Analysis of CD95 Threshold Signaling

Recently we generated a mathematical model (Bentele, M., Lavrik, I., Ulrich, M., Stosser, S., Heermann, D. W., Kalthoff, H., Krammer, P. H., and Eils, R. (2004) J. Cell Biol. 166, 839-851) of signaling in CD95(Fas/APO-1)-mediated apoptosis. Mathematical modeling in combination with experimental data provided new insights into CD95-mediated apoptosis and allowed us to establish a threshold mechanism of life and death. Here, we further assessed the predictability of the model experimentally by a detailed analysis of the threshold behavior of CD95 signaling. Using the model predictions for the mechanism of the threshold behavior we found that the CD95 DISC (death-inducing signaling complex) is formed at the cell membrane upon stimulation with low concentrations of agonistic anti-APO-1 monoclonal antibodies; however, activation of procaspase-8 at the DISC is blocked due to high cellular FLICE-inhibitory protein recruitment into the DISC. Given that death signaling does not occur upon CD95 stimulation at low (threshold) anti-APO-1 concentrations, we also analyzed survival signaling, focusing on mitogen-activated protein kinase activation. Interestingly, we found that mitogen-activated protein kinase activation takes place under threshold conditions. These findings show that triggering of CD95 can signal both life or death, depending on the strength of the stimulus.

[1]  M. Peter,et al.  Cytotoxicity‐dependent APO‐1 (Fas/CD95)‐associated proteins form a death‐inducing signaling complex (DISC) with the receptor. , 1995, The EMBO journal.

[2]  S. Korsmeyer,et al.  Pro-apoptotic cascade activates BID, which oligomerizes BAK or BAX into pores that result in the release of cytochrome c , 2000, Cell Death and Differentiation.

[3]  P. Möller,et al.  Monoclonal antibody-mediated tumor regression by induction of apoptosis. , 1989, Science.

[4]  S. Nagata,et al.  Apoptosis by Death Factor , 1997, Cell.

[5]  P. Krammer,et al.  Death receptor signaling , 2005, Journal of Cell Science.

[6]  Matthias Mann,et al.  FLICE is activated by association with the CD95 death‐inducing signaling complex (DISC) , 1997, The EMBO journal.

[7]  A Krueger,et al.  The active caspase-8 heterotetramer is formed at the CD95 DISC , 2003, Cell Death and Differentiation.

[8]  Ingo Schmitz,et al.  Differential Modulation of Apoptosis Sensitivity in CD95 Type I and Type II Cells* , 1999, The Journal of Biological Chemistry.

[9]  P. Krammer,et al.  CD95's deadly mission in the immune system , 2000, Nature.

[10]  Takashi Suda,et al.  Molecular cloning and expression of the fas ligand, a novel member of the tumor necrosis factor family , 1993, Cell.

[11]  P. Krammer,et al.  c-FLIPR, a New Regulator of Death Receptor-induced Apoptosis* , 2005, Journal of Biological Chemistry.

[12]  M. Peter,et al.  The CD95(APO-1/Fas) DISC and beyond , 2003, Cell Death and Differentiation.

[13]  P. Möller,et al.  Induction of apoptosis by monoclonal antibody anti-APO-1 class switch variants is dependent on cross-linking of APO-1 cell surface antigens. , 1992, Journal of immunology.

[14]  R. Eils,et al.  Mathematical modeling reveals threshold mechanism in CD95-induced apoptosis , 2004, The Journal of cell biology.

[15]  P. Krammer,et al.  The CD95 (APO-1/Fas) and the TRAIL (APO-2L) apoptosis systems. , 2000, Experimental cell research.

[16]  A. Davies,et al.  The death receptor antagonist FAIM promotes neurite outgrowth by a mechanism that depends on ERK and NF-κB signaling , 2004, The Journal of cell biology.

[17]  P. Krammer,et al.  Cellular FLICE-inhibitory Protein Splice Variants Inhibit Different Steps of Caspase-8 Activation at the CD95 Death-inducing Signaling Complex* , 2001, The Journal of Biological Chemistry.

[18]  P. Krammer,et al.  Regulation of death receptor-mediated apoptosis pathways. , 2000, The international journal of biochemistry & cell biology.

[19]  R. Birge,et al.  Fas engagement induces neurite growth through ERK activation and p35 upregulation , 2003, Nature Cell Biology.

[20]  Xiaolu Yang,et al.  c‐FLIPL is a dual function regulator for caspase‐8 activation and CD95‐mediated apoptosis , 2002, The EMBO journal.

[21]  I. Herr,et al.  Control of neuronal branching by the death receptor CD95 (Fas/Apo-1) , 2006, Cell Death and Differentiation.

[22]  M. Peter,et al.  Does CD95 have tumor promoting activities? , 2005, Biochimica et biophysica acta.

[23]  M. Peter,et al.  Induction of apoptosis and activation of NF‐κB by CD95 require different signalling thresholds , 2004, EMBO reports.