Regulating insulin-receptor-gene expression by differentiation and hormones
Regulating insulin-receptor-gene expression by differentiation and hormones. P W Mamula , A R McDonald , A Brunetti , Y Okabayashi , K Y Wong , B A Maddux , C Logsdon and I D Goldfine Division of Diabetes and Endocrine Research, Mount Zion Hospital and Medical Center, San Francisco, CA 94120. Abstra...
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Published in | Diabetes care Vol. 13; no. 3; pp. 288 - 301 |
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Main Authors | , , , , , , , |
Format | Journal Article |
Language | English |
Published |
United States
American Diabetes Association
01.03.1990
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Subjects | |
Online Access | Get full text |
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Summary: | Regulating insulin-receptor-gene expression by differentiation and hormones.
P W Mamula ,
A R McDonald ,
A Brunetti ,
Y Okabayashi ,
K Y Wong ,
B A Maddux ,
C Logsdon and
I D Goldfine
Division of Diabetes and Endocrine Research, Mount Zion Hospital and Medical Center, San Francisco, CA 94120.
Abstract
Insulin regulates cell function by first binding to the insulin receptor (IR) localized on the cell surface. With the cloning
of IR cDNA and the IR-gene promoter, the regulation of the IR gene during differentiation and by various hormones can be studied.
Muscle is a major target tissue for insulin action. BC3H1 cells, a mouse muscle cell line in culture, are a model cell type
for studying insulin action. Differentiation in these cells results in a 5- to 10-fold increase in IR binding and a 5- to
10-fold increase in IR content. Studies of IR mRNA by Northern and slot-blot analyses reveal a 10-fold increase in IR mRNA
after differentiation. These studies indicate that there is a selective increase in IR-gene expression during muscle differentiation.
A similar increase in IR-gene expression is observed for the IR during pancreatic acinar cell differentiation. Glucocorticoids
increase IR content in several target tissues. Studies in cultured IM-9 lymphocytes indicate that glucocorticoids induce a
5-fold increase in IR mRNA levels. Studies of IR mRNA half-life indicate that glucocorticoids do not alter IR mRNA stability.
When the transcription of the IR is measured by elongation assays, glucocorticoids directly stimulate IR transcription 5-
to 10-fold. The effect is detectable within 30 min of glucocorticoid treatment and is maximal within 2 h. Therefore, these
studies demonstrate that the IR gene is under the direct regulation of glucocorticoids. Insulin downregulates the IR in various
target tissues. Prior studies indicate that this downregulation was partly because of accelerated IR degradation. Studying
AR42J pancreatic acinar cells, we also found that insulin accelerates IR degradation. Moreover, in these cells, insulin decreases
IR biosynthesis by approximately 50%. Studies of IR mRNA indicate there is a concomitant decrease in IR mRNA levels after
insulin treatment. Thus, insulin decreases IR-gene expression. The genomic structure of the IR promoter has been elucidated.
Primer extension and nuclease S1 analysis indicate that IR mRNA has multiple start sites. The promoter fragment was ligated
to a promoterless "reporter" plasmid containing the bacterial gene chloramphenicol acetyltransferase (CAT). When this plasmid
is transfected into cultured cells, CAT activity is detected, indicating promoter activity. Various portions of a genomic
fragment were ligated to a promoter to study glucocorticoid regulation of the IR promoter. These studies indicate that IR-gene
expression is regulated by differentiation and hormonal agents. |
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Bibliography: | ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-3 content type line 23 ObjectType-Review-1 |
ISSN: | 0149-5992 1935-5548 |
DOI: | 10.2337/diacare.13.3.288 |