Palmitoylation of human FasL modulates its cell death-inducing function

F Guardiola-Serrano,I Melzer,N Cahuzac,M Zörnig,S Mailfert,K Lückerath,A Rossin,A-O Hueber,D Marguet

doi:10.1038/cddis.2010.62

Abstract

Fas ligand (FasL) is a transmembrane protein that regulates cell death in Fas-bearing cells. FasL-mediated cell death is essential for immune system homeostasis and the elimination of viral or transformed cells. Because of its potent cytotoxic activity, FasL expression at the cell surface is tightly regulated, for example, via processing by ADAM10 and SPPL2a generating soluble FasL and the intracellular fragments APL (ADAM10-processed FasL form) and SPA (SPPL2a-processed APL). In this study, we report that FasL processing by ADAM10 counteracts Fas-mediated cell death and is strictly regulated by membrane localization, interactions and modifications of FasL. According to our observations, FasL processing occurs preferentially within cholesterol and sphingolipid-rich nanodomains (rafts) where efficient Fas–FasL contact occurs, Fas receptor and FasL interaction is also required for efficient FasL processing, and FasL palmitoylation, which occurs within its transmembrane domain, is critical for efficient FasL-mediated killing and FasL processing.

Highlights

In addition to its pro-apoptotic activity, Fas ligand (FasL) has been implicated in retrograde signal transduction within FasLexpressing cells, called reverse signaling, which is thought to be important in the modulation of T-cell activation
HFasL cleavage in WSU B cells stably transfected with hFasL was prevented by using the SPPL2a inhibitor (Z-LL)[2] or the matrix metalloproteinase (MMP) inhibitor TAPI-2, and cells were cocultured with Fas-expressing JH6.2 Jurkat target cells
These data indicate that Fas-mediated cell death is regulated by A disintegrin and metallopeptidase 10 (ADAM10)-processing of hFasL, which may function to hinder the pro-apoptotic function of hFasL

Summary

Introduction

In addition to its pro-apoptotic activity, FasL has been implicated in retrograde signal transduction within FasLexpressing cells, called reverse signaling, which is thought to be important in the modulation of T-cell activation. While Fas is expressed by several tissues, the expression of FasL is tightly regulated at both transcriptional and posttranscriptional levels to avoid undesirable cell death. The latter include FasL storage in intracellular compartments,[7] recruitment into cholesterol- and sphingolipid-rich nanodomains (rafts),[8,9] and FasL proteolysis by matrix metalloproteinases (MMPs) and the intramembrane protease SPPL2a.10,11. We have demonstrated that the partitioning of both FasL and Fas into rafts is necessary for efficient cell death transduction Both the regulation of FasL targeting into the rafts and the importance of this localization for FasL proteolytic processing remain unclear.

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Conclusion