Annexin A1 is a new functional linker between actin filaments and phagosomes during phagocytosis

DM Patel, SF Ahmad, DG Weiss, V Gerke… - Journal of cell …, 2011 - journals.biologists.com
DM Patel, SF Ahmad, DG Weiss, V Gerke, SA Kuznetsov
Journal of cell science, 2011journals.biologists.com
Remodelling of the actin cytoskeleton plays a key role in particle internalisation and the
phagosome maturation processes. Actin-binding proteins (ABPs) are the main players in
actin remodelling but the precise role of these proteins in phagocytosis needs to be clarified.
Annexins, a group of ABPs, are known to be present on phagosomes. Here, we identified
annexin A1 as a factor that binds to isolated latex bead phagosomes (LBPs) in the presence
of Ca2+ and facilitates the F-actin–LBP interaction in vitro. In macrophages the association …
Remodelling of the actin cytoskeleton plays a key role in particle internalisation and the phagosome maturation processes. Actin-binding proteins (ABPs) are the main players in actin remodelling but the precise role of these proteins in phagocytosis needs to be clarified. Annexins, a group of ABPs, are known to be present on phagosomes. Here, we identified annexin A1 as a factor that binds to isolated latex bead phagosomes (LBPs) in the presence of Ca2+ and facilitates the F-actin–LBP interaction in vitro. In macrophages the association of endogenous annexin A1 with LBP membranes was strongly correlated with the spatial and temporal accumulation of F-actin at the LBP. Annexin A1 was found on phagocytic cups and around early phagosomes, where the F-actin was prominently concentrated. After uptake was completed, annexin A1, along with F-actin, dissociated from the nascent LBP surface. At later stages of phagocytosis annexin A1 transiently concentrated only around those LBPs that showed transient F-actin accumulation (‘actin flashing’). Downregulation of annexin A1 expression resulted in impaired phagocytosis and actin flashing. These data identify annexin A1 as an important component of phagocytosis that appears to link actin accumulation to different steps of phagosome formation.
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