Inhibition of Retinoic Acid Receptor Function and Retinoic Acid-regulated Gene Expression in Mouse Melanoma Cells by Calreticulin
A POTENTIAL PATHWAY FOR CYCLIC AMP REGULATION OF RETINOID ACTION*
- From the ‡ Department of Biochemistry and Molecular Biology, Marshall University School of Medicine, Huntington, West Virginia 25755, the Medical Research Council Group in Molecular Biology of Membranes, Department of Biochemistry, University of Alberta, Edmonton, Canada T6G 2S2, and the Center for Biologics, Evaluation and Research, Food and Drug Administration, Bethesda, Maryland 20892
- ∥To whom correspondence should be addressed: Dept. of Biochemistry and Molecular Biology, Marshall University School of Medicine, 1542 Spring Valley Dr., Huntington, WV 25755. Tel.: 304-696-7322; Fax: 304-696-7253.
Abstract
Calcium is a second messenger that controls a wide variety of cellular functions. Because of its multiple actions, there is a stringent requirement for calcium homeostasis, and this is achieved in part by a system of transport and storage proteins such as calreticulin located in the endoplasmic reticulum. Calreticulin is also found in the nucleus, suggesting that it may have a role in transcriptional regulation. It has been reported that calreticulin can inhibit steroid-regulated gene transcription by preventing receptor binding to DNA. Here we report that overexpression of the calreticulin gene in B16 mouse melanoma cells resulted in a decrease in retinoic acid (RA)-stimulated reporter gene expression. Gel shift analysis showed that purified calreticulin inhibited the binding of endogenous RAR to a β-RA response element oligonucleotide, only if added prior to the addition of the oligonucleotide. Co-immunoprecipitation studies suggest a physical interaction between RAR and calreticulin. Transfection of the calreticulin gene into B16 cells inhibited the RA induction of protein kinase Cα, a marker of RA-induced differentiation. We also found that cyclic AMP increased the expression of calreticulin. Cyclic AMP may act to antagonize RA action by both decreasing RAR expression (Y. Xiao, D. Desai, T. Quick, and R. M. Niles, J. Cell Physiol., in press) and stimulating calreticulin levels.
Footnotes
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↵* This work was supported in part by Grant CA 59530 from the National Cancer Institute and Grant 94B19 from the American Institute for Cancer Research. 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.
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↵1 The abbreviations used are:
- RA
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retinoic acid
- RAR
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RA receptor
- RARE
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RA response element
- PKC
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protein kinase C.
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↵2 Y. Xiao, D. Desai, T. Quick, and R. M. Niles, J. Cell Physiol., in press.
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↵3 Weser and M. Michalak, manuscript in preparation.
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- Received February 22, 1996.
- © 1996 by The American Society for Biochemistry and Molecular Biology, Inc.
