EMAP-II facilitates TNF-R1 apoptotic signalling in endothelial cells and induces TRADD mobilization.
Endothelial monocyte-activating polypeptide-II (EMAP-II), a proinflammatory cytokine with antiangiogenic properties, renders tumours sensitive to tumour necrosis factor-alpha (TNF) treatment. The exact mechanisms for this effect remain unclear. Here we show that human endothelial cells (EC) are insensitive to TNF-induced apoptosis but after a short pre-treatment with EMAP-II, EC quickly undergo TNF-induced apoptosis. We further analysed this EMAP-II pre-treatment effect and found no increase of TNF-R1 protein expression but rather an induction of TNF-R1 redistribution from Golgi storage pools to cell membranes. In addition, we observed EMAP-II induced mobilization and membrane expression of the TNF-R1-Associated Death Domain (TRADD) protein. Immunofluorescence co-staining experiments revealed that these two effects occurred at the same time in the same cell but TNF-R1 and TRADD were localized in different vesicles. These findings suggest that EMAP-II sensitises EC to apoptosis by facilitating TNF-R1 apoptotic signalling via TRADD mobilization and introduce a molecular and antiangiogenic explanation for the TNF sensitising properties of EMAP-II in tumours.
van Horssen
Remco
R
Laboratory of Experimental Surgical Oncology, Department of Surgical Oncology, 3000 Daniel den Hoed Cancer Centre, Erasmus MC-Room Ee 0104, PO Box 1738, Rotterdam, The Netherlands.
Rens
Joost A P
JA
Schipper
Debby
D
Eggermont
Alexander M M
AM
ten Hagen
Timo L M
TL
D017209:Apoptosis / Q000187:drug effects*; D002462:Cell Membrane / Q000187:drug effects; D002478:Cells, Cultured; D016207:Cytokines / Q000494:pharmacology*; D042783:Endothelial Cells / Q000166:cytology* / Q000187:drug effects*; D006801:Humans; D009363:Neoplasm Proteins / Q000494:pharmacology*; D021381:Protein Transport / Q000187:drug effects; D016601:RNA-Binding Proteins / Q000494:pharmacology*; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D053199:TNF Receptor-Associated Death Domain Protein / Q000378:metabolism*; D022161:Transport Vesicles / Q000187:drug effects
D016207:Cytokines; D009363:Neoplasm Proteins; D016601:RNA-Binding Proteins; D047888:Receptors, Tumor Necrosis Factor, Type I; D053199:TNF Receptor-Associated Death Domain Protein; C077219:small inducible cytokine subfamily E, member 1