Premium
Receptors couple to L‐type calcium channels via distinct G o proteins in rat neuroendocrine cell lines
Author(s) -
Degtiar Vadim E.,
Harhammer Rainer,
Nürnberg Bernd
Publication year - 1997
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1997.321bk.x
Subject(s) - g protein , pertussis toxin , galanin , somatostatin , carbachol , agonist , medicine , cell culture , endocrinology , receptor , neuropeptide , gi alpha subunit , biology , voltage dependent calcium channel , gtp' , microbiology and biotechnology , chemistry , calcium , biochemistry , genetics , enzyme
1 The present study examines the hypothesis of G protein subtype selectivity in receptor‐induced inhibition of calcium channel currents ( I Ca ) in the insulin‐secreting RINm5F and pituitary GH 3 rat cell lines. Specificity of receptor coupling to G proteins was studied by infusion of purified Ga isoforms into cells via a patch pipette. 2 In RINm5F cells, the neuropeptide galanin inhibited dihydropyridine (DHP)‐ and ω‐conotoxin‐sensitive components of I Ca and slowed down their activation kinetics. In GH 3 cells, DHP‐sensitive I Ca was inhibited by galanin, as well as by somatostatin and carbachol. Agonist‐induced I Ca inhibition was suppressed by pertussis toxin (PTX) pretreatment of the cells. In PTX‐pretreated cells of either cell line, the response to galanin was restored only by the Gα 01 subunit. Following PTX treatment of GH 3 cells, only the Gα 01 subunit restored carbachol‐induced inhibition of I Ca , whereas only the Gα o2 subunit restored somatostatin‐induced inhibition of I Ca . G l subtypes had no effect on I Ca inhibition. 3 Both cell lines expressed two distinct immunoreactive G o proteins. Whereas in RINm5F cell membranes G 01 was found to be the predominant isoform, we detected more G 02 than G 01 in GH 3 cell membranes. Nevertheless, all agonists stimulated incorporation of the photoreactive GTP analogue [α‐ 32 P]GTP azidoanilide into both G o isoforms. 4 The results indicate that the same G o subtype, i.e. G 01 , mediates galanin‐induced inhibition of I Ca in both cell lines and that the G o subtype specificity of receptor‐G protein coupling is confined to intact cells.