Disruption of LTBP-4 function reduces TGF-beta activation and enhances BMP-4 signaling in the lung.
Disruption of latent TGF-beta binding protein (LTBP)-4 expression in the mouse leads to abnormal lung development and colorectal cancer. Lung fibroblasts from these mice produced decreased amounts of active TGF-beta, whereas secretion of latent TGF-beta was significantly increased. Expression and secretion of TGF-beta2 and -beta3 increased considerably. These results suggested that TGF-beta activation but not secretion would be severely impaired in LTBP-4 -/- fibroblasts. Microarrays revealed increased expression of bone morphogenic protein (BMP)-4 and decreased expression of its inhibitor gremlin. This finding was accompanied by enhanced expression of BMP-4 target genes, inhibitors of differentiation 1 and 2, and increased deposition of fibronectin-rich extracellular matrix. Accordingly, increased expression of BMP-4 and decreased expression of gremlin were observed in mouse lung. Transfection of LTBP-4 rescued the -/- fibroblast phenotype, while LTBP-1 was inefficient. Treatment with active TGF-beta1 rescued BMP-4 and gremlin expression to wild-type levels. Our results indicate that the lack of LTBP-4-mediated targeting and activation of TGF-beta1 leads to enhanced BMP-4 signaling in mouse lung.
Department of Virology, Haartman Institute and Helsinki University Hospital, University of Helsinki, 00014 Helsinki, Finland. katri.koli@helsinki.fi
Katri
K
Koli
Frank
F
Wempe
Anja
A
Sterner-Kock
Anna
A
Kantola
Martina
M
Komor
Wolf-K
WK
Hofmann
Harald
H
von Melchner
Jorma
J
Keski-Oja
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D015152:Blotting, Northern; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000378:metabolism*; D002454:Cell Differentiation; D018076:DNA, Complementary / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005109:Extracellular Matrix / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D053779:Latent TGF-beta Binding Proteins; D008168:Lung / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D008856:Microscopy, Fluorescence; D020411:Oligonucleotide Array Sequence Analysis; D009841:Oligonucleotides / Q000737:chemistry; D010641:Phenotype; D012313:RNA / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D015854:Up-Regulation
D048868:Adaptor Proteins, Signal Transducing; C525809:BMP4 protein, human; C525810:Bmp4 protein, mouse; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; D018076:DNA, Complementary; C486399:GREM1 protein, human; D036341:Intercellular Signaling Peptides and Proteins; C509032:LTBP1 protein, human; C509040:LTBP4 protein, human; D053779:Latent TGF-beta Binding Proteins; C509033:Ltbp1 protein, mouse; D009841:Oligonucleotides; D016212:Transforming Growth Factor beta; D012313:RNA