ceruleus neurons that naturally coexpress these receptors. These results identify a cell-autonomous mechanism that may underlie the highly specific effects of NK1R on opioid signaling and suggest, more generally, that receptor-specific trafficking of arrestins may represent a fundamental mechanism for coordinating distinct GPCR-mediated signals at the level of individual CNS neurons.

Key words: trafficking; opioid; arrestin; morphine; endocytosis; neurokinin

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Received Sept. 9, 2008; revised Oct. 29, 2008; accepted Nov. 28, 2008.

Correspondence should be addressed to Mark von Zastrow, Room N212 Genentech Hall, University of California at San Francisco Mission Bay Campus, 600 16th Street, San Francisco, CA 94158-2140. Email: mark.vonzastrow{at}ucsf.edu

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