Involvement of a guanine nucleotide-exchange protein, ARF-GEP100/BRAG2a, in the apoptotic cell death of monocytic phagocytes.
We previous identified adenosine 5'-diphosphate-ribosylation factor (ARF)-guanine nucleotide-exchange protein, 100 kDa (GEP(100)), as a novel GEP with a molecular size of approximately 100 kDa, which preferentially activates ARF6. In this study, we examined the effect of ARF-GEP(100) on monocytic cell apoptosis. Overexpression of ARF-GEP(100) in PMA-differentiated human monocyte-macrophage-like U937 cells and mouse macrophage RAW264.7 cells induced apoptotic cell death, which was detected by morphological changes (chromatin condensation, nucleus fragmentation, and shrinking of cytoplasm), annexin V-staining, and TUNEL assay. It is interesting that a mutant lacking the Sec7 domain, which is responsible for ARF activation, was able to induce apoptosis of the target cells to the level of that of a wild-type ARF-GEP(100). Furthermore, ARF-GEP(100)-silencing experiments indicated that the TNF-alpha-induced apoptosis was significantly suppressed among ARF-GEP(100)-depressed cells. These observations apparently suggest that ARF-GEP(100) is involved in the induction of apoptosis in monocytic phagocytes, possibly independent of ARF activation.
Someya
Akimasa
A
Department of Host Defense and Biochemical Research, Juntendo University School of Medicine, Bunkyo-ku, Tokyo 113-8421, Japan. someya@med.juntendo.ac.jp
Moss
Joel
J
Nagaoka
Isao
I
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D020662:Guanine Nucleotide Exchange Factors / Q000096:biosynthesis / Q000187:drug effects / Q000494:pharmacology*; D006801:Humans; D051379:Mice; D010586:Phagocytes / Q000187:drug effects*; D034741:RNA, Small Interfering / Q000494:pharmacology; D013329:Structure-Activity Relationship; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D020298:U937 Cells
D020662:Guanine Nucleotide Exchange Factors; C504483:IQSEC1 protein, human; D034741:RNA, Small Interfering; D014409:Tumor Necrosis Factor-alpha; D013755:Tetradecanoylphorbol Acetate