NIK, but not conventional noncanonical NF-κB signaling components, colocalizes on MAC+ endosomes. (A) Confocal images of TRAF2, TRAF3, cIAP1, and cIAP2 were analyzed for MAC colocalization (C9) in ECs treated with PRA for 30 min. (B) NIK and pIKK-α were assessed by IF for MAC colocalization (C9) in ECs treated with PRA for 30 min.(Scale bar: 10 μm.)