Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0002871 (anemia)
 52,094 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The function of viral protein 2 (VP2) of the immunosuppressive circovirus chicken anemia virus (CAV) has not yet been established. We show that the CAV VP2 amino acid sequence has some similarity to a number of eukaryotic, receptor, protein-tyrosine phosphatase (PTPase) alpha proteins as well as to a cluster of human TT viruses within the Sanban group. To investigate if CAV VP2 functions as a PTPase, purified glutathione S-transferase (GST)-VP2 fusion protein was assayed for PTPase activity using the generalized peptide substrates ENDpYINASL and DADEpYLIPQQG (where pY represents phosphotyrosine), with free phosphate detected using the malachite green colorimetric assay. CAV GST-VP2 was shown to catalyze dephosphorylation of both substrates. CAV GST-VP2 PTPase activity for the ENDpYINASL substrate had a V(max) of 14,925 units/mg.min and a K(m) of 18.88 microm. Optimal activity was observed between pH 6 and 7, and activity was specifically inhibited by 0.01 mm orthovanadate. We also show that the ORF2 sequence of the CAV-related human virus TT-like minivirus (TLMV) possessed PTPase activity and steady state kinetics equivalent to CAV GST-VP2 when expressed as a GST fusion protein. To establish whether these viral proteins were dual specificity protein phosphatases, the CAV GST-VP2 and TLMV GST-ORF2 fusion proteins were also assayed for serine/threonine phosphatase (S/T PPase) activity using the generalized peptide substrate RRApTVA, with free phosphate detected using the malachite green colorimetric assay. Both CAV GST-VP2 and TLMV GST-ORF2 fusion proteins possessed S/T PPase activity, which was specifically inhibited by 50 mm sodium fluoride. CAV GST-VP2 exhibited S/T PPase activity with a V(max) of 28,600 units/mg.min and a K(m) of 76 microm. Mutagenesis of residue Cys(95) to serine in CAV GST-VP2 abrogated both PTPase and S/T PPase activity, identifying it as the catalytic cysteine within the proposed signature motif. These studies thus show that the circoviruses CAV and TLMV encode dual specificity protein phosphatases (DSP) with an unusual signature motif that may play a role in intracellular signaling during viral replication. This is the first DSP gene to be identified in a small viral genome.
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PMID:Chicken anemia virus VP2 is a novel dual specificity protein phosphatase. 1215 84

Infectious salmon anaemia virus (ISAV) infects cells via the endocytic pathway and, like many other enveloped viruses, ISAV contains a receptor-destroying enzyme. We have analysed this acetylesterase activity with respect to substrate specificity, enzyme kinetics, inhibitors, temperature and pH stability. The ISAV acetylesterase was inhibited by di-isopropyl fluorophosphate (DFP) in a dose-dependent fashion but not by other known hydrolase inhibitors, suggesting that a serine residue is part of the active site. The pH optimum of the enzyme was in the range 7.5-8.0 and the enzymatic activity was lessened at temperatures above 40 degrees C. The effect of DFP on agglutination/elution of erythrocytes by ISAV demonstrated that the acetylesterase activity is the bona fide receptor-destroying enzyme. A haemadsorption assay was used to analyse whether the esterase was active on the surface of infected cells or not.
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PMID:Characterization of the receptor-destroying enzyme activity from infectious salmon anaemia virus. 1238 4

Infectious salmon anemia virus (ISAV) is an unclassified Orthomyxovirus that has been shown to contain a segmented genome with eight single-stranded RNA species coding for 10 viral proteins. Four major structural proteins were characterized in the present study: two glycosylated proteins with estimated molecular masses of 42 and 50 kDa, one 66-kDa phosphoprotein, and one 22-kDa protein. Examination of lysed virions revealed the two glycoproteins and the 22-kDa protein in the soluble fraction, while the 66-kDa phosphoprotein and a minor part of the 22-kDa protein were found in the pelleted fraction. Immunofluorescence staining of infected cells demonstrated that the 22-kDa protein was a late protein accumulating in the nucleus. We conclude that the 66-kDa protein is the nucleoprotein, the 22-kDa protein is the matrix protein, and the 42- and 50-kDa proteins are the surface proteins. Radioimmunoprecipitation analysis of the 42-kDa glycoprotein, which was previously shown to represent the ISAV hemagglutinin, indicated that this protein exists at least as dimers. Further, by labeling of purified ISAV with [1,3-(3)H]diisopropyl fluorophosphate, it was also demonstrated that the viral esterase is located with the hemagglutinin. This finding was confirmed by demonstration of acetylesterase activity in affinity-purified hemagglutinin preparations. Finally, the active-site serine residue could be tentatively identified at position 32 within the amino acid sequence of the hemagglutinin of ISAV strain Glesvaer/2/90. It is proposed that the ISAV vp66 protein be termed nucleoprotein, the gp42 protein be termed HE protein, and the vp22 protein be termed matrix protein.
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PMID:Identification and characterization of viral structural proteins of infectious salmon anemia virus. 1499 Jul 25

