Mechanisms of action of prostaglandin E2 and prostaglandin F2α: PGE and PGFα receptors

Prostaglandins are autocoids which normally function near their sites of synthesis to co-ordinate net biological responses among different neighbouring cell types. Responses to PGE2 and PGF2α, the major prostanoids of the E and Fα series of prostaglandins, are mediated by PGE and PGFα receptors. PGE and PGFα receptors are membrane-bound proteins which interact specifically with PGE2 or PGF2α, respectively, and, when occupied with ligand, elicit cascades of biochemical events which, in turn, lead to generalized physiological responses, such as luteolysis, contraction or relaxation of smooth muscle, inhibition of water or solute transport and inhibition of lipolysis. In this chapter, we develop the thesis that agonist-occupied prostaglandin receptors interact with specific guanine nucleotide regulatory (N) proteins to cause changes in the concentrations of cAMP, inositol trisphosphate, Ca2+ or perhaps other intracellular second messengers. There appear to be at least three different types of PGE receptors interactive with different types of N proteins (Ns, Ni Np) and perhaps having different ligand binding properties. In contrast, PGFα receptors may act only through Np-like proteins.