Restricted accumulation of phosphatidylinositol 3-kinase products in a plasmalemmal subdomain during Fc gamma receptor-mediated phagocytosis.
Phagocytosis is a highly localized and rapid event, requiring the generation of spatially and temporally restricted signals. Because phosphatidylinositol 3-kinase (PI3K) plays an important role in the innate immune response, we studied the generation and distribution of 3' phosphoinositides (3'PIs) in macrophages during the course of phagocytosis. The presence of 3'PI was monitored noninvasively in cells transfected with chimeras of green fluorescent protein and the pleckstrin homology domain of either Akt, Btk, or Gab1. Although virtually undetectable in unstimulated cells, 3'PI rapidly accumulated at sites of phagocytosis. This accumulation was sharply restricted to the phagosomal cup, with little 3'PI detectable in the immediately adjacent areas of the plasmalemma. Measurements of fluorescence recovery after photobleaching were made to estimate the mobility of lipids in the cytosolic monolayer of the phagosomal membrane. Stimulation of phagocytic receptors induced a marked reduction of lipid mobility that likely contributes to the restricted distribution of 3'PI at the cup. 3'PI accumulation during phagocytosis was transient, terminating shortly after sealing of the phagosomal vacuole. Two factors contribute to the rapid disappearance of 3'PI: the dissociation of the type I PI3K from the phagosomal membrane and the persistent accumulation of phosphoinositide phosphatases.
Marshall
J G
JG
Division of Cell Biology, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada.
Booth
J W
JW
Stambolic
V
V
Mak
T
T
Balla
T
T
Schreiber
A D
AD
Meyer
T
T
Grinstein
S
S
D048868:Adaptor Proteins, Signal Transducing; D000077329:Agammaglobulinaemia Tyrosine Kinase; D000818:Animals; D001798:Blood Proteins / Q000235:genetics; D002460:Cell Line; D021961:Cell Membrane Structures / Q000378:metabolism*; D008264:Macrophages / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D008954:Models, Biological; D010587:Phagocytosis / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D011485:Protein Binding / Q000502:physiology; D017346:Protein Serine-Threonine Kinases; D017434:Protein Structure, Tertiary / Q000502:physiology; D011505:Protein-Tyrosine Kinases / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000235:genetics; D051057:Proto-Oncogene Proteins c-akt; D017452:Receptors, IgG / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D048868:Adaptor Proteins, Signal Transducing; D000077329:Agammaglobulinaemia Tyrosine Kinase; D001798:Blood Proteins; D019869:Phosphatidylinositol 3-Kinases; D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols; D010750:Phosphoproteins; D010744:Phosphoric Monoester Hydrolases; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D017452:Receptors, IgG; D011993:Recombinant Fusion Proteins; C490897:Gab1 protein, mouse; C060974:phosphatidylinositol 3,4,5-triphosphate; C039077:platelet protein P47