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Wisinski JA, Reuter A, Peter DC, Schaid MD, Fenske RJ, Kimple ME. Prostaglandin EP3 receptor signaling is required to prevent insulin hypersecretion and metabolic dysfunction in a non-obese mouse model of insulin resistance. Am J Physiol Endocrinol Metab 2021; 321:E479-E489. [PMID: 34229444 PMCID: PMC8560379 DOI: 10.1152/ajpendo.00051.2021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
When homozygous for the LeptinOb mutation (Ob), Black-and-Tan Brachyury (BTBR) mice become morbidly obese and severely insulin resistant, and by 10 wk of age, frankly diabetic. Previous work has shown prostaglandin EP3 receptor (EP3) expression and activity is upregulated in islets from BTBR-Ob mice as compared with lean controls, actively contributing to their β-cell dysfunction. In this work, we aimed to test the impact of β-cell-specific EP3 loss on the BTBR-Ob phenotype by crossing Ptger3 floxed mice with the rat insulin promoter (RIP)-CreHerr driver strain. Instead, germline recombination of the floxed allele in the founder mouse-an event whose prevalence we identified as directly associated with underlying insulin resistance of the background strain-generated a full-body knockout. Full-body EP3 loss provided no diabetes protection to BTBR-Ob mice but, unexpectedly, significantly worsened BTBR-lean insulin resistance and glucose tolerance. This in vivo phenotype was not associated with changes in β-cell fractional area or markers of β-cell replication ex vivo. Instead, EP3-null BTBR-lean islets had essentially uncontrolled insulin hypersecretion. The selective upregulation of constitutively active EP3 splice variants in islets from young, lean BTBR mice as compared with C57BL/6J, where no phenotype of EP3 loss has been observed, provides a potential explanation for the hypersecretion phenotype. In support of this, high islet EP3 expression in Balb/c females versus Balb/c males was fully consistent with their sexually dimorphic metabolic phenotype after loss of EP3-coupled Gαz protein. Taken together, our findings provide a new dimension to the understanding of EP3 as a critical brake on insulin secretion.NEW & NOTEWORTHY Islet prostaglandin EP3 receptor (EP3) signaling is well known as upregulated in the pathophysiological conditions of type 2 diabetes, contributing to β-cell dysfunction. Unexpected findings in mouse models of non-obese insulin sensitivity and resistance provide a new dimension to our understanding of EP3 as a key modulator of insulin secretion. A previously unknown relationship between mouse insulin resistance and the penetrance of rat insulin promoter-driven germline floxed allele recombination is critical to consider when creating β-cell-specific knockouts.
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Affiliation(s)
- Jaclyn A Wisinski
- Department of Biology, University of Wisconsin-LaCrosse, La Crosse, Wisconsin
| | - Austin Reuter
- Research Service, William S. Middleton Memorial VA Hospital, Madison, Wisconsin
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison, Madison, Wisconsin
| | - Darby C Peter
- Research Service, William S. Middleton Memorial VA Hospital, Madison, Wisconsin
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison, Madison, Wisconsin
| | - Michael D Schaid
- Research Service, William S. Middleton Memorial VA Hospital, Madison, Wisconsin
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison, Madison, Wisconsin
- Interdepartmental Graduate Program in Nutritional Sciences, University of Wisconsin-Madison, Madison, Wisconsin
| | - Rachel J Fenske
- Research Service, William S. Middleton Memorial VA Hospital, Madison, Wisconsin
- Interdepartmental Graduate Program in Nutritional Sciences, University of Wisconsin-Madison, Madison, Wisconsin
| | - Michelle E Kimple
- Research Service, William S. Middleton Memorial VA Hospital, Madison, Wisconsin
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison, Madison, Wisconsin
- Interdepartmental Graduate Program in Nutritional Sciences, University of Wisconsin-Madison, Madison, Wisconsin
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, Wisconsin
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Protein kinase CK2: a potential therapeutic target for diverse human diseases. Signal Transduct Target Ther 2021; 6:183. [PMID: 33994545 PMCID: PMC8126563 DOI: 10.1038/s41392-021-00567-7] [Citation(s) in RCA: 136] [Impact Index Per Article: 45.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 03/19/2021] [Accepted: 03/22/2021] [Indexed: 02/04/2023] Open
Abstract
CK2 is a constitutively active Ser/Thr protein kinase, which phosphorylates hundreds of substrates, controls several signaling pathways, and is implicated in a plethora of human diseases. Its best documented role is in cancer, where it regulates practically all malignant hallmarks. Other well-known functions of CK2 are in human infections; in particular, several viruses exploit host cell CK2 for their life cycle. Very recently, also SARS-CoV-2, the virus responsible for the COVID-19 pandemic, has been found to enhance CK2 activity and to induce the phosphorylation of several CK2 substrates (either viral and host proteins). CK2 is also considered an emerging target for neurological diseases, inflammation and autoimmune disorders, diverse ophthalmic pathologies, diabetes, and obesity. In addition, CK2 activity has been associated with cardiovascular diseases, as cardiac ischemia-reperfusion injury, atherosclerosis, and cardiac hypertrophy. The hypothesis of considering CK2 inhibition for cystic fibrosis therapies has been also entertained for many years. Moreover, psychiatric disorders and syndromes due to CK2 mutations have been recently identified. On these bases, CK2 is emerging as an increasingly attractive target in various fields of human medicine, with the advantage that several very specific and effective inhibitors are already available. Here, we review the literature on CK2 implication in different human pathologies and evaluate its potential as a pharmacological target in the light of the most recent findings.
