title: IGFBP-3 and IGFBP-5 production by human intestinal muscle: reciprocal regulation by endogenous TGF-beta1.
abstract: Insulin-like growth factor-I (IGF-I)-mediated growth of cells can be modulated by specific IGF binding proteins (IGFBPs) that inhibit or augment IGF-I ligand-receptor interaction. IGFBP expression and production by human intestinal muscle cells in culture was characterized in rapidly growing cells (day 3 of culture), in confluent cells (day 7), and in postconfluent cells (day 14). RT-PCR analysis identified IGFBP-3, IGFBP-4, and IGFBP-5 mRNA during all three phases of growth. The production of IGFBP-3 and IGFBP-5 was regulated in reciprocal fashion. IGFBP-5 production was high on day 3 and decreased two- to fivefold by day 14, and IGFBP-3 production was low on day 3 and increased five- to eightfold by day 14. IGFBP-4 production remained constant. IGFBP-3 inhibited and IGFBP-5 augmented IGF-I-induced proliferation. IGFBP-3 and IGFBP-5 production was regulated in reciprocal fashion by transforming growth factor-beta1 (TGF-beta1). Immunoneutralization of endogenous TGF-beta1 decreased the production of IGFBP-3 and increased the production of IGFBP-5. Addition of exogenous recombinant human TGF-beta1 had the opposite effect. We conclude that the expression and time-dependent production of IGFBP-3, IGFBP-4, and IGFBP-5 and their regulation by endogenous TGF-beta1 represent mechanisms by which human intestinal muscle cells regulate autocrine IGF-I-mediated growth.
authors.affiliation: Departments of Medicine and Physiology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia 23298-0711, USA.
authors.forename: T L
authors.initials: TL
authors.lastname: Bushman
authors.forename: J F
authors.initials: JF
authors.lastname: Kuemmerle
mesh_terms: D015153:Blotting, Western; D002455:Cell Division / Q000502:physiology; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000096:biosynthesis* / Q000737:chemistry / Q000502:physiology; D018975:Insulin-Like Growth Factor Binding Protein 5 / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000737:chemistry / Q000502:physiology; D018969:Insulin-Like Growth Factor Binding Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000502:physiology; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000166:cytology; D009130:Muscle, Smooth / Q000166:cytology / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016212:Transforming Growth Factor beta / Q000502:physiology*
chemical_list: D018972:Insulin-Like Growth Factor Binding Protein 3; D018975:Insulin-Like Growth Factor Binding Protein 5; D018969:Insulin-Like Growth Factor Binding Proteins; D016212:Transforming Growth Factor beta; D007334:Insulin-Like Growth Factor I