The
activating transcription factor 3 (ATF3) is a member of the cAMP-responsive
element-binding (
CREB) protein family of
transcription factors. ATF3 is expressed in H295R human
adrenocortical carcinoma cells and considered a rapid-responder gene to
angiotensin-II stimulation. However, the functions of ATF3 in human adrenocortical tissues have remained unknown. In this study, we analyzed the localization and possible regulatory mechanisms of ATF3 in human adrenocortical cells and tissues. The expression levels of ATF3
mRNA were analyzed in 66
aldosterone-producing
adenomas (APA) and 14
cortisol-producing
adenomas (CPA) using real-time RT-PCR. To localize the ATF3
protein, we performed immunohistochemical analysis in 20 non-pathological adrenal glands, 9 adrenal glands with idiopathic
hyperaldosteronism (IHA), 20 APA, and 5 CPA using a mouse
monoclonal antibody against human ATF3. We showed that ATF3
mRNA levels were higher in APA compared to CPA (P = 0.0053). ATF3 was immunolocalized to the zona glomerulosa of non-pathological adrenal glands and adrenal glands with IHA, and diffusely detected in the
tumor cells of APA and CPA. Subsequently, H295R cells were treated for 6 h with each inhibitor of
Src kinase (SRC), PKC, JAK2, and
calcium-dependent
calmodulin kinase-II (
CaMKII) in the presence or absence of
angiotensin-II. The expression levels of ATF3
mRNA were increased by
angiotensin-II (about 3.5-fold induction), but the magnitude of the induction was significantly decreased in the presence of an inhibitor for SRC (PP2) or
CaMKII (
KN93). These results suggest that ATF3 is a downstream target of SRC and
CaMKII signaling, and may be involved in adrenocortical
aldosterone synthesis.