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3
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Borgo C, D'Amore C, Cesaro L, Sarno S, Pinna LA, Ruzzene M, Salvi M. How can a traffic light properly work if it is always green? The paradox of CK2 signaling. Crit Rev Biochem Mol Biol 2021; 56:321-359. [PMID: 33843388 DOI: 10.1080/10409238.2021.1908951] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
CK2 is a constitutively active protein kinase that assuring a constant level of phosphorylation to its numerous substrates supports many of the most important biological functions. Nevertheless, its activity has to be controlled and adjusted in order to cope with the varying needs of a cell, and several examples of a fine-tune regulation of its activity have been described. More importantly, aberrant regulation of this enzyme may have pathological consequences, e.g. in cancer, chronic inflammation, neurodegeneration, and viral infection. Our review aims at summarizing our current knowledge about CK2 regulation. In the first part, we have considered the most important stimuli shown to affect protein kinase CK2 activity/expression. In the second part, we focus on the molecular mechanisms by which CK2 can be regulated, discussing controversial aspects and future perspectives.
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Affiliation(s)
- Christian Borgo
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Claudio D'Amore
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Luca Cesaro
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Stefania Sarno
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Lorenzo A Pinna
- Department of Biomedical Sciences, University of Padova, Padova, Italy.,CNR Institute of Neurosciences, Padova, Italy
| | - Maria Ruzzene
- Department of Biomedical Sciences, University of Padova, Padova, Italy.,CNR Institute of Neurosciences, Padova, Italy
| | - Mauro Salvi
- Department of Biomedical Sciences, University of Padova, Padova, Italy
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4
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Hashemolhosseini S. The role of protein kinase CK2 in skeletal muscle: Myogenesis, neuromuscular junctions, and rhabdomyosarcoma. Neurosci Lett 2020; 729:135001. [DOI: 10.1016/j.neulet.2020.135001] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Revised: 04/14/2020] [Accepted: 04/16/2020] [Indexed: 01/08/2023]
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5
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Weßbecher IM, Hinrichsen I, Funke S, Oellerich T, Plotz G, Zeuzem S, Grus FH, Biondi RM, Brieger A. DNA mismatch repair activity of MutLα is regulated by CK2-dependent phosphorylation of MLH1 (S477). Mol Carcinog 2018; 57:1723-1734. [DOI: 10.1002/mc.22892] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 06/22/2018] [Accepted: 08/18/2018] [Indexed: 12/15/2022]
Affiliation(s)
- Isabel M. Weßbecher
- Medical Clinic I; Biomedical Research Laboratory; Goethe-University; Frankfurt Germany
| | - Inga Hinrichsen
- Medical Clinic I; Biomedical Research Laboratory; Goethe-University; Frankfurt Germany
| | - Sebastian Funke
- Department of Ophthalmology; Experimental Ophthalmology; University Medical Center; Gutenberg University; Mainz Germany
| | - Thomas Oellerich
- Department of Medicine II, Hematology/Oncology; Goethe-University; Frankfurt Germany
| | - Guido Plotz
- Medical Clinic I; Biomedical Research Laboratory; Goethe-University; Frankfurt Germany
| | - Stefan Zeuzem
- Medical Clinic I; Biomedical Research Laboratory; Goethe-University; Frankfurt Germany
| | - Franz H. Grus
- Department of Ophthalmology; Experimental Ophthalmology; University Medical Center; Gutenberg University; Mainz Germany
| | - Ricardo M. Biondi
- Medical Clinic I; Biomedical Research Laboratory; Goethe-University; Frankfurt Germany
- Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA)-CONICET-Partner Institute of the Max Planck Society; Buenos Aires Argentina
