Chang Young-Ja, Kim Yu-Lee, Lee Yun-Kyung, Sacket Santosh J, Kim Kyeok, Kim Hyo-Lim, Han Mijin, Bae Yoe-Sik, Okajima Fumikazu, Im Dong-Soon
Laboratory of Pharmacology, College of Pharmacy and Research Institute for Drug Development, Pusan National University, San 30, Jang-Jun-dong, Geum-Jung-gu, Busan 609-735, Republic of Korea.
Prostaglandins Other Lipid Mediat. 2007 Jun;83(4):268-76. doi: 10.1016/j.prostaglandins.2007.01.014. Epub 2007 Feb 3.
Phosphatidic acid (PA) increased intracellular Ca(2+) concentration (Ca(2+)) in C6 rat glioma and L2071 mouse fibroblast cells. Dioleoyl PA (PA, 18:1) was the most efficacious, followed by dipalmitoyl PA (16:0 PA) and dimyristoyl PA (14:0 PA). Lysophosphatidic acid (LPA) also increased the Ca(2+) in the both cells. PA desensitized LPA-induced Ca(2+) response completely in C6 cells, but partly in L2071 cells. Treatment of pertussis toxin (PTX), a specific inhibitor of G(i/o)-type G proteins, completely ameliorated LPA- and PA-induced Ca(2+) response in C6 cells. However, in L2071 cells, PTX inhibited PA-induced Ca(2+) increase by 80% and LPA-induced one by 20%. Ki16425, a specific inhibitor of LPA(1)/LPA(3) receptors, completely inhibited both LPA- and PA-induced Ca(2+) responses in C6 cells. On the other hand, in L2071 cells, Ki16425 completely inhibited PA-induced Ca(2+) response, but partly LPA-induced one. VPC32183, another specific inhibitor of LPA(1)/LPA(3) receptors, completely inhibited LPA- and PA-induced Ca(2+) responses in both C6 and L2071 cells. Therefore, PA and LPA appear to increase Ca(2+) through Ki16425/VPC32183-sensitive LPA receptor coupled to PTX-sensitive G proteins in C6 cells. In L2071 cells, however, LPA increases Ca(2+) through Ki16425-insensitive LPA receptor coupled to PTX-insensitive G proteins and Ki16425-sensitive LPA receptor coupled to PTX-sensitive G protein, whereas PA utilized only the latter pathway. Our results suggest that PA acts as a partial agonist on endogenous LPA receptors, which are sensitive to Ki16425 and coupled to PTX-sensitive G protein, but not on LPA receptors, which are not sensitive to Ki16425 and coupled to PTX-insensitive G protein.
磷脂酸（PA）可提高C6大鼠胶质瘤细胞和L2071小鼠成纤维细胞内的钙离子浓度（Ca(2+)）。二油酰磷脂酸（PA，18:1）最为有效，其次是二棕榈酰磷脂酸（16:0 PA）和二肉豆蔻酰磷脂酸（14:0 PA）。溶血磷脂酸（LPA）也可提高这两种细胞内的Ca(2+)。在C6细胞中，PA可完全使LPA诱导的钙离子反应脱敏，但在L2071细胞中仅部分使其脱敏。百日咳毒素（PTX）是G(i/o)型G蛋白的特异性抑制剂，其处理可完全改善C6细胞中LPA和PA诱导的钙离子反应。然而，在L2071细胞中，PTX可使PA诱导的钙离子增加减少80%，使LPA诱导的钙离子增加减少20%。Ki16425是LPA(1)/LPA(3)受体的特异性抑制剂，可完全抑制C6细胞中LPA和PA诱导的钙离子反应。另一方面，在L2071细胞中，Ki16425可完全抑制PA诱导的钙离子反应，但仅部分抑制LPA诱导的钙离子反应。VPC32183是LPA(1)/LPA(3)受体的另一种特异性抑制剂，可完全抑制C6和L2071细胞中LPA和PA诱导的钙离子反应。因此，在C6细胞中，PA和LPA似乎通过与PTX敏感的G蛋白偶联的、对Ki16425/VPC32183敏感的LPA受体来提高Ca(2+)。然而，在L2071细胞中，LPA通过与PTX不敏感的G蛋白偶联的、对Ki16425不敏感的LPA受体以及与PTX敏感的G蛋白偶联的、对Ki16425敏感的LPA受体来提高Ca(2+)，而PA仅利用后一条途径。我们的结果表明，PA对内源性LPA受体起部分激动剂的作用，这些受体对Ki16425敏感且与PTX敏感的G蛋白偶联，但对不敏感于Ki16425且与PTX不敏感的G蛋白偶联的LPA受体不起作用。
