Involvement of raft aggregates enriched in Fas/CD95 death-inducing signaling complex in the antileukemic action of edelfosine in Jurkat cells.

Abstract

BACKGROUND:

Recent evidence suggests that co-clustering of Fas/CD95 death receptor and lipid rafts plays a major role in death receptor-mediated apoptosis.

METHODOLOGY/PRINCIPAL FINDINGS:

By a combination of genetic, biochemical, and ultrastructural approaches, we provide here compelling evidence for the involvement of lipid raft aggregates containing recruited Fas/CD95 death receptor, Fas-associated death domain-containing protein (FADD), and procaspase-8 in the induction of apoptosis in human T-cell leukemia Jurkat cells by the antitumor drug edelfosine, the prototype compound of a promising family of synthetic antitumor lipids named as synthetic alkyl-lysophospholipid analogues. Co-immunoprecipitation assays revealed that edelfosine induced the generation of the so-called death-inducing signaling complex (DISC), made up of Fas/CD95, FADD, and procaspase-8, in lipid rafts. Electron microscopy analyses allowed to visualize the formation of raft clusters and their co-localization with DISC components Fas/CD95, FADD, and procaspase-8 following edelfosine treatment of Jurkat cells. Silencing of Fas/CD95 by RNA interference, transfection with a FADD dominant-negative mutant that blocks Fas/CD95 signaling, and specific inhibition of caspase-8 prevented the apoptotic response triggered by edelfosine, hence demonstrating the functional role of DISC in drug-induced apoptosis. By using radioactive labeled edelfosine and a fluorescent analogue, we found that edelfosine accumulated in lipid rafts, forming edelfosine-rich membrane raft clusters in Jurkat leukemic T-cells. Disruption of these membrane raft domains abrogated drug uptake and drug-induced DISC assembly and apoptosis. Thus, edelfosine uptake into lipid rafts was critical for the onset of both co-aggregation of DISC in membrane rafts and subsequent apoptotic cell death.

CONCLUSIONS/SIGNIFICANCE:

This work shows the involvement of DISC clusters in lipid raft aggregates as a supramolecular and physical entity responsible for the induction of apoptosis in leukemic cells by the antitumor drug edelfosine. Our data set a novel framework and paradigm in leukemia therapy, as well as in death receptor-mediated apoptosis.

• Authors: Consuelo Gajate, Fernando Gonzalez-Camacho, Faustino Mollinedo
• Journal: PloS one (PLoS One) Vol. 4 Issue 4 Pg. e5044 ( 2009) ISSN: 1932-6203 [Electronic] United States
• PMID: 19352436 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antineoplastic Agents
• FADD protein, human
• Fas-Associated Death Domain Protein
• Membrane Lipids
• Phospholipid Ethers
• fas Receptor
• edelfosine
• Caspase 8

Topics

• Antineoplastic Agents (pharmacology)
• Apoptosis
• Caspase 8 (metabolism)
• Fas-Associated Death Domain Protein (metabolism)
• Humans
• In Situ Nick-End Labeling
• Jurkat Cells
• Leukemia, T-Cell (pathology)
• Membrane Lipids (metabolism)
• Microscopy, Fluorescence
• Phospholipid Ethers (pharmacology)
• Signal Transduction
• fas Receptor (metabolism)