期刊
MOLECULAR BIOLOGY OF THE CELL
卷 13, 期 2, 页码 402-411出版社
AMER SOC CELL BIOLOGY
DOI: 10.1091/mbc.01-05-0273
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- NIAID NIH HHS [R21 AI035950, R01 AI035950, AI-35950, R01 AI035950-09] Funding Source: Medline
- NIGMS NIH HHS [GM-44428, R01 GM044428] Funding Source: Medline
Particle ingestion by phagocytosis results from sequential rearrangements of the actin cytoskeleton and overlying membrane. To assemble a chronology of molecular events during phagosome formation ana to examine the contributions of phosphoinositide 3-kinase (PI 3-kinase) to these dynamics, a method was developed for synchronizing Fcgamma receptor-mediated phagocytosis by murine macrophages. Erythrocytes opsonized with complement component C3bi were bound to macrophages at 37degreesC, a condition that does not favor particle phagocytosis. Addition of soluble anti-erythrocyte IgG resulted in rapid opsonization of the bound erythrocytes, followed by their immediate internalization via phagocytosis. Cellular content of F-actin, as measured by binding of rhodamine-phalloidin, increased transiently during phagocytosis, and this increase was not diminished by inhibitors of PI 3-kinase. Immunofluorescence localization of myosins in macrophages fixed at various times during phagocytosis indicated that myosins II and IXb were concentrated in early phagosomes, myosin IC increased later, and myosin V appeared after phagosome closure. Other cytoskeletal proteins showed similar variations in the timing of their appearance in phagosomes. The PI 3-kinase inhibitor wortmannin did not change the dynamics of PI 3-kinase or ezrin localization but prevented the loss of PAK1 from phagosomes. These results suggest that PI 3-kinase deactivates PAK1, and that this may be needed for phagosome closure.
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