Hookworm infection is a major cause of iron deficiency anemia and malnutrition in developing countries. The Ancylostoma ceylanicum Kunitz-type inhibitor (AceKI) is a 7.9-kDa broad-spectrum inhibitor of trypsin, chymotrypsin, and pancreatic elastase that has previously been isolated from adult hookworms. Site-directed mutagenesis of the predicted P1 inhibitory reactive site amino acid confirmed the role of Met(26) in mediating inhibition of the three target serine proteases. By using reverse transcription-PCR, it was demonstrated that the level of AceKI gene expression increased following activation of third-stage larvae with serum and that the highest level of expression was reached in the adult stage of the parasite. Immunohistochemistry studies performed with polyclonal immunoglobulin G raised against recombinant AceKI showed that the inhibitor localized to the subcuticle of the adult hookworm, suggesting that it has a potential in vivo role in neutralizing intestinal proteases at the surface of the parasite. Immunization with recombinant AceKI was shown to confer partial protection against hookworm-associated growth delay without a measurable effect on anemia. Taken together, the data suggest that AceKI plays a role in the pathogenesis of hookworm-associated malnutrition and growth delay, perhaps through inhibition of nutrient absorption in infected hosts.
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PMID:Molecular characterization of Ancylostoma ceylanicum Kunitz-type serine protease inhibitor: evidence for a role in hookworm-associated growth delay. 1503 45

We describe a novel missense mutation of ceruloplasmin in a patient with aceruloplasminaemia causing the replacement of a neutral amino acid (phenylalanine) with a polar one (serine) at position 198, probably leading to abnormal folding and secretion of the protein. The patient showed mild microcytic anaemia, mild hepatic iron overload, and marked brain iron overload. Six months of therapy with deferiprone was ineffective in removing iron from the tissues. Deferoxamine was more efficient in removing excess iron from the liver but aggravated the disease related anaemia. After more than one year of chelation treatment, the brain magnetic resonance imaging signal did not change. Overall, these findings indicate that treatment of iron overload in aceruloplasminaemia is a difficult challenge and that new iron chelators, more efficient in crossing the blood-brain barrier, are needed.
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PMID:Iron chelation therapy in aceruloplasminaemia: study of a patient with a novel missense mutation. 1508 97

The Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway is an essential cascade for mediating normal functions of different cytokines in the development of the hematopoietic and immune systems. Chronic exposure to arsenic has been found to cause immunotoxicity and has been associated with the suppression of hematopoiesis (anemia and leukopenia). Here, we report the novel finding of arsenic-mediated inactivation of the JAK-STAT signaling pathway by its direct interaction with JAK tyrosine kinase. Pretreatment with sodium arsenite strongly inhibited IL-6-inducible STAT3 tyrosine phosphorylation in HepG2 cells and did not affect its serine phosphorylation. As a result, sodium arsenite completely abolished STAT activity-dependent expression of suppressors of cytokine signaling (SOCS). Both cellular and subcelluar experiments showed that the inhibition of JAK-STAT signaling resulted from JAK tyrosine kinase's direct interaction with arsenite, and that arsenic's suppression of JAK tyrosine kinase activity also occurred in the interferon gamma (IFNgamma) pathway. The ligand-independent inhibition by arsenic indicates that JAK was the direct target of arsenic action. Other inflammatory stimulants, stress agents, and metal cadmium failed to induce similar effects on the tyrosine phosphorylation of STAT3 as arsenic does. Our experiments also revealed that arsenic inactivation of the JAK-STAT pathway occurred independent of arsenic activation of MAP kinases. Taken together, our findings indicate that arsenic directly inhibits JAK tyrosine kinase activity and suggest that this direct interference in the JAK-STAT pathway may play a role in arsenic-associated pathogenesis.
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PMID:Arsenic inhibition of the JAK-STAT pathway. 1511 95

