CysLT1 signal transduction in differentiated U937 cells involves the activation of the small GTP-binding protein Ras

Biochem Pharmacol. 2004 Apr 15;67(8):1569-77. doi: 10.1016/j.bcp.2003.12.027.


We investigated the signal transduction pathway(s) of leukotriene D(4) (LTD(4)) in the human promonocytic U937 cells, a cell line known to constitutively express CysLT(1) receptors. Herein, we demonstrate that LTD(4) specifically acts on a CysLT(1) receptor to dose-dependently increase (three to five-fold over basal) RasGTP through a G(i/o) protein. In fact, while cytosolic Ca(2+) ([Ca(2+)](i)) increase was only partially sensitive to pertussis toxin (PTx), Ras activation was almost completely inhibited by the same toxin. Furthermore, the phospholipase C (PLC) inhibitor U73122 completely inhibited both [Ca(2+)](i) and RasGTP increase, suggesting that in these cells PLC is the point of convergence for both PTx insensitive and sensitive pathways leading to [Ca(2+)](i) release and Ras activation. Indeed, chelating intracellular Ca(2+) strongly (>70%) prevented LTD(4)-induced Ras activation, indicating that this ion plays an essential role for CysLT(1)-induced downstream signaling in differentiated U937 (dU937) cells. In addition, while Src did not appear to be substantially involved in CysLT(1)-induced signaling, genistein was able to partially inhibit LTD(4)-induced [Ca(2+)](i) transient ( approximately 34%) and almost completely prevented Ras activation (>90%), suggesting a potential role for other Ca(2+)-dependent tyrosine kinases in LTD(4)-induced signaling. Finally, agonist-induced CysLT(1) stimulation was followed by a specific extracellular regulated kinase (ERK) 1/2 phosphorylation, an event with a pharmacological profile similar to that of Ras activation, partially ( approximately 40%) sensitive to Clostridium sordellii lethal toxin and totally blocked by PTx. In conclusion, LTD(4)-induced CysLT(1) receptor activation in dU937 cells leads to Ras activation and ERK phosphorylation mostly through a PTx-sensitive G(i/o) protein, PLC, and Ca(2+)-dependent tyrosine kinase(s).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Calcium / metabolism
  • Cysteine / pharmacology*
  • Egtazic Acid / analogs & derivatives*
  • Egtazic Acid / pharmacology
  • Enzyme Activation
  • Estrenes / pharmacology
  • GTP-Binding Proteins / metabolism
  • Genistein / pharmacology
  • Humans
  • Inflammation Mediators / pharmacology*
  • Leukotriene D4 / pharmacology
  • Leukotrienes / pharmacology*
  • Membrane Proteins / metabolism
  • Mitogen-Activated Protein Kinases / metabolism
  • Pertussis Toxin / pharmacology
  • Pyrimidines / pharmacology
  • Pyrrolidinones / pharmacology
  • Receptors, Leukotriene / metabolism
  • Signal Transduction / physiology*
  • U937 Cells
  • ras Proteins / metabolism*


  • AG 1879
  • Estrenes
  • Inflammation Mediators
  • Leukotrienes
  • Membrane Proteins
  • Pyrimidines
  • Pyrrolidinones
  • Receptors, Leukotriene
  • cysteinyl-leukotriene
  • 1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione
  • Egtazic Acid
  • Leukotriene D4
  • Genistein
  • Pertussis Toxin
  • Mitogen-Activated Protein Kinases
  • GTP-Binding Proteins
  • ras Proteins
  • 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid
  • Cysteine
  • leukotriene D4 receptor
  • Calcium