| | - Angela Brieger
- Medical Clinic I; Biomedical Research Laboratory; Goethe-University; Frankfurt Germany
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6
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CK2 modulates adipocyte insulin-signaling and is up-regulated in human obesity. Sci Rep 2017; 7:17569. [PMID: 29242563 PMCID: PMC5730587 DOI: 10.1038/s41598-017-17809-w] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Accepted: 12/01/2017] [Indexed: 12/13/2022] Open
Abstract
Insulin plays a major role in glucose metabolism and insulin-signaling defects are present in obesity and diabetes. CK2 is a pleiotropic protein kinase implicated in fundamental cellular pathways and abnormally elevated in tumors. Here we report that in human and murine adipocytes CK2-inhibition decreases the insulin-induced glucose-uptake by counteracting Akt-signaling and GLUT4-translocation to the plasma membrane. In mice CK2 acts on insulin-signaling in adipose tissue, liver and skeletal muscle and its acute inhibition impairs glucose tolerance. Notably, CK2 protein-level and activity are greatly up-regulated in white adipose tissue from ob/ob and db/db mice as well as from obese patients, regardless the severity of their insulin-resistance and the presence of pre-diabetes or overt type 2 diabetes. Weight loss obtained by both bariatric surgery or hypocaloric diet reverts CK2 hyper-activation to normal level. Our data suggest a central role of CK2 in insulin-sensitivity, glucose homeostasis and adipose tissue remodeling. CK2 up-regulation is identified as a hallmark of adipose tissue pathological expansion, suggesting a new potential therapeutic target for human obesity.
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Chan T, Cheung FSG, Zheng J, Lu X, Zhu L, Grewal T, Murray M, Zhou F. Casein Kinase 2 Is a Novel Regulator of the Human Organic Anion Transporting Polypeptide 1A2 (OATP1A2) Trafficking. Mol Pharm 2015; 13:144-54. [DOI: 10.1021/acs.molpharmaceut.5b00576] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Ting Chan
- Faculty
of Pharmacy, The University of Sydney, Sydney, New South Wales 2006, Australia
| | | | - Jian Zheng
- Alkali
Soil Natural Environmental Science Center, Northeast Forestry University/Key
Laboratory of Saline-alkali Vegetation Ecology Restoration in Oil
Field, Ministry of Education, Harbin, 150040, China
| | - Xiaoxi Lu
- Faculty
of Pharmacy, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Ling Zhu
- Retinal
Therapeutics Research Group, Save Sight Institute, The University of Sydney, Sydney, New South Wales 2000, Australia
| | - Thomas Grewal
- Faculty
of Pharmacy, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Michael Murray
- Discipline
of Pharmacology, School of Medical Sciences, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Fanfan Zhou
- Faculty
of Pharmacy, The University of Sydney, Sydney, New South Wales 2006, Australia
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8
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Abstract
CK2 is a pleiotropic, ubiquitous, and constitutively active protein kinase (PK), with both cytosolic and nuclear localization in most mammalian cells. The holoenzyme is generally composed of two catalytic (alpha and/or alpha') and two regulatory (beta) subunits, but the free alpha/alpha' subunits are catalytically active by themselves and can be present in cells under some circumstances. CK2 catalyzes the phosphorylation of more than 300 substrates characterized by multiple acidic residues surrounding the phosphor-acceptor amino acid, and, consequently, it plays a key role in several physiological and pathological processes. But how can one kinase orchestrate all these tasks faithfully? How is it possible that one kinase can, despite all pleiotropic characteristics of PKs in general, be involved in so many different biochemical events? Is CK2 a druggable target? Several questions are still to be clearly answered, and this review is an occasion for a fruitful discussion.
