期刊
JOURNAL OF EXPERIMENTAL MEDICINE
卷 193, 期 8, 页码 955-966出版社
ROCKEFELLER UNIV PRESS
DOI: 10.1084/jem.193.8.955
关键词
actin remodeling; ARF family GTPases; ARFGAP; membrane remodeling; Rho family GTPases
The Fc gamma receptor (Fc gammaR)-mediated phagocytosis of macrophages is a complex process where remodeling of both the actin-based cytoskeleton and plasma membrane occur coordinately. Several different families of small GTPases are involved. We have isolated a GTPase-activating protein (GAP) for ADP-ribosylation factor (ARF), paxillin-associated protein with ARFGAP activity (PAG)3/Pap alpha /KIAA0400, from mature monocytes and macrophage-like cells. Mam malian ARFs fall into three classes, and the class III isoform (ARF6) has been shown to be involved in Fc gammaR-mediated phagocytosis. Here we report that PAG3 is enriched together with ARF6 and F-actin at phagocytic cups formed beneath immunoglobulin G-opsonized beads in P388D1 macrophages, in which overexpression of ARF6, but not ARF1 (class I) or ARF5 (class II), inhibits the phagocytosis. Overexpression of PAG3, but riot its GAP-inactive mutant, attenuated the focal accumulation of F-actin and blocked phagocytosis, although surface levels of the Fc gamma Rs were not affected. Other ubiquitously expressed ARFGAPs, G protein-coupled receptor kinase interactors GIT2 and GIT2-short/KIAA0148, which we have shown to exhibit GAP activity for ARF1 in COS-7 cells, did not accumulate at the phagocytic cups or inhibit phagocytosis. Moreover, cooverexpression of ARF6, but not ARF1 or ARF5, restored the phagocytic activity of PAG3-overexpressing cells. We propose that PAG3 acts as a GAP for ARF6 and is hence involved in Fc gammaR-mediated phagocytosis in mouse macrophages.
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