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Transepithelial Transport Characteristics of the Antihypertensive Peptide, Lys-Val-Leu-Pro-Val-Pro, in Human Intestinal Caco-2 Cell Monolayers. Biosci Biotechnol Biochem 2014; 73:293-8. [DOI: 10.1271/bbb.80473] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Gloria-Bottini F, Antonacci E, Cozzoli E, De Acetis C, Bottini E. The effect of genetic variability on the correlation between blood glucose and glycated hemoglobin levels. Metabolism 2011; 60:250-5. [PMID: 20152999 DOI: 10.1016/j.metabol.2010.01.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2009] [Revised: 01/05/2010] [Accepted: 01/06/2010] [Indexed: 10/19/2022]
Abstract
The disturbing results of recent clinical trials aimed to control cardiovascular risk of diabetes by aggressive control of blood glucose prompted us to analyze the effect of genetic variability of 2 polymorphic enzymes abundant in red blood cells on the correlation between blood glucose and glycated hemoglobin (Hb). Two hundred eighty subjects with type 2 diabetes mellitus were studied. Adenylate kinase locus 1 (AK₁) and acid phosphatase locus 1 were determined. Correlation between blood glucose and glycated Hb was determined for phenotypes of the 2 systems. The correlation between blood glucose and glycated Hb is higher in carriers of AK₁*2 allele than in subjects with AK₁1 phenotype. The highest coefficient is observed in acid phosphatase locus 1 phenotypes with the highest enzymatic activity; and the lowest, in phenotypes with the lowest activity. Effects of sex, blood glucose level, age, age at onset, and duration of disease have been also considered. Our data are in agreement with recent observation in healthy subjects suggesting a role of genetic factors on glycated Hb level. If glycation of structural and functional protein is dependent not only on blood glucose level but also on genetic factors, these factors could have an important role in the susceptibility and clinical course of diabetes.
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Affiliation(s)
- Fulvia Gloria-Bottini
- Division of Biopathology of Human population and Environmental Pathology, Department of Biopathology and Imaging Diagnostics, University of Rome Tor Vergata, Rome, Italy.
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Gloria-Bottini F, Magrini A, Di Renzo L, De Lorenzo A, Bergamaschi A, Bottini E. Body mass index and acid phosphatase locus 1 in diabetic disorders. Acta Diabetol 2010; 47 Suppl 1:139-43. [PMID: 19855922 DOI: 10.1007/s00592-009-0153-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2008] [Accepted: 04/30/2009] [Indexed: 11/26/2022]
Abstract
The polymorphic enzyme acid phosphatase locus 1 (ACP1) is a candidate gene for obesity disorders. The enzyme is able to dephosphorylate the insulin receptor. Our group has observed a lower plasma glucose level in diabetic subjects carrying the low activity ACP1 phenotypes A and BA, and a positive association between these genotypes and body mass index (BMI). We have now analysed the relationship between BMI and ACP1 in gestational diabetes and in women with type 1 diabetes. We have studied 106 Caucasian women with type 1 diabetes who had previously delivered a liveborn infant, 99 Caucasian women who had had gestational diabetes and 387 healthy fertile women from the same population as controls. ACP1 phenotype was determined by starch gel electrophoresis. In overweight women (BMI > 25), the proportion of low activity ACP1 phenotypes is much lower in type 1 diabetes than in gestational diabetes and in healthy females. In women with BMI ≤ 25, the proportion of low activity ACP1 phenotypes is slightly lower in gestational diabetes than in type 1 diabetes. Low activity ACP1 phenotypes have diverse effects on susceptibility to overweight depending on the class of diabetic disorder: in subjects with type 2 diabetes and in subjects with gestational diabetes low activity ACP1 phenotypes predispose to an increase in BMI, while in type 1 diabetes these ACP1 phenotypes seem to protect from overweight.
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Affiliation(s)
- F Gloria-Bottini
- Department of Biopathology and Imaging Diagnostics, University of Rome Tor Vergata, School of Medicine, Via Montpellier 1, 00133 Rome, Italy.
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Sun XM, Canda-Sánchez A, Manjeri GR, Cohen GM, Pinkoski MJ. Phenylarsine oxide interferes with the death inducing signaling complex and inhibits tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induced apoptosis. Exp Cell Res 2009; 315:2453-62. [PMID: 19465019 DOI: 10.1016/j.yexcr.2009.05.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2009] [Revised: 05/08/2009] [Accepted: 05/14/2009] [Indexed: 12/15/2022]
Abstract
The mechanism by which tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces death is the subject of intense scrutiny due to its preferential targeting of transformed cells for deletion. Based on recent findings that the TRAIL-dependent death inducing signaling complex (DISC) forms and signals at the plasma membrane without being internalized, we investigated the possibility that agents that prevent endocytosis may stabilize the surface bound DISC and thereby enhance TRAIL-dependent signaling. We utilized phenylarsine oxide (PAO), a trivalent arsenical that has been reported to inhibit endocytosis and to induce mitochondrial permeability transition. Therefore PAO could, by two separate and independent activities, enhance TRAIL-induced killing. Paradoxically, we found that rather than synergizing with TRAIL, PAO was an effective inhibitor of TRAIL-induced killing. Recruitment of FADD and caspase-8 to the TRAIL-dependent DISC was diminished in a concentration-dependent manner in cells exposed to PAO. The effects of PAO could not be reversed by washing cells under non-reducing conditions, suggesting covalent linkage of PAO with its cellular target(s); however, 2,3-dimercaptoethanol effectively overcame the inhibitory action of PAO and restored sensitivity to TRAIL-induced apoptosis. PAO inhibited formation of the TRAIL-dependent DISC and therefore prevented all subsequent apoptotic events.
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Affiliation(s)
- Xiao-Ming Sun
- Medical Research Council Toxicology Unit, University of Leicester, Hodgkin Building, PO Box 138, Leicester LE1 9HN, UK
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De Lorenzo A, Di Renzo L, Puja A, Saccucci P, Gloria-Bottini F, Bottini E. A study of acid phosphatase locus 1 in women with high fat content and normal body mass index. Metabolism 2009; 58:351-4. [PMID: 19217450 DOI: 10.1016/j.metabol.2008.10.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/07/2008] [Accepted: 10/13/2008] [Indexed: 01/12/2023]
Abstract
De Lorenzo and coworkers have recently described a class of women with normal body mass index (BMI) and high fat content (normal weight obese syndrome [NWO]). This observation prompted us to study the possible role of acid phosphatase locus 1 (ACP(1)) in the differentiation of this special class of obese subjects. Acid phosphatase locus 1 is a polymorphic gene associated with severe obesity and with total cholesterol and triglycerides levels. The enzyme is composed by 2 isoforms--F and S--that have different biochemical properties and probably different functions. The sample study was composed of 130 white women from the population of Rome. Total fat mass and percentage of fat mass were measured by dual-energy x-ray absorptiometry. Thirty-six women had a BMI less than 25 and percentage of fat mass greater than 30 (high fat, normal BMI [HFHB]), and 94 women showed a BMI greater than 25 and a percentage of fat mass greater than 30 (high fat, high BMI [HFHB]). In the whole sample, the proportion of low-activity ACP(1) genotypes (*A/*A and *B/*A) was higher than in controls. However, whereas HFNB showed a very high frequency of ACP(1) *A/*A genotype, high-fat, high-BMI women showed an increase of *B/*A genotype. These 2 genotypes differ in the concentration of F isoform and the F/S ratio, which are lower in ACP(1)*A/*A genotype than in ACP(1)*B/*A genotype. The genetic differentiation of the class of women with normal BMI and high fat content from the class showing a concordant level of the 2 parameters supports the hypothesis that HFNB class represents a special cluster of obese subjects not revealed by BMI evaluation. Because ACP(1) is present in adipocytes, the present observation suggests that F isoform may have a specific role in the regulation of quantity of adipose tissue.
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Affiliation(s)
- Antonino De Lorenzo
- Department of Neurosciences, Human Nutrition Unit, University of Rome Tor Vergata, 00133 Rome, Italy
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Lei L, Sun H, Liu D, Liu L, Li S. Transport of Val-Leu-Pro-Val-Pro in human intestinal epithelial (Caco-2) cell monolayers. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2008; 56:3582-3586. [PMID: 18442243 DOI: 10.1021/jf703640p] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Angiotensin converting enzyme (ACE) inhibitory peptides are biologically active peptides that play a very important role in blood pressure regulation. In previous experiments, we obtained an ACE inhibitory peptide Val-Leu-Pro-Val-Pro (VLPVP) by DNA recombinant technology. The purpose of this study was to examine the bidirectional transport of VLPVP by using the human intestinal Caco-2 monolayers. The permeability coefficient ( P app) values of VLPVP over 4-8 mmol/L ranged from 7.44 x 10(-8) to 1.35 x 10(-6) cm/s for apical (AP) to basolateral (BL) transport, while the P app values for BL to AP flux were significantly lower than those for the AP to BL flux, with efflux ratio values of 0.74-0.13 over 4-8 mM. Preincubation of the paracellular transport enhancer (sodium deoxycholate), the inhibitor of multidrug resistant protein (MK-571), or sodium azide stimulated efflux of VLPVP significantly ( p < 0.01); these results indicate that the transport of VLPVP across Caco-2 monolayers was involved in paracellular diffusion and MRP2 transport.
