Rap1 controls activation of the αMβ2 integrin in a talin‐dependent manner |
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Authors: | Jenson Lim Aurélien G. Dupuy David R. Critchley Emmanuelle Caron |
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Affiliation: | 1. Centre for Molecular Microbiology and Infection, Division of Cell and Molecular Biology, Imperial College London, London, UK;2. Department of Biochemistry, University of Leicester, Leicester, UK |
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Abstract: | The small GTPase Rap1 and the cytoskeletal protein talin regulate binding of C3bi‐opsonised red blood cells (RBC) to integrin αMβ2 in phagocytic cells, although the mechanism has not been investigated. Using COS‐7 cells transfected with αMβ2, we show that Rap1 acts on the β2 and not the αM chain, and that residues 732–761 of the β2 subunit are essential for Rap1‐induced RBC binding. Activation of αMβ2 by Rap1 was dependent on W747 and F754 in the β2 tails, which are required for talin head binding, suggesting a link between Rap1 and talin in this process. Using talin1 knock‐out cells or siRNA‐mediated talin1 knockdown in the THP‐1 monocytic cell line, we show that Rap1 acts upstream of talin but surprisingly, RIAM knockdown had little effect on integrin‐mediated RBC binding or cell spreading. Interestingly, Rap1 and talin influence each other's localisation at phagocytic cups, and co‐immunoprecipitation experiments suggest that they interact together. These results show that Rap1‐mediated activation of αMβ2 in macrophages shares both common and distinct features from Rap1 activation of αIIbβ3 expressed in CHO cells. J. Cell. Biochem. 111: 999–1009, 2010. © 2010 Wiley‐Liss, Inc. |
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Keywords: | phagocytosis CR3 macrophage talin Rap1 RIAM |
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