Soluble insulin-like growth factor II/mannose 6-phosphate receptor carries multiple high molecular weight forms of insulin-like growth factor II in fetal bovine serum.
We have characterized a soluble form of the insulin-like growth factor II/mannose 6-phosphate receptor (sIGF-II/MPR) and bound ligands from bovine serum. Fetal serum contained 2-8 mg/liter sIGF-II/MPR. Affinity-purified receptor isolated by adsorption to phosphomannan-agarose and elution with mannose 6-phosphate contained nearly stoichiometric amounts of bound 7.5-kDa IGF-II. In addition, at least 12 distinct 12-20-kDa proteins immunologically related to IGF-II also copurified with receptor. Receptor was separated from its associated ligands by acidification and gel filtration chromatography. Sequence analysis revealed that the 12-20-kDa proteins have the same amino termini as mature 7.5-kDa IGF-II. Protease and glycosidase treatments revealed that the different high molecular weight IGF-II species contain an identical COOH-terminal extension that is differentially glycosylated with O-linked sugars. Radiolabeled tracer experiments demonstrated that the sIGF-II/MPR carries approximately 1/4 of the IGF-II in fetal bovine serum. These results support a significant role for sIGF-II/MPR in the transport of circulating IGF-II isoforms during development.
Valenzano
K J
KJ
Center for Advanced Biotechnology and Medicine, University of Medicine and Dentistry of New Jersey, Piscataway 08854, USA.
Remmler
J
J
Lobel
P
P
D000818:Animals; D001692:Biological Transport; D001798:Blood Proteins / Q000737:chemistry* / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism; D001826:Body Fluids / Q000737:chemistry; D002417:Cattle / Q000196:embryology / Q000254:growth & development; D002846:Chromatography, Affinity; D003429:Cross Reactions; D005312:Fetal Blood / Q000737:chemistry; D014644:Genetic Variation; D006031:Glycosylation; D007335:Insulin-Like Growth Factor II / Q000032:analysis* / Q000378:metabolism; D008024:Ligands; D008970:Molecular Weight; D011499:Protein Processing, Post-Translational; D017527:Receptor, IGF Type 2 / Q000096:biosynthesis / Q000737:chemistry* / Q000276:immunology / Q000302:isolation & purification; D017421:Sequence Analysis; D012995:Solubility
D001798:Blood Proteins; D008024:Ligands; D017527:Receptor, IGF Type 2; D007335:Insulin-Like Growth Factor II