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Affiliation(s)
- Lin Lei
- Department of Applied Biotechnology, Shenzhen Polytechnic, Shenzhen, Guangdong, People's Republic of China
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Montaudon D, Palle K, Rivory LP, Robert J, Douat-Casassus C, Quideau S, Bjornsti MA, Pourquier P. Inhibition of topoisomerase I cleavage activity by thiol-reactive compounds: importance of vicinal cysteines 504 and 505. J Biol Chem 2007; 282:14403-12. [PMID: 17355975 DOI: 10.1074/jbc.m611673200] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
DNA topoisomerase I (Top1) is a nuclear enzyme that plays a crucial role in the removal of DNA supercoiling associated with replication and transcription. It is also the target of the anticancer agent, camptothecin (CPT). Top1 contains eight cysteines, including two vicinal residues (504 and 505), which are highly conserved across species. In this study, we show that thiol-reactive compounds such as N-ethylmaleimide and phenylarsine oxide can impair Top1 catalytic activity. We demonstrate that in contrast to CPT, which inhibits Top1-catalyzed religation, thiolation of Top1 inhibited the DNA cleavage step of the reaction. This inhibition was more pronounced when Top1 was preincubated with the thiol-reactive compound and could be reversed in the presence of dithiothreitol. We also established that phenylarsine oxide-mediated inhibition of Top1 cleavage involved the two vicinal cysteines 504 and 505, as this effect was suppressed when cysteines were mutated to alanines. Interestingly, mutation of Cys-505 also altered Top1 sensitivity to CPT, even in the context of the double Cys-504 to Cys-505 mutant, which relaxed supercoiled DNA with a comparable efficiency to that of wild-type Top1. This indicates that cysteine 505, which is located in the lower Lip domain of human Top1, is critical for optimal poisoning of the enzyme by CPT and its analogs. Altogether, our results suggest that conserved vicinal cysteines 504 and 505 of human Top1 play a critical role in enzyme catalytic activity and are the target of thiol-reactive compounds, which may be developed as efficient Top1 catalytic inhibitors.
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Affiliation(s)
- Danièle Montaudon
- Groupe de Pharmacologie Moléculaire INSERM E347 and Institut Bergonié, 229 Cours de l'Argonne, Université Victor Segalen Bordeaux II, 146 Rue Léo Saignat, 33076 Bordeaux Cedex, France
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Sun L, Nicholson AC, Hajjar DP, Gotto AM, Han J. Adipogenic differentiating agents regulate expression of fatty acid binding protein and CD36 in the J744 macrophage cell line. J Lipid Res 2003; 44:1877-86. [PMID: 12867536 DOI: 10.1194/jlr.m300084-jlr200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Adipocyte fatty acid binding protein (aP2) is a key mediator of intracellular transport and metabolism of fatty acids. Its expression during adipocyte differentiation is regulated through the actions of peroxisome proliferator-activated receptor gamma (PPARgamma) and CCAAT/enhancer binding protein alpha (C/EBPalpha). Macrophages also express aP2, and the lack of macrophage aP2 significantly reduces atherosclerotic lesion size in hypercholesterolemic mice. We investigated the regulation of expression of macrophage aP2 and CD36, a fatty acid membrane binding protein and scavenger receptor, in response to the adipogenic agents isobutylmethylxanthine (IBMX), insulin, and dexamethasone, a combination of agents shown to induce fibroblast-to-adipocyte differentiation. Treatment of J774 macrophages with adipogenic agents significantly induced aP2 mRNA expression, while CD36 expression was inhibited. Dexamethasone was essential and sufficient to induce aP2 expression, and insulin had a synergistic effect. However, IBMX antagonized induced-aP2 expression. aP2 protein expression and [14C]oleic acid uptake by macrophages were also increased by dexamethasone. Unlike what occurs in adipocytes, adipogenic agents had mixed effects on the expression of PPARgamma and C/EBPalpha in macrophages. Our data demonstrate differences in the regulation of aP2 in adipocytes and macrophages and show that macrophage aP2 expression by adipogenic agents is independent of the PPARgamma and/or C/EBPalpha signaling pathway.
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Affiliation(s)
- Li Sun
- Center of Vascular Biology, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10021, USA
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Gerhard R, John H, Aktories K, Just I. Thiol-modifying phenylarsine oxide inhibits guanine nucleotide binding of Rho but not of Rac GTPases. Mol Pharmacol 2003; 63:1349-55. [PMID: 12761345 DOI: 10.1124/mol.63.6.1349] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Phenylarsine oxide (PAO) is a phosphotyrosine phosphatase inhibitor that cross-links vicinal thiol groups, thereby inactivating phosphatases possessing XCysXXCysX motifs. The RhoA-GTPase, but not the Rac1-GTPase, also possesses vicinal cysteines within the guanine nucleotide-binding region (aa 13-20) and the phosphohydrolase activity site. Treatment of Caco-2 cells with PAO showed a dose-dependent reorganization of the actin cytoskeleton, indicating involvement of Rho GTPases. As tested by pull-down experiments, RhoA, but not Rac1, from cell lysates was inactivated by PAO in a concentration-dependent manner. Modification of RhoA by PAO resulted in altered mobility on SDS-polyacrylamide gel electrophoresis, and PAO-modified RhoA was no longer substrate for C3-catalyzed ADP-ribosylation. Furthermore, RhoA treated with PAO, but not Rac1 treated with PAO, lost its property to bind to guanine nucleotides. Matrix-assisted laser desorption ionization-mass analysis of PAO-modified RhoA showed a mass shift according to an adduction of a single PAO molecule per molecule RhoA. Further analysis of Glu-C-generated RhoA peptides confirmed binding of PAO to a peptide harboring the guanine nucleotide binding region. Thus, PAO does not exclusively inhibit phosphotyrosine phosphatases but also inactivates RhoA by alteration of nucleotide binding.
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Affiliation(s)
- Ralf Gerhard
- Institut für Toxikologie, Medizinische Hochschule Hannover, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany.
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Don AS, Kisker O, Dilda P, Donoghue N, Zhao X, Decollogne S, Creighton B, Flynn E, Folkman J, Hogg PJ. A peptide trivalent arsenical inhibits tumor angiogenesis by perturbing mitochondrial function in angiogenic endothelial cells. Cancer Cell 2003; 3:497-509. [PMID: 12781367 DOI: 10.1016/s1535-6108(03)00109-0] [Citation(s) in RCA: 114] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Mitochondria are the powerhouse of the cell and their disruption leads to cell death. We have used a peptide trivalent arsenical, 4-(N-(S-glutathionylacetyl)amino) phenylarsenoxide (GSAO), to inactivate the adenine nucleotide translocator (ANT) that exchanges matrix ATP for cytosolic ADP across the inner mitochondrial membrane and is the key component of the mitochondrial permeability transition pore (MPTP). GSAO triggered Ca(2+)-dependent MPTP opening by crosslinking Cys(160) and Cys(257) of ANT. GSAO treatment caused a concentration-dependent increase in superoxide levels, ATP depletion, mitochondrial depolarization, and apoptosis in proliferating, but not growth-quiescent, endothelial cells. Endothelial cell proliferation drives new blood vessel formation, or angiogenesis. GSAO inhibited angiogenesis in the chick chorioallantoic membrane and in solid tumors in mice. Consequently, GSAO inhibited tumor growth in mice with no apparent toxicity at efficacious doses.
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Affiliation(s)
- Anthony S Don
- Centre for Vascular Research, University of New South Wales and Department of Haematology, Prince of Wales Hospital, Sydney, Australia
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Bottini N, MacMurray J, Peters W, Rostamkhani M, Comings DE. Association of the acid phosphatase (ACP1) gene with triglyceride levels in obese women. Mol Genet Metab 2002; 77:226-9. [PMID: 12409270 DOI: 10.1016/s1096-7192(02)00120-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The acid phosphatase (ACP1) locus codes for a low molecular weight protein tyrosine phosphatase (LMPTP) that is found ubiquitously in human tissues. The *A allele of the ACP1 gene is associated with lower total enzymatic activity than the *B and *C alleles. An association between the *A allele and extreme values of body-mass-index (BMI) and dyslipidemia has previously been described in several samples of obese subjects from the Italian population. In the present study, we investigated the relationship between ACP1 *A allele genotypes (*A/*A, *A/*B, and *A/*C) and non-*A allele genotypes (*B/*B, *B/*C, and *C/*C) and metabolic variables in 277 Caucasian post-menopausal subjects consisting of 82 non-obese subjects (BMI</=29), 60 moderately obese (BMI 30-34) and 135 very obese (BMI>/=35) subjects. ACP1 genotypes were found to be significantly associated with total cholesterol (p</=0.002) and triglyceride (p</=0.001) levels in the obese and very obese women only. The significantly lower levels of triglycerides in *A carriers in this group suggest a protective effect of the *A allele against hypertriglyceridemia. It has been unclear why some individuals who gain weight develop dyslipidemia and other aspects of the metabolic syndrome while others do not. The present study suggests that those who gain weight and carry the ACP1 *A allele may be partially protected against developing the metabolic syndrome. The confirmation of ACP1 as a modifier gene of the metabolic complications could open the door to the prevention of the lethal complications of obesity.
