Inhibition of JNK enhances TGF-beta1-activated Smad2 signaling in mouse embryonic lung.
The Smad2/3 pathway plays a key role in mediating TGF-beta1 inhibition of branching morphogenesis and induction of connective tissue growth factor (CTGF) expression in embryonic lungs. Because a number of cell-specific interactions have been described between TGF-beta1-driven Smad signaling and the c-Jun N-terminal kinase (JNK) pathway, we have investigated the effects of JNK inhibition on TGF-beta1 activation of Smad2, inhibition of branching, induction of CTGF expression, and apoptosis in mouse embryonic lung explants. Mouse embryonic day 12.5 (E12.5) lung explants were treated with TGF-beta1 in the presence or absence of a specific pharmacologic JNK inhibitor (SP600125) and a specific JNK peptide inhibitor (JNKI). We found that TGF-beta1 activated the JNK pathway by stimulating c-Jun phosphorylation, which was blocked by JNK inhibitors. Treatment with SP600125 stimulated Smad2 phosphorylation and enhanced TGF-beta1-induced Smad2 phosphorylation. Treatment with JNK inhibitors also decreased normal branching morphogenesis and induced CTGF expression as well as augmented TGF-beta1 inhibition of branching and induction of CTGF expression. Furthermore, JNK inhibition-induced apoptosis. Our results demonstrate that inhibition of the JNK pathway promotes TGF-beta1-driven Smad2 responses in lung branching morphogenesis. These data suggest that the JNK pathway may antagonize TGF-beta1 dependent Smad2 signaling during mouse embryonic lung development.
Wu
Shu
S
Department of Pediatrics, University of Miami Miller School of Medicine, Miami, Florida 33101, USA. swu2@med.miami.edu
Kasisomayajula
Kalyani
K
Peng
Jinghong
J
Bancalari
Eduardo
E
D000818:Animals; D000873:Anthracenes / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D055513:Connective Tissue Growth Factor / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D005865:Gestational Age; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D008168:Lung / Q000187:drug effects* / Q000196:embryology / Q000201:enzymology; D051379:Mice; D009024:Morphogenesis / Q000187:drug effects; D010455:Peptides / Q000494:pharmacology*; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D051899:Smad2 Protein / Q000378:metabolism*; D013997:Time Factors; D046509:Tissue Culture Techniques; D053773:Transforming Growth Factor beta1 / Q000235:genetics / Q000378:metabolism*
D000873:Anthracenes; C526318:CCN2 protein, mouse; D010455:Peptides; D047428:Protein Kinase Inhibitors; D016755:Proto-Oncogene Proteins c-jun; D051899:Smad2 Protein; C497783:Smad2 protein, mouse; D053773:Transforming Growth Factor beta1; D055513:Connective Tissue Growth Factor; C432165:pyrazolanthrone; D048031:JNK Mitogen-Activated Protein Kinases