Specific combinations of G-protein subunits discriminate hormonal signalling in rat pituitary (GH(3)) cells in culture.
It was previously shown that hormone receptor coupling to voltage-dependent calcium channels in prolactin and growth hormone-producing GH(3) cells was heavily dependent on the specific heterotrimeric combinations of alpha, beta, and gamma subunits of the guanosine triphosphate (GTP)-binding protein family. Consequently, we assessed whether this was also the case for hormonal modulation of the adenylate cyclase (AC) and phospholipase C (PL-C) effector enzymes in GH(3) cells in culture. By employing polyclonal antibodies directed towards C-terminal decapeptides of various alpha subunits in membrane assays, as well as antisense oligonucleotides towards certain beta- and gamma-subunit genes in whole-cell incubations, it was possible to unravel a tentative profile of heterotrimers preferred by some of the seven-transmembrane-stretch receptors in their modulation of AC and PL-C activities. Vasoactive intestinal peptide (VIP) and thyroliberin (TRH) activate membrane-bound AC through alpha(s)beta(2)gamma(2), while somatostatin (SRIH) and dopamine (DA) inhibited the AC through alpha(i2)beta(1)gamma(3). TRH activated membrane-bound PL-C through alpha(q/11)beta(4)gamma(2), while DA inhibition of the PL-C was accomplished via alpha(o)beta(3)gamma(4). Hence, it seems that not only the specificity of alpha subunits determines the coupling between G protein-associated receptors in GH cells, the receptor binding to G proteins also requires certain combinations of beta and gamma subunits.
Johansen
P W
PW
Institute of Medical Biochemistry, University of Oslo, Oslo, Norway. per.w.johansen@rikshospitalet.no
Lund
H W
HW
Gordeladze
J O
JO
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D004298:Dopamine / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D010902:Pituitary Gland / Q000166:cytology*; D017434:Protein Structure, Tertiary; D051381:Rats; D015398:Signal Transduction; D013004:Somatostatin / Q000494:pharmacology; D013936:Thymidine / Q000378:metabolism; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology; D013997:Time Factors; D010738:Type C Phospholipases / Q000378:metabolism; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology
D016376:Oligonucleotides, Antisense; D014660:Vasoactive Intestinal Peptide; D013004:Somatostatin; D013973:Thyrotropin-Releasing Hormone; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases; D013936:Thymidine; D004298:Dopamine