Extracellular fibrillar structure of latent TGF beta binding protein-1: role in TGF beta-dependent endothelial-mesenchymal transformation during endocardial cushion tissue formation in mouse embryonic heart.
Transforming growth factor-beta (TGF beta) is a dimeric peptide growth factor which regulates cellular differentiation and proliferation during development. Most cells secrete TGF beta as a large latent TGF beta complex containing mature TGF beta, latency associated peptide, and latent TGF beta-binding protein (LTBP)-1. The biological role of LTBP-1 in development remains unclear. Using a polyclonal antiserum specific for LTBP-1 (Ab39) and three-dimensional collagen gel culture assay of embryonic heart, we examined the tissue distribution of LTBP-1 and its functional role during the formation of endocardial cushion tissue in the mouse embryonic heart. Mature TGF beta protein was required at the onset of the endothelial-mesenchymal transformation to initiate endocardial cushion tissue formation. Double antibody staining showed that LTBP-1 colocalized with TGF beta 1 as an extracellular fibrillar structure surrounding the endocardial cushion mesenchymal cells. Immunogold electronmicroscopy showed that LTBP-1 localized to 40-100 nm extracellular fibrillar structure and 5-10-nm microfibrils. The anti-LTBP-1 antiserum (Ab39) inhibited the endothelial-mesenchymal transformation in atrio-ventricular endocardial cells cocultured with associated myocardium on a three-dimensional collagen gel lattice. This inhibitory effect was reversed by administration of mature TGF beta proteins in culture. These results suggest that LTBP-1 exists as an extracellular fibrillar structure and plays a role in the storage of TGF beta as a large latent TGF beta complex.
Nakajima
Y
Y
Department of Anatomy, Saitama Medical School, Japan.
Miyazono
K
K
Kato
M
M
Takase
M
M
Yamagishi
T
T
Nakamura
H
H
D000818:Animals; D000918:Antibody Specificity; D019556:COS Cells; D002352:Carrier Proteins / Q000032:analysis* / Q000502:physiology*; D018920:Coculture Techniques; D046508:Culture Techniques; D004699:Endocardium / Q000166:cytology / Q000254:growth & development; D004730:Endothelium, Vascular / Q000196:embryology; D005109:Extracellular Matrix / Q000737:chemistry; D005341:Fibrinolysin; D006321:Heart / Q000196:embryology; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D053779:Latent TGF-beta Binding Proteins; D008648:Mesoderm / Q000166:cytology*; D051379:Mice; D008813:Mice, Inbred ICR; D009206:Myocardium / Q000737:chemistry* / Q000166:cytology; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000032:analysis / Q000494:pharmacology*
D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; C509032:LTBP1 protein, human; D053779:Latent TGF-beta Binding Proteins; C509033:Ltbp1 protein, mouse; D016212:Transforming Growth Factor beta; D005341:Fibrinolysin