ONOO− requires CRD2 and/or CRD3 but not CRD1 of Fas for signaling to JNK. (A) Schematic representation of Fas receptor. (B) C10 cells were transfected with 2 μg of the indicated constructs, and expression was confirmed by probing Western blots (immunoblots [IB]) with antibody directed against HA. Arrows represent the expected proteins. ns, nonspecific reactivity. (C) C10 cells were transfected with either pcDNA3, Fas 1-210, or Fas 67-210 in the presence of HA-JNK1 and then exposed to ONOO− or FasL + M2 for assessment of JNK activity, as described before. Levels of HA-JNK1 are included as a loading control.