title: The regulation of FasL expression during activation-induced cell death (AICD).
abstract: Activation-induced cell death (AICD), a Fas ligand (FasL)-dependent pathway, is important for maintaining T-cell homeostasis. Interleukin-2 (IL-2), an enhancer of AICD, can also enhance FasL expression. However, we show that the level of FasL or FLIP protein did not correlate with the susceptibility to AICD. Some T cells expressed high levels of FasL yet failed to undergo AICD, while others expressed little FasL and were sensitive. AICD susceptibility did not correlate with the kinetics of FasL up-regulation or down-regulation. The down-regulation of FasL can be mediated by a metalloprotease. However, we describe an alternative mechanism for the loss of FasL by endocytosis. Endocytosis inhibitors such as cytochalasins, sodium azide, deoxyglucose, or low temperatures prevented the loss of FasL. KB8301, a metalloprotease inhibitor had no effect on the loss of FasL or AICD in the T cells. Enhancing FasL expression was not crucial for AICD and the down-regulation of FasL proceeded via endocytosis.
authors.affiliation: Department of Molecular Biology and Pharmacology, Washington University School of Medicine, St Louis, MO, USA 63110.
authors.forename: T
authors.initials: T
authors.lastname: Nguyen
authors.forename: J
authors.initials: J
authors.lastname: Russell
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000276:immunology*; D002460:Cell Line; D015536:Down-Regulation / Q000276:immunology; D004492:Edetic Acid / Q000494:pharmacology; D004705:Endocytosis / Q000187:drug effects / Q000276:immunology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D053222:Fas Ligand Protein; D007376:Interleukin-2 / Q000276:immunology; D008024:Ligands; D008213:Lymphocyte Activation / Q000276:immunology*; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008666:Metalloendopeptidases / Q000037:antagonists & inhibitors; D051379:Mice; D008810:Mice, Inbred C57BL; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D004791:Enzyme Inhibitors; D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D007376:Interleukin-2; D008024:Ligands; D008562:Membrane Glycoproteins; D004492:Edetic Acid; D008666:Metalloendopeptidases