Mechanisms of insulin-induced insulin-receptor downregulation. Decrease of receptor biosynthesis and mRNA levels.
The influence of insulin on the downregulation of its receptor was studied in AR42J cultured pancreatic acinar cells, a cell line that has been demonstrated to be metabolically responsive to insulin. Downregulation induced by insulin was time and dose dependent. After a 20-h incubation with 1 microM insulin, Scatchard analysis revealed approximately 80% loss of insulin receptors. Studies of receptor half-life indicated that treatment with insulin accelerated the degradation of both the alpha- and beta-subunits of the insulin receptor by 30-60%. In addition, biosynthetic-labeling studies indicated that insulin inhibited the biosynthesis of the insulin-receptor precursor by greater than 30%. This decreased biosynthesis of the precursor was associated with decreased production of mature receptor subunits. Poly(A)+ RNA was extracted from control cells and cells treated for 24 h with 100 nM insulin. Slot blots and Northern transfers revealed that insulin induced an approximately 50% decrease in insulin-receptor mRNA levels. Therefore, these studies indicate that insulin may diminish the concentration of its receptors in target cells by at least two mechanisms: acceleration of receptor degradation and inhibition of receptor biosynthesis at the level of mRNA.
Okabayashi
Y
Y
Cell Biology Laboratory, Mount Zion Hospital, San Francisco, California 94120.
Maddux
B A
BA
McDonald
A R
AR
Logsdon
C D
CD
Williams
J A
JA
Goldfine
I D
ID
D002460:Cell Line; D005246:Feedback; D006801:Humans; D007328:Insulin / Q000378:metabolism / Q000494:pharmacology*; D010190:Pancreatic Neoplasms; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics*; D011972:Receptor, Insulin / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D011949:Receptors, Cholecystokinin / Q000187:drug effects / Q000378:metabolism
D007328:Insulin; D012333:RNA, Messenger; D011949:Receptors, Cholecystokinin; D011972:Receptor, Insulin