Calmodulin mediates Fas-induced FADD-independent survival signaling in pancreatic cancer cells via activation of Src-extracellular signal-regulated kinase (ERK)

J Biol Chem. 2011 Jul 15;286(28):24776-84. doi: 10.1074/jbc.M110.202804. Epub 2011 May 25.

Abstract

Pancreatic cancer remains a devastating malignancy with a poor prognosis and is largely resistant to current therapies. To understand the resistance of pancreatic tumors to Fas death receptor-induced apoptosis, we investigated the molecular mechanisms of Fas-activated survival signaling in pancreatic cancer cells. We found that knockdown of the Fas-associated protein with death domain (FADD), the adaptor that mediates downstream signaling upon Fas activation, rendered Fas-sensitive MiaPaCa-2 and BxPC-3 pancreatic cells resistant to Fas-induced apoptosis. By contrast, Fas activation promoted the survival of the FADD knockdown MiaPaCa-2 and BxPC-3 cells in a concentration-dependent manner. The pharmacological inhibitor of ERK, PD98059, abrogated Fas-promoted cell survival in FADD knockdown MiaPaCa-2 and BxPC-3 cells. Furthermore, increased phosphorylation of Src was demonstrated to mediate Fas-induced ERK activation and cell survival. Immunoprecipitation of Fas in the FADD knockdown cells identified the presence of increased calmodulin, Src, and phosphorylated Src in the Fas-associated protein complex upon Fas activation. Trifluoperazine, a calmodulin antagonist, inhibited Fas-induced recruitment of calmodulin, Src, and phosphorylated Src. Consistently, trifluoperazine blocked Fas-promoted cell survival. A direct interaction of calmodulin and Src and their binding site were identified with recombinant proteins. These results support an essential role of calmodulin in mediating Fas-induced FADD-independent activation of Src-ERK signaling pathways, which promote survival signaling in pancreatic cancer cells. Understanding the molecular mechanisms responsible for the resistance of pancreatic cells to apoptosis induced by Fas-death receptor signaling may provide molecular insights into designing novel therapies to treat pancreatic tumors.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Calmodulin / genetics
  • Calmodulin / metabolism*
  • Cell Line, Tumor
  • Cell Survival
  • Enzyme Activation
  • Extracellular Signal-Regulated MAP Kinases / genetics
  • Extracellular Signal-Regulated MAP Kinases / metabolism*
  • Fas-Associated Death Domain Protein / genetics
  • Fas-Associated Death Domain Protein / metabolism*
  • Humans
  • MAP Kinase Signaling System*
  • Neoplasm Proteins / genetics
  • Neoplasm Proteins / metabolism*
  • Pancreatic Neoplasms / genetics
  • Pancreatic Neoplasms / metabolism*
  • Pancreatic Neoplasms / therapy
  • Phosphorylation
  • fas Receptor / genetics
  • fas Receptor / metabolism*
  • src-Family Kinases / genetics
  • src-Family Kinases / metabolism*

Substances

  • Calmodulin
  • FADD protein, human
  • FAS protein, human
  • Fas-Associated Death Domain Protein
  • Neoplasm Proteins
  • fas Receptor
  • src-Family Kinases
  • Extracellular Signal-Regulated MAP Kinases