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Affiliation(s)
- Giorgio Cozza
- Molecular Modeling Section, Dipartimento di Scienze Farmaceutiche, Università di Padova, via Marzolo 5, Padova, Italy
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9
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Abstract
The control of glucose uptake and glycogen metabolism by insulin in target organs is in part mediated through the regulation of protein-serine/threonine kinases. In this study, the expression and phosphotransferase activity levels of some of these kinases in rat heart ventricle were measured to investigate whether they might mediate the shift in the energy dependency of the developing heart from glycogen to fatty acids. Following tail-vein injection of overnight fasted adult rats with 2 U of insulin per kg body weight, protein kinase B (PKB), the 70-kDa ribosomal S6 kinase (S6K), and casein kinase 2 (CK2) were activated (30-600%), whereas the MAP/extracellular regulated kinases (ERK)1 and ERK2 were not stimulated under these conditions. When the expression levels of the insulin-activated kinases were probed with specific antibodies in ventricular extracts from 1-, 10-, 20-, 50-, and 365-day-old rats, phosphatidylinositol 3-kinase (PI3K), PKB, S6K, and CK2 were downregulated (40-60%) with age. By contrast, ventricular glycogen synthase kinase-3beta (GSK3beta) protein levels were maintained during postnatal development. Similar findings were obtained when the expression of these kinases was investigated in freshly isolated ventricular myocytes, where they were detected predominantly in the cytosolic fraction of the myocytes. Compared to other adult rat tissues such as brain and liver, the levels of PI3K, PKB, S6K, and GSK3beta were relatively low in the heart. Even though CK2 protein and activity levels were reduced by approximately 60% in 365 day as compared to 1-day-old rats, expression of CK2 in the adult heart was as high as detected in any of the other rat tissues. The high basal activities of CK2 in early neonatal heart may be associated with the proliferating state of myocytes.
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Affiliation(s)
- S O Kim
- Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, Canada
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10
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Roher N, Miró F, José M, Trujillo R, Plana M, Itarte E. Protein kinase CK2 is altered in insulin-resistant genetically obese (fa/fa) rats. FEBS Lett 1998; 437:211-5. [PMID: 9824292 DOI: 10.1016/s0014-5793(98)01230-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Hepatic insulin receptor levels in 6-week-old obese (fa/fa) rats were about 2-fold lower than those from lean (Fa/-) rats, which agrees with their insulin-resistant state. Nuclear protein kinase CK2 activity and protein content in livers from obese (fa/fa) rats were similar to those of lean (Fa/-) animals but the cytosolic levels were reduced to half, due to a decrease in the 39-kD)a catalytic subunit. Marked increases in activity, due to rises in the 44-kDa and 39-kDa catalytic subunits, were seen in the 16000 x g sediments (M1) from insulin-resistant rats, with moderate changes in the 100000xg sediments (M2). The increase in CK2 binding to M1 did not require increases in the molecular chaperone grp94, which was unaltered in insulin-resistant rats.
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Affiliation(s)
- N Roher
- Departament de Bioquímica i Biologia Molecular, Universitat Autònoma de Barcelona, Bellaterra, Spain
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11
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Young AV, Hehn BM, Sanghera JS, Pelech SL, Shah RM. Changes in casein kinase 2 activity during development of the secondary palate in the hamster. Anat Rec (Hoboken) 1996; 245:724-30. [PMID: 8837731 DOI: 10.1002/(sici)1097-0185(199608)245:4<724::aid-ar13>3.0.co;2-r] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
BACKGROUND Casein kinase 2 (CK 2) is a serine/threonine kinase that has been ubiquitously conserved in all eukaryotic cells. The exact functions of this enzyme have not yet been clarified; however, studies have repeatedly suggested that it may play crucial roles in the regulation of cell proliferation. During the formation of the secondary palate in the hamster, bursts of cell proliferation occur during the initial half of vertical shelf development, which decrease during the subsequent steps of palate morphogenesis, thus indicating that the cell cycle in the developing vertical palate may be tightly regulated. METHODS In the present study, palatal shelves were dissected at 12-hour intervals between days 10 and 12 of gestation, which is the period of vertical shelf development in the hamster. The palates were homogenized and cleared by ultracentrifugation and the resultant supernatants were fractionated on a Mono Q column by fast protein liquid chromatography. RESULTS Using phosvitin as a substrate, the phosphotransferase activity in the fractionated samples decreased steadily from days 10 to 11, increased to a fivefold peak on day 11:12, and then decreased on day 12 of gestation. Western blot analysis using two CK 2 specific antibodies demonstrated that both the 42-kDa (alpha) and the 38-kDa (alpha') subunits of the CK 2 holoenzyme were found throughout the formation of the vertical palatal shelves in the hamster. The amount of alpha and alpha' subunits appears to remain constant, which suggested that the differential activity of the CK 2 enzyme may be due to posttranslational modifications. CK 2 activity correlated well with DNA synthesis (i.e., cell proliferation) rates from days 10 to 11, but not from days 11 to 12 of gestation. CONCLUSIONS It is proposed that the activity of CK 2 may regulate the rate of cell proliferation by stimulation of progression through G1 phase of the cell cycle and may also relate to the effects of various growth factors during the vertical development of mammalian palate.
