G protein heterotrimer Galpha13beta1gamma3 couples the angiotensin AT1A receptor to increases in cytoplasmic Ca2+ in rat portal vein myocytes.
The subunit composition of angiotensin AT1 receptor-activated G protein was identified by using antisense oligonucleotide injection into the nucleus of rat portal vein myocytes. In these cells, we have previously shown that increases in the cytoplasmic calcium concentration ([Ca2+]i) induced by activation of angiotensin AT1 receptors were dependent on extracellular Ca2+ entry by L-type Ca2+ channels and subsequent Ca2+-induced Ca2+ release from the intracellular stores. The angiotensin AT1 receptor-activated increases in [Ca2+]i were selectively inhibited by injection of antisense oligonucleotides directed against the mRNAs coding for the alpha13, beta1, and gamma3 subunits. A correlating reduction in Galpha13, Gbeta1, and Ggamma3 protein expression was confirmed by immunocytochemistry. In addition, anti-alpha13 antibody and synthetic peptide corresponding to the carboxyl terminus of the Galpha13 subunit inhibited, in a concentration-dependent manner, the angiotensin AT1 receptor-mediated Ca2+ response. Reverse transcription-polymerase chain reaction analysis showed that only the angiotensin AT1A receptor was expressed in rat portal vein smooth muscle. Furthermore, injection of anti-AT1A oligonucleotides selectively inhibited the angiotensin II-induced increase in [Ca2+]i. We conclude that the receptor-activated signal leading to increases in [Ca2+]i is transduced by the heterotrimeric G13 protein composed of alpha13/beta1/gamma3 subunits and that the carboxyl terminus of the Galpha13 subunit interacts with the angiotensin AT1A receptor.
Macrez-Leprêtre
N
N
Laboratoire de Physiologie Cellulaire et Pharmacologie Moléculaire, CNRS ESA 5017, Université de Bordeaux II, 146 rue Léo Saignat, 33076 Bordeaux Cedex, France.
Kalkbrenner
F
F
Morel
J L
JL
Schultz
G
G
Mironneau
J
J
D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001483:Base Sequence; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D017931:DNA Primers / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D011169:Portal Vein / Q000166:cytology; D011487:Protein Conformation; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D044140:Receptor, Angiotensin, Type 1; D011945:Receptors, Angiotensin / Q000378:metabolism*; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D017931:DNA Primers; D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger; D044140:Receptor, Angiotensin, Type 1; D011945:Receptors, Angiotensin; D014662:Vasoconstrictor Agents; D000804:Angiotensin II; D002110:Caffeine; D019204:GTP-Binding Proteins; D002118:Calcium; D009638:Norepinephrine