Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: HUMANGGP:034761 (insulin)
 211,843 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Extracts of fasted rat diaphragms, previously treated with or without insulin were assayed for glycogen synthase, protein kinase and cyclic [3H]-AMP binding. Treatment with insulin produced an elevation in the % of glycogen synthase I and a concurrent decrease in cyclic AMP-dependent protein kinase activity and cyclic [3H]-AMP binding. Analysis of extracts by disc gel electrophoresis demonstrated the inhibition of cyclic [3H]-AMP binding to involve the Type I protein kinase holoenzyme. Inhibition of protein kinase activity was most apparent in the presence of 0.2 micrometer cyclic AMP, with enzymatic activity of the insulin-treated extracts typically 60--65% of control. Higher assay concentrations diminished the difference between control and insulin-treated extracts and concentrations greater than 20 micrometer abolished it. The inhibition of cyclic AMP-dependent protein kinase activity after insulin was a transient and labile phenomenon. The effect was independent of ATP concentration in the assay, but was sensitive to the pH of tissue extraction, requiring a pH of 7.0 to 8.4 to be observed. Insulin-mediated inhibition of protein kinase activity was reversed upon preincubation of extracts at 0--2 degrees. Relatively concentrated homogenates (less than 4 microliter buffer/mg tissue) yielded extracts which exhibited little or no inhibition of protein kinase activity compared to extracts prepared from more dilute (6--10 microliter/mg) homogenates. A model for the inhibition of the cyclic-AMP dependent protein kinase by an insulin-generated inhibitor which becomes directly associated with the Type 1 holoenzyme is proposed.
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PMID:Reversible inhibition of cyclic AMP-dependent protein kinase by insulin. 2 80

Tyrosine adminotransferase (EC 2.6.1.5) has been found to be phosphorylated in intact rat hepatoma cells in culture. Incorporation of [32p]i into the enzyme is rapid and is exclusively found as phosphoserine. Cycloheximide treatment reduced phosphorylation of the aminotransferase only slightly and in the presence of three different inducers of this enzyme, dexamethasone, insulin, and dibutyryl cyclic AMP, [32P]I incorporation was increased. It is concluded that [32p]i incorporation into this enzyme probably reflects turnover of phosphate groups associated with pre-existing enzyme molecules catalyzed by a cyclic AMP-independent protein kinase.
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PMID:Relationship between phosphorylation of tyrosine aminotransferase and regulation of its synthesis by cyclic AMP and hormones. 2 2

Effects of adrenalectomy and acute insulin insufficiency upon tissue adenosine 3', 5' cyclic monophosphate concentrations, and adenyl cyclase, phosphodiesterase, and protein kinase activities were investigated. Adrenalectomy decreased intracellular adenosine 3', 5' cyclic monophosphate 53% and increased the activities of both adenylcyclase and phosphodiesterase. Cortisol therapy returned these to normal. During insulin insufficiency caused by anti-insulin serum, mammary adenosine 3', 5' cyclic monophosphate concentrations increased. The acute effects of insulin insufficiency and chronic effects of adrenelectomy suggest that insulin acts upon rat mammary glands to decrease and glucocorticoids, acting over longer term, to increase adenosine 3', 5' cyclic monophosphate concentrations.
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PMID:Effect of adrenalectomy and insulin insufficiency upon the adenosine 3', 5' cyclic monophosphate system of the rat mammary glands. 16 26

There appear to be two classes of protein kinases in rat heart and adipose tissue, types I and II. Type I elutes from DEAE-cellulose at smaller than 0.1 M NaCl and type II at greater than 0.1 M NaCl. The type I enzyme is more readily dissociated by salt or histone than is the type II enzyme. If the type I kinase is first dissociated by cAMP, the subunits reassociate very slowly at 0 degrees C on removal of the cAMP by Sephadex G-25 chromatography, whereas those of type II reassociate very rapidly. Rat heart contains mostly type I and a small amount of type II enzyme, whereas adipose tissue contains almost exclusively the type II enzyme. The adipose tissue enzyme resembles the heart type II kinase in all of the above properties, although the two enzymes are not identical as indicated by slight differences in elution patterns from DEAE-cellulose columns. Incubation of rat epididymal adipose tissue with low concentrations of epinephrine (0.11 muM) increases glycerol production and the fraction of the protein kinase in the active form (activity ratio). The change in cAMP under these conditions is not statistically significant. The presence of insulin inhibits the epinephrine effect on glycerol production and protein kinase but has no measurable effect on cAMP levels. Incubation of adipose tissue with high epinephrine concentrations (11 muM) increases the cAMP level, the protein kinase activity ratio, and glycerol production. Under these conditions insulin decreases the cAMP level and kinase activity ratio but does not reduce glycerol production. The data suggest that very small changes in the tissue cAMP level, undetectable by the assay method, are magnified during the stepwise activation of glycerol output aided possibly by cooperative effects between cAMP and protein kinase. The procedure developed for determining the state of activation of the cAMP-dependent protein kinase in adipose tissue must be modified by reducing the salt concentration of the buffers in order to carry out similar studies in the heart. This reflects the different types of protein kinase in the two tissues. The addition of charcoal to crude extracts of heart prevents protein kinase activation by added cyclic AMP. Charcoal should therefore prevent any activation that could occur if any sequestered cAMP were released during homogenization. Charcoal addition thereby provides a means to distinguish intracellular cAMP activation of the kinase from that which might occur following cell rupture. If epinephrine-perfused hearts are homogenized in the presence of charcoal, epinephrine stimulation of the protein kinase is only slightly decreased. This indicates that the protein kinase is activated intracellularly by cAMP and suggests that all of the cAMP in the cell is available to the protein kinase; i.e., cAMP is not released during homogenization.
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PMID:Hormonal regulation of adenosine 3',5'-monophosphate-dependent protein kinase. 16 70

