Collaborative Roles for c-Jun N-terminal Kinase, c-Jun, Serum Response Factor, and Sp1 in Calcium-regulated Myocardial Gene Expression

• Published in: The Journal of biological chemistry 1997-09, Vol.272 (38), p.24046-24053
• Main Authors: McDonough, Patrick M., Hanford, Deanna S., Sprenkle, Amy B., Mellon, Noel R., Glembotski, Christopher C.
• Format: Article
• Language: English
• Subjects: Animals; Atrial Natriuretic Factor - genetics; Calcium - metabolism; Calcium-Calmodulin-Dependent Protein Kinases - metabolism; Cells, Cultured; DNA-Binding Proteins - metabolism; Gene Expression Regulation; Heart Ventricles - cytology; Heart Ventricles - metabolism; JNK Mitogen-Activated Protein Kinases; Mitogen-Activated Protein Kinases; Nuclear Proteins - metabolism; Promoter Regions, Genetic; Proto-Oncogene Proteins c-jun - metabolism; Rats; Serum Response Factor; Sp1 Transcription Factor - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.272.38.24046

Electrical stimulation of contractions (pacing) of primary neonatal rat ventricular myocytes increases intracellular calcium and activates a hypertrophic growth program that includes expression of the cardiac-specific gene, atrial natriuretic factor (ANF). To investigate the mechanism whereby pacing increases ANF, pacing was tested for its ability to regulate mitogen-activated protein kinase family members, ANF promoter activity, and thetrans-activation domain of the transcription factor, Sp1. Pacing and the calcium channel agonist BAYK 8644 activated c-Jun N-terminal kinase (JNK) but not extracellular signal-regulated kinase. Pacing stimulated ANF-promoter activity approximately 10-fold. Furthermore, transfection with an expression vector for c-Jun, a substrate for JNK, also activated the ANF promoter, and the combination of pacing and c-Jun was synergystic, consistent with roles for JNK and c-Jun in calcium-activated ANF expression. Proximal serum response factor and Sp1 binding sites were required for the effects of pacing or c-Jun on the ANF promoter. Pacing and c-Jun activated a GAL4-Sp1 fusion protein by 3- and 12-fold, respectively, whereas the two stimuli together activated GAL4-Sp1 synergistically, similar to their effect on the ANF promoter. Transfection with an expression vector for c-Fos inhibited the effects of c-Jun, suggesting that c-Jun acts independently of AP-1. These results demonstrate an interaction between c-Jun and Sp1 and are consistent with a novel mechanism of calcium-mediated transcriptional activation involving the collaborative actions of JNK, c-Jun, serum response factor, and Sp1.