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Activation of PKC is required for arsenite-induced signal transduction
Abstract:
Trivalent arsenic (arsenite) is a human carcinogen. However, the molecular mechanism of arsenite-induced carcinogenesis is still not well understood. In this study, we found that arsenite induced translocation of PKCepsilon, PKCdelta, and PKCalpha from cytosol to membranes. Rottlerin, a selective inhibitor for PKCdelta, and safingol, a specific inhibitor for PKCalpha, both markedly inhibited arsenite-induced AP-1 activity. These inhibitory effects by rottlerin and safingol appeared to be dose dependent. Arsenite-induced phosphorylation of Erks was inhibited by rottlerin, while safingol inhibited arsenite-induced phosphorylation of JNKs and p38 kinases. Dominant negative mutant transfectant of PKCepsilon markedly blocked arsenite-induced AP-1 activity and the phosphorylation of Erks, JNKs, and p38 kinases. These data demonstrate that PKCdelta, PKCepsilon, and PKCalpha mediate arsenite-induced AP-1 activation in JB6 cells through different MAP kinase (Erks, JNKs, and p38 kinases) pathways.
Insights
Trivalent arsenic (arsenite), a carcinogen, activates AP-1 via protein kinase C (PKC) signaling. PKCdelta, PKCepsilon, and PKCalpha mediate this activation through distinct MAP kinase pathways, clarifying arsenite
Area of Science:
- Molecular carcinogenesis
- Cell signaling pathways
- Toxicology
Background:
- Trivalent arsenic (arsenite) is a known human carcinogen.
- The precise molecular mechanisms underlying arsenite-induced carcinogenesis remain incompletely understood.
- Protein kinase C (PKC) signaling is implicated in cellular responses to carcinogens.
Purpose of the Study:
- To elucidate the role of specific PKC isoforms (PKCepsilon, PKCdelta, PKCalpha) in arsenite-induced carcinogenesis.
- To investigate the involvement of mitogen-activated protein kinase (MAPK) pathways in arsenite-mediated AP-1 activation.
- To identify the molecular targets through which arsenite promotes cellular transformation.
Main Methods:
- Assessed the translocation of PKCepsilon, PKCdelta, and PKCalpha from cytosol to membranes upon arsenite exposure.
- Utilized selective inhibitors (rottlerin for PKCdelta, safingol for PKCalpha) to evaluate their impact on arsenite-induced AP-1 activity.
- Employed dominant-negative mutant transfectants of PKCepsilon to determine its specific role in signaling pathways.
- Measured the phosphorylation status of extracellular signal-regulated kinases (Erks), c-Jun N-terminal kinases (JNKs), and p38 kinases.
Main Results:
- Arsenite induced the translocation of PKCepsilon, PKCdelta, and PKCalpha to cellular membranes.
- Rottlerin and safingol dose-dependently inhibited arsenite-induced activator protein-1 (AP-1) activity.
- PKCdelta inhibition by rottlerin suppressed arsenite-induced Erk phosphorylation; PKCalpha inhibition by safingol reduced JNK and p38 phosphorylation.
- PKCepsilon deficiency blocked arsenite-induced AP-1 activity and phosphorylation of Erks, JNKs, and p38 kinases.
Conclusions:
- PKCdelta, PKCepsilon, and PKCalpha are critical mediators of arsenite-induced AP-1 activation in JB6 cells.
- These PKC isoforms differentially regulate distinct MAP kinase pathways (Erks, JNKs, p38) in response to arsenite.
- Understanding these signaling cascades provides insight into arsenite's carcinogenic mechanisms.