Insulin receptor and insulin sensitivity in a chicken hepatoma cell line.
Insulin receptors have been characterized in a cell line recently isolated from a chicken hepatoma (LMH). The binding of 125I-insulin to LMH cells or membranes displayed the expected criteria for insulin receptors: affinity, temperature dependency, curvilinearity of Scatchard plot, rank order of potency for insulin analogs and insulin induced down-regulation. The alpha-subunit of LMH cell insulin receptors exhibited a normal size of 135 kDa. Following autophosphorylation, LMH WGA-purified receptors revealed a 95 kDa beta-subunit and a 72 kDa protein (pp72). Both proteins were phosphorylated in a time-, insulin- (and insulin-like growth factor 1; IGF-1) and manganese-dependent manner, and were precipitated by antiphosphotyrosine and two anti-insulin receptor antibodies. The 72 kDa protein was not present under non-reducing condition PAGE or in normal chicken liver. These results strongly suggest that pp72 is either a truncated form of the insulin receptor beta-subunit specific to LMH cells or a degradation product. Lectin-purified insulin receptors from LMH cells or chicken liver membranes exhibited similar tyrosine kinase activity, using artificial substrate poly(Glu-Tyr) 4:1. Finally, amino acid uptake by LMH cells was insulin stimulatable.
Taouis
M
M
Endocrinologie de la Croissance et du Métabolisme, Station de Recherches Avicoles, INRA, Nouzilly, France.
Derouet
M
M
Caffin
J P
JP
Chavanieu
A
A
Simon
J
J
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D006528:Carcinoma, Hepatocellular; D002645:Chickens; D004591:Electrophoresis, Polyacrylamide Gel; D007328:Insulin / Q000502:physiology*; D036341:Intercellular Signaling Peptides and Proteins; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D008969:Molecular Sequence Data; D010455:Peptides / Q000378:metabolism; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011972:Receptor, Insulin / Q000378:metabolism*; D013379:Substrate Specificity; D014407:Tumor Cells, Cultured
D000596:Amino Acids; D007328:Insulin; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; C027606:L-glutamic acid-L-tyrosine copolymer; D011505:Protein-Tyrosine Kinases; D011972:Receptor, Insulin