Differential activation of G_i and G_s proteins by E- and I-type prostaglandins in membranes from the human erythroleukaemia cell line, HEL

摘要

The group of prostaglandin (PG) E2- and prostacyclin receptors consists of different subtypes, which exibit different affinities for prostaglandins and synthetic analogues. PGE2 activates the E-type PG receptor subtypes EP^ EP2 and EP3, whereas the PGE2 analogue, sulprostone, binds only to the EPL and EP3 receptor subtypes. The stable PGI2 analogues, iloprost and cicaprost, both activate the PGI2 receptor (IP) and iloprost, additionally, bind to the EPX subtype. Using these subtype-selective PG receptor agonists, we studied the interaction of PG receptor subtypes with Gs and Gj-type heterotrimeric guanine nucleotide-binding proteins (G proteins) in membranes from the human erythroleukaemia cell line, HEL. Sulprostone stimulated high-affinity GTPase in HEL membranes in a pertussis toxin (PTX)-sensitive manner. In contrast, the stimulations induced by PGE2, iloprost and cicaprost were only partially inhibited by PTX. PGE2, sulprostone, iloprost and cicaprost stimulated cholera toxin-catalysed ADP-ribosylation as well as labelling with GTP azidoanilide of membrane proteins comigrating with immunologically identified Gj protein a subunits. Furthermore, PGE2, iloprost and cicaprost enhanced GTP azidoanilide-labelling of Gs protein a subunits, whereas sulprostone did not. We suggest that in HEL cells (1) EPX and EP3 receptor subtypes activate G{ proteins, that (2) the EP2 receptor subtype activates Gs proteins and that (3) the IP receptor activates both Gj and Gs proteins.