RT Journal Article
SR Electronic
T1 Voltage-Gated R-Type Calcium Channel Inhibition via Human <em>μ</em>-, <em>δ</em>-, and <em>κ</em>-opioid Receptors Is Voltage-Independently Mediated by G<em>βγ</em> Protein Subunits
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 187
OP 196
DO 10.1124/mol.115.101154
VO 89
IS 1
A1 Géza Berecki
A1 Leonid Motin
A1 David J. Adams
YR 2016
UL http://molpharm.aspetjournals.org/content/89/1/187.abstract
AB Elucidating the mechanisms that modulate calcium channels via opioid receptor activation is fundamental to our understanding of both pain perception and how opioids modulate pain. Neuronal voltage-gated N-type calcium channels (Cav2.2) are inhibited by activation of G protein–coupled opioid receptors (ORs). However, inhibition of R-type (Cav2.3) channels by μ- or κ-ORs is poorly defined and has not been reported for δ-ORs. To investigate such interactions, we coexpressed human μ-, δ-, or κ-ORs with human Cav2.3 or Cav2.2 in human embryonic kidney 293 cells and measured depolarization-activated Ba2+ currents (IBa). Selective agonists of μ-, δ-, and κ-ORs inhibited IBa through Cav2.3 channels by 35%. Cav2.2 channels were inhibited to a similar extent by κ-ORs, but more potently (60%) via μ- and δ-ORs. Antagonists of δ- and κ-ORs potentiated IBa amplitude mediated by Cav2.3 and Cav2.2 channels. Consistent with G protein βγ (Gβγ) interaction, modulation of Cav2.2 was primarily voltage-dependent and transiently relieved by depolarizing prepulses. In contrast, Cav2.3 modulation was voltage-independent and unaffected by depolarizing prepulses. However, Cav2.3 inhibition was sensitive to pertussis toxin and to intracellular application of guanosine 5′-[β-thio]diphosphate trilithium salt and guanosine 5′-[γ-thio]triphosphate tetralithium salt. Coexpression of Gβγ-specific scavengers—namely, the carboxyl terminus of the G protein–coupled receptor kinase 2 or membrane-targeted myristoylated-phosducin—attenuated or abolished Cav2.3 modulation. Our study reveals the diversity of OR-mediated signaling at Cav2 channels and identifies neuronal Cav2.3 channels as potential targets for opioid analgesics. Their novel modulation is dependent on pre-existing OR activity and mediated by membrane-delimited Gβγ subunits in a voltage-independent manner.