Vanadium is a metal widely distributed in the environment. Although vanadate-containing compounds exert potent toxic effects on a wide variety of biological systems, the mechanisms by which vanadate mediates adverse effects are not well understood. The present study investigated the vanadate-induced phosphorylation of Akt and p70S6K, two kinases known to be vital for cell survival, growth, transformation, and transition of the cell cycle in mammals. Exposure of mouse epidermal JB6 cells to vanadium led to phosphorylation of Akt and p70S6K in a time- and dose-dependent manner. Vanadium exposure also caused translocation of atypical isoforms of PKC ( from the cytosol to the membrane, but had no effect on PKCα translocation, suggesting that the atypical PKCs (aPKC) were specifically involved in vanadium-induced cellular response. Importantly, over expression of a dominant negative mutant PKCλ blocked Akt phosphorylation at Ser473 and Thr308, whereas it did not inhibit p70S6k phosphorylation at Thr389 and Thr421 /Ser424, suggesting that aPKC activation is specifically involved in vanadium-induced activation of Akt, but not in activation of p70S6k. Furthermore, vanadium-induced p70S6k phosphorylation at Thr389 and Thr421/Ser424 and Akt phosphorylation at Thr308 occurred through a PI-3K-dependent pathway because a PI-3K dominant negative mutant inhibited induction as compared with vector control cells. These results indicate that there was a differential role of aPKC in vanadate-induced phosphorylation of Akt and p70S6k, suggesting that signal transduction pathways leading to the activation of Akt and p706S6k were different.
|Number of pages||9|
|Journal||Molecular and Cellular Biochemistry|
|State||Published - Jan 2004|
Bibliographical noteFunding Information:
This work was partially supported by grants CA103180 and CA094964 from NIH/NCI and ES05512, ES10344, ES00260 from the NIH.
ASJC Scopus subject areas
- Molecular Biology
- Clinical Biochemistry
- Cell Biology