Focal adhesion kinase mediates MEF2 and c-Jun activation by stretch: role in the activation of the cardiac hypertrophic genetic program.
OBJECTIVE
We have previously reported that myocyte enhancer factor-2 (MEF2) transcription factors and c-Jun are rapidly activated by pressure overload and that these events are involved in the early activation of the myocardial hypertrophic genetic program. In this study, we investigated whether focal adhesion kinase (FAK) mediates the activation of MEF2 and c-Jun by mechanical stress in isolated neonatal rat ventricular myocytes (NRVMs).


METHODS
NRVMs were subjected to cyclic stretch up to 4 h and studied by immunoblotting, reverse transcriptase-polymerase chain reaction, laser confocal analysis, and reporter gene and electrophoretic mobility shift assays. Analysis was extended to NRVMs transfected with FAK-antisense oligodeoxynucleotide, treated with FAK/Src inhibitor PP2 or JNK/c-Jun inhibitor SP600125.


RESULTS
Cyclic stretch increased c-Jun expression, JNK/c-Jun phosphorylation, and MEF2-DNA binding activity in NRVMs. Reporter gene assays indicated that the MEF2 site is critical to c-jun transcription in stretched cells. FAK-antisense transfection abolished MEF2 and c-jun promoter activation, while either FAK-antisense or PP2 treatment inhibited the stretch-induced c-Jun expression and JNK/c-Jun phosphorylation. Finally, treatment of NRVMs with the specific JNK/c-Jun inhibitor SP600125 significantly reduced the stretch-induced increase of atrial natriuretic factor promoter activity.


CONCLUSIONS
The present data indicate that FAK regulates the activation of MEF2 and JNK/c-Jun pathways, which in turn have a key role in the early activation of the hypertrophic genetic program by mechanical stress in cardiac myocytes.
Nadruz
Wilson
W
Department of Internal Medicine, School of Medicine, State University of Campinas, Campinas, SP, Brazil.
Corat
Marcus A F
MA
Marin
Talita M
TM
Guimarães Pereira
Gonçalo A
GA
Franchini
Kleber G
KG
D000818:Animals; D006332:Cardiomegaly / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D024202:Electrophoretic Mobility Shift Assay; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D066298:In Vitro Techniques; D064326:MEF2 Transcription Factors; D018613:Microscopy, Confocal; D032383:Myocytes, Cardiac / Q000378:metabolism*; D018006:Myogenic Regulatory Factors / Q000378:metabolism*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013314:Stress, Mechanical
D064326:MEF2 Transcription Factors; D018006:Myogenic Regulatory Factors; D016376:Oligonucleotides, Antisense; D016755:Proto-Oncogene Proteins c-jun; D051416:Focal Adhesion Protein-Tyrosine Kinases