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Affiliation(s)
- A V Young
- Department of Oral Biology, Faculty of Dentistry, Vancouver, British Columbia, Canada
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12
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Litchfield DW, Lüscher B. Casein kinase II in signal transduction and cell cycle regulation. Mol Cell Biochem 1993; 127-128:187-99. [PMID: 7935350 DOI: 10.1007/bf01076770] [Citation(s) in RCA: 130] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Casein kinase II is a protein serine/threonine kinase that is ubiquitously distributed in eukaryotes. Molecular cloning studies and protein sequence analysis of purified proteins have demonstrated the existence of two related, but distinct, isoenzymic forms of its catalytic subunit in mammals and birds. At present, the precise role of the individual casein kinase II isoforms in biological responses is poorly understood. However, a great deal of evidence indicates that casein kinase II is an important component of signalling pathways that control the growth and division of cells. In particular, casein kinase II is known to phosphorylate, and in several cases, regulate the activity of a variety of regulatory nuclear proteins including nuclear oncoproteins, transcription factors, and enzymes involved in other aspects of DNA metabolism. In this review, we will summarize evidence relating to the involvement of casein kinase II in signal transduction events that are relevant to cell proliferation.
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13
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Tanasijevic M, Myers M, Thoma R, Crimmins D, White M, Sacks D. Phosphorylation of the insulin receptor substrate IRS-1 by casein kinase II. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(17)46824-4] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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14
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Yang Q, Co D, Sommercorn J, Tonks N. Cloning and expression of PTP-PEST. A novel, human, nontransmembrane protein tyrosine phosphatase. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)53296-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Sommercorn J, Fields R, Raz I, Maeda R. Abnormal regulation of ribosomal protein S6 kinase by insulin in skeletal muscle of insulin-resistant humans. J Clin Invest 1993; 91:509-13. [PMID: 8432859 PMCID: PMC287969 DOI: 10.1172/jci116229] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Insulin resistance in Pima Indians appears to result from a post-receptor impairment of insulin signal transduction that affects only some responses to insulin. To identify the primary lesion responsible for insulin resistance, we investigated the influence of insulin on ribosomal protein S6 kinase activities in skeletal muscle of insulin-sensitive and insulin-resistant nondiabetic Pima Indians during a 2-h hyperinsulinemic, euglycemic clamp. In sensitive subjects, S6 kinase activity was transiently activated fivefold over basal activity by 45 min of insulin infusion. Although basal activities in the two groups were similar, the response to insulin was delayed and restricted to about threefold over basal in subjects resistant to insulin. Two major S6 kinase activities in extracts of human muscle were resolved by chromatography on Mono Q. Peak 1, which accounted for basal activity owes to an enzyme antigenically related to the 90-kD S6 kinase II, a member of the rsk gene family. The major insulin-stimulated S6 kinase eluted as peak 2 and is antigenically related to a 70-kD S6 kinase. Our results show that insulin resistance impairs signaling to the 70-kD S6 kinase.
