Stabilization of the μ-Opioid Receptor by Truncated Single Transmembrane Splice Variants through a Chaperone-like Action

• Published in: The Journal of biological chemistry 2013-07, Vol.288 (29), p.21211-21227
• Main Authors: Xu, Jin, Xu, Ming, Brown, Taylor, Rossi, Grace C., Hurd, Yasmin L., Inturrisi, Charles E., Pasternak, Gavril W., Pan, Ying-Xian
• Format: Article
• Language: English
• Subjects: Alternative Splicing; Alternative Splicing - genetics; Amino Acid Sequence; Analgesia; Animals; Antisense Oligodeoxynucleotide; Base Sequence; Brefeldin A - pharmacology; Cell Membrane - metabolism; Cloning, Molecular; Dimerization; DNA, Complementary - genetics; Endoplasmic Reticulum - drug effects; Endoplasmic Reticulum - metabolism; Enkephalin, Ala-MePhe-Gly; G Protein-coupled Receptors (GPCR); Gene Expression Profiling; Guanosine 5'-O-(3-Thiotriphosphate); Humans; Mice; Molecular Bases of Disease; Molecular Chaperone; Molecular Chaperones - metabolism; Morphine; Morphine - pharmacology; Oligonucleotides, Antisense - pharmacology; Opiate Opioid; Protein Binding; Protein Multimerization; Protein Stability; Protein Structure, Tertiary; Rats; Receptor Regulation; Receptors, Opioid, mu - chemistry; Receptors, Opioid, mu - genetics; Receptors, Opioid, mu - metabolism; RNA, Messenger - genetics; RNA, Messenger - metabolism; Ubiquitination - drug effects
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M113.458687

The μ-opioid receptor gene, OPRM1, undergoes extensive alternative pre-mRNA splicing, as illustrated by the identification of an array of splice variants generated by both 5′ and 3′ alternative splicing. The current study reports the identification of another set of splice variants conserved across species that are generated through exon skipping or insertion that encodes proteins containing only a single transmembrane (TM) domain. Using a Tet-Off system, we demonstrated that the truncated single TM variants can dimerize with the full-length 7-TM μ-opioid receptor (MOR-1) in the endoplasmic reticulum, leading to increased expression of MOR-1 at the protein level by a chaperone-like function that minimizes endoplasmic reticulum-associated degradation. In vivo antisense studies suggested that the single TM variants play an important role in morphine analgesia, presumably through modulation of receptor expression levels. Our studies suggest the functional roles of truncated receptors in other G protein-coupled receptor families. Background: The μ-opioid receptor gene undergoes extensive alternative splicing. Results: The single transmembrane (TM) splice variants function as a chaperone to stabilize 7-TM MOR-1, enhancing morphine analgesia. Conclusion: Single TM variants play an important role in expression and function of 7-TM MOR-1. Significance: The function of truncated variants is significant for understanding the regulation of μ-opioid receptors or other GPCR families.