COS-1 cells bearing Fcγ RIIA were used as it model to demonstrate co-localization of several enzymes previously shown to regulate neutrophil phagocytosis. In COS-1 cells, phospholipase D (PLD) in the membrane fraction was activated during phagocytosis, PLD was found almost exclusively in lipid rafts, along with RhoA and ARFI. Protein kinase C-δ (PKCδ) and Raf-1 translocated to lipid rafts. In neutrophils, ceramide levels increase during phagocytosis, indicating that Feγ RIIA engagement initiates ceramide generation. Applying this model, we transfected COS-1 cells with Feγ RIIA that had been mutated in the ITAM region, rendering them unable to ingest particles. When the mutant receptors were engaged. ceramide was generated and MAPK was activated normally, thus these processes did not require actual ingestion of particles. These results indicate that signaling proteins for phagocytosis are either constitutively present in, or are recruited to, lipid rafts where they are readily available to activate one mother, © 2005 Elsevier Inc. All rights reserved.