Abe Akira, Hinkovska-Galcheva Vania, Verma Rakesh, Shayman James A
Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA.
Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA.
J Lipid Res. 2025 Mar 29;66(5):100789. doi: 10.1016/j.jlr.2025.100789.
Bis(monoacylglycero)phosphates (BMPs) are biologically functional acidic lipids present in late endosomes and lysosomes. We recently reported that lysosomal phospholipase A2 (LPLA2, PLA2G15), the lysosomal enzyme mediating BMP catabolism, degrades BMP isomers with distinct substrate specificity. Specifically, sn-(3-oleoyl-2-hydroxy)-glycerol-1-phospho-sn-1'-(3'-oleoyl-2'-hydroxy)-glycerol (S,S-(3,3'-diC)-BMP) is a significantly better substrate for LPLA2 than S,S-(2,2'-diC)-BMP. S,S-(2,2'-diC)-BMP is generally considered the only biologically relevant BMP isomer. We investigated the isomerization of S,S-(2,2'-diC)-BMP to (S,S-(3,3'-diC)-BMP) in vitro and in cells. Thin-layer chromatography was used to distinguish S,S-(3,3'-diC)-BMP from S,S-(2,2'-diC)-BMP. S,S-(2,2'-diC)-BMP/1,2-di-O-(9Z-octadecenyl)-sn-glycero-3-phosphocholine liposomes were incubated at varying pH in the presence or absence of test substances. First, we studied bovine serum albumin, which is known to promote isomerization of 1-acyl-2-lysophosphatidylcholine. The formation of S,S-(3,3'-diC)-BMP in the presence of albumin increased in a time-dependent and albumin concentration-dependent manner under neutral conditions and was dependent on pH and the molar ratio of S,S-(2,2'-diC)-BMP in liposomes. Treatment of isomeric products generated during isomerization reaction with sn-1,3-specific lipase produced both oleic acid but also lyso-phosphatidylglycerol, indicating that the conversion of S,S-(2,2'-diC)-BMP to S,S-(3,3'-diC)-BMP is preceded via S,S-(2,3'-diC)-BMP. S,S-(3,3'-diC)-BMP formed was preferentially degraded by LPLA2 over the S,S-(2,2'-diC)-BMP. Proteins such as HSP70 and human serum albumin and metal ions such as Fe and Zn acted as cofactors promoting the isomerization of S,S-(2,2'-diC)-BMP under neutral conditions. At baseline, RAW 264.7 cells showed nonnegligible amounts of sn-1,3-specific lipase-sensitive BMPs. However, lipase-sensitive BMPs were increased by exposure to chloroquine or NHCl, suggesting that cells undergo S,S-(2,2'-diacyl)-BMP isomerization upon alkalinization of intracellular acidic compartments.
双（单酰甘油）磷酸酯（BMPs）是存在于晚期内体和溶酶体中的具有生物功能的酸性脂质。我们最近报道，溶酶体磷脂酶A2（LPLA2，PLA2G15），即介导BMP分解代谢的溶酶体酶，能以不同的底物特异性降解BMP异构体。具体而言，sn-（3-油酰基-2-羟基）-甘油-1-磷酸-sn-1'-（3'-油酰基-2'-羟基）-甘油（S,S-（3,3'-二C）-BMP）是LPLA2比S,S-（2,2'-二C）-BMP更好的底物。S,S-（2,2'-二C）-BMP通常被认为是唯一具有生物学相关性的BMP异构体。我们在体外和细胞中研究了S,S-（2,2'-二C）-BMP向（S,S-（3,3'-二C）-BMP）的异构化。采用薄层色谱法区分S,S-（3,3'-二C）-BMP和S,S-（2,2'-二C）-BMP。将S,S-（2,2'-二C）-BMP/1,2-二-O-（9Z-十八碳烯基）-sn-甘油-3-磷酸胆碱脂质体在不同pH下于有或无测试物质存在的情况下孵育。首先，我们研究了牛血清白蛋白，已知其可促进1-酰基-2-溶血磷脂酰胆碱的异构化。在中性条件下，白蛋白存在时S,S-（3,3'-二C）-BMP的形成呈时间依赖性和白蛋白浓度依赖性增加，且依赖于pH和脂质体中S,S-（2,2'-二C）-BMP的摩尔比。用sn-1,3特异性脂肪酶处理异构化反应过程中产生的异构产物，既产生了油酸，也产生了溶血磷脂酰甘油，这表明S,S-（2,2'-二C）-BMP向S,S-（3,3'-二C）-BMP的转化是通过S,S-（2,3'-二C）-BMP进行的。与S,S-（2,2'-二C）-BMP相比，形成的S,S-（3,3'-二C）-BMP优先被LPLA2降解。诸如HSP70和人血清白蛋白等蛋白质以及诸如Fe和Zn等金属离子在中性条件下作为辅助因子促进S,S-（2,2'-二C）-BMP的异构化。在基线时，RAW
