FIGURE 2.

Endogenous arrestin-3 interacts with endogenous JNK1/2 in non-neuronal and neuronal cells. A, immunoprecipitation of endogenous arrestin-3 from arrestin-2 knock-out MEFs using rabbit polyclonal arrestin antibody (ab) F431 (upper panels) or mouse monoclonal arrestin-3 antibody (lower panels). Respective rabbit or mouse IgGs were used as controls. Co-immunoprecipitated JNK isoforms were visualized using mouse or rabbit JNK antibodies. Black arrows point to arrestin-3 bands, black arrowheads point to JNK bands, and white arrows point to IgG bands. IB, immunoblot. B, immunoprecipitation experiments performed in Neuro2a cells. All conditions and labels are the same as in panel A. Rabbit arrestin antibody immunoprecipitated arrestin-3 much more efficiently than mouse arrestin-3 antibody, as seen in the images in the left in A and in B. Note that the amount of arrestin-3 standard loaded on each gel was the same (Arr3 Std), but the exposure times differed. Thus, the amount of co-precipitated JNK1/2 was also higher when rabbit arrestin antibody was used.