Insulin resistance is a characteristic feature of obesity and type 2 diabetes mellitus, but it is also present in up to 25% of healthy nonobese individuals. The molecular mechanisms causing insulin resistance are not yet fully understood. Recently, overexpression of several potential inhibitors of the insulin receptor tyrosine-kinase activity, a key step in insulin signaling, has been described in insulin-resistant subjects . PC-1 is expressed in many tissues and inhibits insulin signaling either at the level of the insulin receptor or downstream at a postreceptor site. An elevated PC-1 content in insulin target tissues may play an important role in the development of insulin resistance in obesity and type 2 diabetes mellitus. A polymorphism in PC-1 has been demonstrated to be associated with insulin resistance. This was a DNA polymorphism in exon 4 that causes an amino acid change from lysine to glutamine at codon 121 (K121Q). PC-1 121Q allele might predispose independently of other well established risk factors for early myocardial infarction. Testing for the PC-1 K121Q polymorphism might be valuable in patients with a family history of atherosclerotic vascular disease and myocardial infarction. There is growing evidence that genetic factors play an important role in the development of diabetic nephropathy (DN). Efforts to identify these factors rely primarily on the candidate gene approach; candidate genes for insulin resistance may be considered candidates for DN as well. In a stratified analysis according to duration of diabetes, the risk of early-onset end-stage renal disease (ESRD) for carriers of the Q variant was 2.3 times that for noncarriers. The cellular mechanisms for the insulin resistance of pregnancy and gestational diabetes mellitus (GDM) are unknown. Women with GDM have an increased PC-1 content and excessive phosphorylation of serine/threonine residues in muscle insulin receptors. The postreceptor defects in insulin signaling may contribute to the pathogenesis of GDM and the increased risk for type 2 diabetes later in life. Although widely explored, the true cause of insulin resistance in uremic patients is not entirely elucidated yet. During the last decade it was found that erythropoietin (EPO) therapy, used for correction of anemia in patients with end stage renal failure, ameliorates insulin resistance. An increased lymphocyte PC-1 activity over control was found in hemodialysis patients. A two-month EPO therapy significantly decreased PC-1 activity to the control values, suggesting that an effect on PC-1 expression could be implicated in the amelioration of insulin resistance in uremic patients treated with EPO. Current investigations implicate that therapeutic modification of PC-1 expression would be of great benefit for insulin-resistant type 2 diabetics. Metformin, a biguanide oral antidiabetic agent, was shown to affect insulin resistance by decreasing enzymatic activity of overexpressed PC-1 molecules in obese type 2 diabetics. Thiazolidinedione (TZD) insulin-sensitizing drugs are a class of compounds that improve insulin action in vivo. Treatment of patients with TZDs seems to have a beneficial effect on most, if not all, components of metabolic syndrome. TZDs have also been used in the treatment of nondiabetic human insulin-resistant states, and have demonstrated an improvement in insulin sensitivity. Although much remains to be learned about PPAR gamma receptor and TZD action, the advent of TZD insulin-sensitizing agents has an enormous impact on our understanding of insulin resistance. The great potential of insulin resistance therapy illuminated by the TZDs will continue to catalyze research in this area directed toward the discovery of new insulin-sensitizing agents that work through other mechanisms.
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PMID:Plasma cell membrane glycoprotein 1 (PC-1): a marker of insulin resistance in obesity, uremia and diabetes mellitus. 1520 35

Fanconi anemia (FA) is an autosomal recessive disease of cancer susceptibility. FA cells exhibit a characteristic hypersensitivity to DNA cross-linking agents. The molecular mechanism for the disease is unknown as few of the FA proteins have functional motifs. Several post-translational modifications of the proteins have been described. We and others have reported that the FANCG protein (Fanconi complementation group G) is phosphorylated. We show that in an in vitro kinase reaction FANCG is radioactively labeled. Mass spectrometry analysis detected a peptide containing phosphorylation of serine 7. Using PCR-mediated site-directed mutagenesis we mutated serine 7 to alanine. Only wild-type FANCG cDNA fully corrected FA-G mutant cells. We also tested the effect of human wild-type FANCG in Chinese hamster ovary cells in which the FANCG homologue is mutant. Human FANCG complemented these cells, whereas human FANCG(S7A) did not. Unexpectedly, FANCG(S7A) bound to and stabilized the endogenous forms of the FANCA and FANCC proteins in the FA-G cells. FANCG(S7A) aberrantly localized to globules in chromatin and did not abrogate the internuclear bridges seen in the FA-G mutant cells. Phosphorylation of serine 7 in FANCG is functionally important in the FA pathway.
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PMID:Phosphorylation of fanconi anemia (FA) complementation group G protein, FANCG, at serine 7 is important for function of the FA pathway. 1529 17

