scholarly journals Tyrosine phosphorylation of two cytosolic proteins of 50 kDa and 35 kDa in rat liver by insulin-receptor kinase in vitro

1987 ◽  
Vol 248 (1) ◽  
pp. 27-33 ◽  
Author(s):  
Y C Kwok ◽  
C C Yip
Keyword(s):  
Insulin Receptor ◽  
Rat Liver ◽  
Growth Factor Receptor ◽  
Insulin Receptors ◽  
Artificial Substrates ◽  
Receptor Kinase ◽  
Insulin Receptor Tyrosine Kinase ◽  
Cytosolic Proteins ◽  
Insulin Receptor Kinase

Insulin-receptor tyrosine kinase can phosphorylate a variety of artificial substrates in vitro. Its physiological substrate(s), however, remains unknown. In the present study, we show that immobilized insulin receptors phosphorylate tyrosine residues of two cytosolic proteins of 50 kDa and 35 kDa in rat liver. Phosphorylation of these two proteins required Mn2+- or Mg2+-ATP as the phosphate donor. Phosphorylation was time- and temperature-dependent. Furthermore, the rate of phosphorylation of the two proteins was related to the autophosphorylated state of the insulin receptor. The pI of the phosphorylated 50 kDa and 35 kDa proteins was 5.4 and 5.6 respectively. These proteins were present in low abundance. They were not related to each other, nor to the insulin receptor, as demonstrated by in-gel proteolytic digestion and by immunoprecipitation using antibodies produced against them. They were specific substrates for the insulin receptor kinase, since they were not phosphorylated by epidermal-growth-factor-receptor kinase. These observations suggest that the 50 kDa and 35 kDa cytosolic proteins may be endogenous substrates for the insulin-receptor kinase.

Insulin receptor kinase is hyperresponsive in adipocytes of young obese Zucker rats

1987 ◽  
Vol 252 (2) ◽  
pp. E273-E278 ◽  
Author(s):  
A. Debant ◽  
M. Guerre-Millo ◽  
Y. Le Marchand-Brustel ◽  
P. Freychet ◽  
M. Lavau ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Insulin Receptor ◽  
Insulin Action ◽  
Kinase Activity ◽  
Insulin Receptors ◽  
Zucker Rats ◽  
Receptor Kinase ◽  
Insulin Receptor Tyrosine Kinase ◽  
Obese Zucker Rats ◽  
Insulin Receptor Kinase

Thirty-day-old obese Zucker rats have hyperresponsive adipose tissue, whereas their skeletal muscle normally responds to insulin in vitro. To further substantiate the role of insulin receptor tyrosine kinase in insulin action, we have studied the kinase activity of receptors obtained from adipocytes and skeletal muscle of these young obese Zucker rats. Insulin receptors, partially purified by wheat germ agglutinin agarose chromatography from plasma membranes of isolated adipocytes or from skeletal muscles, were studied in a cell-free system for auto-phosphorylation and for their ability to phosphorylate a synthetic glutamate-tyrosine copolymer. For an identical amount of receptors, the insulin stimulatory action on its beta-subunit receptor phosphorylation was markedly augmented in preparations from hyperresponsive adipocytes of obese animals compared with lean rats. Basal phosphorylation of adipocyte insulin receptors was nearly identical in lean and obese animals. Similarly the capacity of adipocyte insulin receptors to catalyze the phosphorylation of the synthetic substrate in response to insulin was increased. By contrast, the kinase activity of insulin receptors prepared from normally insulin-responsive skeletal muscle was similar in preparations of lean and obese rats. These results show that a state of hyperresponsiveness to insulin is correlated with a parallel increase of insulin receptor kinase activity suggesting an important role for this activity in insulin action.

