TY - JOUR
T1 - Structural and immunological comparison of insulin-like growth factor binding proteins of cerebrospinal and amniotic fluids
AU - Rosenfeld, Ron G.
AU - Pham, Hung
AU - Conover, Cheryl A.
AU - Hintz, Raymond L.
AU - Baxter, Robert C.
PY - 1989/3
Y1 - 1989/3
N2 - The insulin-like growth factors (IGFs) found in plasma and a variety of other body fluids are complexed to specific binding proteins (BPs). The cDNA for a 25K IGF-BP was recently cloned and sequenced, and the primary structure of the BP deduced. This BP is found in amniotic fluid, decidual tissues, conditioned medium from HepG2 human hepatoma cells, and fetal plasma. An additional small IGF-BP has been identified in human cerebrospinal fluid (CSF). We now demonstrate that the IGF-BP found in CSF is structurally and immunologically distinct from that found in HepG2 conditioned medium. While the latter BP has approximately equal affinities for IGF-I and -II, the CSF BP has a 10- to 20-fold greater affinity for IGF-II. In affinity cross-linking studies under reducing conditions, the CSF BP had an apparent mol wt (Mr) of 32, 000, while the HepG2 BP migrated as a doublet, with apparent Mr values of 30, 000 and 28, 000. On Western ligand blots, CSF BPs migrate as five discrete bands, with the most prominent band at an apparent Mr of 34, 000, while HepG2 medium yielded a single band at an apparent Mr of 30, 000. A polyclonal antibody developed against the human amniotic fluid BP immunoprecipitated the HepG2 BP and reacted with both the HepG2 and amniotic fluid BPs on Western blots, but failed to react with the CSF BP. These data indicate that the CSF and amniotic fluid/HepG2 BP are structurally and immunologically distinct small IGF-BPs.
AB - The insulin-like growth factors (IGFs) found in plasma and a variety of other body fluids are complexed to specific binding proteins (BPs). The cDNA for a 25K IGF-BP was recently cloned and sequenced, and the primary structure of the BP deduced. This BP is found in amniotic fluid, decidual tissues, conditioned medium from HepG2 human hepatoma cells, and fetal plasma. An additional small IGF-BP has been identified in human cerebrospinal fluid (CSF). We now demonstrate that the IGF-BP found in CSF is structurally and immunologically distinct from that found in HepG2 conditioned medium. While the latter BP has approximately equal affinities for IGF-I and -II, the CSF BP has a 10- to 20-fold greater affinity for IGF-II. In affinity cross-linking studies under reducing conditions, the CSF BP had an apparent mol wt (Mr) of 32, 000, while the HepG2 BP migrated as a doublet, with apparent Mr values of 30, 000 and 28, 000. On Western ligand blots, CSF BPs migrate as five discrete bands, with the most prominent band at an apparent Mr of 34, 000, while HepG2 medium yielded a single band at an apparent Mr of 30, 000. A polyclonal antibody developed against the human amniotic fluid BP immunoprecipitated the HepG2 BP and reacted with both the HepG2 and amniotic fluid BPs on Western blots, but failed to react with the CSF BP. These data indicate that the CSF and amniotic fluid/HepG2 BP are structurally and immunologically distinct small IGF-BPs.
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U2 - 10.1210/jcem-68-3-638
DO - 10.1210/jcem-68-3-638
M3 - Article
C2 - 2465304
AN - SCOPUS:0024583037
SN - 0021-972X
VL - 68
SP - 638
EP - 646
JO - Journal of Clinical Endocrinology and Metabolism
JF - Journal of Clinical Endocrinology and Metabolism
IS - 3
ER -