Rhodopsin-family receptors associate with small G proteins to activate phospholipase D.
G-protein-coupled receptors of the rhodopsin family transduce many important neural and endocrine signals. These receptors activate heterotrimeric G proteins and in many cases also cause activation of phospholipase D, an enzyme that can be controlled by the small G proteins ARF and RhoA. Here we show that the activation of phospholipase D that is induced by many, but not all, Ca2+-mobilizing G-protein-coupled receptors is sensitive to inhibitors of ARF and of RhoA. Receptors of this type were co-immunoprecipitated with ARF or RhoA on exposure to agonists, and the effects of GTP analogues on ligand binding to the receptor changed to a profile that is characteristic of small G proteins. These receptors contain the amino-acid sequence AsnProXXTyr in their seventh transmembrane domain, whereas receptors capable of activating phospholipase D without involving ARF contain the sequence AspProXXTyr. Mutation of this latter sequence to AsnProXXTyr in the gonadotropin-releasing hormone receptor conferred sensitivity to an inhibitor of ARF, and the reciprocal mutation in the 5-HT2A receptor for 5-hydroxy-tryptamine reduced its sensitivity to the inhibitor. Receptors carrying the AsnProXXTyr motif thus seem to form functional complexes with ARF and RhoA.
Mitchell
R
R
MRC Brain Metabolism Unit, Edinburgh, UK. rmitchell@srv1.bmu.mrc.ac.uk
McCulloch
D
D
Lutz
E
E
Johnson
M
M
MacKenzie
C
C
Fennell
M
M
Fink
G
G
Zhou
W
W
Sealfon
S C
SC
D020727:ADP-Ribosylation Factors; D000818:Animals; D020126:Brefeldin A; D019556:COS Cells; D003517:Cyclopentanes / Q000494:pharmacology; D004789:Enzyme Activation; D004963:Estrenes / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism; D006801:Humans; D008297:Male; D010739:Phospholipase D / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011760:Pyrrolidinones / Q000494:pharmacology; D051381:Rats; D043587:Receptor, Muscarinic M3; D011966:Receptors, LHRH / Q000819:agonists / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011976:Receptors, Muscarinic / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D012243:Rhodopsin / Q000737:chemistry / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism; D020742:rhoA GTP-Binding Protein
D003517:Cyclopentanes; D004963:Estrenes; D011760:Pyrrolidinones; D043587:Receptor, Muscarinic M3; D011966:Receptors, LHRH; D011976:Receptors, Muscarinic; D011994:Recombinant Proteins; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D020126:Brefeldin A; D006160:Guanosine Triphosphate; D012243:Rhodopsin; D010738:Type C Phospholipases; D010739:Phospholipase D; D019204:GTP-Binding Proteins; D020727:ADP-Ribosylation Factors; D020742:rhoA GTP-Binding Protein