Journal of Biological Chemistry
Volume 277, Issue 3, 18 January 2002, Pages 1828-1836
Journal home page for Journal of Biological Chemistry

MECHANISMS OF SIGNAL TRANSDUCTION
Green Tea Polyphenol Stimulates a Ras, MEKK1, MEK3, and p38 Cascade to Increase Activator Protein 1 Factor-dependent Involucrin Gene Expression in Normal Human Keratinocytes*

https://doi.org/10.1074/jbc.M110376200Get rights and content
Under a Creative Commons license
open access

(−)-Epigallocatechin-3-gallate (EGCG) is an important bioactive constituent of green tea that efficiently reduces epidermal cancer cell proliferation. This inhibition is associated with a reduction in activator protein 1 (AP1) transcription factor level and activity. However, its effects on AP1 function in normal epidermal cells have not been extensively explored. Our present studies show that EGCG regulates normal keratinocyte function. To understand the mechanism of action, we examined the effects of EGCG on AP1 factor activity, MAPK signal transduction, and expression of the AP1 factor-regulated human involucrin (hINV) gene. EGCG increases hINV promoter activity in a concentration-dependent manner that requires the presence of an intact hINV promoter AP1 factor binding site. This response appears to be physiologic, as endogenous hINV gene expression is also increased. Fra-1, Fra-2, FosB, JunB, JunD, c-Jun, and c-Fos levels are increased by EGCG treatment, as is AP1 factor binding to hINV promoter AP1 site. Gel mobility shift studies show that this complex contains Fra-1 and JunD. Signal transduction analysis indicates that the EGCG response requires Ras, MEKK1, MEK3, and p38 kinases. Kinase assays and inhibitor studies suggest that p38δ is the p38 isoform responsible for the regulation. These changes are also associated with a cessation of cell proliferation and enhanced cornified envelope formation. These studies show that in normal human keratinocytes EGCG markedly increases, via a MAPK signaling mechanism, AP1 factor-associated responses.

Cited by (0)

Published, JBC Papers in Press, November 6, 2001, DOI 10.1074/jbc.M110376200

*

This work was supported by grants from the National Institutes of Health (to R. L. E.) and by a Dermatology Foundation research fellowship (to T. E.) and used the facilities of the Skin Diseases Research Center of Northeast Ohio, National Institutes of Health Grant AR39750.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.