Hepatic insulin and EGF receptor phosphorylation and dephosphorylation in fetal rats

1992 ◽  
Vol 262 (1) ◽  
pp. E6-E13 ◽  
Author(s):  
P. A. Gruppuso ◽  
J. M. Boylan ◽  
P. A. Carter ◽  
J. A. Madden ◽  
T. Raven
Keyword(s):  
Insulin Receptor ◽  
Egf Receptor ◽  
Artificial Substrates ◽  
Fetal Membrane ◽  
Receptor Kinase ◽  
Receptor Phosphorylation ◽  
Insulin Receptor Tyrosine Kinase ◽  
Kinase Activation ◽  
Fetal Rats

Hepatic insulin receptor and epidermal growth factor (EGF) receptor phosphorylation and dephosphorylation were studied in normal and growth-retarded fetal rats. Insulin receptor autophosphorylation at a subsaturating ATP concentration (0.5 microM) increased by 10-fold from day 17 to 21 of gestation and decreased by 50% in term growth-retarded fetuses of fasted mothers. In vitro kinase activation at 0.5 mM ATP did not change with gestation or maternal fasting. EGF receptor autophosphorylation increased in parallel with receptor number with advancing gestation and did not change with maternal fasting. Protein tyrosine phosphatases (PTPases), which might attenuate receptor signaling in livers from growth-retarded fetuses, were measured using polybasic and polyacidic artificial substrates as well as the insulin receptor kinase domain. Fetal membrane PTPase activities were twofold higher than in the adult and declined with advancing gestation. However, activities were similar in normal and growth-retarded fetuses. We conclude that decreased hepatic growth in growth-retarded fetuses may involve decreased insulin receptor tyrosine kinase activation in vivo, as indicated by diminished receptor autophosphorylation at subsaturating ATP concentrations. Changes in EGF receptor kinase activity and PTPases could not be implicated based on our in vitro findings.

Insulin receptor kinase activity in muscles and white adipose tissue during course of VMH obesity

1992 ◽  
Vol 262 (2) ◽  
pp. E161-E166 ◽  
Author(s):  
A. Pujol ◽  
B. Cousin ◽  
A. F. Burnol ◽  
M. Loizeau ◽  
L. Picon ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
Insulin Receptor ◽  
White Adipose Tissue ◽  
Kinase Activity ◽  
Insulin Receptors ◽  
Ventromedial Hypothalamus ◽  
Receptor Kinase ◽  
Insulin Receptor Tyrosine Kinase ◽  
Insulin Receptor Kinase ◽  
Insulin Receptor Kinase Activity

Early after lesion of the ventromedial hypothalamus nuclei (VMH), insulin-induced glucose utilization is increased in white adipose tissue (WAT), whereas oxidative and glycolytic muscles are, respectively, normoresponsive or resistant to insulin. Five weeks later, all of the muscles are resistant, whereas WAT returns to normal responsiveness. The aim of this study was to characterize the insulin receptor kinase activity in WAT and muscles 1 and 6 wk after lesion. The number and affinity of insulin receptors were not modified in any of the tissues studied. Autophosphorylation and phosphorylation of an exogenous substrate were similar in oxidative and glycolytic muscles of VMH and control rats both 1 and 6 wk after the lesion. Insulin receptors from WAT of 1-wk VMH rats exhibited a 2.5-fold increase in insulin-stimulated autophosphorylation and phosphorylation. Six weeks after the lesion, both autophosphorylation and phosphorylation returned to normal values. This suggests that insulin receptor tyrosine kinase activity does not play a significant role in the insulin resistance of skeletal muscles but has a crucial role in mediating the variations of insulin action on WAT observed during the development of VMH obesity.

scholarly journals Functional characteristics of insulin receptors with a Thr-->Ser1200 mutation overexpressed in Chinese hamster ovary cells

2000 ◽  
pp. 125-131 ◽  
Author(s):  
M Schutt ◽  
H Benecke ◽  
M Drenckhan ◽  
HH Klein
Keyword(s):  
Insulin Receptor ◽  
Kinase Activity ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Insulin Receptors ◽  
Receptor Kinase ◽  
Ovary Cells ◽  
Insulin Receptor Kinase

