Isolation from adult human serum of four insulin-like growth factor (IGF) binding proteins and molecular cloning of one of them that is increased by IGF I administration and in extrapancreatic tumor hypoglycemia.
We have isolated four insulin-like growth factor binding proteins (IGFBPs) from adult human serum by insulin-like growth factor (IGF) I affinity chromatography and high performance liquid chromatography. A 36-kDa binding protein (BP), not digestible with N-glycanase, is increased in patients with extrapancreatic tumor hypoglycemia and during IGF I administration in healthy adults. Its 38 NH2-terminal amino acids are identical to those of an IGFBP sequence derived from a human cDNA that cross-hybridizes with the rat IGFBP-2 cDNA. With probes encoding a NH2-terminal, COOH-terminal, and a middle region of this protein we have obtained three cDNA clones from a Hep G2 cDNA library; one encodes human IGFBP-2, and the other two presumably represent unspliced heteronuclear and alternatively spliced mRNA, respectively. A 28-30-kDa IGFBP represents a novel BP species in human serum. Its 30 NH2-terminal amino acids are not homologous to IGFBP-1, -2, or -3. It is not digestible with N-glycanase and does not bind 125I-IGF I. The NH2-terminal sequences of a 42/45- and a 31-kDa IGFBP are identical to that of human IGFBP-3. The 42/45-kDa proteins are two glycosylation variants of BP-3. The 31-kDa protein presumably is a degradation product of BP-3 that lacks the COOH terminus. It is likely that the different IGFBPs modulate auto-/paracrine and endocrine effects of IGFs on growth and metabolism in a different and specific manner.
Department of Medicine, University Hospital, Zurich CH-8091, Switzerland.
J
J
Zapf
M
M
Kiefer
J
J
Merryweather
F
F
Musiarz
D
D
Bauer
W
W
Born
J A
JA
Fischer
E R
ER
Froesch
D000328:Adult; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D006528:Carcinoma, Hepatocellular; D002352:Carrier Proteins / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D002460:Cell Line; D002846:Chromatography, Affinity; D003001:Cloning, Molecular; D015723:Gene Library; D006801:Humans; D007003:Hypoglycemia / Q000097:blood*; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000378:metabolism / Q000494:pharmacology*; D008024:Ligands; D008113:Liver Neoplasms; D008969:Molecular Sequence Data; D009369:Neoplasms / Q000097:blood* / Q000503:physiopathology; D015345:Oligonucleotide Probes; D010957:Plasmids; D012333:RNA, Messenger / Q000235:genetics / Q000302:isolation & purification; D012016:Reference Values; D012689:Sequence Homology, Nucleic Acid; D013002:Somatomedins / Q000494:pharmacology*
D002352:Carrier Proteins; D018969:Insulin-Like Growth Factor Binding Proteins; D008024:Ligands; D015345:Oligonucleotide Probes; D012333:RNA, Messenger; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I