Fig. 5.

A model to show the different roles of sharpin in regulating integrin α5β1 and αIIbβ3 activation. a Sharpin directly interacts with the integrin β1 CT and kindlin-1 as well, thus being able to competitively inhibit the talin head binding to the β1 CT and leading to a negative regulation on integrin α5β1 activation. b Sharpin fails to interact with the integrin β3 CT, which is unlikely to affect the talin head binding to the β3 CT. In addition, kindlin-3, the dominant kindlin member in platelets to support integrin αIIbβ3 activation, also exhibits significantly compromised binding to sharpin