Inflammation and Regeneration Vol. 26, No. 2, pp.107-112, 2006

Mini Review

ARF-GEP100. a guanine nucleotide-exchange protein for ADP-ribosylation factor 6, involved in the apoptotic cell death of phagocytes

Akimasa SOMEYA1, Joel MOSS2, Martha Vaughan2, Isao NAGAOKA1

1Department of Host Defense and Biochemical Research, Juntendo University, School of Medicine, 2Pulmonary-Critical Care Medicine Branch, NHLBI, NIH, USA

Abstract : ADP-ribosylation factors (ARFs) are 20-kDa GTP-binding proteins involved in the vesicular trafficking, the activation of phospholipase D and phosphatidylinositol 4-phosphate 5-kinase, and the modulation of phagocyte functions. Like other GTP-binding proteins, ARFs cycle between GTP-bound, active and GDP-bound, inactive status. Guanine nucleotide-exchange proteins (GEPs), which catalyze the change of bound GDP for GTP, are necessary for the activation of ARFs. Previously, we found a novel GEP with 100 kDa, named ARF-GEP100. In this study, we elucidated the role in ARF-GEP100 On phagocyte functions by transfection of ARF-GEP100. Overexpression of ARF-GEP100 induced apoptosis of mouse macrophage RAW264.7 cells and phorbol 12-myristate 13-acetate treated human monocyte U937 cells, which could be detected by morphological changes (nuclear condensation and formation of apoptotic bodies), annexin V-staining and TUNEL assay. ARF-GEP100-induced apoptosis was not inhibited by a caspase inhibitor zVAD-FMK. Furthermore, mutant analysis of ARF-GEP100 revealed that two regions (N- and C- termini) of ARF-GEP100 were essential for the induction of apoptosis, but the mutant defective in GDP-GTP exchange domain induced apoptosis. These results suggest that ARF-GEP100 induces apoptosis of monocytic phagocytes independent of both the caspase activation and GDP-GTP exchange activity.