Fig. 4. MEKK1 is required for efficient transmission of the activin B signals to
JNK. (A)
M1+/
KDJ1-/-
and
M1+/
KDJ2-/-
keratinocytes were either untreated (c) or treated with TGF
(T
,
10 ng/ml), TGFβ1 (Tβ, 10 ng/ml) or activin B (Act, 5 ng/ml) for 10
minutes, and cell lysates were analyzed for phosphorylated and total JNK and
c-Jun, phospho-ERK and phospho-Smad2 by western blotting. Similar results were
obtained from at least two independent experiments. The relative ratio of
(B) p-JNK/total JNK and (C) p-c-Jun/total c-Jun in the
Jnk1-null (J1-/-) and
M1+/
KDJ1-/-
keratinocytes either untreated (control) or treated with TGFβ and activin
B were quantified by chemiluminescence imaging analyses and represented
graphically. The levels in untreated cells were used as a standard for
quantification. Similar results were obtained from at least three independent
experiments.