N-terminally Truncated Variant of the Mouse GAIP/RGS19 Lacks Selectivity of Full-length GAIP/RGS19 Protein in Regulating ORL1 Receptor Signaling

• Published in: Journal of molecular biology Vol. 353; no. 5; pp. 1081 - 1092
• Main Authors: Xie, Guo-xi, Yanagisawa, Yuka, Ito, Emi, Maruyama, Kazuo, Han, Xiaokang, Kim, Ki Jun, Han, Kyung Ream, Moriyama, Kumi, Palmer, Pamela Pierce
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 11.11.2005
• Subjects: Alternative Splicing; Animals; Cercopithecus aethiops; COS Cells; Cyclic AMP - metabolism; GTPase; Guanosine Triphosphate - metabolism; Mice; nociceptin/orphanin FQ; opioid receptor; Protein Structure, Tertiary; Receptors, Opioid - genetics; Receptors, Opioid - metabolism; regulator of G protein signaling; RGS Proteins - genetics; RGS Proteins - physiology; RNA, Messenger - analysis; Signal Transduction; Transfection; aa; GAIP; nociceptin/orphanin FQ; U50,488; alternative splicing; DAMGO; DOR; ORL1; DPDPE; KOR; opioid receptor; MOR; U69,593; regulator of G protein signaling; IRES; NOC/OFQ; dyn; GTPase; RGS
• ISSN: 0022-2836; 1089-8638
• DOI: 10.1016/j.jmb.2005.09.040

The regulators of G protein signaling (RGS) are a family of proteins with conserved RGS domains and play essential roles in regulating G protein-mediated signal transduction and physiological events. GAIP/RGS19 (G alpha interacting protein, also classified as RGS19), a member of the RGS family, has been shown to negatively regulate the signaling of many G protein-coupled receptors, including the opioid receptors. Two GAIP/RGS19 mRNA variants, resulted from an alternative splicing of exon 2 of the GAIP/RGS19 gene, were identified in multiple mouse tissues. One of the transcripts consists of a complete set of exons and encodes a full-length GAIP/RGS19 protein, and the other does not have exon 2 and therefore encodes an N-terminal 22 residue truncated short GAIP/RGS19 protein. When co-expressed with either the opioid-receptor-like (ORL1) receptor or one of the μ, δ, and κ opioid receptors, by transfecting dual-expression plasmids into COS-7 cells, the full-length GAIP/RGS19 was more effective than the N-terminally truncated variant and was more selective in regulating the ORL1 receptor signaling than in regulating the μ, δ, and κ opioid receptors, as measured by the effectiveness to increase the agonist-stimulated GTPase activity and to reverse the agonist-induced inhibition of cyclic AMP accumulation. In the same assays, the N-terminally truncated GAIP/RGS19 did not distinguish ORL1 from the μ, δ, and κ opioid receptors. In contrast, co-expression of RGS4 with either ORL1 or opioid receptors showed the selectivity of RGS4 for regulating opioid receptors was μ > κ > δ > ORL1, an order completely different from that of GAIP/RGS19. The results suggest that GAIP/RGS19 prefers regulating ORL1 receptor signaling over other opioid receptors, and that the N-terminal domain of GAIP/RGS19 plays a crucial role in its receptor preference.