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Abstract
Protein phosphatases 2C (PP2Cs) exhibit diverse regulatory functions in signalling pathways of animals, yeast and plants. ABI1 is a PP2C of Arabidopsis that exerts negative control on signalling of the phytohormone abscissic acid (ABA). Characterisation of the redox sensitivity of ABI1 revealed a strong enzymatic inactivation by hydrogen peroxide (H2O2) which has recently been implicated as a secondary messenger of ABA signalling. H2O2 reversibly inhibited ABI1 activity in vitro with an IC(50) of approximately 140 microM in the presence of physiological concentrations of glutathione. In addition, ABI1 was highly susceptible to inactivation by phenylarsine oxide (IC(50)=3-4 microM) indicative for the facile oxidation of vicinal cysteine residues. Thus, H2O2 generated during ABA signalling seems to inactivate the negative regulator of the ABA response.
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Affiliation(s)
- M Meinhard
- Lehrstuhl für Botanik, Technische Universität München, Biologikum Weihenstephan, Am Hochanger 4, 85354, Freising, Germany
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Wang J, Cheung AT, Kolls JK, Starks WW, Martinez-Hernandez A, Dietzen D, Bryer-Ash M. Effects of adenovirus-mediated liver-selective overexpression of protein tyrosine phosphatase-1b on insulin sensitivity in vivo. Diabetes Obes Metab 2001; 3:367-80. [PMID: 11703427 DOI: 10.1046/j.1463-1326.2001.00173.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
AIM Protein tyrosine phosphatase-1B (PTP-1B) is an intracellular PTP known to dephosphorylate and inactivate upstream tyrosine phosphoproteins in the insulin signalling cascade. We and others reported increased abundance of catalytically impaired PTP-1B in tissue lysates from obese human subjects with and without type 2 diabetes, while genetic knockout of PTP-1B improves insulin sensitivity and prevents nutritionally mediated insulin resistance and obesity. The aim of the present work was to further elucidate the role of PTP-1B in glucose metabolism in vivo. METHODS We used adenoviral constructs incorporating cDNAs for either wild-type (W/T) or a catalytically inactive C(215)S (C/S) mutant PTP-1B to achieve liver-selective PTP-1B overexpression in young Sprague-Dawley rats using tail vein injection, based on the high degree of hepatotropism of adenovirus 5 (Ad5). An Ad5-lacZ construct encoding beta-galactosidase was used as a control for viral effects alone. A hyperinsulinaemic euglycaemic clamp was used to study whole body glucose disposal and endogenous glucose production rates. RESULTS Control studies in HIRcB cells confirmed catalytic activity and inactivity of W/T and C/S respectively. Mean PTP-1B abundance was 2.24 +/- 0.02- and 2.33 +/- 0.04-fold of saline-treated control in liver lysates of W/T and C/S rats respectively. Liver selective overexpression was confirmed by analysis of tissue lysates from liver, fat and muscle tissues. Ad5 treatment did not result in a statistically or clinically significant liver injury, as determined by serum alanine aminotransferase and histological examination. Seven days post injection, no significant difference in rate of weight gain, fasting blood glucose or insulin levels were seen in any group. Similarly, under steady-state glucose clamp conditions, glucose disposal rate (R(d)), endogenous glucose production rate (EGP) and serum insulin levels were similar in all groups. CONCLUSION We conclude that moderate medium-term overabundance, to a degree resembling that seen in insulin-resistant states, of PTP-1B in liver tissue does not alter insulin action on glucose metabolism and that the major site of action of PTP-1B is presumably at insulin-responsive target tissue or tissues other than the liver.
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Affiliation(s)
- J Wang
- University of Tennessee, Memphis, TN, USA
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Jin S, Zhai B, Qiu Z, Wu J, Lane MD, Liao K. c-Crk, a substrate of the insulin-like growth factor-1 receptor tyrosine kinase, functions as an early signal mediator in the adipocyte differentiation process. J Biol Chem 2000; 275:34344-52. [PMID: 10926934 DOI: 10.1074/jbc.m004927200] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Differentiation of 3T3-L1 preadipocytes into adipocytes is induced by a combination of inducers, including a glucocorticoid, an agent that elevates cellular cAMP, and a ligand of the insulin-like growth factor-1 receptor. Previous studies have implicated protein-tyrosine phosphatase (PTPase) HA2, a homologue of PTPase 1B, in the signaling cascade initiated by the differentiation inducers. Vanadate, a potent PTPase inhibitor, blocks adipocyte differentiation at an early stage in the program, but has no effect on the mitotic clonal expansion required for differentiation. Exposure of preadipocytes to vanadate along with the inducing agents led to the accumulation of pp35, a phosphotyrosyl protein that is a substrate for PTPase HA2. pp35 was purified to homogeneity and shown by amino acid sequence and mass analyses of tryptic peptides to be c-Crk, a known cytoplasmic target of the insulin-like growth factor-1 receptor tyrosine kinase. Transfection of 3T3-L1 preadipocytes with a c-Crk antisense RNA expression vector markedly reduced c-Crk levels and prevented differentiation into adipocytes. Studies with C3G, a protein that binds to the SH3 domain in c-Crk, showed that phosphorylation of c-Crk rendered the SH3 domain inaccessible to C3G. Taken together, these findings indicate that locking c-Crk in the phosphorylated state with vanadate prevents its participation in the signaling system that initiates adipocyte differentiation.
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Affiliation(s)
- S Jin
- Shanghai Life Sciences Research Center, Chinese Academy of Sciences, Shanghai 200031, China
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Yingst DR, Davis J, Schiebinger R. Inhibitors of tyrosine phosphatases block angiotensin II inhibition of Na(+) pump. Eur J Pharmacol 2000; 406:49-52. [PMID: 11011032 DOI: 10.1016/s0014-2999(00)00664-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
To determine how angiotensin II inhibits the Na(+) pump (Na(+), K(+)-ATPase) in rat zona glomerulosa, we selectively blocked signaling proteins that could be activated by the angiotensin AT(1) receptor and known to affect Na(+) pump activity. Inhibitors of protein kinase C [calphostin C (1 microM); staurosporine (1 microM)], phospholipase A(2) [arachidonyl triflouromethyl ketone (25 microM); quinacrine (75 microM)], diacylgycerol lipase [RHC-80267 (5 microM)], and tyrosine phosphorylation [tyrphostin 47 (100 microM)] had no effect on angiotensin II inhibition of the Na(+) pump. On the other hand, inhibitors of tyrosine phosphatases [phenylarsine oxide (5 microM) and 4-bromotetramisole oxalate (100 microM)] blocked angiotensin II inhibition, where as inhibitors of serine/threonine phosphatases [okadaic acid (1 microM) and microcystin (1.5 microM)] did not. Thus, angiotensin II inhibition of the Na(+) pump may in part be mediated by a tyrosine phosphatase.
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Affiliation(s)
- D R Yingst
- Department of Physiology, Wayne State University School of Medicine, 540 E. Canfield Avenue, Detroit, MI 48201-1928, USA.
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Hresko RC, Mueckler M. A novel 68-kDa adipocyte protein phosphorylated on tyrosine in response to insulin and osmotic shock. J Biol Chem 2000; 275:18114-20. [PMID: 10764780 DOI: 10.1074/jbc.m001937200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Osmotic shock can cause insulin resistance in 3T3-L1 adipocytes by inhibiting insulin activation of glucose transport, p70S6 kinase, glycogen synthesis, and lipogenesis. By further investigating the relationship between insulin and hypertonic stress, we have discovered that osmotic shock enhanced by 10-fold the insulin-stimulated tyrosine phosphorylation of a 68-kDa protein. Phosphorylation by insulin was maximal after 1 min and was saturated with 50-100 nm insulin. The effect of sorbitol was completely reversible by 2.5 min. pp68 was a peripheral protein that was localized to the detergent insoluble fraction of the low density microsomes but was not associated with the cytoskeleton. Stimulation of the p42/44 and the p38 MAP kinase pathways by osmotic shock had no effect on pp68 phosphorylation. Treatment of adipocytes with the phosphotyrosine phosphatase inhibitor phenylarsine oxide also enhanced insulin-activated tyrosine phosphorylation of pp68 suggesting that osmotic shock may increase pp68 phosphorylation by inhibiting a phosphotyrosine phosphatase. Dissociation of pp68 from the low density microsomes with RNase A indicated that pp68 binds to RNA. Failure to immunoprecipitate pp68 using antibodies directed against known 60-70-kDa tyrosine-phosphorylated proteins suggest that pp68 may be a novel cellular target that lies downstream of the insulin receptor.
