THE COUPLING OF PERTUSSIS-TOXIN-SENSITIVE G-PROTEINS TO PHOSPHOLIPASEA(2) AND ADENYLYL-CYCLASE IN CHO CELLS EXPRESSING BOVINE RHODOPSIN

The regulation of phospholipase A(2) by G protein-coupled receptors is examined in CHO cells which normally express the purinergic receptor and have been transfected with bovine rhodopsin. The purinergic recept or has been reported to activate both phospholipase C and phospholipas e A(2) in this cell line. In contrast, bovine rhodopsin by itself is n ot able to activate phospholipase A(2). However, the photoreceptor doe s potentiate purinergic receptor-mediated phospholipase A(2) activatio n in a light-dependent manner. Both the purinergic receptor stimulatio n of phospholipase A(2) and the enhanced activity mediated by rhodopsi n are completely pertussis toxin-sensitive, suggesting the regulation of phospholipase A(2) by a member of the G(i) family of G proteins. Bo th of these receptors also inhibit adenylyl cyclase activity. Rhodopsi n-mediated inhibition of adenylyl cyclase is pertussis toxin-sensitive , whereas inhibition by the purinergic receptor is calcium-sensitive b ut not pertussis toxin-sensitive. These results suggest (1) that rhodo psin is similar to other receptors that normally couple to G(i) when e xpressed in cultured cells and (2) that regulation of adenylyl cyclase and PLA(2) in CHO cells by rhodopsin and the purinergic receptor occu r via distinct pathways. (C) 1995 Academic Press, Inc.