Dioleoyl phosphatidic acid increases intracellular Ca2+ through endogenous LPA receptors in C6 glioma and L2071 fibroblasts

Prostaglandins Other Lipid Mediat. 2007 Jun;83(4):268-76. doi: 10.1016/j.prostaglandins.2007.01.014. Epub 2007 Feb 3.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium / metabolism*
  • Cell Line, Tumor
  • Dose-Response Relationship, Drug
  • Fibroblasts / cytology
  • Fibroblasts / drug effects*
  • Fibroblasts / metabolism
  • Gene Expression / drug effects
  • Glioma / genetics
  • Glioma / metabolism
  • Glioma / pathology
  • Isoxazoles / pharmacology
  • Lysophospholipids / pharmacology
  • Mice
  • Pertussis Toxin / pharmacology
  • Phosphatidic Acids / chemistry
  • Phosphatidic Acids / pharmacology*
  • Propionates / pharmacology
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Rats
  • Receptors, Lysophosphatidic Acid / genetics
  • Receptors, Lysophosphatidic Acid / metabolism*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Time Factors

Substances

  • 3-(4-(4-((1-(2-chlorophenyl)ethoxy)carbonyl amino)-3-methyl-5-isoxazolyl) benzylsulfanyl) propanoic acid
  • Isoxazoles
  • Lysophospholipids
  • Phosphatidic Acids
  • Propionates
  • RNA, Messenger
  • Receptors, Lysophosphatidic Acid
  • Pertussis Toxin
  • lysophosphatidic acid
  • Calcium