title: A voltage-independent calcium current inhibitory pathway activated by muscarinic agonists in rat sympathetic neurons requires both Galpha q/11 and Gbeta gamma.
abstract: Calcium current modulation by the muscarinic cholinergic agonist oxotremorine methiodide (oxo-M) was examined in sympathetic neurons from the superior cervical ganglion of the rat. Oxo-M strongly inhibited calcium currents via voltage-dependent (VD) and voltage-independent (VI) pathways. These pathways could be separated with the use of the specific M(1) acetylcholine receptor antagonist M(1)-toxin and with pertussis toxin (PTX) treatment. Expression by nuclear cDNA injection of the regulator of G-protein signaling (RGS2) or a phospholipase Cbeta1 C-terminal construct (PLCbeta-ct) selectively reduced VI oxo-M modulation in PTX-treated and untreated cells. Expression of the Gbetagamma buffers transducin (Galpha(tr)) and a G-protein-coupled-receptor kinase (GRK3) construct (MAS-GRK3) eliminated oxo-M modulation. Activation of the heterologously expressed neurokinin type 1 receptor, a Galpha(q/11)-coupled receptor, resulted in VI calcium current modulation. This modulation was eliminated with coexpression of Galpha(tr) or MAS-GRK3. Cells expressing Gbeta(1)gamma(2) were tonically inhibited via the VD pathway. Application of oxo-M to these cells produced VI modulation and reduced the amount of current inhibited via the VD pathway. Together, these results confirm the requirement for Gbetagamma in VD modulation and implicate Galpha(q)-GTP and Gbetagamma as components in the potentially novel VI pathway.
authors.affiliation: Laboratory of Molecular Physiology, Guthrie Research Institute, Sayre, PA 18840, USA.
authors.forename: P J
authors.initials: PJ
authors.lastname: Kammermeier
authors.forename: V
authors.initials: V
authors.lastname: Ruiz-Velasco
authors.forename: S R
authors.initials: SR
authors.lastname: Ikeda
mesh_terms: D000818:Animals; D002021:Buffers; D002118:Calcium / Q000378:metabolism; D020864:Calcium Channels, N-Type / Q000502:physiology*; D002478:Cells, Cultured; D004546:Elapid Venoms / Q000494:pharmacology; D004558:Electric Stimulation; D004594:Electrophysiology; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D044387:GTP-Binding Protein beta Subunits; D044388:GTP-Binding Protein gamma Subunits; D019204:GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015870:Gene Expression / Q000502:physiology; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins; D020962:Heterotrimeric GTP-Binding Proteins; D007202:Indicators and Reagents / Q000378:metabolism; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics; D018721:Muscarinic Agonists / Q000494:pharmacology*; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D064729:Neurokinin-1 Receptor Antagonists; D009474:Neurons / Q000166:cytology / Q000201:enzymology*; D010095:Oxotremorine / Q000031:analogs & derivatives* / Q000494:pharmacology; D037342:Pertussis Toxin; D054799:Phospholipase C beta; D020710:RGS Proteins / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D018040:Receptors, Neurokinin-1 / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D017783:Superior Cervical Ganglion / Q000166:cytology / Q000502:physiology; D010738:Type C Phospholipases / Q000235:genetics / Q000378:metabolism; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D002021:Buffers; D020864:Calcium Channels, N-Type; D004546:Elapid Venoms; C118981:G-protein Beta gamma; D044387:GTP-Binding Protein beta Subunits; D044388:GTP-Binding Protein gamma Subunits; D007202:Indicators and Reagents; D007527:Isoenzymes; D008164:Luminescent Proteins; D018721:Muscarinic Agonists; D018727:Muscarinic Antagonists; D064729:Neurokinin-1 Receptor Antagonists; D020710:RGS Proteins; D018040:Receptors, Neurokinin-1; D011994:Recombinant Proteins; C105345:Rgs2 protein, mouse; D010566:Virulence Factors, Bordetella; C083667:m1-toxin; D049452:Green Fluorescent Proteins; D010095:Oxotremorine; C042743:oxotremorine M; D037342:Pertussis Toxin; D010738:Type C Phospholipases; D054799:Phospholipase C beta; D019204:GTP-Binding Proteins; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020962:Heterotrimeric GTP-Binding Proteins; D002118:Calcium