Phospholipase D2 acts as an essential adaptor protein in the activation of Syk in antigen-stimulated mast cells.
Mast cells are responsible for IgE-mediated allergic reactions. Phospholipase D1 (PLD1) and PLD2 regulate mast cell activation, but the mechanisms remain unclear. Here we show that PLD2 associates with and promotes activation of Syk, a key enzyme in mast cell activation. Antigen stimulation resulted in increased association and colocalization of Syk with PLD2 on the plasma membrane as indicated by coimmunoprecipitation and confocal microscopy. This association was dependent on tyrosine phosphorylation of Syk but not on PLD2 activity. In vitro, PLD2 interacted via its Phox homology (PX) domain with recombinant Syk to induce phosphorylation and activation of Syk. Furthermore, overexpression of PLD2 or catalytically inactive PLD2K758R enhanced antigen-induced phosphorylations of Syk and its downstream targets, the adaptor proteins LAT and SLP-76, while expression of a PLD2 siRNA blocked these phosphorylations. Apparently, the interaction of PLD2 with Syk is an early critical event in the activation of mast cells.
Lee
Jun Ho
JH
Department of Immunology, College of Medicine, Konkuk University, Chungju 380-701, Korea.
Kim
Young Mi
YM
Kim
Nam Wook
NW
Kim
Jie Wan
JW
Her
Erk
E
Kim
Bo Kyung
BK
Kim
Jong Hyun
JH
Ryu
Sung Ho
SH
Park
Jong Woo
JW
Seo
Dong Wan
DW
Han
Jeung Whan
JW
Beaven
Michael A
MA
Choi
Wahn Soo
WS
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism / Q000502:physiology; D000818:Animals; D000941:Antigens / Q000502:physiology; D001665:Binding Sites; D015550:Cell Degranulation; D002460:Cell Line; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D008407:Mast Cells / Q000201:enzymology / Q000276:immunology / Q000378:metabolism*; D010739:Phospholipase D / Q000378:metabolism* / Q000502:physiology; D010766:Phosphorylation; D011485:Protein Binding; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D051381:Rats; D000072377:Syk Kinase; D014162:Transfection
D048868:Adaptor Proteins, Signal Transducing; D000941:Antigens; D047908:Intracellular Signaling Peptides and Proteins; D011505:Protein-Tyrosine Kinases; D000072377:Syk Kinase; C000606898:Syk protein, rat; C105606:phospholipase D2; D010739:Phospholipase D