Selective interactions of spinophilin with the C-terminal domains of the [d]- and mu -opioid receptors and G proteins differentially modulate opioid receptor signaling

• Published in: Cellular signalling Vol. 24; no. 12; pp. 2315 - 2328
• Main Authors: Fourla, Danai-Dionysia, Papakonstantinou, Maria-Pagona, Vrana, Stavroula-Maria, Georgoussi, Zafiroula
• Format: Journal Article
• Language: English
• Published: 01.12.2012
• Subjects: Amino acids
• ISSN: 0898-6568
• DOI: 10.1016/j.cellsig.2012.08.002

Previous studies have shown that the intracellular domains of opioid receptors serve as platforms for the formation of a multi-component signaling complex consisting of various interacting partners (Leontiadis et al., 2009, Cell Signal. 21, 1218-1228; Georganta et al., 2010, Neuropharmacology, 59(3), 139-148). In the present study we demonstrate that spinophilin a dendritic-spine enriched scaffold protein associates with [d]- and mu -opioid receptors ([d]-OR, mu -OR) constitutively in HEK293 an interaction that is altered upon agonist administration and enhanced upon forskolin treatment for both mu -OR and [d]-OR. Spinophilin association with the opioid receptors is mediated via the third intracellular loop and a conserved region of the C-terminal tails. The portion of spinophilin responsible for interaction with the [d]-OR and mu -OR is narrowed to a region encompassing amino acids 151-444. Spinophilin, RGS4, G[alpha] and G[beta][gamma] subunits of G proteins form a multi-protein complex using specific regions of spinophilin and a conserved amino acid stretch of the C-terminal tails of both [d]- mu -ORs. Expression of spinophilin in HEK293 cells potentiated DPDPE-mediated adenylyl-cyclase inhibition of [d]-OR leaving unaffected the levels of cAMP accumulation mediated by the mu -OR. Moreover, measurements of extracellular signal regulated kinase (ERK1,2) phosphorylation indicated that the presence of spinophilin attenuated agonist-driven ERK1,2 phosphorylation mediated upon activation of the [d]-OR but not the mu -OR. Collectively, these findings suggest that spinophilin associates with both [d]- and mu -OR and G protein subunits in HEK293 cells participating in a multimeric signaling complex that displays a differential regulatory role in opioid receptor signaling.