Characterization of hepatic lactogen receptor. Subcellular distribution and characterization of N-linked carbohydrate chains.
The types of carbohydrate chains present in a rat liver lactogenic hormone-binding receptor species with an Mr of 82,000, and in its hormone-binding subunits with Mr values of 40,000 and 35,000, were characterized using carbohydrate-chain-cleaving enzymes and affinity cross-linking. The subcellular distribution of lactogenic hormone-binding species was studied in organelle-enriched fractions. The monomeric Mr-40,000 and Mr-35,000 species contain N-linked tri- or tetra-antennary complex and high-mannose chains respectively. The Mr-82,000 species exists in two forms, where the Mr-40,000 and Mr-35,000 subunits are each combined with unglycosylated and, with the technique used, unlabelled subunit(s). Studies with organelle-enriched fractions revealed that the Mr-35,000 species was found in an endoplasmic reticulum-enriched fraction. The Mr-40,000 species was the predominant monomeric binding species in Golgi/endosome- and plasma membrane-enriched fractions. It is suggested that the Mr-35,000 species is a precursor to the Mr-40,000 species. In lysosome/endosome- or lysosome-enriched fractions, a broad distribution in Mr (35,000-40,000) was characteristic of the hormone-binding species. The Mr-82,000 species was only found in a Golgi/endosome-enriched fraction. Labelling of endosome lactogen receptor by injection of 125I-labelled ovine prolactin in vivo and cross-linking yielded only the Mr-40,000 species. Thus, the Mr-40,000 and Mr-35,000 lactogenic hormone-binding species each appear to be combined with the unglycosylated receptor subunit(s) in the Golgi complex to form Mr-82,000 heterodimeric complexes.
Haldosén
L A
LA
Department of Medical Nutrition, Karolinska Institute, Huddinge University Hospital, Sweden.
Andersson
G
G
Gustafsson
J A
JA
D000818:Animals; D001345:Autoradiography; D002241:Carbohydrates / Q000032:analysis*; D002458:Cell Fractionation; D003432:Cross-Linking Reagents; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006026:Glycoside Hydrolases; D007202:Indicators and Reagents; D008099:Liver / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D010928:Placental Lactogen / Q000378:metabolism; D011247:Pregnancy; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000378:metabolism*; D018000:Receptors, Peptide; D011986:Receptors, Somatotropin / Q000378:metabolism
D002241:Carbohydrates; D003432:Cross-Linking Reagents; D007202:Indicators and Reagents; D008565:Membrane Proteins; D011956:Receptors, Cell Surface; D018000:Receptors, Peptide; D011986:Receptors, Somatotropin; C028202:placental lactogen receptor; D010928:Placental Lactogen; D006026:Glycoside Hydrolases; C020668:glycanase