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Rap1 controls activation of the α M β 2 integrin in a talin‐dependent manner
Author(s) -
Lim Jenson,
Dupuy Aurélien G.,
Critchley David R.,
Caron Emmanuelle
Publication year - 2010
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.22788
Subject(s) - rap1 , integrin , microbiology and biotechnology , transfection , gene knockdown , small gtpase , gtpase , immunoprecipitation , protein subunit , actin , integrin, beta 6 , cytoskeleton , chemistry , signal transduction , biology , receptor , cell , biochemistry , gene
The small GTPase Rap1 and the cytoskeletal protein talin regulate binding of C3bi‐opsonised red blood cells (RBC) to integrin α M β 2 in phagocytic cells, although the mechanism has not been investigated. Using COS‐7 cells transfected with α M β 2 , we show that Rap1 acts on the β 2 and not the α M chain, and that residues 732–761 of the β 2 subunit are essential for Rap1‐induced RBC binding. Activation of α M β 2 by Rap1 was dependent on W747 and F754 in the β 2 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 α M β 2 in macrophages shares both common and distinct features from Rap1 activation of α IIb β 3 expressed in CHO cells. J. Cell. Biochem. 111: 999–1009, 2010. © 2010 Wiley‐Liss, Inc.