Defined carboxy-terminal fragments of insulin-like growth factor (IGF) binding protein-2 exert similar mitogenic activity on cultured rat growth plate chondrocytes as IGF-I.
The IGF/IGF binding protein (IGFBP) system is an important component in the hormonal regulation of longitudinal growth. Evidence from in vitro studies indicates that IGFBPs may have IGF-independent effects. We analyzed the biological activity of intact IGFBP-2 and defined carboxy-terminal IGFBP-2 fragments isolated from human hemofiltrate in two cell culture systems of the growth plate: rat growth plate chondrocytes in primary culture and the mesenchymal chondrogenic cell line RCJ3.1C5.18. The IGFBP-2 fragments IGFBP-2(167-279), IGFBP-2(167-289), and IGFBP-2(104-289) exerted a strong (2- to 3-fold) mitogenic effect on growth plate chondrocytes, which was comparable with IGF-I in equimolar concentrations (7.8 nm) but was not mediated through the type 1 IGF receptor. In a dose-response experiment, the most effective concentration of IGFBP-2(104-289) for the stimulation of cell proliferation was 10 nm. This biological activity of IGFBP-2 fragments was associated with cell membrane binding, demonstrated by Western blot analysis of fractionated cell lysates and immunohistochemistry. Whereas intact IGFBP-2 did not modulate chondrocyte proliferation, partially reduced (by dithiothreitol) full-length IGFBP-2 stimulated cell proliferation to a comparable extent (3.4-fold) as carboxy-terminal IGFBP-2 fragments. The mitogenic activity of these IGFBP-2 fragments and of partially reduced full-length IGFBP-2 was mediated through the use of the MAPK/ERK 1/2. These data imply a novel role of naturally occurring IGFBP-2 fragments for the endocrine and paracrine/autocrine regulation of longitudinal growth.
University Children's Hospital, Im Neuenheimer Feld 153, 69120 Heidelberg, Germany. daniela.kiepe@med.uni-heidelberg.de
Daniela
D
Kiepe
Anke
A
Van Der Pas
Sonia
S
Ciarmatori
Ludger
L
Ständker
Burkhardt
B
Schütt
Andreas
A
Hoeflich
Ulrike
U
Hügel
Jun
J
Oh
Burkhard
B
Tönshoff
D000818:Animals; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D019902:Chondrocytes / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism; D006132:Growth Plate / Q000166:cytology*; D006801:Humans; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism / Q000494:pharmacology*; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008934:Mitogens / Q000494:pharmacology; D010446:Peptide Fragments / Q000235:genetics / Q000494:pharmacology; D051381:Rats
D018971:Insulin-Like Growth Factor Binding Protein 2; D008934:Mitogens; D010446:Peptide Fragments; D007334:Insulin-Like Growth Factor I; D051416:Focal Adhesion Protein-Tyrosine Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D020928:Mitogen-Activated Protein Kinases