OBJECTIVE: To investigate the functional properties of insulin receptors with a Thr-->Ser(1200)-mutation that is associated with severe insulin resistance in humans. DESIGN AND METHODS: The effect of in situ insulin-stimulation on insulin receptor kinase activity was studied in Chinese hamster ovary cells with overexpressed human Ser(1200)-mutated, non-mutated, and ATP-binding site-mutated (Lys-->Arg(1030)) receptors using a microwell-based assay that only detects human (and not hamster) insulin receptors. Moreover, the fraction of anti-phosphotyrosine antibody-binding receptors following in situ stimulation was separated, and autophosphorylation and kinase activity resulting from in situ and/or in vitro activation evaluated in this fraction. RESULTS: Although insulin-stimulated kinase activity of human-specific anti-insulin receptor antibody-binding receptors in cells with Ser(1200)-mutated insulin receptors represented only 3.3% of that reached in cells with non-mutated receptors, a clear insulin-induced increase in kinase activity was observed (3.4-fold; P<0.05). This increase was associated with a 2.3+/-0.6% (P<0.05) increase in anti-phosphotyrosine-binding receptors with a kinase activity representing 43+/-8% of that found in activated non-mutated receptors. In vitro autophosphorylation and kinase activation proceeded much more slowly in Ser(1200)-mutated receptors (t(1/2)): 100 min) compared with non-mutated receptors (t(1/2)): 1 min) and were inhibitable by lower alkaline phosphatase concentrations (EC(50): 3 U/ml and 70 U/ml respectively). No activation of insulin receptor kinase was observed with Arg(1030)-mutated receptors. CONCLUSIONS: Overexpressed Ser(1200)-mutated human insulin receptors possess insulin-stimulated kinase activity and can be activated in situ and in vitro. They are characterized by a markedly slower autophosphorylation reaction, which, in a phosphatase-containing environment, results in a small fraction of phosphorylated and activated receptors.

scholarly journals Internalization and Activation of the Rat Liver Insulin Receptor Kinase in vivo

1989 ◽  
Vol 264 (22) ◽  
pp. 12931-12940 ◽  
Author(s):  
M N Khan ◽  
G Baquiran ◽  
C Brule ◽  
J Burgess ◽  
B Foster ◽  
...  
Keyword(s):  
Insulin Receptor ◽  
Rat Liver ◽  
Receptor Kinase ◽  
Insulin Receptor Kinase

scholarly journals Insulin receptor function is inhibited by guanosine 5′-[γ-thio]triphosphate (GTP[S])

1990 ◽  
Vol 270 (2) ◽  
pp. 401-407 ◽  
Author(s):  
H W Davis ◽  
J M McDonald
Keyword(s):  
Insulin Receptor ◽  
G Proteins ◽  
Plasma Membranes ◽  
Insulin Receptors ◽  
Insulin Binding ◽  
Peptide Sequence ◽  
Receptor Kinase ◽  
Receptor Function ◽  
Gtp Binding ◽  
Insulin Receptor Kinase

The regulatory role of GTP-binding proteins (G-proteins) in insulin receptor function was investigated using isolated insulin receptors and plasma membranes from rat adipocytes. Treatment of isolated insulin receptors with 1 mM-guanosine 5′-[gamma-thio]triphosphate (GTP[S]) inhibited insulin-stimulated phosphorylation of the beta-subunit, histone Hf2b and poly(GluNa4,Tyr1) by 22%, 65% and 65% respectively. Phosphorylation of calmodulin by the insulin receptor kinase was also inhibited by 1 mM-GTP[S] both in the absence (by 88%) and in the presence (by 81%) of insulin. In the absence of insulin, 1 mM-GTP had the same effect on calmodulin phosphorylation as 1 mM-GTP[S]. However, when insulin was present, GTP was less effective than GTP[S] (41% versus 81% inhibition). Concentrations of GTP[S] greater than 250 microM are necessary to inhibit phosphorylation. Although these concentrations are relatively high, the effect of GTP[S] is not due to competition with [32P]ATP for the insulin receptor kinase since (1) other nucleotide triphosphates did not inhibit phosphorylation as much as did GTP[S] (or GTP) and (2) the Vmax of the ATP-dependent kinase reaction was decreased in the presence of GTP[S]. GTP[S] (1 mM) also inhibited insulin binding to isolated receptors and plasma membranes, by 80% and 50% respectively. Finally, an antibody raised to a peptide sequence common to the alpha-subunits of G-proteins Gs, Gi, Go and transducin detected G-proteins in plasma membranes but failed to detect them in the insulin receptor preparation. These results indicate that GTP inhibits insulin receptor function, but does so through a mechanism that does not require a conventional GTP-binding protein.

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