Sequential binding of cytosolic Phox complex to phagosomes through regulated adaptor proteins: evaluation using the novel monomeric Kusabira-Green System and live imaging of phagocytosis.
We engineered a method for detecting intramolecular and intermolecular phox protein interactions in cells by fluorescence microscopy using fusion proteins of complementary fragments of a coral fluorescent reporter protein (monomeric Kusabira-Green). We confirmed the efficacy of the monomeric Kusabira-Green system by showing that the PX and PB1 domains of p40phox interact in intact cells, which we suggested maintains this protein in an inactive closed conformation. Using this system, we also explored intramolecular interactions within p47phox and showed that the PX domain interacts with the autoinhibited tandem Src homology 3 domains maintained in contact with the autoinhibitory region, along with residues 341-360. Furthermore, we demonstrated sequential interactions of p67phox with phagosomes involving adaptor proteins, p47phox and p40phox, during FcgammaR-mediated phagocytosis. Although p67phox is not targeted to phagosomes by itself, p47phox functions as an adaptor for the ternary complex (p47phox-p67phox-p40phox) in early stages of phagocytosis before phagosome closure, while p40phox functions in later stages after phagosomal closure. Interestingly, a mutated "open" form of p40phox linked p47phox to closed phagosomes and prolonged p47phox and p67phox retention on phagosomes. These results indicate that binding of the ternary complex to phagosomes can be temporally regulated by switching between adaptor proteins that have PX domains with distinct lipid-binding specificities.
Laboratory of Molecular Pharmacology, Biosignal Research Center, Kobe University, Kobe, Japan.
Takehiko
T
Ueyama
Tomoko
T
Kusakabe
Satoshi
S
Karasawa
Takumi
T
Kawasaki
Aya
A
Shimizu
Jeonghyun
J
Son
Thomas L
TL
Leto
Atsushi
A
Miyawaki
Naoaki
N
Saito
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D020816:Amino Acid Motifs; D000818:Animals; D002460:Cell Line; D002470:Cell Survival; D003600:Cytosol / Q000378:metabolism*; D006801:Humans; D051379:Mice; D019255:NADPH Oxidases / Q000235:genetics / Q000378:metabolism*; D010587:Phagocytosis / Q000276:immunology*; D010588:Phagosomes / Q000276:immunology / Q000378:metabolism*; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D017452:Receptors, IgG / Q000276:immunology; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D010750:Phosphoproteins; D017452:Receptors, IgG; D011994:Recombinant Proteins; C085072:neutrophil cytosol factor 40K; C079789:neutrophil cytosol factor 67K; D019255:NADPH Oxidases; C060505:neutrophil cytosolic factor 1