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Affiliation(s)
- R C Hresko
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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Gurr JR, Bau DT, Liu F, Lynn S, Jan KY. Dithiothreitol enhances arsenic trioxide-induced apoptosis in NB4 cells. Mol Pharmacol 1999; 56:102-9. [PMID: 10385689 DOI: 10.1124/mol.56.1.102] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Recently, arsenic trioxide (As2O3) was reported to induce clinical remission in patients with acute promyelocytic leukemia. Modulation of protein phosphorylation by binding to the vicinal thiols has been suggested as a possible mechanism. We found that phenylarsine oxide, a strong vicinal thiol-binding agent, neither induced nuclear fragmentation or DNA laddering nor increased caspase activity in NB4 cells; however, As2O3 and a weak thiol-binding agent, dimethylarsinic acid, did increase activity. Dithiothreitol (DTT) effectively suppressed the phenylarsine oxide-inhibited cellular reductive capacity, but unexpectedly, enhanced As2O3-induced apoptosis in NB4 cells. As2O3-induced and As2O3-plus-DTT-induced apoptosis in NB4 cells was modulated by oxidant modifiers, but not by nitric oxide synthase inhibitors. These results demonstrate that DTT, a dithiol agent and known antidote for trivalent inorganic arsenic, enhances the toxicity of As2O3, thereby opening a new research direction for the mechanisms of arsenic toxicity and perhaps also helping in the development of new therapeutic strategies for treating leukemias.
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Affiliation(s)
- J R Gurr
- Institute of Zoology, Academia Sinica, Taipei, Republic of China
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19
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Ponnappan U, Trebilcock GU, Zheng MZ. Studies into the effect of tyrosine phosphatase inhibitor phenylarsine oxide on NFkappaB activation in T lymphocytes during aging: evidence for altered IkappaB-alpha phosphorylation and degradation. Exp Gerontol 1999; 34:95-107. [PMID: 10197731 DOI: 10.1016/s0531-5565(98)00059-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Nuclear Factor kappa B (NFkappaB) is a critical regulator of several genes involved in immune and inflammatory responses. Treatment of T cells with a variety of stimuli, including TNF-alpha, leads to the translocation of the active p65-50 heterodimer to the nucleus, albeit at a lower level in T cells from the elderly. We demonstrate here that pretreatment with PAO results in the inhibition of NFkappaB induction in TNF-alpha treated T cells, suggesting a role for PAO-sensitive phosphatase in the activation of the NFkappaB via this pathway in human T cells. Furthermore, it demonstrates that aging does not influence the sensitivity of this phosphatase. Treatment with DMP prior to treatment with PAO and TNF abolishes the inhibition induced by PAO, in T cells from both young and old donors, alike. Finally, we demonstrate that a failure to degrade IkappaB-alpha in cytosols of TNF-treated T cells pretreated with PAO is due to its interference with the phosphorylation of IkappaB-alpha and not due to its inhibitory effect on proteasomal degradation. These data collectively suggest that PAO interferes with the phosphorylation and the regulated degradation of IkappaB-alpha, induced by TNF, without affecting the chymotryptic activity of the proteasome, independent of age.
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Affiliation(s)
- U Ponnappan
- Department of Geriatrics, University of Arkansas for Medical Sciences and GRECC, John L. McClellan Memorial Hospital, VA Medical Research, Little Rock 72205, USA.
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20
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Vecchi M, Rudolph-Owen LA, Brown CL, Dempsey PJ, Carpenter G. Tyrosine phosphorylation and proteolysis. Pervanadate-induced, metalloprotease-dependent cleavage of the ErbB-4 receptor and amphiregulin. J Biol Chem 1998; 273:20589-95. [PMID: 9685416 DOI: 10.1074/jbc.273.32.20589] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Enhancement of tyrosine phosphorylation in cells by the application of pervanadate, an extremely potent phosphotyrosine phosphatase inhibitor, provokes the rapid metalloprotease-dependent cleavage of ErbB-4, a transmembrane receptor tyrosine kinase. The pervanadate-induced proteolysis occurs in NIH 3T3 cells expressing transfected human ErbB-4 and in several cell lines that express endogenous ErbB-4. One product of this proteolytic event is a membrane-anchored molecule of approximately 80 kDa, which is heavily tyrosine phosphorylated and which possesses tyrosine kinase catalytic activity toward an exogenous substrate in vitro. This response to pervanadate is not dependent on protein kinase C activation, which has previously been demonstrated to also activate ErbB-4 cleavage. Hence, the pervanadate and 12-O-tetradecanoylphorbol-13-acetate-induced proteolytic cleavage of ErbB-4 seem to proceed by different mechanisms, although both require metalloprotease activity. Moreover, pervanadate activation of ErbB-4 cleavage, but not that of 12-O-tetradecanoylphorbol-13-acetate , is blocked by the oxygen radical scavenger pyrrolidine dithiocarbomate. A second phosphotyrosine phosphatase inhibitor, phenylarsine oxide, also stimulates a similar cleavage of ErbB-4 but, unlike pervanadate, is not sensitive to pyrrolidine dithiocarbomate. Last, pervanadate is shown to stimulate the proteolytic cell surface processing of a second and unrelated transmembrane molecule: the precursor for amphiregulin, an epidermal growth factor-related molecule. Amphiregulin cleavage by pervanadate occurred in the absence of a cytoplasmic domain and tyrosine phosphorylation of this substrate.
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Affiliation(s)
- M Vecchi
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA
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21
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Natarajan V, Scribner WM, Vepa S. Phosphatase inhibitors potentiate 4-hydroxynonenal-induced phospholipase D activation in vascular endothelial cells. Am J Respir Cell Mol Biol 1997; 17:251-9. [PMID: 9271314 DOI: 10.1165/ajrcmb.17.2.2623] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
We have previously reported that endothelial cell phospholipase D (PLD), activated by 4-hydroxynonenal (4-HNE), was independent of protein kinase C activation. To determine whether PLD stimulation by 4-HNE is related to protein tyrosine phosphorylation, the effects of tyrosine kinase (Tyrk) and protein tyrosine phosphatase (PTPase) inhibitors on PLD activation were investigated. Pretreatment of bovine pulmonary artery endothelial cells (BPAEC) with Tyrk inhibitors, such as genistein, erbstatin, and herbimycin attenuated 4-HNE-induced PLD activation. Furthermore, vanadate, phenylarsine oxide, and diamide, inhibitors of PTPases, markedly increased the 4-HNE-induced PLD activation. The effects of Tyrk and PTPase inhibitors were specific towards the 4-HNE, as these agents had no effect on the agonist- or TPA-induced PLD activation. In addition to PLD activation, treatment of BPAEC with 4-HNE increased tyrosine phosphorylation of proteins including bands of molecular weights 40,000-60,000, 70,000-90,000, and 110,000-130,000. The 4-HNE-mediated increase in protein tyrosine phosphorylation was partly inhibited by genistein (100 microM). Vanadate (10 microM) pretreatment also potentiated 4-HNE-induced protein tyrosine phosphorylation. These data suggest that 4-HNE-mediated stimulation of PLD may occur as a result of activation of tyrosine kinases.
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Affiliation(s)
- V Natarajan
- Department of Medicine, Indiana University School of Medicine, Indianapolis 46202, USA
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22
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Huyer G, Liu S, Kelly J, Moffat J, Payette P, Kennedy B, Tsaprailis G, Gresser MJ, Ramachandran C. Mechanism of inhibition of protein-tyrosine phosphatases by vanadate and pervanadate. J Biol Chem 1997; 272:843-51. [PMID: 8995372 DOI: 10.1074/jbc.272.2.843] [Citation(s) in RCA: 647] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Vanadate and pervanadate (the complexes of vanadate with hydrogen peroxide) are two commonly used general protein-tyrosine phosphatase (PTP) inhibitors. These compounds also have insulin-mimetic properties, an observation that has generated a great deal of interest and study. Since a careful kinetic study of the two inhibitors has been lacking, we sought to analyze their mechanisms of inhibition. Our results show that vanadate is a competitive inhibitor for the protein-tyrosine phosphatase PTP1B, with a Ki of 0.38+/-0.02 microM. EDTA, which is known to chelate vanadate, causes an immediate and complete reversal of the inhibition due to vanadate when added to an enzyme assay. Pervanadate, by contrast, inhibits by irreversibly oxidizing the catalytic cysteine of PTP1B, as determined by mass spectrometry. Reducing agents such as dithiothreitol that are used in PTP assays to keep the catalytic cysteine reduced and active were found to convert pervanadate rapidly to vanadate. Under certain conditions, slow time-dependent inactivation by vanadate was observed; since catalase blocked this inactivation, it was ascribed to in situ generation of hydrogen peroxide and subsequent formation of pervanadate. Implications for the use of these compounds as inhibitors and rationalization for some of their in vivo effects are considered.
