ASK1, MKK4, and JNK3 bind arrestin3. A, COS-7 cells were
transfected with FLAG-arrestin3 (FLAG-Arr3) with GFP-JNK3, HA-ASK1, HA-MKK4,
or with indicated combinations of these kinases. Cell lysates were
immunoprecipitated with rabbit anti-FLAG antibody, and then immunoblotted with
mouse anti-HA, anti-GFP and anti-FLAG antibodies. B, COS-7 cells were
transfected with HA-MKK4 with indicated FLAG-tagged arrestins. Cell lysates
were immunoprecipitated and immunoblotted as in panel A. C, HEK-293A
cells were transfected with HA-ASK-NLS alone or with indicated FLAG-tagged
arrestins. Arrestins were visualized with M2 anti-FLAG, HA-ASK1 with rat
anti-HA high affinity antibody, followed by Alexa 593 anti-mouse (Red) and
Alexa 488 anti-rat (Green) secondary antibodies, respectively. The
representative images show arrestins (red), HA-ASK1-NLS
(green), and both channels merged. At least 20 cells expressing
indicated proteins were scored for the subcellular distribution of
HA-ASK1-NLS. Means ± S.D. (n = 3) of the fraction of cells
with more ASK1 in the cytoplasm than in the nucleus are shown.
****, p < 0.0001.