Endogenous and hormone-induced protein (polypeptide) phosphorylations were studied in isolated rat fat cells, in fat pads, and in subcellular fractions obtained from fat tissue under different physiological conditions. Insulin (25-100 muU/ml) increased the incorporation of 32P into two proteins: insulin-phosphorylated proteins (IPP 140 and IPP 50; similar to 140,000 and 50,000 daltons, respectively). Epinephrine (10(-7)-10(-6) M) increased the incorporation of 32P into another protein: epinephrine-phosphorylated protein (EPP 60-65; similar to 60,000-65,000 daltons). Endogenous IPP 140 phosphorylation in fat cells obtained from fasted and refed rats was similar to that of insulin in normal cells. Studies of insulin and epinephrine interactions showed that insulin increased IPP 140 phosphorylation even in the presence of epinephrine or lithium (25 mM times 10(-3) M). dibutyryl cyclic AMP (5 times 10(-4) M) markedly stimulated EPP 60-65 phosphorylation, but neither epinephrine (10(-7)-10(-6) M) nor dibutyryl cyclic AMP reproduced insulin's phosphorylation of APP 140. Lithium inhibited both endogenous and epinephrine-stimulate EPP 60-65 phosphorylation, but did not inhibit that induced by dibutyryl cyclic AMP. These findings suggest that insulin stimulated a specific, cyclic AMP independent protein kinase for IPP 140 phosphorylation. Cell-free extracts from insulin-treated fat tissue catalyzed the specific transfer of 32P from ATP to IPP 140 more rapidly than control extracts. No differences in the total receptor protein or total protein kinase activity using [gamma(-32P]ATP were noted between insulin-treated and control preparations. IPP 140 may be either (a) an insulin-sensitive protein kinase (phosphotransferase) or (b) a protein whose function is regulated by an insulin-sensitive protein kinase or phosphatase.
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PMID:Actions of insulin, epinephrine, and dibutyryl cyclic adenosine 5'-monophosphate on fat cell protein phosphorylations. Cyclic adenosine 5'-monophosphate dependent and independent mechanisms. 16 23

The effects of epinephrine, glucagon, insulin and 1-methyl-3-isobutylxanthine on adenosine 3:5-monophosphate (cAMP)-dependent protein kinase activity were investigated in the perfused rat heart. The conditions for homogenization of heart tissue and assay of protein kinase are described. The activation state of the enzyme is expressed as the ratio of the rate of phosphorylation of histone in the absence to that in the presence of 2 mu-M cAMP. This activity ratio is stable in crude homogenates over 15 min of incubation; it is not affected by up to 30-fold dilution of the tissue volume. The ratio is elevated to a variable degree in hearts taken immediately from the animal but falls to a stable, basal level of 0.15 to 0.20 after 15 min of perfusion in vitro. An optimal concentration of epinephrine (10 mu-M) in the perfusate elevates cAMP from 0.5 to 1.3 nmol per g of tissue and increases the protein kinase activity ratio from 0.20 to 0.65. When hearts are perfused with a steady, submaximal concentration of epinephrine (0.4 mu-M), the level of cAMP and the protein kinase activity ratio rise in parallel within 15 s and remain elevated for at least 10 min. When epinephrine is removed from the perfusion medium, the level of cAMP and enzyme activity ratio decline rapidly to basal levels. Both glucagon and the phosphodiesterase inhibitor 1-methyl-3-isobutylxanthine also increase the cardiac cAMP levels and protein kinase activity ratio in a dose-dependent manner. Glucagon acts as rapidly as does epinephrine whereas 1-methyl-3-isobutylxanthine requires at least 30 s before any effect can be observed. Insulin by itself does not significantly affect the cyclic nucleotide level or enzyme activity. The hormone has not been observed to lower the cAMP level or protein kinase activity in the heart under any conditions tested. In concentrations of 10 microunits per ml or greater, it does, however, cause a slight rise in the tissue level of cAMP and the protein kinase activity when these have been elevated to intermediate levels by exposure to epinephrine. This effect could only be observed when hearts were treated with catecholamine and could not be detected with glucagon or 1-methyl-3-isobutylxanthine. In all cases tested, slight increases in the protein kinase activity ratio (from 0.2 to 0.3) were accompanied by much greater increases in the amount of phosphorylase in the a form (20% to 70%). It was observed that at perfusion times greater than 3 min, there was a significant reduction in phosphorylase activity even though both the cAMP level and protein kinase activity remained elevated. In these studies, changes in the protein kinase activity correlate well with the tissue cAMP levels under all conditions tested.
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PMID:Regulation of adenosine 3:5-monophosphate-dependent protein kinase. 16 93

