A family of glycerol-based lysolipid mediators comprises lysophosphatidic acid as a representative phospholipidic member but also a monoacylglycerol as a non-phosphorus-containing member. These critical lysolipid mediators are known to be produced from different lysophospholipids by actions of lysophospholipases C and D in mammals. Some members of the glycerophosphodiesterase (GDE) family have attracted recent attention due to their phospholipid-metabolizing activity. In this study, we found selective depletion of lysophosphatidylinositol among lysophospholipids in the culture medium of COS-7 cells transfected with a vector containing glycerophosphodiester phosphodiesterase 2 (GDPD2, GDE3). Thin-layer chromatography and liquid chromatography-tandem mass spectrometry of lipids extracted from GDE3-transfected COS-7 cells exposed to fluorescent analogs of phosphatidylinositol (PI) revealed that GDE3 acted as an ecto-type lysophospholipase C preferring endogenous lysophosphatidylinositol and PI having a long-chain acyl and a short-chain acyl group rather than endogenous PI and its fluorescent analog having two long chain acyl groups. In MC3T3-E1 cells cultured with an osteogenic or mitogenic medium, mRNA expression of GDE3 was increased by culturing in 10% fetal bovine serum for several days, concomitant with increased activity of ecto-lysophospholipase C, converting arachidonoyl-lysophosphatidylinositol, a physiological agonist of G protein-coupled receptor 55, to arachidonoylglycerol, a physiological agonist of cannabinoid receptors 1 and 2. We suggest that GDE3 acts as an ecto-lysophospholipase C, by switching signaling from lysophosphatidylinositol to that from arachidonoylglycerol in an opposite direction in mouse bone remodeling.

甘油基溶血脂介体家族包含溶血磷脂酸作为代表性的磷脂成员，但也包含单酰基甘油作为不含磷的成员。已知这些关键的溶血脂介体是通过哺乳动物中的溶血磷脂酶C和D的作用由不同的溶血磷脂产生的。甘油磷酸二酯酶（GDE）家族的某些成员由于其磷脂代谢活性而引起了近期的关注。在这项研究中，我们发现转染了含有甘油二磷酸二酯磷酸二酯酶2（GDPD2，GDE3）的载体转染的COS-7细胞培养基中的溶血磷脂中的溶血磷脂酰肌醇选择性消耗。从暴露于磷脂酰肌醇（PI）荧光类似物的GDE3转染的COS-7细胞提取的脂质的薄层色谱和液相色谱-串联质谱分析显示，GDE3充当胞外型溶血磷脂酶C，更倾向于内源性溶血磷脂酰肌醇和PI链酰基和短链酰基而不是内源性PI及其荧光类似物具有两个长链酰基。在成骨或促有丝分裂培养基中培养的MC3T3-E1细胞中，GDE3的mRNA表达通过在10％的胎牛血清中培养数天而增加，同时伴随着外部溶血磷脂酶C活性的增加，转化了花生四烯酸-溶血磷脂酰肌醇， G蛋白偶联受体55，对花生四烯酸甘油酯，