CAMP‐stimulated Expression of DGKθ Requires Steroidogenic Factor‐1 and Sterol Regulatory Element Binding Protein

Abstract

Diacylglycerol kinase theta (DGKθ) plays a key role in cortisol production in the adrenal cortex by generating phosphatidic acid (PA), an agonist of the nuclear receptor steroidogenic factor‐1 (SF‐1). In an attempt to identify the role of cAMP signaling in DGKθ gene expression regulation, we found that dibutyryl cAMP (Bt2cAMP) increases the mRNA and protein expression of DGKθ in H295R human adrenocortical cells. Reporter gene assays using 1.5 kB of the DGKθ promoter fused to the luciferase gene identified two regions of the promoter that were required for cAMP responsiveness. Moreover, overexpression of SF‐1 and sterol regulatory element binding protein 1 (SREBP1) increased the DGKθ transcriptional activity and mutation of the cAMP responsive regions abolished the ability of SF‐1 and SREBP1 to activate DGKθ luciferase activity. Chromatin immunoprecipitation assays revealed that Bt2cAMP promoted the recruitment of SF‐1 and SREBP1 to the endogenous DGKθ promoter. Finally, silencing SF‐1 or SREBP1 reduced both basal and cAMP‐stimulated DGKθ gene expression and diminished cAMP‐stimulated PA production. Taken together, we identify SF‐1 and SREBP1 as regulators of DGKθ transcription and PA production in human adrenocortical cells.