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This Article Full Text Full Text (PDF) All Versions of this Article: 286/6/E975    most recent 00520.2003v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via ISI Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Urban, R. J. Articles by Chedrese, J. Search for Related Content PubMed PubMed Citation Articles by Urban, R. J. Articles by Chedrese, J.

Protein kinase C enhances the transcriptional activity of the porcine P-450 side-chain cleavage insulin-like response element

¹Department of Internal Medicine, The University of Texas Medical Branch, Galveston, Texas 77555-1060; and ²Department of Obstetrics/Gynecology and Reproductive Sciences, University of Saskatchewan, Saskatoon, SK S7N 0W8, Canada

Submitted 14 November 2003 ; accepted in final form 25 January 2004

IGF-I enhances steroidogenesis in granulosa cells by stimulating the expression of the rate-limiting steroidogenic enzyme, cytochrome P-450 side-chain cleavage (P-450_scc). This effect is mediated through an IGF response element (IGFRE) that binds polypyrimidine tract-binding protein (PTB)-associated splicing factor (PSF) and Sp1. Sp1 is essential for activation of the IGFRE, and PSF functions as a repressor. We investigated mechanisms of modulation of the IGFRE by the atypical protein kinase C (PKC) in a porcine stable granulosa cell line, JC-410. PKC was found in nuclear extracts, and levels were increased by IGF-I after 24 and 48 h of treatment. Immunoprecipitation experiments demonstrated that PSF and PKC associated with each other in nuclear extracts from JC-410 cells. Transient transfection with expression plasmids of kinase-active and kinase-deficient PKC isoforms enhanced transcriptional activity of the IGFRE regardless of kinase catalytic activity. Depletion of PKC protein by small interfering RNA suppressed basal IGFRE activity but did not prevent IGF-I stimulation of the IGFRE. We conclude that PKC enhances transcriptional activity of the porcine P-450_scc IGFRE independently of kinase activity by a mechanism involving protein-protein interaction with PSF.

protein kinase C iota; polypyrimidine tract-binding protein-associated splicing factor; insulin-like growth factor I