The mechanism for the activation of latent TGF-beta during co-culture of endothelial cells and smooth muscle cells: cell-type specific targeting of latent TGF-beta to smooth muscle cells.
Transforming growth factor-beta (TGF-beta) is secreted in a latent form and activated during co-culture of endothelial cells and smooth muscle cells. Plasmin located on the surface of endothelial cells is required for the activation of latent TGF-beta (LTGF-beta) during co-culture, and the targeting of LTGF-beta to the cellular surface is requisite for its activation. In the present study, the cellular targeting of LTGF-beta was examined. We detected the specific binding of 125I-large LTGF-beta 1 isolated from human platelets to smooth muscle cells but not to endothelial cells. A mAb against the latency-associated peptide (LAP) of large LTGF-beta 1 complex, which blocked the binding of 125I-large LTGF-beta 1 to smooth muscle cells, inhibited the activation of LTGF-beta during co-culture. The binding of 125I-large LTGF-beta 1 could not be competed either by mannose-6-phosphate (300 microM) or by the synthetic peptide Arg-Gly-Asp-Ser (300 micrograms/ml). These results indicate that the targeting of LTGF-beta to smooth muscle cells is required for the activation of LTGF-beta during co-culture of endothelial cells and smooth muscle cells. The targeting of LTGF-beta to smooth muscle cells is mediated by LAP, and the domain of LAP responsible for the targeting to smooth muscle cells may not be related to mannose-6-phosphate or an Arg-Gly-Asp sequence, both of which have been previously proposed as candidates for the cellular binding domains within LAP.
Sato
Y
Y
Department of Internal Medicine 1, Oita Medical University, Japan.
Okada
F
F
Abe
M
M
Seguchi
T
T
Kuwano
M
M
Sato
S
S
Furuya
A
A
Hanai
N
N
Tamaoki
T
T
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001011:Aorta; D001692:Biological Transport; D001792:Blood Platelets / Q000737:chemistry; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000378:metabolism*; D006801:Humans; D008360:Mannosephosphates / Q000494:pharmacology; D008954:Models, Biological; D008969:Molecular Sequence Data; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D009842:Oligopeptides / Q000494:pharmacology; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D011498:Protein Precursors / Q000378:metabolism; D013552:Swine; D016212:Transforming Growth Factor beta / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D008360:Mannosephosphates; D009842:Oligopeptides; D010975:Platelet Aggregation Inhibitors; D011498:Protein Precursors; D016212:Transforming Growth Factor beta; C027693:mannose-6-phosphate; C046617:arginyl-glycyl-aspartyl-serine