Fanconi anemia (FA) is an autosomal recessive disease marked by congenital defects, bone marrow failure, and high incidence of leukemia and solid tumors. Eight genes have been cloned, with the accompanying protein products participating in at least two complexes, which appear to be functionally dependent upon one another. Previous studies have described chromatin localization of the FA core complex, except at mitosis, which is associated with phosphorylation of the FANCG protein (F. Qiao, A. Moss, and G. M. Kupfer, J. Biol. Chem. 276:23391-23396, 2001). The phosphorylation of FANCG at serine 7 by using mass spectrometry was previously mapped. The purpose of this study was to map the phosphorylation sites of FANCG at mitosis and to assess their functional importance. Reasoning that a potential kinase might be cdc2, which was previously reported to bind to FANCC, we showed that cdc2 chiefly phosphorylated a 14-kDa fragment of the C-terminal half of FANCG. Mass spectrometry analysis demonstrated that this fragment contains amino acids 374 to 504. Kinase motif analysis demonstrated that three amino acids in this fragment were leading candidates for phosphorylation. By using PCR-directed in vitro mutagenesis we mutated S383, S387, and T487 to alanine. Mutation of S383 and S387 abolished the phosphorylation of FANCG at mitosis. These results were confirmed by use of phosphospecific antibodies directed against phosphoserine 383 and phosphoserine 387. Furthermore, the ability to correct FA-G mutant cells of human or hamster (where S383 and S387 are conserved) origin was also impaired by these mutations, demonstrating the functional importance of these amino acids. S387A mutant abolished FANCG fusion protein phosphorylation by cdc2. The FA pathway, of which FANCG is a part, is highly regulated by a series of phosphorylation steps that are important to its overall function.
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PMID:FANCG is phosphorylated at serines 383 and 387 during mitosis. 1536 77

The aim of the study was to investigate, whether (a) patients with homozygous sickle cell disease (SCD, HbSS) have abnormal blood fatty acids; (b) the abnormality, if it exists, affects all the plasma and erythrocyte lipids or it is restricted to a particular lipid moiety; (c) there is an association between levels of membrane n-3 or n-6 long-chain polyunsaturated fatty acids (LCPUFA) and the degree of anaemia. Fatty acids of erythrocyte choline (CPG), serine (SPG) and ethanolamine (EPG) phosphoglycerides and sphingomyelin (SPM); and plasma CPG, triglycerides and cholesterol esters of 43 steady-state HbSS patients and 43 ethnically matched, healthy, HbAA controls were analysed. The levels of the n-6 LCPUFA, arachidonic (AA), adrenic and docosapentaenoic acids in erythrocyte CPG (P<0.001) and EPG (P<0.01) were higher in the patients compared with the controls. In contrast, the proportions of eicosapentaenoic acid (EPA) in CPG and EPG (P<0.001) and docosahexaenoic acid (DHA) and total n-3 metabolites in CPG (P<0.001) were lower in the patients. The steady-state haemoglobin level of the patients correlated with erythrocyte DHA (r=0.55, P<0.01), EPA (r=0.38, P<0.05) and total n-3 metabolites (r=0.51, P<0.001) in CPG. Also, it correlated with erythrocyte EPA (r=0.64, P<0.01) and total n-3 metabolites (r=0.42, P<0.01) in EPG. The study revealed an imbalance between n-3 and n-6 LCPUFA in erythrocyte and plasma lipid moieties of the HbSS group. Furthermore, it suggested that correction of the imbalance by supplementation with EPA and DHA could ameliorate anaemia in the patients. This observation is consistent with the results of pilot studies, which demonstrated that treatment with n-3 fatty acids confers clinical benefit to sickle cell patients.
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PMID:Steady-state haemoglobin level in sickle cell anaemia increases with an increase in erythrocyte membrane n-3 fatty acids. 1587 28


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