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Affiliation(s)
- G Huyer
- Department of Biochemistry and Molecular Biology, Merck Frosst Centre for Therapeutic Research, Kirkland, Quebec, Canada
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23
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Rozsnyay Z, Sarmay G, Zoller M, Gergely J. Membrane-bound ezrin is involved in B-cell receptor-mediated signaling: potential role of an ITAM-like ezrin motif. Immunol Lett 1996; 54:163-9. [PMID: 9052872 DOI: 10.1016/s0165-2478(96)02667-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Ezrin is a cytoskeleton-plasma membrane linker molecule which is implicated in the T-cell antigen receptor signaling as one of the major tyrosine phosphorylated components. Its function in B-lymphocyte activation has not yet been clarified. Here we studied the potential involvement of ezrin in the B-cell receptor (BCR) signaling in BL41 Burkitt lymphoma cells. Our data demonstrate that ezrin, which shows predominantly cytosolic distribution in unstimulated cells, undergoes only a moderate tyrosine phosphorylation in response to BCR triggering, with no concomitant translocation of the protein from the cytosol to the plasma membrane. Instead, BCR-independent stimulants like oxidant stress induced by phenylarsine oxide, resulted in rapid redistribution of ezrin to the plasma membrane. When BCR triggering was preceded by membrane recruitment of ezrin, it became one of the main and earliest substrates of tyrosine kinases activated by BCR. No detectable influence on distribution or phosphorylation of ezrin was triggered by the tyrosine phosphatase inhibition by orthovanadate, suggesting that these effects of phenylarsine oxide are not attributable to its tyrosine phosphatase inhibitory capacity. The notion that BCR-mediated phosphorylation of ezrin negatively correlates with activation events such as phosphorylation of tyrosine kinase, syk and induction of calcium mobilization response, suggests that ezrin might be implicated in the regulation of transmembrane signaling and cellular responsiveness. As will be discussed, the regulatory function of ezrin may be due to an immunoreceptor tyrosine-based activation motif (ITAM)-like sequence.
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Affiliation(s)
- Z Rozsnyay
- Department of Immunoregulation, Vienna International Research Cooperation Center at Sandoz Research Institute, Austria.
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24
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Meili R, Ballmer-Hofer K. Activation-independent nuclear translocation of mitogen activated protein kinase ERK1 mediated by thiol-modifying chemicals. FEBS Lett 1996; 394:34-8. [PMID: 8925922 DOI: 10.1016/0014-5793(96)00927-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The extracellular signal-regulated kinases ERK1 and ERK2 are key mediators of mitogenic signals in most cell types. In fibroblasts, sustained activation and nuclear translocation are mandatory for S-phase induction. The events leading to activation of these kinases are well understood, whereas little is known about the mechanism of their translocation. Using indirect immunofluorescence and biochemical analysis we show that ERK1 can translocate to the nucleus in the absence of activation and phosphorylation by upstream kinases when cells are treated with thiol-modifying chemicals. We propose that these chemicals inactivate a protein contributing to the cytoplasmic localization of ERK1.
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Affiliation(s)
- R Meili
- Friedrich Miescher Institute, Basel, Switzerland
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25
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Rusciano D, Lorenzoni P, Burger MM. Constitutive activation of c-Met in liver metastatic B16 melanoma cells depends on both substrate adhesion and cell density and is regulated by a cytosolic tyrosine phosphatase activity. J Biol Chem 1996; 271:20763-9. [PMID: 8702829 DOI: 10.1074/jbc.271.34.20763] [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: 02/01/2023] Open
Abstract
Serial selection in vivo for liver colonization of B16 murine melanoma cells consistently resulted in cell lines expressing elevated amounts of the hepatocyte growth factor/scatter factor receptor (c-Met), which is constitutively activated in the absence of its cognate ligand. In this paper we present evidence suggesting that c-Met constitutive activation in liver-specific B16 melanoma cells depends on both receptor concentration on the cell surface and a cytosolic tyrosine phosphatase activity. In fact, c-Met constitutive activation is suddenly lost upon detachment of the cells from the substrate and is dramatically decreased in adherent cells plated at low density. The loss of tyrosine phosphorylation of c-Met in suspension appears to depend, at least partly, on an increased cytosolic tyrosine phosphatase activity. Instead, lower activation of c-Met at low density mostly results from a decrease in receptor concentration on the membrane. Moreover, we show that c-Met activation does not occur homogeneously on the surface of adherent cells. In fact, receptor concentration and activation appear to be higher on the ventral surface (adherent to the substrate) than on the apical surface. Upon detachment, compartmentalization is lost, leading to a decrease in average receptor density on the plasma membrane and hence to a lower activation.
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Affiliation(s)
- D Rusciano
- Friedrich Miescher Institut, P. O. Box 2543, CH-4002 Basel, Switzerland
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26
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Kumada T, Nakashima S, Nakamura Y, Miyata H, Nozawa Y. Phenylarsine oxide (PAO)-mediated activation of phospholipase D in rat basophilic leukemia (RBL-2H3) cells: possible involvement of calcium and protein kinase C. Immunobiology 1996; 195:347-59. [PMID: 8877408 DOI: 10.1016/s0171-2985(96)80051-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Addition of phenylarsine oxide (PAO) to [3H]oleic acid-labeled rat basophilic leukemia (RBL-2H3) cells gave rise to the remarkable formation of [3H]phosphatidylbutanol (PBut), a specific product of phospholipase D (PLD) activation. Preincubation of cells with 2,3-dimercaptopropanol (DMP) or dithiothreitol (DTT), compounds containing sulfhydryls, prevented PAO-stimulated [3H]PBut formation, indicating that PAO-stimulated PLD through interacting with vicinal thiol groups. Treatment of cells with PAO resulted in increase in intracellular Ca2+ concentration without significant production of inositol phosphates. Removal of extracellular free Ca2+ by chelating with EGTA was found to inhibit [3H]PBut formation by PAO. Incubation of cells with 20 nM phorbol 12-myristate 13-acetate (PMA) for 6 h caused down-regulation of protein kinase C (PKC) alpha and beta isozymes, whereas it had no effect on PKC delta, epsilon and zeta isozymes. Under this condition, decrease in PAO-stimulated [3H]PBut formation was observed to occur with a concomitant decrease in the level of PKC alpha and beta isozymes. These results suggest that a covalent bridge between vicinal thiol groups of cell surface proteins induced by PAO potentiates PLD activation and that PAO-induced PLD activation is regulated by Ca2+ and PKC alpha and/or beta isozymes.
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Affiliation(s)
- T Kumada
- Department of Otolaryngology, Gifu University School of Medicine, Japan
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27
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Li J, Elberg G, Shechter Y. Phenylarsine oxide and vanadate: apparent paradox of inhibition of protein phosphotyrosine phosphatases in rat adipocytes. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1312:223-30. [PMID: 8703991 DOI: 10.1016/0167-4889(96)00038-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Vanadate mimics, whereas phenylarsine oxide (PAO) antagonizes, the effects of insulin in rat adipocytes. Both vanadate and PAO are documented inhibitors of protein-phosphotyrosine phosphatases. The relationship between the inhibition of 'inhibitory' PTPase and 'stimulatory' PTPase has been studied here in primary rat adipocytes. Low concentrations of PAO (IC50 = 0.6-2.0 microM) blocked the stimulating effects of insulin, vanadate and pervanadate on hexose uptake and glucose metabolism. Inhibition of isoproterenol-mediating lipolysis by vanadate and insulin was not blocked by PAO. The activating effects of okadaic acid on hexose uptake and glucose metabolism, which occur at points downstream to tyrosine phosphorylation, were also not blocked by PAO. Subsequent studies suggested that the PAO-sensitive PTPase comprises a minute fraction of the total adipocytic PTPase activity. To identify its location we applied procedures involving fractionations and activation of non-receptor adipocytic protein tyrosine kinase by PAO and vanadate in cell free assays. We found that the 'inhibitory' PTPase is exclusively associated with the membrane fraction whereas the 'stimulatory' PTPases are present in both the cytosolic and plasma membrane compartments. We next searched for markers, possibly associated with PAO-dependent desensitization and found that several proteins became phosphorylated on tyrosine moieties in the supernatant of PAO but not in vanadate pretreated adipocytes. In summary, we propose the presence of a minute, plasma membrane associated PTPase in primary rat adipocytes, inhibition of which arrests the activation of glucose metabolism. In contrast, inhibition of all the other cellular adipose PTPases, ultimately activates rather than inhibits these same bioeffects.
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Affiliation(s)
- J Li
- Department of Biochemistry, Weizmann Institute of Science, Rehovot, Israel
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28
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Blanquet PR, Croquet F. Activation of phosphotyrosine phosphatase activity is associated with decreased differentiation in adult bovine lens. J Cell Physiol 1995; 165:358-66. [PMID: 7593214 DOI: 10.1002/jcp.1041650217] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The postnatal vertebrate eye lens provides an opportunity to study possible involvement of reversible protein phosphorylation in the differentiation process of epithelial cells. Epithelial cells at the lens equator, indeed, differentiate continuously into fiber cells throughout life but this capacity progressively decreases with age. Here we describe the characterization of a phosphotyrosine-protein phosphatase(s) (PTPase(s)) in the equatorial epithelium of bovine lens which exhibits a high level of specific activity. PTPase(s) is detected in cellular detergent extracts using phospholabeled synthetic peptides, p-nitrophenyl phosphate, and lens epithelial membranes as substrates. We show that activity of this PTPase(s) is increased in the equatorial epithelium as the age is increased. We also show that this enzyme(s) exerts its dephosphorylating activity predominantly on a calpactin-like protein associated with lens epithelial membranes. Dephosphorylation of this protein is only obtained when membranes are subjected to extracts in the presence of fibroblast growth factor (FGF). It is suggested that an FGF-activated PTPase(s) might conceivably counteract effects of differentiation stimulatory factors for limiting differentiation of lens throughout life.
