TY - JOUR
T1 - The endomorphin-1/2 and dynorphin-B peptides display biased agonism at the mu opioid receptor
AU - LaVigne, Justin
AU - Keresztes, Attila
AU - Chiem, Daniel
AU - Streicher, John M.
N1 - Funding Information:
We would like to acknowledge institutional funds from the University of New England and the University of Arizona used to complete these studies. The authors have no other relevant conflicts of interest to declare.
Publisher Copyright:
© 2020, Maj Institute of Pharmacology Polish Academy of Sciences.
PY - 2020/4/1
Y1 - 2020/4/1
N2 - Background: Opioid agonist activation at the mu opioid receptor (MOR) can lead to a wide variety of physiological responses. Many opioid agonists share the ability to selectively and preferentially activate specific signaling pathways, a term called biased agonism. Biased opioid ligands can theoretically induce specific physiological responses and might enable the generation of drugs with improved side effect profiles. Methods: Dynorphins, enkephalins, and endomorphins are endogenous opioid agonist peptides that may possess distinct bias profiles; biased agonism of endogenous peptides could explain the selective roles of these ligands in vivo. Our purpose in the present study was to investigate biased signaling and potential underlying molecular mechanisms of bias using 35S-GTPγS and cAMP assays, specifically focusing on the role of adenylyl cyclases (ACs) and regulators of G-protein signaling proteins (RGSs) in CHO, N2a, and SH-SY5Y cell lines, all expressing the human MOR. Results: We found that endomorphin-1/2 preferentially activated cAMP signaling, while dynorphin-B preferentially activated 35S-GTPγS signaling in most cell lines. Experiments carried out in the presence of an isoform selective RGS-4 inhibitor, and siRNA knockdown of AC6 in N2a cells did not significantly affect the bias properties of endomorphins, suggesting that these proteins may not play a role in endomorphin bias. Conclusion: We found that endomorphin-1/2 and dynorphin-B displayed contrasting bias profiles at the MOR, and ruled out potential AC6 and RGS4 mechanisms in this bias. This identified signaling bias could be involved in specifying endogenous peptide roles in vivo, where these peptides have low selectivity between opioid receptor family members.
AB - Background: Opioid agonist activation at the mu opioid receptor (MOR) can lead to a wide variety of physiological responses. Many opioid agonists share the ability to selectively and preferentially activate specific signaling pathways, a term called biased agonism. Biased opioid ligands can theoretically induce specific physiological responses and might enable the generation of drugs with improved side effect profiles. Methods: Dynorphins, enkephalins, and endomorphins are endogenous opioid agonist peptides that may possess distinct bias profiles; biased agonism of endogenous peptides could explain the selective roles of these ligands in vivo. Our purpose in the present study was to investigate biased signaling and potential underlying molecular mechanisms of bias using 35S-GTPγS and cAMP assays, specifically focusing on the role of adenylyl cyclases (ACs) and regulators of G-protein signaling proteins (RGSs) in CHO, N2a, and SH-SY5Y cell lines, all expressing the human MOR. Results: We found that endomorphin-1/2 preferentially activated cAMP signaling, while dynorphin-B preferentially activated 35S-GTPγS signaling in most cell lines. Experiments carried out in the presence of an isoform selective RGS-4 inhibitor, and siRNA knockdown of AC6 in N2a cells did not significantly affect the bias properties of endomorphins, suggesting that these proteins may not play a role in endomorphin bias. Conclusion: We found that endomorphin-1/2 and dynorphin-B displayed contrasting bias profiles at the MOR, and ruled out potential AC6 and RGS4 mechanisms in this bias. This identified signaling bias could be involved in specifying endogenous peptide roles in vivo, where these peptides have low selectivity between opioid receptor family members.
KW - Biased agonism
KW - Endogenous opioid peptides
KW - Endomorphin
KW - Forskolin-stimulated cAMP accumulation
KW - S-GTPγS coupling
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U2 - 10.1007/s43440-020-00061-x
DO - 10.1007/s43440-020-00061-x
M3 - Article
C2 - 32112361
AN - SCOPUS:85080110578
SN - 2299-5684
VL - 72
SP - 465
EP - 471
JO - Pharmacological Reports
JF - Pharmacological Reports
IS - 2
ER -