High-affinity binding sites for 125I-labelled pancreatic secretory phospholipase A2 in rat brain.
Porcine pancreatic secretory phospholipase A2 (ppsPLA2) has been shown to modulate agonist and antagonist binding to alpha-amino-3-hydroxy-5-methylisoxazolepropionate (AMPA) receptors and to effect neurotransmission in the central nervous system (CNS). To further elucidate the mechanism of action of ppsPLA2 in the CNS, the binding profile of 125I-labelled ppsPLA2 to rat whole-brain membranes was assessed. Two classes of calcium-dependent binding sites were detected using unlabelled ppsPLA2 as a displacer with IC50 values of 3 and 217 nM. Similar values were obtained for [125I]ppsPLA2 binding to membranes prepared from isolated cortical and hippocampal rat brain regions. [125I]ppsPLA2 binding displayed bell-shaped concentration-dependence curves to Ca2+, Zn2 + and pH. Binding was not inhibited by AMPA, the false substrate, oleoyloxyethyl phosphocholine (OOPC), or by BSA-galactose or wheat germ agglutinin. [125I]ppsPLA2 binding was reduced by treatment of the rat brain membranes with mercaptoethanol and proteinase K treatment or by their pre-incubation at 95 degrees C. These results show a different binding profile to the previously characterised snake venom sPLA2 N-type receptors and suggest the existence of novel class of sPLA2 N-type binding sites.
Dev
K K
KK
Department of Anatomy, University of Bristol, Medical School, UK.
Foged
C
C
Andersen
H
H
Honoré
T
T
Henley
J M
JM
D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002118:Calcium / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D002540:Cerebral Cortex / Q000378:metabolism*; D005260:Female; D006624:Hippocampus / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007425:Intracellular Membranes / Q000378:metabolism; D007457:Iodine Radioisotopes; D007700:Kinetics; D010179:Pancreas / Q000201:enzymology*; D010741:Phospholipases A / Q000378:metabolism*; D054467:Phospholipases A2; D051381:Rats; D017208:Rats, Wistar; D013552:Swine; D013574:Synaptosomes / Q000378:metabolism*; D015032:Zinc / Q000494:pharmacology
D007457:Iodine Radioisotopes; D010741:Phospholipases A; D054467:Phospholipases A2; D015032:Zinc; D002118:Calcium