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Affiliation(s)
- P R Blanquet
- Unité de Recherches Gérontologiques, INSERM U118, affiliée CNRS, Association Claude Bernard, Paris, France
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29
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Liao K, Lane MD. The blockade of preadipocyte differentiation by protein-tyrosine phosphatase HA2 is reversed by vanadate. J Biol Chem 1995; 270:12123-32. [PMID: 7744861 DOI: 10.1074/jbc.270.20.12123] [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: 01/26/2023] Open
Abstract
A tyrosine phosphatase, i.e. PTPase HA2, was previously isolated from 3T3-L1 cells and characterized using O-phospho Tyrosine19-422/aP2 protein (a target of the insulin receptor tyrosine kinase) as substrate. The nucleotide sequence of a PTPase HA2 cDNA showed it to be a homologue of PTPase 1B. When induced to differentiate into adipocytes, confluent 3T3-L1 preadipocytes undergo mitotic clonal expansion followed by growth arrest and then coordinate expression of adipocyte genes. During clonal expansion, expression of PTPase HA2 increases abruptly and then decreases concomitant with the transcriptional activation of adipocyte genes. Constitutive expression of the PTPase by 3T3-L1 preadipocytes using a PTPase HA2 expression vector prevents adipocyte gene expression and differentiation into adipocytes. Appropriately timed exposure of transfected preadipocytes to vanadate (a PTPase inhibitor), just as clonal expansion ceases restores their capacity to differentiate. Treatment of transfected preadipocytes with vanadate prior to or during clonal expansion fails to reverse PTPase HA2-blocked differentiation, whereas treatment of untransfected preadipocytes during mitotic clonal expansion blocks differentiation. Vanadate added following clonal expansion has no effect on differentiation. Thus, a critical tyrosine phosphorylation event(s) occurs between termination of clonal expansion and initiation of adipocyte gene expression while a critical tyrosine dephosphorylation event(s) occurs during clonal expansion.
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Affiliation(s)
- K Liao
- Department of Biological Chemistry, Johns Hopkins University, School of Medicine, Baltimore, Maryland 21205, USA
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30
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Le Cabec V, Maridonneau-Parini I. Complete and reversible inhibition of NADPH oxidase in human neutrophils by phenylarsine oxide at a step distal to membrane translocation of the enzyme subunits. J Biol Chem 1995; 270:2067-73. [PMID: 7530716 DOI: 10.1074/jbc.270.5.2067] [Citation(s) in RCA: 77] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The effects of the trivalent arsenical phenylarsine oxide (PAO) on the activity of NADPH oxidase in human neutrophils were studied. PAO caused a rapid dose-dependent inhibition of superoxide generation which was maximal at a concentration of 1 microM, irrespective of the stimulating agent. This inhibitory effect was not due to impaired transduction of activation signals since neither degranulation nor phagocytosis were modified. When cytosolic and membrane fractions from resting neutrophils were combined to reconstitute the NADPH oxidase, O2-. generation was inhibited by PAO while translocation of the NADPH oxidase components to the plasma membrane fraction was not affected. The inhibition was completely and specifically reversed by 2,3-dimercaptopropanol, not by dithiothreitol or beta-mercaptoethanol, indicating that PAO binds covalently to spatially vicinal thiol groups. PAO inhibited the plasma membrane's capacity to initiate O2-. generation while it apparently did not affect the cytosol. When PAO was added subsequently to NADPH oxidase activation, no inhibition was observed, indicating that PAO cannot reach its target once the oxidase is functionally assembled. In conclusion, PAO is the first complete and reversible inhibitor of NADPH oxidase which could provide the basis for new therapeutical approaches in inflammatory diseases.
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Affiliation(s)
- V Le Cabec
- Centre National de la Recherche Scientifique, UPR 8221, Toulouse, France
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31
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Rozsnyay Z, Sarmay G, Gergely J. Rapid desensitization of B-cell receptor by a dithiol-reactive protein tyrosine phosphatase inhibitor: uncoupling of membrane IgM from syk inhibits signals leading to Ca2+ mobilization. Immunol Lett 1995; 44:149-56. [PMID: 7541023 DOI: 10.1016/0165-2478(94)00207-8] [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: 01/25/2023]
Abstract
B-cell antigen receptor (BCR)-mediated calcium response can be blocked by phenylarsine oxide (PAO), a dithiol group-reactive protein tyrosine phosphatase inhibitor. We have examined the mechanism of this inhibition in BL41 Burkitt lymphoma cells. PAO-dependent inhibition is not restricted to the BCR-mediated functions, as evidenced by the failure of the same cells to mobilize Ca2+ in response to CD19 cross-linking. In contrast, calcium response induced by a putative syk activator, H2O2, exhibited only a moderate sensitivity to PAO, demonstrating that PAO did not cause general suppression of all the functions leading to Ca2+ mobilization. BCR cross-linking or H2O2 treatment leads to the induction of almost complete non-responsiveness for the reciprocal stimulation. Since BCR cross-linking did not generate non-responsiveness to H2O2 in the presence of PAO, and PAO-treated cells remained responsive to syk activation by H2O2, we suppose that PAO may inhibit BCR-mediated signal transduction events upstream of syk activation. This assumption was supported by additional data, indicating that PAO was able to modulate functions of at least 2 different protein tyrosine kinase enzymes involved in BCR-mediated signaling. PAO induced rapid and dose-dependent tyrosine phosphorylation of lyn and selectively inhibited BCR-mediated tyrosine phosphorylation of syk. The results presented in this paper demonstrate that PAO may provoke cellular desensitization process by alteration of the signal transducer functions of lyn and syk tyrosine kinase enzymes.
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Affiliation(s)
- Z Rozsnyay
- Laboratory of Immunoregulation, VIRCC, Sandoz Research Institute, Vienna, Austria
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32
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Oustrin ML, Belenguer P, Leroy D, Hoffmann I, Ducommun B. Effect of phenylarsine oxide on the fission yeast Schizosaccharomyces pombe cell cycle. Biochimie 1995; 77:279-87. [PMID: 8589058 DOI: 10.1016/0300-9084(96)88137-5] [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: 01/31/2023]
Abstract
Phosphotyrosyl turnover is an essential regulatory mechanism for many biological processes, and the balance between tyrosine kinases and phosphatases plays a major role in the control of cell proliferation. Phenylarsine oxide (PAO), a potent inhibitor of tyrosine phosphatases (PTPase), was used to investigate the involvement of PTPase in the growth and control of the cell cycle of the fission yeast Schizosaccharomyces pombe. Cell proliferation was arrested by treatment with PAO, which was found to inhibit cdc25 PTPase in vitro but appeared not to act in vivo on this mitosis inducer. The PAO-treated cells displayed a mono- or binucleated phenotype and a DNA content that was either 2C or 4C, indicating a cell cycle arrest with a failure to complete cytokinesis. Entry into the cell division cycle from the G0 quiescent stage was also delayed by treatment with PAO. These results suggest that a number of key events in the mitotic cell cycle are regulated by as yet unidentified PTPases.
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Affiliation(s)
- M L Oustrin
- CNRS, Laboratoire de Pharmacologie et de Toxicologie Foundamentales, Toulouse, France
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33
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Greenwalt DE, Tandon NN. Platelet shape change and Ca2+ mobilization induced by collagen, but not thrombin or ADP, are inhibited by phenylarsine oxide. Br J Haematol 1994; 88:830-8. [PMID: 7819106 DOI: 10.1111/j.1365-2141.1994.tb05124.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
In this report we have examined the effects of the protein tyrosine phosphatase inhibitor phenylarsine oxide (PAO) on receptor-mediated platelet shape change, secretion and aggregation. PAO was found to inhibit platelet aggregation induced by collagen, thrombin, ADP and epinephrine at IC50 values of 0.35 mumol/l, 2.5 mumol/l, 0.2 mumol/l and 0.3 mumol/l, respectively. Agonist-induced secretion of ATP was inhibited at similar or lower concentrations of PAO. The specificity of the interaction of PAO with platelet proteins was demonstrated by the ability of the disulfhydryl compound 2,3-dimercaptopropanol, which abstracts PAO from proteins to form a stable cyclic adduct, to reverse PAO inhibition of both agonist-induced platelet secretion and aggregation. Dimercaptopropanesulphonic acid, a membrane-impermeable analogue of dimercaptopropanol, did not reverse inhibition of collagen-induced shape change or aggregation by PAO, thereby demonstrating that PAO acted intracellularly. PAO inhibited collagen-induced shape change and internal Ca2+ mobilization but had no effect on these two phenomena when induced by thrombin or ADP. PAO was also unable to prevent arachidonic acid-induced shape change, indicating that PAO acts at a site prior to the phospholipase A2-mediated release of arachidonic acid to inhibit collagen-induced shape change. PAO induced the accumulation of a number of phosphotyrosine-containing proteins and inhibited the collagen-induced phosphorylation of a 40 kD protein. The potency and agonist-specific effects of PAO on platelet activation suggest that this inhibitor will be of value in elucidation of signal transduction pathways involved in receptor-mediated platelet function.
