Abstract
Signal transduction mediated by phosphatidylinositol 3-kinase (PI 3-kinase) is regulated by hydrolysis of its products, a function performed by the 145-kDa SH2 domain-containing inositol phosphatase (SHIP). Here, we show that bone marrow macrophages of SHIP(-/-) animals have elevated levels of phosphatidylinositol 3,4,5-trisphosphate [PI (3,4,5)P(3)] and displayed higher and more prolonged chemotactic responses to macrophage colony-stimulating factor (M-CSF) and elevated levels of F-actin relative to wild-type macrophages. We also found that the small GTPase Rac was constitutively active and its upstream activator Vav was constitutively phosphorylated in SHIP(-/-) macrophages. Furthermore, we show that Vav in wild-type macrophages is recruited to the membrane in a PI 3-kinase-dependent manner through the Vav pleckstrin homology domain upon M-CSF stimulation. Dominant inhibitory mutants of both Rac and Vav blocked chemotaxis. We conclude that Vav acts as a PI 3-kinase-dependent activator for Rac activation in macrophages stimulated with M-CSF and that SHIP regulates macrophage M-CSF-triggered chemotaxis by hydrolysis of PI (3,4,5)P(3).
Publication types
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Research Support, N.I.H., Extramural
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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Cell Cycle Proteins / chemistry
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Cell Cycle Proteins / metabolism*
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Cell Membrane / metabolism
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Cells, Cultured
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Chemotaxis / drug effects*
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Enzyme Activation
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Macrophage Colony-Stimulating Factor / pharmacology*
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Macrophages / cytology
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Macrophages / drug effects*
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Macrophages / metabolism
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Mice
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Mice, Inbred C57BL
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Phosphatidylinositol 3-Kinases / metabolism
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Phosphatidylinositol Phosphates / metabolism
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Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases
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Phosphoric Monoester Hydrolases / deficiency
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Phosphoric Monoester Hydrolases / metabolism
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Protein Structure, Tertiary
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Protein Transport
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Proto-Oncogene Proteins / chemistry
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Proto-Oncogene Proteins / metabolism*
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Proto-Oncogene Proteins c-vav
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Signal Transduction / drug effects
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rac GTP-Binding Proteins / chemistry
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rac GTP-Binding Proteins / metabolism*
Substances
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Cell Cycle Proteins
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Phosphatidylinositol Phosphates
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Proto-Oncogene Proteins
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Proto-Oncogene Proteins c-vav
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Vav1 protein, mouse
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phosphatidylinositol 3,4,5-triphosphate
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Macrophage Colony-Stimulating Factor
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Phosphatidylinositol 3-Kinases
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Phosphoric Monoester Hydrolases
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INPPL1 protein, human
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Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases
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rac GTP-Binding Proteins