title: On the role of endogenous G-protein beta gamma subunits in N-type Ca2+ current inhibition by neurotransmitters in rat sympathetic neurones.
abstract: 1. Using whole-cell and perforated-patch recordings, we have examined the part played by endogenous G-protein beta gamma subunits in neurotransmitter-mediated inhibition of N-type Ca2+ channel current (ICa) in dissociated rat superior cervical sympathetic neurones. 2. Expression of the C-terminus domain of beta-adrenergic receptor kinase 1 (beta ARK1), which contains the consensus motif (QXXER) for binding G beta gamma, reduced the fast (pertussis toxin (PTX)-sensitive) and voltage-dependent inhibition of ICa by noradrenaline and somatostatin, but not the slow (PTX-insensitive) and voltage-independent inhibition induced by angiotensin II. beta ARK1 peptide reduced GTP-gamma-S-induced voltage-dependent and PTX-sensitive inhibition of ICa but not GTP-gamma-S-mediated voltage-independent inhibition. 3. Overexpression of G beta 1 gamma 2, which mimicked the voltage-dependent inhibition by reducing ICa density and enhancing basal facilitation, occluded the voltage-dependent noradrenaline- and somatostatin-mediated inhibitions but not the inhibition mediated by angiotensin II. 4. Co-expression of the C-terminus of beta ARK1 with beta 1 and gamma 2 subunits prevented the effects of G beta gamma dimers on basal Ca2+ channel behaviour in a manner consistent with the sequestering of G beta gamma. 5. The expression of the C-terminus of beta ARK1 slowed down reinhibition kinetics of ICa following conditioning depolarizations and induced long-lasting facilitation by cumulatively sequestering beta gamma subunits. 6. Our findings identify endogenous G beta gamma as the mediator of the voltage-dependent, PTX-sensitive inhibition of ICa induced by both noradrenaline and somatostatin but not the voltage-independent. PTX-insensitive inhibition by angiotensin II. They also support the view that voltage-dependent inhibition results from a direct G beta gamma-Ca2+ channel interaction.
authors.affiliation: Wellcome Laboratory for Molecular Pharmacology, Department of Pharmacology, University College London, UK. ucklpds@ucl.ac.uk
authors.forename: P
authors.initials: P
authors.lastname: Delmas
authors.forename: D A
authors.initials: DA
authors.lastname: Brown
authors.forename: M
authors.initials: M
authors.lastname: Dayrell
authors.forename: F C
authors.initials: FC
authors.lastname: Abogadie
authors.forename: M P
authors.initials: MP
authors.lastname: Caulfield
authors.forename: N J
authors.initials: NJ
authors.lastname: Buckley
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics / Q000502:physiology; D004594:Electrophysiology; D019204:GTP-Binding Proteins / Q000235:genetics / Q000502:physiology*; D015870:Gene Expression / Q000235:genetics / Q000502:physiology; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006801:Humans; D015640:Ion Channel Gating; D007700:Kinetics; D009474:Neurons / Q000737:chemistry / Q000187:drug effects / Q000502:physiology; D018377:Neurotransmitter Agents / Q000502:physiology*; D009638:Norepinephrine / Q000037:antagonists & inhibitors / Q000494:pharmacology; D037342:Pertussis Toxin; D051381:Rats; D017207:Rats, Sprague-Dawley; D011942:Receptors, Adrenergic, alpha / Q000502:physiology; D017481:Receptors, Somatostatin / Q000502:physiology; D011994:Recombinant Proteins / Q000235:genetics; D013004:Somatostatin / Q000037:antagonists & inhibitors / Q000494:pharmacology; D017783:Superior Cervical Ganglion / Q000737:chemistry / Q000166:cytology*; D013997:Time Factors; D010566:Virulence Factors, Bordetella / Q000494:pharmacology; D051552:beta-Adrenergic Receptor Kinases
chemical_list: D015220:Calcium Channels; D018377:Neurotransmitter Agents; D011942:Receptors, Adrenergic, alpha; D017481:Receptors, Somatostatin; D011994:Recombinant Proteins; D010566:Virulence Factors, Bordetella; D000804:Angiotensin II; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D013004:Somatostatin; D037342:Pertussis Toxin; D017868:Cyclic AMP-Dependent Protein Kinases; D051552:beta-Adrenergic Receptor Kinases; D019204:GTP-Binding Proteins; D009638:Norepinephrine