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Affiliation(s)
- D E Greenwalt
- American Red Cross, Holland Laboratory, Rockville, Maryland 20855
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34
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Chrzanowska-Wodnicka M, Burridge K. Tyrosine phosphorylation is involved in reorganization of the actin cytoskeleton in response to serum or LPA stimulation. J Cell Sci 1994; 107 ( Pt 12):3643-54. [PMID: 7706413 DOI: 10.1242/jcs.107.12.3643] [Citation(s) in RCA: 97] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Tyrosine phosphorylation is known to regulate the formation of focal adhesions in cells adhering to extracellular matrix (ECM). We have investigated the possible involvement of tyrosine phosphorylation and the focal adhesion kinase (FAK) in the cytoskeletal changes induced by serum or lysophosphatidic acid (LPA) in quiescent Swiss 3T3 fibroblasts. As shown previously by others, quiescent cells stimulated with serum or LPA reveal a rapid reappearance of focal adhesions and stress fibers. Here we show that this is accompanied by an increase in phosphotyrosine in focal adhesions and specifically an increase in the tyrosine phosphorylation of FAK. The LPA-stimulated reappearance of focal adhesions and stress fibers is blocked by inhibitors of phospholipase C but not by pertussis toxin (PTX), indicating that this LPA signaling pathway is mediated by phospholipase C activation and does not involve PTX-sensitive G proteins. In the absence of serum or LPA, these cytoskeletal effects and the tyrosine phosphorylation of FAK can be mimicked by sodium orthovanadate in conjunction with hydrogen peroxide, agents that inhibit protein tyrosine phosphatases and thereby elevate levels of phosphotyrosine. Two tyrosine kinase inhibitors, erbstatin and genistein block both the serum-induced tyrosine phosphorylation of FAK and the assembly of focal adhesions and stress fibers. Two other tyrosine kinase inhibitors, tyrphostins 47 and 25, previously shown to inhibit FAK, failed to prevent FAK phosphorylation or the reassembly of focal adhesions and stress fibers in response to serum. However, these inhibitors did prevent FAK phosphorylation and cytoskeletal assembly in response to lysophosphatidic acid (LPA), one component of serum previously shown to stimulate assembly of focal adhesions and stress fibers. Our findings suggest that the response to serum is complex and that although FAK phosphorylation is important, other tyrosine kinases may also be involved.
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Affiliation(s)
- M Chrzanowska-Wodnicka
- Department of Cell Biology and Anatomy, University of North Carolina, Chapel Hill 27599-7090
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35
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Mei L, Liao K, Huganir RL. Characterization of substrate specificity of the protein tyrosine phosphatase purified from the electric organ of Torpedo californica. Neurosci Lett 1994; 182:21-4. [PMID: 7891879 DOI: 10.1016/0304-3940(94)90195-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The nicotinic receptor is highly phosphorylated on tyrosine residues both in vivo and in vitro. Tyrosine phosphorylation has been shown to regulate the functional properties of the receptor. We have purified a protein tyrosine phosphatase from the electric organ of Torpedo californica that dephosphorylates the nicotinic receptor. The unique biochemical properties of the purified enzyme suggest that it may be a novel phosphotyrosine protein phosphatase. In this report, substrate specificity of the protein purified from T. californica was characterized using four different tyrosine-phosphorylated substrate proteins. In addition to the nicotinic receptor, the Torpedo phosphatase dephosphorylated insulin receptor and Reduced Carboxamidomethylated and Meleylated lysozyme (RCM lysozyme), however, at a rate much slower than for the nicotinic receptor. In contrast, it appeared to have no effect on the phosphotyrosine level of pp15, a fatty acid binding protein (O-phospho-tyr19-422/aP2) phosphorylated by insulin receptor kinase in 3T3-L1 adipocytes. Interestingly, a protein tyrosine phosphatase (HA1) purified from adipocyte dephosphorylated both nicotinic receptor and pp15 at a similar rate. These results suggest that the Torpedo protein tyrosine phosphatase is relatively specific for the nicotinic receptor.
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Affiliation(s)
- L Mei
- Department of Neuroscience, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205-2185
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36
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Berti A, Rigacci S, Raugei G, Degl'Innocenti D, Ramponi G. Inhibition of cellular response to platelet-derived growth factor by low M(r) phosphotyrosine protein phosphatase overexpression. FEBS Lett 1994; 349:7-12. [PMID: 7519150 DOI: 10.1016/0014-5793(94)00620-2] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The role of low M(r) phosphotyrosine protein phosphatase (PTPase) in the control of cell proliferation was studied. A synthetic gene coding for PTPase was transfected and expressed in NIH/3T3 fibroblasts. The effects of the enzyme were particularly evident when cells were stimulated by platelet-derived growth factor (PDGF). The mitogenic response to PDGF was decreased and the inhibition reached 90%. This effect was more pronounced with respect to fetal calf serum stimulation. Hormone-dependent autophosphorylation of the PDGF receptor was significantly reduced. These results demonstrate that low M(r) PTPase, a cytosolic enzyme, not only affects cellular response to PDGF but also reduces the membrane receptor autophosphorylation.
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Affiliation(s)
- A Berti
- Dipartimento di Scienze Biochimiche, Università di Firenze, Florence, Italy
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37
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Begum N. Phenylarsine oxide inhibits insulin-stimulated protein phosphatase 1 activity and GLUT-4 translocation. THE AMERICAN JOURNAL OF PHYSIOLOGY 1994; 267:E14-23. [PMID: 8048502 DOI: 10.1152/ajpendo.1994.267.1.e14] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Phenylarsine oxide (PAO) has previously been shown to inhibit insulin-stimulated glucose transport without affecting insulin binding and tyrosine kinase activity of insulin receptor (S. C. Frost and M. D. Lane. J. Biol. Chem. 260: 2646-2652, 1985). This study examines the effect of PAO on insulin's ability to activate adipocyte protein phosphatase 1 (PP-1) and dephosphorylate GLUT-4, the insulin-sensitive glucose transporter. In particulate fractions, insulin stimulated PP-1 activity (40% increase over basal with phosphorylase a) in a time- and dose-dependent manner (half-maximal effect of 0.89 nM in 1 min). Insulin did not alter cytosolic PP-1 activity. With GLUT-4 as a substrate, insulin caused more than twofold stimulation of particulate PP-1 activity. Addition of PAO (5 microM) before or after insulin treatment abolished insulin's effect on PP-1 activation. The presence of 2,3-dimercaptopropanol (200 microM) prevented the effect of PAO on PP-1 activation and glucose uptake. In addition, PAO significantly increased GLUT-4 phosphorylation, blocked insulin-stimulated dephosphorylation, and partially diminished insulin-stimulated translocation of GLUT-4. We conclude that PAO may interfere with the components of insulin signal transduction pathways that lead to the activation of PP-1 and this may be responsible for the observed inhibition in insulin action.
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Affiliation(s)
- N Begum
- Diabetes Research Laboratory, Winthrop University Hospital, Mineola 11501
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38
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Schaefer T, Wiedemann C, Gitler C, Burger MM. Effects of arsenicals on the secretory process in chromaffin cells. Ann N Y Acad Sci 1994; 710:356-67. [PMID: 8154761 DOI: 10.1111/j.1749-6632.1994.tb26642.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- T Schaefer
- Friedrich Miescher Institute, Basel, Switzerland
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39
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Gitler C, Mogyoros M, Kalef E. Labeling of protein vicinal dithiols: role of protein-S2 to protein-(SH)2 conversion in metabolic regulation and oxidative stress. Methods Enzymol 1994; 233:403-15. [PMID: 8015476 DOI: 10.1016/s0076-6879(94)33047-6] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- C Gitler
- Department of Membrane Research and Biophysics, Weizmann Institute of Science, Rehovot, Israel
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40
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Veerkamp JH, van Kuppevelt TH, Maatman RG, Prinsen CF. Structural and functional aspects of cytosolic fatty acid-binding proteins. Prostaglandins Leukot Essent Fatty Acids 1993; 49:887-906. [PMID: 8140117 DOI: 10.1016/0952-3278(93)90174-u] [Citation(s) in RCA: 93] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- J H Veerkamp
- Department of Biochemistry, University of Nijmegen, The Netherlands
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41
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Kenner KA, Hill DE, Olefsky JM, Kusari J. Regulation of protein tyrosine phosphatases by insulin and insulin-like growth factor I. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(19)74413-5] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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42
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Fischer Y, Rose H, Thomas J, Deuticke B, Kammermeier H. Phenylarsine oxide and hydrogen peroxide stimulate glucose transport via different pathways in isolated cardiac myocytes. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1153:97-104. [PMID: 8241256 DOI: 10.1016/0005-2736(93)90280-d] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The aim of this study was to investigate the stimulating effects of sulfhydryl reagents on glucose transport in isolated rat heart muscle cells and to compare them with the action of insulin. Low concentrations of the sulfhydryl oxidants hydrogen peroxide (H2O2) and diamide (5-100 microM), but also of phenylarsine oxide (PAO) (0.5-3 microM), that is known to specifically react with vicinal SH-groups, stimulated the rate of 2-deoxy-D-glucose uptake by a factor of 4 to 8 in these cells, while higher concentrations were inhibitory. The stimulating effects of H2O2 or diamide, and, to a significantly lesser extent, those of PAO or insulin, were depressed in cells pretreated with the sulfhydryl-alkylating agent N-ethylmaleimide (56-100 microM). H2O2 raised the Vmax and lowered the Km of 3-O-methyl-D-glucose uptake, while PAO or insulin solely increased Vmax. The increase in glucose transport caused by H2O2 was antagonized by the beta-adrenergic agonist isoprenaline (1 microM) or by a membrane-permeant cyclic AMP analog, whereas the effects of PAO or insulin were not altered. The action of H2O2 was additive with the stimulation induced by the protein phosphatase inhibitors okadaic acid (1 microM) or vanadate (6 mM), whereas the responses to PAO or insulin were reduced in the presence of these agents. Finally, H2O2 and PAO, but not insulin, acted additively with the protein kinase C ligand phorbol myristate acetate (0.8 microM) and with phospholipase C (0.03 units/ml). We conclude that, in cardiac myocytes, H2O2, on the one hand, and PAO (and possibly insulin), on the other hand, stimulate glucose transport via at least two distinct, SH-dependent pathways. These pathways, in turn, differ from a protein kinase C- and from a phospholipase C-mediated mechanism.
