Regulation of endothelial IGFBP-3 synthesis and secretion by IGF-I and TGF-beta.
We have examined the regulation of endothelial IGFBP-3 production by IGF-I and TGF-beta, two growth factors thought to play a major roles in the complications of diabetes mellitus. In addition, we developed a sensitive method for IGFBP-3 mRNA quantitation by adapting the fluorescent modification of the competitive PCR strategy. Our results using both Northern analysis and the fluorescent competitive PCR method indicate that: (1) IGFBP-3 mRNA is increased 2- to 10-fold by IGF-I and maximally reduced to 20% of control by TGF-beta; (2) the changes in mRNA levels correlate with the levels of IGFBP-3 protein secreted into the media by these cells; (3) the induction of IGFBP-3 mRNA and protein by IGF-I analogs was directly related to their ability to bind to the type I IGF receptor, reflecting an IGF-I receptor-mediated process; and (4) steady state IGFBP-3 mRNA levels did not change significantly after a 6 h incubation with actinomycin D in the presence or absence of the growth factors suggesting that the observed IGF-I/TGF-beta effects occur at the level of gene transcription rather than mRNA stability.
Erondu
N E
NE
Department of Internal Medicine, University of Iowa, Iowa City, USA.
Dake
B L
BL
Moser
D R
DR
Lin
M
M
Boes
M
M
Bar
R S
RS
D000273:Adipose Tissue; D000818:Animals; D001011:Aorta; D001483:Base Sequence; D015152:Blotting, Northern; D002417:Cattle; D002478:Cells, Cultured; D017931:DNA Primers; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000096:biosynthesis*; D007334:Insulin-Like Growth Factor I / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology*; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D017526:Receptor, IGF Type 1 / Q000187:drug effects / Q000502:physiology; D014158:Transcription, Genetic / Q000187:drug effects*; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D017931:DNA Primers; D018972:Insulin-Like Growth Factor Binding Protein 3; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1