AP-1 activation and altered AP-1 composition in association with increasedphosphorylation and expression of specific Jun and Fos family proteins induced by vinblastine in KB-3 cells

Berry, A Goodwin, M Moran, CL Chambers, TC

A. Berry et al., AP-1 activation and altered AP-1 composition in association with increasedphosphorylation and expression of specific Jun and Fos family proteins induced by vinblastine in KB-3 cells, BIOCH PHARM, 62(5), 2001, pp. 581-591

39

INGLESE

Article

Pharmacology & Toxicology

BIOCHEMICAL PHARMACOLOGY

0006-2952 → ACNP

62

5

2001

581 - 591

ISI

0006-2952(20010901)62:5<581:AAAAAC>2.0.ZU;2-L

Vinblastine and other microtubule inhibitors are important antitumor agents that cause mitotic arrest, and induce apoptosis through poorly understood mechanisms, in a wide variety of cell lines. The activating protein 1 (AP-1 ) transcription factor is a major target of the c-Jun NH2-terminal kinase ( JNK) signaling pathway, which is activated by microtubule inhibitors, There fore, we examined the effect of vinblastine on AP-1 composition and activit y in human KB-3 carcinoma cells. Vinblastine caused highly selective effect s on AP-1 proteins in a concentration- and time-dependent manner. Specifica lly, c-Jun, expressed at a low level in control cells, was greatly increase d and phosphorylated, Jun D was phosphorylated, Jun B underwent phosphoryla tion and subsequently became undetectable, and Fra 1 expression was also gr eatly increased. In contrast, Fra 2, c-Fos, and Fos B were relatively uncha nged by vinblastine. Changes in AP-1 preceded caspase 3 activation and, the refore, occurred prior to the commitment phase of apoptosis. With the excep tion of c-Jun, which was not affected by paclitaxel, the same alterations i n AP-1 proteins occurred after exposure to vincristine, paclitaxel, and col chicine, demonstrating that these are general responses to microtubule inhi bition. Supershift assays demonstrated that in control cells, AP-1 binding activity was mediated by Jun D/Fra 2 heterodimers, whereas after vinblastin e treatment, AP-1 complexes also containing c-Jun and Fra 1 were present, s uggesting that induction of these latter proteins by vinblastine is functio nally significant. Consistent with these observations, vinblastine stimulat ed AP-1-dependent luciferase reporter gene transcription. These findings su ggest that alterations in AP-1 composition and activity may be key events i n the early response of KB-3 cells to microtubule inhibitors. (C) 2001 Else vier Science Inc. All rights reserved.