We have previously shown that liposomes coated with a neoglycolipid constructed from mannotriose and dipalmitoylphosphatidylethanolamine (Man3-DPPE) activate peritoneal macrophages to induce enhanced expression of co-stimulatory molecules and MHC class II. In this study, we investigated the signaling pathways activated by the Man3-DPPE-coated liposomes (OMLs) in a murine macrophage cell line, J774A.1. In response to OML stimulation, ERK among MAPKs was clearly and transiently phosphorylated in J774 cells. ERK phosphorylation was also induced by treatment of the cells with Man3-DPPE and Man3-BSA, but not by uncoated liposomes. In addition, rapid and transient phosphorylation of Akt and Src family kinases (SFKs) was observed in response to OMLs. OML-induced ERK phosphorylation was inhibited by specific inhibitors of PI3K and SFKs, and OML-induced Akt phosphorylation was inhibited by a inhibitor of SFKs. Therefore, OMLs may activate the PI3K/Akt pathway through phosphorylation of Src family kinases to induce ERK activation. (c) 2008 Elsevier Inc. All rights reserved.