A Calcium-Dependent Nuclear Signaling Pathway Transcriptionally Silences Atrial Natriuretic Factor Gene Expression

Zeng, Hong, A Calcium-Dependent Nuclear Signaling Pathway Transcriptionally Silences Atrial Natriuretic Factor Gene Expression. Master of Science (Biomedical Science), August, 1995, 85 pp., 2 tables, 20 illustrations, bibliography, 90 titles. A cultured myocardial cell model was used to examine a potential role of calcium-dependent protein kinases and phosphatases in regulating the induction of the atrial natriuretic factor (ANF) gene mediated through adrenoreceptor signaling. In primary culture, rat neonate cardiomyocytes supplemented with phenylephrine (PE) following transfection (24 h) with a full length ANF promoter-reporter construct, showed elevated levels of promoter activity when compared to transfected cardiomyocytes cultured in the absence of PE. Prazosin, a dedicated α1-antagonist, completely blocked the transcriptional induction mediated through PE stimulation. Two different calcium mobilizing agents, BAY K8644 and gramicidin D, significantly reduced PE-stimulated ANF promoter activity. The over-expression of co-transfected exogenous CaM kinase II isoforms resulted in transcriptional silencing of PE-induced promoter activity for cardiac ANF. Transfection of a constitutively active, mutant form of the calcium-dependent phosphatase 2B, calcineurin, gene also transcriptionally silenced ANF gene expression. Exposure of PE-induced cardiomyocytes to either FK-506-treated cells in the absence of PE exposure suggesting that transcriptional silencing may be mediated through a transcriptional repression mechanism. Taken together, these results suggest that the activation of a Ca2+-dependent nuclear signaling pathway mediated through either CaM kinase II or calcineurin leads to complete transcriptional silencing of the embryonic ANF gene expression.