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Affiliation(s)
- Y Fischer
- Institute of Physiology, Medical Faculty RWTH, Aachen, Germany
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43
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Fletcher M, Samelson L, June C. Complex effects of phenylarsine oxide in T cells. Induction of tyrosine phosphorylation and calcium mobilization independent of CD45 expression. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(19)49517-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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44
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Quentmeier A, Klein H, Unthan-Fechner K, Probst I. Attenuation of insulin actions in primary rat hepatocyte cultures by phenylarsine oxide. BIOLOGICAL CHEMISTRY HOPPE-SEYLER 1993; 374:965-71. [PMID: 8297499 DOI: 10.1515/bchm3.1993.374.7-12.965] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Phenylarsine oxide (PAO), a trivalent arsenical which complexes vicinal dithiols, prevented the action of insulin in primary cultured adult rat hepatocytes. Simultaneous short-term treatment of 48-h old cells with insulin and 2 microM PAO resulted in complete attenuation of the insulin-dependent increase in the level of fructose 2,6-bisphosphate and the activation of phosphofructokinase 2, pyruvate kinase, glucokinase flux and glycolysis. Basal rates of glucose transport and glycolysis were not affected. PAO also abolished stimulation of glycogen synthesis and amino-acid transport and the decrease of glycogenolysis evoked by insulin. The 20-fold activation of the insulin receptor tyrosine kinase by insulin was, however, not reduced by PAO. The data suggest that in differentiated hepatocytes insulin signal transduction involves vicinal sulhydryls located at a post-receptor step.
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Affiliation(s)
- A Quentmeier
- Institut für Biochemie, Fachbereich Medizin, Georg-August-Universität Göttingen
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45
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Rozsnyay Z, Sarmay G, Gergely J. Phenylarsine oxide (PAO) blocks antigen receptor-induced calcium response and tyrosine phosphorylation of a distinct group of proteins. Immunol Lett 1993; 37:197-205. [PMID: 8258460 DOI: 10.1016/0165-2478(93)90031-v] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Antigen receptor (AgR) crosslinking by antigens or AgR-specific antibodies induces a cascade of enzymatic events in lymphocytes which involves activation of several non-receptor tyrosine- and serine/threonine kinases, phosphatases, phospholipases, etc. Here we show data demonstrating that a thiol group-reactive protein tyrosine phosphatase (PTP) inhibitor, phenylarsine oxide (PAO), uncouples a crucial part of the signaling events induced by anti-IgM or anti-Leu-4 (CD3) in human tonsil B lymphocytes, BL41 and Daudi B cell lines and Jurkat T lymphoma cells. PAO treatment (10 microM) resulting in distinct modification of AgR-induced tyrosine phosphorylation pattern inhibited the AgR-mediated calcium response (Ca++ release and influx) of all of these cells completely. Since this treatment did not alter the cell viability and the binding capacity of the AgR crosslinking antibodies, alteration of the tyrosine phosphorylation pattern and blockage of the calcium response indicate prompt inactivation of essential signal transduction element(s).
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Affiliation(s)
- Z Rozsnyay
- Laboratory of Immunoregulation, Vienna International Research Cooperation Center at SFI, Austria
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46
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Donella-Deana A, Ostojić S, Pinna LA, Barbarić S. Specific dephosphorylation of phosphopeptides by the yeast alkaline phosphatase encoded by PHO8 gene. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1177:221-8. [PMID: 8499492 DOI: 10.1016/0167-4889(93)90044-p] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Partially purified nonspecific phosphate-repressible alkaline phosphatase from Saccharomyces cerevisiae encoded by PHO8 gene (rALPase), efficiently dephosphorylates phosphohistones and a variety of phosphopeptides. The pho8 mutant, constructed by disruption of the chromosomal counterpart of the PHO8 gene, is lacking in phosphatase activity toward phosphopeptides, confirming that this activity is actually due to rALPase. rALPase activity tested on phosphopeptides is maximum in the pH range 6.5-7.5 and the Km values for these substrates are in the micromolar range, suggesting a possible physiological relevance of this enzyme as a protein phosphatase. rALPase dephosphorylates phosphotyrosyl more efficiently than phosphoseryl peptides, but is poorly active on phosphothreonyl peptides. Its specificity towards synthetic peptides and insensitivity to specific inhibitors and activators of authentic protein phosphatases indicate that rALPase differs from both Ser/Thr- and Tyr-specific protein phosphatases. This conclusion is consistent with the lack of homology with any class of known protein phosphatases.
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Affiliation(s)
- A Donella-Deana
- Dipartimento di Chimica Biologica, Università di Padova, Italy
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47
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Panneerselvam K, Balasubramanian AS. Stimulation by lysosomal enzymes and mannose-6-phosphate of a phosphoprotein phosphatase activity associated with the lysosomal enzyme binding receptor protein from monkey brain. Cell Signal 1993; 5:269-77. [PMID: 8394096 DOI: 10.1016/0898-6568(93)90017-g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Previously we have isolated a lysosomal enzyme binding receptor protein from monkey brain that exhibits protein kinase activity and undergoes phosphorylation on serine and tyrosine residues. Using the 32P-labelled receptor protein, we have found that the lysosomal enzyme fucosidase and mannose-6-phosphate, which are ligands for the receptor, stimulated a protein phosphatase activity associated with the receptor protein. Stimulation of protein phosphatase activity using the 32P-labelled receptor protein was demonstrated both by the loss in radioactivity of the receptor and by the release of 32P-phosphate. There was no stimulation by a non-lysosomal glycoprotein enzyme, or by the sugars mannose or glucose. Both serine-phosphate and tyrosine-phosphate residues were dephosphorylated. Stimulation of protein phosphatase activity by fucosidase and mannose-6-phosphate was also demonstrated using as substrate histone 32P-labelled, on serine/threonine or tyrosine residues. Insulin-like growth factor II, another known ligand for the lysosomal enzyme binding receptor, did not show any significant effect, either on the phosphorylation or dephosphorylation of the receptor protein. Our previous and present results suggest that a phosphorylation/dephosphorylation mechanism may be operative in the ligand binding and functions of the receptor.
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Affiliation(s)
- K Panneerselvam
- Department of Neurological Sciences, Christian Medical College Hospital, Vellore, India
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48
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Najjar S, Accili D, Philippe N, Jernberg J, Margolis R, Taylor S. pp120/ecto-ATPase, an endogenous substrate of the insulin receptor tyrosine kinase, is expressed as two variably spliced isoforms. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)54060-6] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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49
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Pronk G, Medema R, Burgering B, Clark R, McCormick F, Bos J. Interaction between the p21ras GTPase activating protein and the insulin receptor. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)35945-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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50
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Hecht D, Zick Y. Selective inhibition of protein tyrosine phosphatase activities by H2O2 and vanadate in vitro. Biochem Biophys Res Commun 1992; 188:773-9. [PMID: 1445322 DOI: 10.1016/0006-291x(92)91123-8] [Citation(s) in RCA: 215] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Acute (10-30 min) treatment of intact rat hepatoma (Fao) cells with H2O2, inhibits in vivo protein tyrosine phosphatase activity. Vanadate markedly potentiates this effect although it has only trivial effects of its own. Here we show that H2O2 inhibits a protein tyrosine phosphatase activity, but not a p-nitro phenyl phosphate hydrolysing activity, in cytosolic extracts of these cells. This effect is completely reversed by 10 mM dithiothreitol. Other oxidants have similar inhibitory effects. Vanadate inhibits the protein tyrosine phosphatase activity in vitro, and its effects are additive with those of H2O2. These findings suggest that H2O2 and vanadate interact with the protein tyrosine phosphatases at two independent sites. They also suggest that in intact cells H2O2 has a direct inhibitory effect on protein tyrosine phosphatase activity and an indirect effect of facilitating the entry of vanadate.
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Affiliation(s)
- D Hecht
- Department of Chemical Immunology, Weizmann Institute of Science, Rehovot, Israel
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