title: Sorting of Fas ligand to secretory lysosomes is regulated by mono-ubiquitylation and phosphorylation.
abstract: Fas ligand (FasL), a potent mediator of apoptosis expressed by CTL and NK cells, is sorted into the inner vesicles of secretory lysosomes for release via exosome-like vesicles. Previous studies identified a proline-rich domain in the cytoplasmic tail required for sorting FasL to secretory lysosomes, but the mechanisms by which this occurs have not been identified. Here we demonstrate that the PRD of FasL binds Fgr, Fyn and Lyn tyrosine kinases, leading to phosphorylation of FasL. Loss of phosphorylation reduces internalisation of FasL into multivesicular bodies. FasL is also directly mono-ubiquitylated at lysines flanking the PRD and mutation of these lysines reduces MVB localisation of FasL. Phosphorylation is not required for ubiquitylation because FasL lacking all tyrosines undergoes mono-ubiquitylation. These studies show that phosphorylation and ubiquitin signals regulate the sorting of FasL to secretory lysosomes by controlling entry into multivesicular bodies.
authors.affiliation: Sir William Dunn School of Pathology, South Parks Rd, Oxford, OX1 3RE, UK.
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Zuccato
authors.forename: Emma J
authors.initials: EJ
authors.lastname: Blott
authors.forename: Oliver
authors.initials: O
authors.lastname: Holt
authors.forename: Sara
authors.initials: S
authors.lastname: Sigismund
authors.forename: Michael
authors.initials: M
authors.lastname: Shaw
authors.forename: Giovanna
authors.initials: G
authors.lastname: Bossi
authors.forename: Gillian M
authors.initials: GM
authors.lastname: Griffiths
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D011992:Endosomes / Q000378:metabolism; D053222:Fas Ligand Protein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D019169:Jurkat Cells; D015471:Leukemia, Basophilic, Acute; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism*; D008969:Molecular Sequence Data; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D051076:Proto-Oncogene Proteins c-fyn / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D051381:Rats; D022142:Secretory Vesicles / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D025801:Ubiquitin / Q000378:metabolism*; D018909:src Homology Domains / Q000502:physiology; D019061:src-Family Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D053222:Fas Ligand Protein; D011518:Proto-Oncogene Proteins; D025801:Ubiquitin; C494957:FYN protein, human; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D051076:Proto-Oncogene Proteins c-fyn; C060902:lyn protein-tyrosine kinase; C053102:proto-oncogene proteins c-fgr; D019061:src-Family Kinases