REGULATION OF PROSTAGLANDIN-D(2)-RECEPTOR AND PROSTAGLANDIN-E(2)-RECEPTOR BINDING IN THE CENTRAL-NERVOUS-SYSTEM

Prostaglandin (PG) D2 and PGE2 receptor binding activities are regulated in various fashions. The protein phosphorylation by exogenous cAMP-dependent protein kinase or calmodulin-dependent protein kinase II significantly increased PGE2 binding activity through an increase in the apparent amount of the maximal binding, suggesting that the PGE2 receptor may be regulated through protein phosphorylation-dephosphorylation. Other possible regulatory mechanisms were found as the result of studies on functional modification of glycoconjugates. Pretreatment with glycoprotein-specific endoglycosidases (peptide N-glycohydrolase F, endo-alpha-N-acetylgalactosaminidase) decreased both PGD2 and PGE2 receptor binding activities and consequently these activities became nonspecific ones. In addition, these binding activities were increased by the addition of a ganglioside or cerebroside mixture, but not ceramide. The addition of separate purified glycolipids showed more specifically their effect on each PG binding. PGD2 binding activity was increased by GD1a and GQ1b and decreased by GM1 and GT1a, while PGE2 binding activity was increased by GQ1b and galactocerebroside. In such a way, PG receptors may require some specific microenvironment for their maximal binding activity.