Injection of the insulin receptor alpha subunit increases blood glucose levels in mice.
Using the expression vector of the truncated human insulin receptor (hIR), we have constructed a stable Chinese hamster ovary (CHO) cell line which secretes the His-tagged alpha subunit (insulin-binding domain) of hIR into medium. To examine characteristics of the His-tagged hIRalpha, we purified the protein secreted from the CHO cells. The His-tagged hIRalpha was glycosylated and processed a dimer. The molecule bound insulin with an affinity similar to that of the intact hIR. The His-tagged full length of hIR was autophosphorylated by insulin stimulation in CHO cells. Injection of the purified His-tagged hIRalpha into veins of mice increased in the concentration of blood glucose within 30 min. The intraperitoneal glucose tolerance test (ipGTT) done after injection of the purified His-tagged hIRalpha showed evidence of a marked hyperglycemia. These findings provide direct evidence that the presence of hIRalpha in the blood stream inhibits insulin actions by binding with plasma insulin.
Kanezaki
Yoshiko
Y
Division of Molecular Genetics, Institutes for Enzyme Research, The University of Tokushima, 3-18-15 Kuramoto, Tokushima 770-8503, Japan.
Matsushima
Rie
R
Obata
Toshiyuki
T
Nakaya
Yutaka
Y
Matsumoto
Toshio
T
Ebina
Yousuke
Y
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism*; D016466:CHO Cells; D006224:Cricetinae; D005951:Glucose Tolerance Test; D006031:Glycosylation; D006801:Humans; D007274:Injections, Intraperitoneal; D007328:Insulin / Q000378:metabolism / Q000494:pharmacology; D051379:Mice; D010766:Phosphorylation; D017510:Protein Folding; D021122:Protein Subunits; D011972:Receptor, Insulin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology
D001786:Blood Glucose; D007328:Insulin; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins; D011972:Receptor, Insulin