Multiple pathways originate at the Fas/APO-1 (CD95) receptor: Sequential involvement of phosphatidylcholine-specific phospholipase C and acidic sphingomyelinase in the propagation of the apoptotic signal

Maria Grazia Cifone, Paola Roncaioli, Ruggero De Maria, Grazia Camarda, Angela Santoni, Giovina Ruberti, Roberto Testi

Research output: Contribution to journalArticlepeer-review

Abstract

The early signals generated following cross-linking of Fas/APO-1, a transmembrane receptor whose engagement by ligand results in apoptosis induction, were investigated in human HuT78 lymphoma cells. Fas/ APO-1 cross-linking by mAbs resulted in membrane sphingomyelin hydrolysis and ceramide generation by the action of both neutral and acidic sphingomyelinases. Activation of a phosphatidylcholine-specific phospholipase C (PC-PLC) was also detected which appeared to be a requirement for subsequent acidic sphingomyelinase (aSMase) activation, since PC-PLC inhibitor D609 blocked Fas/APO-1-induced aSMase activation, but not Fas/APO-1-induced neutral sphingomyelinase (nSMase) activation. Fas/APO-1 cross-linking resulted also in ERK-2 activation and in phospholipase A2 (PLA2) induction, independently of the PC-PLC/aSMase pathway. Evidence for the existence of a pathway directly involved in apoptosis was obtained by selecting HuT78 mutant clones spontaneously expressing a newly identified death domaindefective Fas/APO-1 splice isoform which blocks Fas/ APO-1 apoptotic signalling in a dominant negative fashion. Fas/APO-1 cross-linking in these clones fails to activate PC-PLC and aSMase, while nSMase, ERK-2 and PLA2 activities are induced. These results strongly suggest that a PC-PLC/aSMase pathway contributes directly to the propagation of Fas/APO-1-generated apoptotic signal in lymphoid cells.

Original languageEnglish
Pages (from-to)5859-5868
Number of pages10
JournalEMBO Journal
Volume14
Issue number23
Publication statusPublished - 1995

Keywords

  • APO-1
  • Apoptosis
  • aSMase
  • Fas
  • PC-PLC

ASJC Scopus subject areas

  • Cell Biology
  • Genetics

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