Phagocytic signaling molecules in lipid rafts of COS-1 cells transfected with FcgammaRIIA.
COS-1 cells bearing FcgammaRIIA were used as a 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 ARF1. Protein kinase C-delta (PKCdelta) and Raf-1 translocated to lipid rafts. In neutrophils, ceramide levels increase during phagocytosis, indicating that FcgammaRIIA engagement initiates ceramide generation. Applying this model, we transfected COS-1 cells with FcgammaRIIA 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 another.
Mansfield
Pamela J
PJ
Department of Pediatrics, Division of Hematology/Oncology, University of Michigan, Ann Arbor, MI 48109, USA.
Hinkovska-Galcheva
Vania
V
Borofsky
Michael S
MS
Shayman
James A
JA
Boxer
Laurence A
LA
D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism*; D019556:COS Cells; D002522:Chlorocebus aethiops; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D021962:Membrane Microdomains / Q000201:enzymology*; D010587:Phagocytosis; D010739:Phospholipase D / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D051745:Protein Kinase C-delta; D017452:Receptors, IgG / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D014162:Transfection
D015703:Antigens, CD; C080568:Fc gamma receptor IIA; D017452:Receptors, IgG; D011493:Protein Kinase C; D051745:Protein Kinase C-delta; D048049:Extracellular Signal-Regulated MAP Kinases; D010739:Phospholipase D