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Fig. 4. Role of Src family tyrosine kinases in gastrin-induced JNK activation. CHO cells expressing CCKBR (CHO-CCKB) and CHO-CCKB cells stably transfected with the CSK or the p60Src kinase-inactive mutant (SRC- clones 1 and 2) were stimulated for the time indicated with 10 nM gastrin. A, C, and E, whole cell lysates were immunoblotted with an anti-phospho-Thr183 and -Tyr185 JNK antibody or an anti-p60Src antibody as indicated. B and F, after IP with an anti-JNK1 antibody, JNK activity was measured using GST-c-Jun-(1–79) as an exogenous substrate as described in "Materials and Methods." D, after IP with an anti-p60Src antibody, Src kinase activity was assayed using enolase as an exogenous substrate as described in "Materials and Methods." Comparable amounts of proteins were detected in whole cell lysates or immunoprecipitates of all of the above-mentioned experiments (data not shown).