Pertussis Toxin‐Insensitive Signaling of the ORL₁ Receptor: Coupling to G_z and G₁₆ Proteins

Abstract

Nociceptin/OFQ is the endogenous ligand for the G protein-coupled opioid receptor-like (ORL1) receptor. To elucidate the cellular functions of the ORL1 receptor, we examined its ability to interact with Gãnd G16, two pertussis toxin (PTX) -insensitive G proteins that are known molecular partners for the opioid receptors. In HEK 293 cells transiently expressing the ORL1 and dopamine D1 receptors, nociceptin/OFQ dose-dependently inhibited dopamine-stimulated cyclic AMP (cAMP) accumulation in a PTX-sensitive manner. However, PTX failed to block the nociceptin/OFQ-induced inhibition of dopamine-stimulated cAMP accumulation in HEK 293 cells co-expressing the £6-subunit of G~. This result indicates functional interaction between the ORL1 receptor and G0. A similar result was obtained with retinoic acid-differentiated SH-SY5Y cells, which endogenously express both the ORL1 receptor and G~. When the ORL1 receptor was transiently co-expressed in COS-7 cells with the a-subunit of G16, nociceptin/OFQ dose-dependently stimulated the formation of inositol phosphates. Nociceptininduced stimulation of phospholipase C was absolutely dependent on the co-expression of £616 and exhibited the appropriate ligand selectivity. In terms of its ability to interact with PTX-insensitive G proteins, the ORL1 receptor behaves very much like the opioid receptors. Key Words: Adenylyl cyclase-G16-G0-Phospholipase C-ORL1 receptor-Signal transduction.

Modulation of Ca2+Channels by Opioid Receptor-Like 1 Receptors Natively Expressed in Rat Stellate Ganglion Neurons Innervating Cardiac Muscle

“…Similar findings have been previously published (Morikawa et al, 1998;Connor et al, 1999;Larsson et al, 2000;Beedle et al, 2004;Yeon et al, 2004). Nevertheless, it has been reported that ORL1 receptors are also capable of coupling to other PTX-insensitive G␣ protein subunits to modulate other effectors (Chan et al, 1998;Chan and Wong, 2000).…”

Nociceptin/Orphanin FQ Receptor Structure, Signaling, Ligands, Functions, and Interactions with Opioid Systems

“…Several reports have confirmed that NOP receptor activation inhibits adenylyl cyclase activity similarly and it is widely accepted that the NOP receptor couples to pertussistoxin-sensitive G-proteins, including Gai, to cause inhibition of cAMP formation (Zhang et al, 2012a). However, it has also been suggested that NOP receptors can promiscuously couple to other G proteins, although this has been less well characterized in physiologically relevant systems, and has only been demonstrated in heterologous expression studies and SH-SY5Y cells (Chan et al, 1998).…”

Cellular Mechanisms of Nociceptin/Orphanin FQ (N/OFQ) Peptide (NOP) Receptor Regulation and Heterologous Regulation by N/OFQ

“…The NOP receptor, like other opioid receptors, is a prototypical G protein-coupled receptor (GPCR) that couples to pertussis toxin-sensitive and -insensitive (Chan et al, 1998) G proteins. After agonist activation, the NOP receptor triggers intracellular signaling events, including inhibition of adenylyl cyclase and activation of protein kinase C (PKC) (Lou et al, 1997), phospholipase A and C (Lou et al, 1997), extracellular signal-regulated kinases 1 and 2 (ERK1/2) (Fukuda et al, 1997;Lou et al, 1997), p38 mitogen-activated protein kinase (Zhang et al, 1999a), c-Jun N-terminal kinase (JNK) (Chan and Wong, 2000), nuclear factor kB (NFkB) (Donica et al, 2011), and modulation of calcium (Connor et al, 1996b) and potassium channel conductance (Connor et al, 1996a).…”

“…Clathrin-coated vesicles are trafficked to early endosomal compartments, where the receptor is completely internalized. Agonist-induced receptor internalization is (Cannarsa et al, 2012;Connor et al, 1996b;Donica et al, 2011;Mandyam et al, 2003;Thakker et al, 2007;Thakker and Standifer, 2002a,b) (Barnes et al, 2007;Bevan et al, 1998;Fukuda et al, 1998;Fukuda et al, 1997;Hashimoto et al, 2002;Hawes et al, 1998;Lou et al, 1997;McDonald et al, 2003;Okawa et al, 1999;Pan et al, 2002;Peluso et al, 2001;Spampinato and Baiula, 2006;Spampinato et al, 2002;Waits et al, 2004) COS-7 African green monkey kidney fibroblast-like cells transformed with SV40 ++++ G-protein coupling and NOP receptor expression (Chan and Wong, 2000;Chan et al, 1998;Ho et al, 2002 (Altier et al, 2006;Beedle et al, 2004;Evans et al, 2010) the intermediate phase of GPCR desensitization, where the receptor is now inaccessible for activation by the extracellular agonist, thereby inhibiting further agonist-mediated cellular responses. However, it is also an essential process for resensitization of receptors (Gainetdinov et al, 2004), as explained below.…”