Stimulatory Effect of Guanine Nucleotides on Prostaglandin E_1 Binding to Murine Renal Outer Medulla

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Prostaglandin E_1 (PGE_1) specifically bound to the membrane prepared from murine renal outer medulla. The extent of binding of [^3H] PGE_1 to the membrane was increased about 4-fold by guanosine triphosphate (GTP) and its analogs, but the dissociation of bound [^3H] PGE_1 from the membrane was in turn enhanced by GTPγS. Scatchard plot analyses revealed that GTPγS increased the binding affinity more than 2-fold without a major change in the number of binding sites. When [^3H] PGE_1-bound proteins were cross-linked in the membrane by dithiobis (succinimidyl propionate), bound [^3H] PGE_1 was no longer dissociated by GTPγS treatment, suggesting that cross-linking produced a stable complex of PGE receptor with a GTP-binding protein. The cross-linked [^3H] PGE_1-specifically bound proteins solubilized from the membranes labeled with [^3H] PGE_1 in the presence or absence of GTPγS were eluted as an apparently single radioactive peak at the same position of M_r=150000 by gel filtration, indicating that the PGE receptor forms a complex with a GTP-binding protein regardless of the treatment with GTPγS by which [^3H] PGE_1 binding is promoted. The ability of GTPγS to stimulate [^3H] PGE_1 binding was eliminated by pretreatment of the membrane with pertussis toxin, but not cholera toxin, indicating that the PGE receptor is coupled to a pertussis toxin-sensitive GTP-binding protein.
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