Pancreatic-type phospholipase A2 stimulates prostaglandin synthesis in mouse osteoblastic cells (MC3T3-E1) via a specific binding site.
Previously, we have reported a novel proliferative action of pancreatic group I phospholipase A2 (PLA2-I) via a specific binding site in Swiss 3T3 fibroblasts, vascular smooth muscle cells, and chondrocytes. In this study, we characterized the PLA2-I specific binding site in osteoblastic cell line (MC3T3-E1 cells) with an equilibrium binding constant (Kd) value of 1.13 nM and maximum binding capacity of 40.1 fmol/10(6) cells. PLA2-I stimulated prostaglandin E2 (PGE2) production in a concentration-dependent manner in MC3T3-E1 cells, and its EC50 value was similar to the Kd value for PLA2-I binding. This effect of PLA2-I was type-specific and did not depend on its hydrolytic activity. PLA2-I increased the activity of prostaglandin endoperoxide synthase (PES), and PLA2-I-stimulated PGE2 synthesis was inhibited by cycloheximide. Northern blot analysis showed the increase in both type-1 and type-2 PES mRNAs. These findings indicated that PLA2-I stimulated PGE2 synthesis by induction of PES via a specific binding site in osteoblastic cells.
Tohkin
M
M
Shionogi Research Laboratories, Shionogi and Co., Ltd., Osaka, Japan.
Kishino
J
J
Ishizaki
J
J
Arita
H
H
D016475:3T3 Cells; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D001665:Binding Sites; D001920:Bradykinin / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D015232:Dinoprostone / Q000096:biosynthesis*; D004790:Enzyme Induction / Q000187:drug effects; D015870:Gene Expression / Q000187:drug effects; D051379:Mice; D019301:Oleic Acid; D009829:Oleic Acids / Q000378:metabolism; D010006:Osteoblasts / Q000378:metabolism*; D010741:Phospholipases A / Q000502:physiology*; D054467:Phospholipases A2; D011451:Prostaglandin-Endoperoxide Synthases / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D009829:Oleic Acids; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D016718:Arachidonic Acid; D019301:Oleic Acid; D000001:Calcimycin; D011451:Prostaglandin-Endoperoxide Synthases; D010741:Phospholipases A; D054467:Phospholipases A2; D015232:Dinoprostone; D001920:Bradykinin