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Affiliation(s)
- J Sommercorn
- Clinical Diabetes and Nutrition Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Phoenix, Arizona 85016
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16
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Abstract
The present review on casein kinases focuses mainly on the possible metabolic role of CK-2, with special emphasis on its behavior in pathological tissues. From these data at least three ways to regulate CK-2 activity emerge: (i) CK-2 activity changes during embryogenesis, being high at certain stages of development and showing basal activity values at others; (ii) CK-2 activity can be enhanced in vitro by treatment of tissue culture cells with various growth factors and serum and (iii) CK-2 activity is constitutively enhanced in rapidly proliferating cells. The regulated CK-2 activity changes during embryogenesis cannot be explained as yet. In the case of the constitutive high expression of CK-2 in tumors, genetic changes may be responsible, e.g. through alterations of the regulatory genetic elements and/or regulation by specific transcription factors. In the case of serum induction, no genetic changes are necessarily involved; the observed changes may be entirely due to a signal transduction pathway where CK-2 could be phosphorylated by another kinase(s). CK-2 cDNAs from various organisms have been isolated and characterized. From the deduced amino acid sequence it turns out that CK-2 subunits are highly conserved during evolution. The relationship between CK-2 alpha from humans and plants is still 73%. Similar relationships are reported for the beta-subunit. Chromosomal assignment of CK-2 alpha shows two gene loci, one of which is a pseudogene. They are located on different chromosomes. Expression of the CK-2 subunits in Escherichia coli and the Baculo expression system is shown. The recombinant subunits can self-assemble to a functional holoenzyme in vitro. Biochemical and biophysical analysis of the recombinant beta-subunit suggests it to be trifunctional in association with the alpha-subunit affecting: (i) stability, (ii) enzyme specificity and (iii) enzyme activity. The question where CK-2 and its subunits are located throughout the cell cycle has also been addressed, mainly because of the large discrepancies that still exist between results obtained by different investigators. Tissue-specific expression of CK-2 at the mRNA and at the protein level has also been given attention. The fact that the enzyme activity is surprisingly high in brain and low in heart and lung may be indicative of involvement of CK-2 in processes other than proliferation.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- O G Issinger
- Medizinische Fakultät, Universität des Saarlandes, Homburg (Saar), Germany
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17
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Abstract
More than half the Pima Indians over 35 years of age have non-insulin dependent diabetes mellitus (NIDDM). They have been the focus of prospective epidemiologic and metabolic studies for over two decades and the data collected during these studies are now proving invaluable in efforts to find genetic markers for NIDDM in humans. The Pima Indian model of this disease affords two major advantages. The population is genetically homogeneous compared to Caucasian populations, and therefore the causes of NIDDM are less heterogeneous, simplifying genetic linkage studies. Equally important, based on results from metabolic studies, two pre-diabetic phenotypes have been identified in the Pimas: insulin resistance and a low metabolic rate. Use of these phenotypes in genetic linkage analyses should greatly improve chances of finding genetic markers for NIDDM since these phenotypes may be more closely related to the putative abnormal gene products, and actual disease genes, than is the hyperglycemia of the fully developed phenotype of NIDDM.
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Affiliation(s)
- C Bogardus
- Clinical Diabetes and Nutrition Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Phoenix, Arizona 85016
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18
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Kida Y, Raz I, Maeda R, Nyomba BL, Stone K, Bogardus C, Sommercorn J, Mott DM. Defective insulin response of phosphorylase phosphatase in insulin-resistant humans. J Clin Invest 1992; 89:610-7. [PMID: 1737850 PMCID: PMC442894 DOI: 10.1172/jci115627] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Insulin-stimulated glycogen synthase activity in human muscle is reduced in insulin-resistant subjects. Insulin regulation of human muscle glycogen synthase may require activation of a type-1 protein phosphatase (PP-1). We investigated the change of phosphorylase phosphatase and glycogen synthase activities in muscle biopsies obtained during a 2-h hyperinsulinemic euglycemic clamp in 12 insulin-sensitive (group S) and 8 insulin-resistant (group R) subjects. Fasting phosphorylase phosphatase activity was lower in group R than in group S, and did not increase significantly with insulin infusion in group R until 20 min. In group S, phosphorylase phosphatase was significantly stimulated by 10 min, remaining significantly higher than in group R at all time points. The insulin-mediated changes in phosphatase activities were not decreased by 3 nM okadaic acid but were completely inhibited by 1 microM okadaic acid, thereby verifying that insulin-stimulated phosphorylase phosphatase is accounted for by a PP-1. Subcellular fractionation demonstrated reduced fasting PP-1 activities in both the glycogen and cytosolic fractions of muscle obtained from subjects in group R compared to those in group S. These results suggest that insulin activation of PP-1 could contribute to the stimulation of glycogen synthase by this hormone in human muscle. Lower fasting PP-1 activity in cytosol and glycogen fractions plus lower insulin-stimulated PP-1 activity could explain, in part, reduced insulin-stimulated glycogen synthase in skeletal muscle of insulin-resistant subjects.
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Affiliation(s)
- Y Kida
- Clinical Diabetes & Nutrition Section, National Institutes of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Phoenix, Arizonia 85016
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