The effect of intravenous epinephrine on heart glycogen synthase and phosphorylase systems in control and insulin-pretreated rats was studied. The percent of synthase in the I form decreased rapidly after epinephrine treatment but the change was small and sometimes not significant. In insulin-pretreated rats in which the percent synthase I was increased, epinephrine produced a definate and highly significant decrease. There was a simultaneous increase in percent phosphorylase a in both groups. The synthase and phosphorylase responses were statiscally significant at 2.5 mug epinephrine/kgor more. These data are compatible with a mechanism in which protein kinase is activated by an increased cAMP concentration and affects both the synthase and phosphorylasesystems simultaneously. Propranolol blocked the epinephrine effects on cAMP, synthase I, and phosphorylase a. Although insulin had little effect on the response ofthe synthase and phosphorylase systems to epinephrine, it nealry completely blocked glycogen degradation. The mechanism is unknown, but it appears to be due to an inhibition of phosphorylase a catalytic activity in vivo. Acetylcholine had no effect on synthase I, phosphorylase a, or cAMP in control or in insulin-pretreated animals.
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PMID:Insulin and epinephrine effects on heart glycogen synthase and phosphorylase activity. 16 84

Cadmium, in addition to producing a variety of toxic manifestations, is known to accumulate in certain "target" organs which include liver and kidney where histological and functional damage becomes apparent. The daily intraperitoneal injection of cadmium chloride for 21 or 45 days stimulated the activities of hepatic pyruvate carboxylase, phosphoenolpyruvate carboxykinase, fructose-1, 6-diphosphatase and glucose-6-phosphatase elevated blood glucose and urea, and lowered hepatic glycogen in rats. Whereas chronic Cd treatment failed to alter adenosine-3', 5'-monophosphate phosphodiesterase (PDE) activity, cyclic AMP (cAMY and the activity of basal and fluoride-stimulated forms of hepatic adenylate cyclase (AC) were markedly increased. However, the cAMP binding to hepatic protein kinase was decreased as was the kinase activity ration. An acute dose of Cd decreased hepatic glycogen content and increased blood glucose, serum urea, and hepatic cAMP. Chronic exposure to Cd induced adrenal hypertrophy and augmented adrenal norepinephrine and epinephrine as well as the activity of adrenal tyrosine hydroxylase. This treatment decreased prostatic and testicular weights of mature rats. Although cAMP as well as AC activity of the prostate gland were reduced, cAMP binding to the prostatic protein kinase was increased as was the activity of the cAMP-dependent form of the enzyme. Testicular AC and PDE activities, however, were stimulated, although cAMP remained unaffected. Whereas the activities of the cAMP-dependent and the independent forms of testicular protein kinase were significantly depressed, the binding of cAMP to protein kinase from testes of Cd-treated rats was not affected. In most cases, the observed metabolic alterations persisted up to 28 days on cessation of Cd administration. Subacute Cd treatment suppressed pancreatic function as evidenced by lowered serum immunoreactive insulin (IRI) in presence of hyperglycemia, as well as by partial inhibition of phentolamine-stimulated increases in serum IRI. Although chronic Cd treatment failed to alter the concentration of brain stem norepinephrine and cerebrocortical acetylcholine esterase activity, serotonin levels of brain stem were depressed and the concentration of striatal dopamine and cerebrocortical acetylcholine were significantly elevated when compared with the values seen in control nonexposed animals.
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PMID:Aspects of the biochemical toxicology of cadmium. 17 84

