PT  - JOURNAL ARTICLE
AU  - Isabelle Müller
AU  - Oliver G. Rössler
AU  - Gerald Thiel
TI  - Pregnenolone Sulfate Activates Basic Region Leucine Zipper Transcription Factors in Insulinoma Cells: Role of Voltage-Gated Ca<sup>2+</sup> Channels and Transient Receptor Potential Melastatin 3 Channels
AID  - 10.1124/mol.111.074781
DP  - 2011 Dec 01
TA  - Molecular Pharmacology
PG  - 1179--1189
VI  - 80
IP  - 6
4099  - http://molpharm.aspetjournals.org/content/80/6/1179.short
4100  - http://molpharm.aspetjournals.org/content/80/6/1179.full
SO  - Mol Pharmacol2011 Dec 01; 80
AB  - The neurosteroid pregnenolone sulfate activates a signaling cascade in insulinoma cells involving activation of extracellular signal-regulated protein kinase and enhanced expression of the transcription factor Egr-1. Here, we show that pregnenolone sulfate stimulation leads to a significant elevation of activator protein-1 (AP-1) activity in insulinoma cells. Expression of the basic region leucine zipper (bZIP) transcription factors c-Jun and c-Fos is up-regulated in insulinoma cells and pancreatic β-cells in primary culture after pregnenolone sulfate stimulation. Up-regulation of a chromatin-embedded c-Jun promoter/luciferase reporter gene transcription in pregnenolone sulfate-stimulated insulinoma cells was impaired when the AP-1 binding sites were mutated, indicating that these motifs function as pregnenolone sulfate response elements. In addition, phosphorylation of cAMP response element (CRE)-binding protein is induced and transcription of a CRE-controlled reporter gene is stimulated after pregnenolone sulfate treatment, indicating that the CRE functions as a pregnenolone sulfate response element as well. Pharmacological and genetic experiments revealed that both L-type Ca2+ channels and transient receptor potential melastatin 3 (TRPM3) channels are essential for connecting pregnenolone sulfate stimulation with enhanced AP-1 activity and bZIP-mediated transcription in insulinoma cells. In contrast, pregnenolone sulfate stimulation did not enhance AP-1 activity or c-Jun and c-Fos expression in pituitary corticotrophs that express functional L-type Ca2+ channels but only trace amounts of TRPM3. We conclude that expression of L-type Ca2+ channels is not sufficient to activate bZIP-mediated gene transcription by pregnenolone sulfate. Rather, additional expression of TRPM3 or depolarization of the cells is required to connect pregnenolone sulfate stimulation with enhanced gene transcription.