Transforming growth factor-beta 1 regulation of collagenase-3 expression in osteoblastic cells by cross-talk between the Smad and MAPK signaling pathways and their components, Smad2 and Runx2.
Transforming growth factor-beta (TGF-beta) plays a key role in osteoblast differentiation and bone development and remodeling. Collagenase-3 (matrix metalloproteinase-13) is expressed by osteoblasts and seems to be involved in osteoclastic bone resorption. Here, we show that TGF-beta 1 stimulates collagenase-3 expression in the rat osteoblastic cell line UMR 106-01 and requires de novo protein synthesis. Dominant-negative Smad2/3 constructs indicated that Smad signaling is essential for TGF-beta 1-stimulated collagenase-3 promoter activity. Inhibitors of the ERK1/2 and p38 MAPK pathways, but not the JNK pathway, reduced TGF-beta 1-stimulated collagenase-3 expression, indicating that the p38 MAPK and ERK1/2 pathways are also required for TGF-beta 1-stimulated collagenase-3 expression in UMR 106-01 cells. These inhibitors did not prevent nuclear localization of Smad proteins, but they inhibited Smad-mediated transcriptional activation. We have shown for the first time that Runx2 (a bone transcription factor and a potential substrate for the MAPK pathway) is phosphorylated in response to TGF-beta 1 treatment in osteoblastic cells. Cotransfection of Smad2 and Runx2 constructs had a cooperative effect on TGF-beta 1-stimulated collagenase-3 promoter activity in these cells. We further identified ligand-independent physical interaction between Smad2 and Runx2. Taken together, our results provide an important role for cross-talk between the Smad and MAPK pathways and their components in expression of collagenase-3 following TGF-beta 1 treatment in UMR 106-01 cells.
Department of Physiology and Biophysics, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA. selvamn2@umdnj.edu
Nagarajan
N
Selvamurugan
Sukyee
S
Kwok
Tamara
T
Alliston
Michael
M
Reiss
Nicola C
NC
Partridge
D000818:Animals; D045744:Cell Line, Tumor; D017364:Collagenases / Q000235:genetics*; D050659:Core Binding Factor Alpha 1 Subunit; D004268:DNA-Binding Proteins / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D053509:Matrix Metalloproteinase 13; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009363:Neoplasm Proteins / Q000378:metabolism; D010006:Osteoblasts / Q000166:cytology*; D011401:Promoter Regions, Genetic / Q000187:drug effects; D051381:Rats; D020239:Receptor Cross-Talk; D015398:Signal Transduction; D051785:Smad Proteins; D051899:Smad2 Protein; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D053773:Transforming Growth Factor beta1
D050659:Core Binding Factor Alpha 1 Subunit; D004268:DNA-Binding Proteins; D009363:Neoplasm Proteins; D051785:Smad Proteins; D051899:Smad2 Protein; C497784:Smad2 protein, rat; C508962:Tgfb1 protein, rat; D015534:Trans-Activators; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D020928:Mitogen-Activated Protein Kinases; D017364:Collagenases; D053509:Matrix Metalloproteinase 13; C507083:Mmp13 protein, rat