Originally published In Press as doi:10.1074/jbc.M403473200 on May 15, 2004
J. Biol. Chem., Vol. 279, Issue 30, 31813-31822, July 23, 2004
Lens Major Intrinsic Protein (MIP)/Aquaporin 0 Expression in Rat Lens Epithelia Explants Requires Fibroblast Growth Factor-induced ERK and JNK Signaling*
Nady Golestaneh
,
Jianguo Fan
,
Robert N. Fariss
,
Woo-Kuen Lo
,
Peggy S. Zelenka
, and
Ana B. Chepelinsky
¶
From the
Laboratory of Molecular and Developmental Biology, NEI, National Institutes of Health, Bethesda, Maryland 20892 and the
Department of Anatomy and Neurobiology, Morehouse School of Medicine, Atlanta, Georgia 30310
Lens major intrinsic protein (MIP), exclusive to the vertebrate lens, otherwise known as MIP26 and Aquaporin 0, is abundantly expressed as a lens fiber membrane protein. Although relatively less efficient compared with other aquaporins, MIP is suggested to function as a water channel, as an adhesion molecule, and is required for lens transparency. Because MIP is specifically expressed in lens fiber cells, we investigated in this study the activation of Mip expression after triggering differentiation of rat lens epithelia explants by fibroblast growth factor (FGF)-2. Here, we show that Mip expression in the lens cells is regulated by FGF-2. Using Real time PCR we demonstrate that endogenous Mip levels in the explants were up-regulated upon FGF-2 stimulation, in a concentration-dependent manner. Up-regulation of Mip at the transcriptional level was simultaneous with the activation of the FGF down-stream signaling components, ERK1/2 and JNK. Specific inhibitors, UO126 for ERK1/2 and SP600125 for JNK, abrogated Mip expression in response to FGF-2 in the explants. This inhibition pattern was recapitulated in reporter assays for transfection of the rat lens epithelia explants, driven by the Mip promoter (-1648/+44). Our studies show that ERK1/2 and JNK signaling pathways are required for Mip expression in lens epithelia explants induced to differentiate by FGF-2.
Received for publication, March 29, 2004
, and in revised form, May 12, 2004.
* This work was supported in part by a grant from the National Institutes of Health (to W.-K. L.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
¶ To whom correspondence should be addressed: National Institutes of Health, 7 Memorial Dr., MSC 0704 Bldg. 7, Rm. 105, Bethesda, MD 20892-0704. Tel.: 301-435-7245; Fax: 301-480-7933.

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Copyright © 2004 by the American Society for Biochemistry and Molecular Biology.