Binding of the Intracellular Fas Ligand (FasL) Domain to the Adaptor Protein PSTPIP Results in a Cytoplasmic Localization of FasL

• Published in: The Journal of biological chemistry 2005-12, Vol.280 (48), p.40012-40024
• Main Authors: Baum, Wiebke, Kirkin, Vladimir, Fernández, Sara B. Mateus, Pick, Robert, Lettau, Marcus, Janssen, Ottmar, Zörnig, Martin
• Format: Article
• Language: English
• Subjects: Adaptor Proteins, Signal Transducing - chemistry; Adaptor Proteins, Signal Transducing - physiology; Animals; Apoptosis; Binding Sites; Cell Line; Cell Line, Tumor; Cell Separation; Chlorocebus aethiops; Coculture Techniques; COS Cells; Cytoplasm - metabolism; Cytoskeletal Proteins - chemistry; Cytoskeletal Proteins - physiology; DNA, Complementary - metabolism; Fas Ligand Protein; Flow Cytometry; Glutathione Transferase - metabolism; Green Fluorescent Proteins - metabolism; HeLa Cells; Humans; Immunoprecipitation; Lysosomes - chemistry; Lysosomes - metabolism; Membrane Glycoproteins - metabolism; Mice; Mice, Inbred C57BL; Microscopy, Confocal; Models, Biological; Plasmids - metabolism; Proline - chemistry; Protein Binding; Protein Biosynthesis; Protein Structure, Tertiary; Protein Tyrosine Phosphatase, Non-Receptor Type 12; Protein Tyrosine Phosphatases - chemistry; Rats; Signal Transduction; Spleen - cytology; src Homology Domains; T-Lymphocytes - cytology; T-Lymphocytes - metabolism; Transfection; Tumor Necrosis Factors - metabolism; Two-Hybrid System Techniques; Tyrosine - chemistry
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M502222200

The tumor necrosis factor family member Fas ligand (FasL) induces apoptosis in Fas receptor-expressing target cells and is an important cytotoxic effector molecule used by CTL- and NK-cells. In these hematopoietic cells, newly synthesized FasL is stored in specialized secretory lysosomes and only delivered to the cell surface upon activation and target cell recognition. FasL contains an 80-amino acid-long cytoplasmic tail, which includes a proline-rich domain as a bona fide Src homology 3 domain-binding site. This proline-rich domain has been implicated in FasL sorting to secretory lysosomes, and it may also be important for reverse signaling via FasL, which has been described to influence T-cell activation. Here we report the identification of the Src homology 3 domain-containing adaptor protein PSTPIP as a FasL-interacting partner, which binds to the proline-rich domain. PSTPIP co-expression leads to an increased intracellular localization of Fas ligand, thereby regulating extracellular availability and cytotoxic activity of the molecule. In addition, we demonstrate recruitment of the tyrosine phosphatase PTP-PEST by PSTPIP into FasL·PSTPIP·PTP-PEST complexes which may contribute to FasL reverse signaling.