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rdf:type |
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lifeskim:mentions |
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pubmed:issue |
17
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pubmed:dateCreated |
1991-10-3
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pubmed:abstractText |
The insulin-like growth factors (IGF-I and IGF-II) are present in extracellular fluids bound to specific IGF-binding proteins (IGFBPs). We and others have reported varying biologic activity of different preparations of IGFBP-1 that appeared to have identical amino acid sequences and molecular sizes. This observation prompted us to determine whether IGFBP-1 undergoes posttranslational modifications. Immunoprecipitation was used to show that Chinese hamster ovary cells (transfected with a human IGFBP-1 cDNA construct) and human hepatoma (HepG2) cells secrete 32P-labeled IGFBP-1 following incubation with [32P]orthophosphate. Phospho amino acid analysis of 32P-labeled IGFBP-1 revealed only phosphoserine residues. A method was developed that could separate nonphosphorylated IGFBP-1 from four or five phosphorylated isoforms. Using this technique we demonstrated that human amniotic fluid and human fetal serum contain a large proportion of nonphosphorylated IGFBP-1, as well as phosphorylated forms. In contrast, HepG2 cells and human decidual cells secrete predominantly the phosphorylated isoforms. These observations suggest that IGFBP-1 is secreted as a phosphoprotein and is subsequently dephosphorylated in vivo. Binding studies showed that the phosphorylated IGFBP-1 secreted by HepG2 cells has a 6-fold higher affinity for IGF-I than it does after dephosphorylation. We conclude that IGFBP-1 is phosphorylated and that this phosphorylation is a physiologically important posttranslational modification.
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pubmed:grant |
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pubmed:commentsCorrections |
http://linkedlifedata.com/resource/pubmed/commentcorrection/1715565-1697605,
http://linkedlifedata.com/resource/pubmed/commentcorrection/1715565-2140913,
http://linkedlifedata.com/resource/pubmed/commentcorrection/1715565-2211731,
http://linkedlifedata.com/resource/pubmed/commentcorrection/1715565-2411754,
http://linkedlifedata.com/resource/pubmed/commentcorrection/1715565-2422981,
http://linkedlifedata.com/resource/pubmed/commentcorrection/1715565-2442186,
http://linkedlifedata.com/resource/pubmed/commentcorrection/1715565-2448300,
http://linkedlifedata.com/resource/pubmed/commentcorrection/1715565-2452077,
http://linkedlifedata.com/resource/pubmed/commentcorrection/1715565-2454104,
http://linkedlifedata.com/resource/pubmed/commentcorrection/1715565-2461381,
http://linkedlifedata.com/resource/pubmed/commentcorrection/1715565-2461386,
http://linkedlifedata.com/resource/pubmed/commentcorrection/1715565-2473891,
http://linkedlifedata.com/resource/pubmed/commentcorrection/1715565-2547801,
http://linkedlifedata.com/resource/pubmed/commentcorrection/1715565-2555997,
http://linkedlifedata.com/resource/pubmed/commentcorrection/1715565-2592418,
http://linkedlifedata.com/resource/pubmed/commentcorrection/1715565-2698313,
http://linkedlifedata.com/resource/pubmed/commentcorrection/1715565-2707157,
http://linkedlifedata.com/resource/pubmed/commentcorrection/1715565-2781536,
http://linkedlifedata.com/resource/pubmed/commentcorrection/1715565-2808373,
http://linkedlifedata.com/resource/pubmed/commentcorrection/1715565-2971653,
http://linkedlifedata.com/resource/pubmed/commentcorrection/1715565-3473993,
http://linkedlifedata.com/resource/pubmed/commentcorrection/1715565-3603434,
http://linkedlifedata.com/resource/pubmed/commentcorrection/1715565-3660346,
http://linkedlifedata.com/resource/pubmed/commentcorrection/1715565-4089825,
http://linkedlifedata.com/resource/pubmed/commentcorrection/1715565-6196603,
http://linkedlifedata.com/resource/pubmed/commentcorrection/1715565-6575393,
http://linkedlifedata.com/resource/pubmed/commentcorrection/1715565-7117261
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pubmed:language |
eng
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pubmed:journal |
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pubmed:citationSubset |
IM
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pubmed:chemical |
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pubmed:status |
MEDLINE
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pubmed:month |
Sep
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pubmed:issn |
0027-8424
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pubmed:author |
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pubmed:issnType |
Print
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pubmed:day |
1
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pubmed:volume |
88
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
7481-5
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pubmed:dateRevised |
2009-11-18
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pubmed:meshHeading |
pubmed-meshheading:1715565-Animals,
pubmed-meshheading:1715565-Carrier Proteins,
pubmed-meshheading:1715565-Cell Line,
pubmed-meshheading:1715565-Electrophoresis, Polyacrylamide Gel,
pubmed-meshheading:1715565-Humans,
pubmed-meshheading:1715565-Immunoblotting,
pubmed-meshheading:1715565-Insulin-Like Growth Factor Binding Proteins,
pubmed-meshheading:1715565-Insulin-Like Growth Factor I,
pubmed-meshheading:1715565-Kinetics,
pubmed-meshheading:1715565-Molecular Weight,
pubmed-meshheading:1715565-Phosphorylation,
pubmed-meshheading:1715565-Protein Binding,
pubmed-meshheading:1715565-Transfection
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pubmed:year |
1991
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pubmed:articleTitle |
Phosphorylation of insulin-like growth factor (IGF)-binding protein 1 in cell culture and in vivo: effects on affinity for IGF-I.
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pubmed:affiliation |
Department of Medicine, University of North Carolina School of Medicine, Chapel Hill 27599-7170.
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pubmed:publicationType |
Journal Article,
Research Support, U.S. Gov't, P.H.S.
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