The two isotypes of the human insulin receptor (HIR-A and HIR-B) follow different internalization kinetics.
Human insulin receptor (HIR) is expressed in two isoforms which differ in the C-terminal end of the alpha-subunit (HIR-A = -12 aa, HIR-B = +12 aa). We studied internalization kinetics of HIR-A and HIR-B in Rat1 fibroblasts. Internalized receptors were quantified by 125I-insulin binding after cell trypsinisation and solubilization, surface receptors were determined by 125I-insulin binding to intact cells and by chemical crosslinking with B26-125I-insulin. HIR-A and HIR-B show different kinetics of receptor internalization. While in HIR-A cells the maximum of internalization (approx. 65% of total) is reached after 10 min followed by a high recycling rate (approx. 80% of internalized receptors after 20 min), the internalization in HIR-B cells reaches a maximum (approx. 60% of total) after 15 min without detectable recycling within 30 min. The data show that the different alpha-subunits of both receptor types determine different velocities of internalization and determine whether a fast recycling occurs.
Vogt
B
B
Institut für Diabetesforschung, München, Germany.
Carrascosa
J M
JM
Ermel
B
B
Ullrich
A
A
Häring
H U
HU
D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000378:metabolism; D007527:Isoenzymes / Q000378:metabolism; D007700:Kinetics; D046911:Macromolecular Substances; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D051381:Rats; D011972:Receptor, Insulin / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
D007328:Insulin; D007527:Isoenzymes; D046911:Macromolecular Substances; D011505:Protein-Tyrosine Kinases; D011972:Receptor, Insulin