Evidence for a molecular complex consisting of Fyb/SLAP, SLP-76, Nck, VASP and WASP that links the actin cytoskeleton to Fcgamma receptor signalling during phagocytosis.
Phagocytosis by macrophages and neutrophils involves the spatial and temporal reorganisation of the actin-based cytoskeleton at sites of particle ingestion. Local polymerisation of actin filaments supports the protrusion of pseudopodia that eventually engulf the particle. Here we have investigated in detail the cytoskeletal events initiated upon engagement of Fc receptors in macrophages. Ena/vasodilator-stimulated phosphoprotein (VASP) proteins were recruited to phagosomes forming around opsonised particles in both primary and immortalised macrophages. Not only did the localisation of Ena/VASP proteins coincide, spatially and temporally, with the phagocytosis-induced reorganisation of actin filaments, but their recruitment to the phagocytic cup was required for the remodelling of the actin cytoskeleton, extension of pseudopodia and efficient particle internalisation. We also report that SLP-76, Vav and profilin were recruited to forming phagosomes. Upon induction of phagocytosis, a large molecular complex, consisting in part of Ena/VASP proteins, the Fyn-binding/SLP-76-associated protein (Fyb/SLAP), Src-homology-2 (SH2)-domain-containing leukocyte protein of 76 kDa (SLP-76), Nck, and the Wiskott-Aldrich syndrome protein (WASP), was formed. Our findings suggest that activation of Fcgamma receptors triggers two signalling events during phagocytosis: one through Fyb/SLAP that leads to recruitment of VASP and profilin; and another through Nck that promotes the recruitment of WASP. These converge to regulate actin polymerisation, controlling the assembly of actin structures that are essential for the process of phagocytosis.
Coppolino
M G
MG
Programme in Cell Biology, Research Institute, The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, M5G 1X8, Canada.
Krause
M
M
Hagendorff
P
P
Monner
D A
DA
Trimble
W
W
Grinstein
S
S
Wehland
J
J
Sechi
A S
AS
D000199:Actins / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins; D002460:Cell Line; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000378:metabolism; D006801:Humans; D008264:Macrophages / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D009000:Monocytes / Q000166:cytology / Q000378:metabolism; D015513:Oncogene Proteins / Q000378:metabolism*; D010587:Phagocytosis / Q000502:physiology*; D010588:Phagosomes / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051567:Proto-Oncogene Proteins c-vav; D017452:Receptors, IgG / Q000378:metabolism*; D015398:Signal Transduction; D051316:Wiskott-Aldrich Syndrome Protein; D020741:rho GTP-Binding Proteins / Q000378:metabolism; D000098662:Vasodilator-Stimulated Phosphoprotein
D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D015815:Cell Adhesion Molecules; D018797:Cell Cycle Proteins; C106957:FYB1 protein, human; C491468:Fyb protein, mouse; D008565:Membrane Proteins; D008840:Microfilament Proteins; C078332:Nck protein; D015513:Oncogene Proteins; D010750:Phosphoproteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D051567:Proto-Oncogene Proteins c-vav; D017452:Receptors, IgG; C109742:SLMAP protein, human; C092947:SLP-76 signal Transducing adaptor proteins; C496618:VAV1 protein, human; C496619:Vav1 protein, mouse; C495767:WAS protein, human; C495768:Was protein, mouse; D051316:Wiskott-Aldrich Syndrome Protein; D000098662:Vasodilator-Stimulated Phosphoprotein; D020741:rho GTP-Binding Proteins