Effects of prostaglandin E{sub 2} on the subcellular localization of Epac-1 and Rap1 proteins during Fc{gamma}-receptor-mediated phagocytosis in alveolar macrophages
- Department of Internal Medicine, Division of Pulmonary and Critical Care Medicine, University of Michigan Health System, Ann Arbor, MI 48109 (United States)
- Department of Internal Medicine, Division of Infectious Diseases, University of Michigan Health System, Ann Arbor, MI 48109 (United States)
Recent studies have demonstrated a central role for the exchange protein activated by cAMP (Epac) in the inhibition of Fc{gamma}-receptor-mediated phagocytosis and bacterial killing by prostaglandin E{sub 2} (PGE{sub 2}) in macrophages. However, the subcellular localization of Epac, and its primary target Rap1, has yet to be determined in primary macrophages. Therefore, we used immunofluorescent techniques and phagosome isolation to localize Epac-1 and Rap1 in alveolar macrophages. Epac-1 was predominantly expressed on punctate and tubular membranes throughout the cell body; on the plasma membrane; and co-localized with microtubule organizing centers (MTOCs). Rap1 was abundant on punctate membranes, less abundant on plasma membrane, and also found on MTOCs. Following PGE{sub 2} treatment, Epac-1, but not Rap1, accumulated on the nuclear envelope and disappeared from MTOCs. By immunofluorescent microscopy, both Epac-1 and Rap1 were seen to associate with phagosomes containing IgG-opsonized beads, but this association appeared weak, as we failed to observe such interactions in phagosomes isolated from cells at various time points after bead ingestion. Strikingly, however, Epac-1, but not Rap1, appeared to accumulate on maturing phagosomes, but only after PGE{sub 2} treatment (or treatment with a selective Epac-1 agonist). This association was confirmed in isolated phagosome preparations. The changes in Epac-1 localization were too slow to account for the inhibitory effects of PGE{sub 2} on phagocytosis. However, the appearance of Epac-1 on late phagosomes following PGE{sub 2} treatment might be important for suppressing H{sub 2}O{sub 2} production and inhibiting the killing of intraphagosomal pathogens. The absence of Rap1 on late phagosomes suggests that the effect of Epac-1 might not require Rap1.
- OSTI ID:
- 21045927
- Journal Information:
- Experimental Cell Research, Vol. 314, Issue 2; Other Information: DOI: 10.1016/j.yexcr.2007.10.011; PII: S0014-4827(07)00491-0; Copyright (c) 2007 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0014-4827
- Country of Publication:
- United States
- Language:
- English
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