Rap1a-induced LFA-1 activation. (A-D) HL-60 cells with stable expression of shRNA to knock down talin-1 or kindlin-3, or nonspecific shRNA (NS), were incubated with cell-permeable wild-type (WT; open bars) or constitutively active (CA; closed bars) Rap1a peptides (1μM) in the presence of fluorescently labeled conformation-specific reporter mAbs. Flow cytometry was used to measure the binding of isotype (Iso) or (A) NKI-L16 mAb, (B) KIM127 mAb, (C) 2E8 mAb, and (D) mAb 24. Data are mean fluorescence intensity ± SEM (n = 4). *Significantly different from all conditions without the asterisk.