title: Dioleoyl phosphatidic acid increases intracellular Ca2+ through endogenous LPA receptors in C6 glioma and L2071 fibroblasts.
abstract: Phosphatidic acid (PA) increased intracellular Ca(2+) concentration ([Ca(2+)](i)) 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+)](i) 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+)](i) through Ki16425/VPC32183-sensitive LPA receptor coupled to PTX-sensitive G proteins in C6 cells. In L2071 cells, however, LPA increases [Ca(2+)](i) 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.
authors.affiliation: 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.
authors.forename: Young-Ja
authors.initials: YJ
authors.lastname: Chang
authors.forename: Yu-Lee
authors.initials: YL
authors.lastname: Kim
authors.forename: Yun-Kyung
authors.initials: YK
authors.lastname: Lee
authors.forename: Santosh J
authors.initials: SJ
authors.lastname: Sacket
authors.forename: Kyeok
authors.initials: K
authors.lastname: Kim
authors.forename: Hyo-Lim
authors.initials: HL
authors.lastname: Kim
authors.forename: Mijin
authors.initials: M
authors.lastname: Han
authors.forename: Yoe-Sik
authors.initials: YS
authors.lastname: Bae
authors.forename: Fumikazu
authors.initials: F
authors.lastname: Okajima
authors.forename: Dong-Soon
authors.initials: DS
authors.lastname: Im
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D005910:Glioma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D007555:Isoxazoles / Q000494:pharmacology; D008246:Lysophospholipids / Q000494:pharmacology; D051379:Mice; D037342:Pertussis Toxin / Q000494:pharmacology; D010712:Phosphatidic Acids / Q000737:chemistry / Q000494:pharmacology*; D011422:Propionates / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D049368:Receptors, Lysophosphatidic Acid / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors
chemical_list: C477898:3-(4-(4-((1-(2-chlorophenyl)ethoxy)carbonyl amino)-3-methyl-5-isoxazolyl) benzylsulfanyl) propanoic acid; D007555:Isoxazoles; D008246:Lysophospholipids; D010712:Phosphatidic Acids; D011422:Propionates; D012333:RNA, Messenger; D049368:Receptors, Lysophosphatidic Acid; D037342:Pertussis Toxin; C032881:lysophosphatidic acid; D002118:Calcium