Protein kinase C regulates transcription of the human guanylate cyclase C gene

Roy, Nivedita and Guruprasad, Medigeshi R and Kondaiah, Paturu and Mann, Elizabeth A and Giannella, Ralph A and Visweswariah, Sandhya S (2001) Protein kinase C regulates transcription of the human guanylate cyclase C gene. In: European Journal of Biochemistry, 268 (7). pp. 2160-2171.

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Abstract

Guanylate cyclase C is the receptor for the bacterial heatstable enterotoxins and guanylin family of peptides, and mediates its action by elevating intracellular cGMP levels. Potentiation of ligand-stimulated activity of guanylate cyclase C in human colonic T84 cells is observed following activation of protein kinase C as a result of direct phosphorylation of guanylate cyclase C. Here, we show that prolonged exposure of cells to phorbol esters results in a decrease in guanylate cyclase C content in 4b-phorbol 12-myristate 13-acetate-treated cells, as a consequence of a decrease in guanylate cyclase C mRNA levels. The reduction in guanylate cyclase C mRNA was inhibited when cells were treated with 4b-phorbol 12-myristate 13-acetate (PMA) in the presence of staurosporine, indicating that a primary phosphorylation event by protein kinase C triggered the reduction in RNA levels. The reduction in guanylate cyclase C mRNA levels was not due to alterations in the half-life of guanylate cyclase C mRNA, but regulation occurred at the level of transcription of guanylate cyclase C mRNA. Expression in T84 cells of a guanylate cyclase C promoter-luciferase reporter plasmid,containing 1973 bp of promoter sequence of the guanylate cyclase C gene, indicated that luciferase activity was reduced markedly on PMA treatment of cells, and the protein kinase C-responsive element was present in a 129-bp region of the promoter, containing a HNF4 binding element. Electrophoretic mobility shift assays using an oligonucleotide corresponding to the HNF4 binding site, indicated a decrease in binding of the factor to its cognate sequence in nuclear extracts prepared from PMA-treated cells. We therefore show for the first time that regulation of guanylate cyclase C activity can be controlled at the transcriptional level by cross-talk with signaling pathways that modulate protein kinase C activity. We also suggest a novel regulation of the HNF4 transcription factor by protein kinase C.

Item Type:	Journal Article
Publication:	European Journal of Biochemistry
Publisher:	Blackwell Publishing
Additional Information:	Copyright for this article belongs to Blackwell Publishing.
Keywords:	guanylate cyclase C;HNF4;protein kinase transcription
Department/Centre:	Division of Biological Sciences > Molecular Reproduction, Development & Genetics
Date Deposited:	15 Sep 2004
Last Modified:	19 Sep 2010 04:16
URI:	http://eprints.iisc.ac.in/id/eprint/1939

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