Agonist-specific alterations in receptor-phospholipase coupling following inactivation of Gi2alpha gene.
Different forms of phospholipase A2, together with pertussis toxin-sensitive G-proteins, [Ca2+]i (intracellular Ca2+ concentration), protein kinase C, calmodulin, protein tyrosine kinases, mitogen-activated protein kinases and Ca2+/calmodulin-dependent protein kinase appear to play a role in agonist-mediated release of arachidonic acid. Here we report that fibroblasts from 14-day-old mouse embryos with inactivated Gi2alpha (alpha-subunit of the heterotrimeric G-protein Gi2) gene display a marked decrease in the ability of lysophosphatidic acid, thrombin and Ca2+ ionophores to release arachidonic acid compared with their normal counterparts. The requirement for Gi2alpha in the release of arachidonic acid following increased [Ca2+]i may be explained by the incomplete translocation of cytosolic phospholipase A2 observed in Gi2alpha-deficient cells. Paradoxically, inactivation of the Gi2alpha gene resulted in up-regulation of bradykinin receptors and their coupling to increased arachidonic acid release, phospholipase C activity and [Ca2+]i. A concomitant increase in basal phospholipase C activity was also observed in the Gi2alpha-deficient cells. These observations establish a pleiotropic and essential role for Gi2alpha in receptor-phospholipase coupling that contrasts with its less obligatory participation in agonist-mediated inhibition of adenylate cyclase.
Mattera
R
R
Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH 44106-4970, USA. rmattera@research.mhmc.org
Hayek
S
S
Summers
B A
BA
Grove
D L
DL
D037361:Adenylate Cyclase Toxin; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism*; D001920:Bradykinin / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D005347:Fibroblasts; D051960:GTP-Binding Protein alpha Subunit, Gi2; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D019204:GTP-Binding Proteins / Q000819:agonists / Q000235:genetics* / Q000502:physiology*; D007295:Inositol Phosphates / Q000378:metabolism; D008246:Lysophospholipids / Q000494:pharmacology; D051379:Mice; D018345:Mice, Knockout / Q000196:embryology; D037342:Pertussis Toxin; D010713:Phosphatidylcholines / Q000378:metabolism; D010741:Phospholipases A / Q000378:metabolism*; D054467:Phospholipases A2; D011518:Proto-Oncogene Proteins / Q000819:agonists / Q000235:genetics*; D018002:Receptors, Bradykinin / Q000378:metabolism; D013917:Thrombin / Q000494:pharmacology; D010738:Type C Phospholipases / Q000378:metabolism; D015854:Up-Regulation / Q000502:physiology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D037361:Adenylate Cyclase Toxin; D007295:Inositol Phosphates; D008246:Lysophospholipids; D010713:Phosphatidylcholines; D011518:Proto-Oncogene Proteins; D018002:Receptors, Bradykinin; D010566:Virulence Factors, Bordetella; D016718:Arachidonic Acid; D000001:Calcimycin; D000242:Cyclic AMP; D037342:Pertussis Toxin; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D010741:Phospholipases A; D054467:Phospholipases A2; D010738:Type C Phospholipases; D013917:Thrombin; D019204:GTP-Binding Proteins; D051960:GTP-Binding Protein alpha Subunit, Gi2; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; C498016:Gnai2 protein, mouse; D001920:Bradykinin; D002118:Calcium