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Regulation of c-Jun N-terminal kinase by the ORL(1) receptor through multiple G proteins
1Department of Biochemistry and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
Abstract:
Nociceptin is an endogenous peptide that produces its biological effects by binding to the opioid receptor-like (ORL(1)) receptor. It has been shown that activation of ORL(1) receptor leads to inhibition of the adenylyl cyclase activity, but stimulation of the extracellular signal-regulated kinase and p38 subgroups of mitogen-activated protein kinases. In this report, we demonstrate that activation of the G protein-coupled ORL(1) receptor in transfected COS-7 cells leads to stimulation of the JNK subgroup of mitogen-activated protein kinases in a Ras/Rac-dependent manner, and it was insensitive to wortmannin. This increased JNK activity was mainly mediated by PTX-sensitive G(i) proteins, and partially contributed by a PTX-insensitive component. Among all known PTX-insensitive G proteins, G(z), G(12), G(14), and G(16) seemed to have functional coupling with the ORL(1) receptor in terms of JNK activation. Stimulation of the endogenous ORL(1) receptor in NG108-15 cells also led to activation of a PTX-sensitive JNK activity in a wortmannin-insensitive manner. The induced JNK activation is accompanied by the active phosphorylation of c-Jun and activating transcription factor-2. This is the first report that demonstrates the stimulatory effect of ORL(1) receptor on JNK, and the subsequent activation of c-Jun and activating transcription factor-2.
Insights
Nociceptin activates the opioid receptor-like (ORL1) receptor, stimulating JNK signaling pathways. This study reveals ORL1 receptor
Area of Science:
- Molecular biology
- Cell signaling
- Neuroscience
Background:
- Nociceptin, an endogenous peptide, signals through the opioid receptor-like (ORL1) receptor.
- ORL1 receptor activation is known to inhibit adenylyl cyclase but stimulate ERK and p38 MAPK pathways.
Purpose of the Study:
- To investigate the effect of ORL1 receptor activation on the JNK subgroup of mitogen-activated protein kinases.
- To elucidate the signaling pathways and G proteins involved in ORL1 receptor-mediated JNK activation.
Main Methods:
- Utilized transfected COS-7 cells and endogenous ORL1 receptors in NG108-15 cells.
- Investigated JNK activation, Ras/Rac dependency, wortmannin insensitivity, and pertussis toxin (PTX)-sensitive/insensitive G protein involvement.
- Assessed phosphorylation of c-Jun and activating transcription factor-2.
Main Results:
- ORL1 receptor activation stimulates JNK activity in a Ras/Rac-dependent and wortmannin-insensitive manner.
- JNK activation is primarily mediated by PTX-sensitive G(i) proteins, with contributions from PTX-insensitive G proteins (G(z), G(12), G(14), G(16)).
- Stimulation of endogenous ORL1 receptors also induced PTX-sensitive, wortmannin-insensitive JNK activation, leading to c-Jun and ATF-2 phosphorylation.
Conclusions:
- This study is the first to demonstrate ORL1 receptor stimulation of JNK signaling.
- ORL1 receptor activation leads to downstream phosphorylation of c-Jun and activating transcription factor-2.
- The findings highlight a novel signaling pathway involving ORL1 receptor and JNK activation.