The protein kinase activities of a transplantable, insulin-producing hamster islet cell tumor were characterized using gel filtration, sucrose density gradient centrifugation and acrylamide gel electrophoresis. The post-microsomal supernatant fluid contains 70-80% of the protein kinase activity present in crude homogenates. A cAMP-dependent protein kinase, PK I (Mr 170,000), represents 25% of the soluble protein kinase activity assayed with protamine as substrate. It dissociates in the presence of cAMP into a cAMP-binding protein, R2 (Mr 90,000) and a catalytic subunit C (Mr 33,000). The dissociation induced by cAMP seems to be facilitated by the addition of Mg2+ and ATP. The regulatory subunit, R2, changes its gel filtration pattern in the presence of 0.5 M NaCl suggesting dissociation into a smaller subunit, R1 (Mr 44,000). By analogy with purified beef heart protein kinase (Erlichman et al., 1973) and skeletal muscle protein kinase, PK I. The presence in crude homogenates of a free cAMP-binding protein indistinguishable from the R2 derived by dissociation of PK I, suggests that PK I is partially dissociated in vivo. A cAMP-independent (casein) kinase (Mr 210,000) elutes with PK I on columns of Sepharose 6B. Another cAMP-independent protein kinase, PK II (Mr 88,000), is the predominatn form of soluble protein kinase accounting for approximately 75% of the soluble protein kinase activity detected using protaimine as substrate. This cAMP-independent protein kinase changes its gel filtration pattern in the presence of 0.5 M NaCl giving rise to a form which appears to have the same Mr (33,000) as the catalytic subunit of PK I. Studies comparing the catalytic subunit C of PK I with PK II and its salt-induced smaller molecular form demonstrate facile association of C with the cAMP-binding protein of purified bovine heart protein kinase to yield a hybrid holoenzyme, whereas PK II and its smaller form fail to recombine in this fashion. The 33,000 dalton forms derived from PK I (by cAMP) and PK II (by salt) also show different substrate specificities. It would appear, therefore, that pK II is a cAMP-independent protein kinase unrelated to PK I.
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PMID:Characterization of the protein kinases in a transplantable islet cell tumor of the Syrian hamster. 17 65

Isolated adipocytes, incubated in the presence of extracellular 32Pi to steady state 32P incorporation into cellular phosphopeptides, were exposed to hormones for 5 min. Epinephrine (10(-6) M) stimulated 32P incorporation into at least 12 major phosphopeptides, distributed in the cytoplasm, endoplasmic reticulum, and plasma membrane. Quantitatively pre-eminent among these were peptides of molecular weight 123,000 and 69,000, each located both in the cytoplasm and endoplasmic reticulum. The effect of epinephrine (10(-7) M) on 32P incorporation into these two peptides was augmented by theophylline (10(-3) M) in a synergistic fashion. Norepinephrine, dibutyryl N6,O2'-dibutyryl adenosine 3':5'-monophosphate, adrenocorticotropic hormone (ACTH) (synthetic 1 to 24 fragment), and glucagon mimicked the effect of epinephrine. Insulin modified adipocyte peptide phosphorylation in two ways. When present as the sole hormone, insulin (100 microunits/ml) consistently and selectively stimulated the 32P incorporation into a peptide of molecular weight 123,000 (endoplasmic reticulum, cytoplasm) without significant alteration in the 32P content of any other major peptide. A second effect of insulin was evident when epinephrine (10(-6) M) was present simultaneously. Insulin significantly inhibited the epinephrine-stimulated phosphorylation of the molecular weight 69,000 (endoplasmic reticulum, cytoplasm) and 26,000 (plasma membrane) peptides. Nevertheless, persistence of insulin-stimulated phosphorylation of the 123,000 peptide in the presence of epinephrine was shown by a 32P content of this peptide that was greater in the presence of both hormones than with either individually. These findings indicate that in intact adipocytes: (a) epinephrine acutely alters the phosphorylation of a large number of adipocyte peptides, partly at least, via activation of adenosine 3':5'-monophosphate (cyclic AMP)-dependent protein kinase; (b) insulin opposes several epinephrine-stimulated phosphorylations in a manner consitent with its ability to lower epinephrine-stimulated intracellular cyclic AMP accumulation in adipocytes; and (c) insulin, in addition, exerts a unique stimulatory effect on adipocyte peptide phosphorylation that is independent of its effects on cyclic AMP metabolism and may be medicated by the generation of an as yet undefined intracellular "messenger" unique to insulin.
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PMID:Effects of epinephrine and insulin on phosphopeptide metabolism in adipocytes. 17 55


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