Cytokine that binds to TNFRSF6/FAS, a receptor that transduces the apoptotic signal into cells. Involved in cytotoxic T-cell-mediated apoptosis, natural killer cell-mediated apoptosis and in T-cell development. Initiates fratricidal/suicidal activation-induced cell death (AICD) in antigen-activated T-cells contributing to the termination of immune responses. TNFRSF6/FAS-mediated apoptosis has also a role in the induction of peripheral tolerance. Binds to TNFRSF6B/DcR3, a decoy receptor that blocks apoptosis. Induces FAS-mediated activation of NF-kappa-B, initiating non-apoptotic signaling pathways. Can induce apoptosis but does not appear to be essential for this process. Cytoplasmic form induces gene transcription inhibition. Homotrimer. Interacts with ARHGAP9, BAIAP2L1, BTK, CACNB3, CACNB4, CRK, DLG2, DNMBP, DOCK4, EPS8L3, FGR, FYB1, FYN, HCK, ITK, ITSN2, KALRN, LYN, MACC1, MIA, MPP4, MYO15A, NCF1, NCK1, NCK2, NCKIPSD, OSTF1, PIK3R1, PSTPIP1, RIMBP3C, SAMSN1, SH3GL3, SH3PXD2B, SH3PXD2A, SH3RF2, SKAP2, SNX33, SNX9, SORBS3, SPTA1, SRC, SRGAP1, SRGAP2, SRGAP3, TEC, TJP3 and YES1. Colocalizes with the SPPL2A protease at the cell membrane. Is internalized into multivesicular bodies of secretory lysosomes after phosphorylation by FGR and monoubiquitination. May be released into the extracellular fluid by cleavage from the cell surface. The FasL ICD cytoplasmic form is translocated into the nucleus. The soluble form derives from the membrane form by proteolytic processing. The membrane-bound form undergoes two successive intramembrane proteolytic cleavages. The first one is processed by ADAM10 producing an N-terminal fragment, which lacks the receptor-binding extracellular domain. This ADAM10-processed FasL (FasL APL) remnant form is still membrane anchored and further processed by SPPL2A that liberates the FasL intracellular domain (FasL ICD). FasL shedding by ADAM10 is a prerequisite for subsequent intramembrane cleavage by SPPL2A in T-cells. Phosphorylated by FGR on tyrosine residues; this is required for ubiquitination and subsequent internalization. N-glycosylated. Glycosylation enhances apoptotic activity. Monoubiquitinated. Belongs to the tumor necrosis factor family.