Scaffold protein enigma homolog activates CREB whereas a short splice variant prevents CREB activation in cardiomyocytes

• Published in: Cellular signalling 2015-12, Vol.27 (12), p.2425-2433
• Main Authors: Ito, Jumpei, Iijima, Masumi, Yoshimoto, Nobuo, Niimi, Tomoaki, Kuroda, Shun’ichi, Maturana, Andrés D.
• Format: Article
• Language: English
• Subjects: Adaptor Proteins, Signal Transducing - physiology; Animals; CREB; Cyclic AMP Response Element-Binding Protein - metabolism; Enzyme Activation; Gene Expression; Gene Expression Regulation; Heart Ventricles - cytology; HEK293 Cells; Humans; Myocytes, Cardiac - metabolism; Phosphorylation; Protein Binding; Protein Interaction Domains and Motifs; Protein Isoforms - physiology; Protein Kinase C - metabolism; Protein Processing, Post-Translational; Rats, Wistar; Scaffold protein
• ISSN: 0898-6568; 1873-3913
• DOI: 10.1016/j.cellsig.2015.09.007

Enigma Homolog (ENH1 or Pdlim5) is a scaffold protein composed of an N-terminal PDZ domain and three LIM domains at the C-terminal end. The enh gene encodes for several splice variants with opposing functions. ENH1 promotes cardiomyocytes hypertrophy whereas ENH splice variants lacking LIM domains prevent it. ENH1 interacts with various Protein Kinase C (PKC) isozymes and Protein Kinase D1 (PKD1). In addition, the binding of ENH1's LIM domains to PKC is sufficient to activate the kinase without stimulation. The downstream events of the ENH1-PKC/PKD1 complex remain unknown. PKC and PKD1 are known to phosphorylate the transcription factor cAMP-response element binding protein (CREB). We tested whether ENH1 could play a role in the activation of CREB. We found that, in neonatal rat ventricular cardiomyocytes, ENH1 interacts with CREB, is necessary for the phosphorylation of CREB at ser133, and the activation of CREB-dependent transcription. On the contrary, the overexpression of ENH3, a LIM-less splice variant, inhibited the phosphorylation of CREB. ENH3 overexpression or shRNA knockdown of ENH1 prevented the CREB-dependent transcription. Our results thus suggest that ENH1 plays an essential role in CREB's activation and dependent transcription in cardiomyocytes. At the opposite, ENH3 prevents the CREB transcriptional activity. In conclusion, these results provide a first molecular explanation to the opposing functions of ENH splice variants. •Enigma Homolog (ENH) a PDZ-LIM scaffold protein has short LIM-less splice variants.•ENH binds to CREB, promotes CREB activation and CREB-dependent transcription.•ENH short splice variant prevents CREB activation and CREB-dependent transcription.•These results can explain the opposing functions of ENH splice variants.