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Ronca F, Raggi A. Role of the interaction between troponin T and AMP deaminase by zinc bridge in modulating muscle contraction and ammonia production. Mol Cell Biochem 2024; 479:793-809. [PMID: 37184757 PMCID: PMC11016001 DOI: 10.1007/s11010-023-04763-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Accepted: 05/06/2023] [Indexed: 05/16/2023]
Abstract
The N-terminal region of troponin T (TnT) does not bind any protein of the contractile machinery and the role of its hypervariability remains uncertain. In this review we report the evidence of the interaction between TnT and AMP deaminase (AMPD), a regulated zinc enzyme localized on the myofibril. In periods of intense muscular activity, a decrease in the ATP/ADP ratio, together with a decrease in the tissue pH, is the stimulus for the activation of the enzyme that deaminating AMP to IMP and NH3 displaces the myokinase reaction towards the formation of ATP. In skeletal muscle subjected to strong tetanic contractions, a calpain-like proteolytic activity produces the removal in vivo of a 97-residue N-terminal fragment from the enzyme that becomes desensitized towards the inhibition by ATP, leading to an unrestrained production of NH3. When a 95-residue N-terminal fragment is removed from AMPD by trypsin, simulating in vitro the calpain action, rabbit fast TnT or its phosphorylated 50-residue N-terminal peptide binds AMPD restoring the inhibition by ATP. Taking in consideration that the N-terminus of TnT expressed in human as well as rabbit white muscle contains a zinc-binding motif, we suggest that TnT might mimic the regulatory action of the inhibitory N-terminal domain of AMPD due to the presence of a zinc ion connecting the N-terminal and C-terminal regions of the enzyme, indicating that the two proteins might physiologically associate to modulate muscle contraction and ammonia production in fast-twitching muscle under strenuous conditions.
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Affiliation(s)
- Francesca Ronca
- Laboratory of Biochemistry, Department of Pathology, University of Pisa, Via Roma 55, 56126, Pisa, Italy.
| | - Antonio Raggi
- Laboratory of Biochemistry, Department of Pathology, University of Pisa, Via Roma 55, 56126, Pisa, Italy
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2
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Ronca F, Raggi A. Regulation of skeletal muscle AMP deaminase. Carbethoxylation of His-51 belonging to the zinc coordination sphere of the rabbit enzyme promotes its desensitization towards the inhibition by ATP. Biochim Biophys Acta Gen Subj 2021; 1866:130044. [PMID: 34710488 DOI: 10.1016/j.bbagen.2021.130044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Revised: 10/03/2021] [Accepted: 10/21/2021] [Indexed: 11/17/2022]
Abstract
BACKGROUND Skeletal muscle AMP deaminase (AMPD1) regulates the concentration of adenine nucleotides during muscle contraction. We previously provided evidence that rabbit AMPD1 is composed by two HPRG 73 kDa subunits and two 85 kDa catalytic subunits with a dinuclear zinc site with an average of two histidine residues at each metal site. AMPD1 is mainly expressed in fast twitching fibers and is inhibited by ATP. The limited trypsinization of the 95-residue N-terminal domain of rabbit AMPD1 desensitizes the enzyme towards ATP inhibition at the optimal pH 6.5, but not at pH 7.1. METHODS The modified residues of rabbit AMPD1 after incubation with radioactive diethyl pyrocarbonate ([14C]DEP) causing the desensitization to inhibition by ATP at pH 7.1 have been identified by sequence analysis and MS analysis of the radioactive peptides liberated from the carbethoxylated enzyme by limited proteolysis with trypsin. RESULTS The study confirms the presence of a dinuclear zinc site in rabbit AMPD1 and shows that carbethoxylation of His-51 at the N-terminus of the catalytic subunit removes the inhibition of the enzyme by ATP at pH 7.1. CONCLUSIONS The desensitization to ATP is due to the modification of His-51 of the Zn2 coordination sphere which is transduced in a conformational change of the enzyme C-terminus, where an ATP-binding site has been localized. GENERAL SIGNIFICANCE The progress in the study of the complex regulation of rabbit AMPD1 that shares an identical amino acid sequence with the human enzyme is important in relation to the role of the enzyme during mammalian evolution.
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Affiliation(s)
- Francesca Ronca
- Laboratory of Biochemistry, Department of Pathology, University of Pisa, via Roma 55, 56126 Pisa, Italy.
| | - Antonio Raggi
- Laboratory of Biochemistry, Department of Pathology, University of Pisa, via Roma 55, 56126 Pisa, Italy.
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3
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Mattii L, Bianchi F, Falleni A, Frascarelli S, Masini M, Alì G, Chiellini G, Sabbatini ARM. Ultrastructural Localization of Histidine-rich Glycoprotein in Skeletal Muscle Fibers: Colocalization With AMP Deaminase. J Histochem Cytochem 2019; 68:139-148. [PMID: 31880188 DOI: 10.1369/0022155419897573] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Histidine-rich glycoprotein (HRG) is a plasma protein synthesized by the liver. We have given the first evidence of a tissue localization of HRG demonstrating its presence in skeletal muscle, associated with the zinc enzyme AMP deaminase (AMPD1). Moreover, we have shown that muscle cells do not synthesize HRG, but they can internalize it from plasma. We have recently demonstrated by confocal laser scanning microscopy that in human skeletal muscle, HRG is mainly localized in the myofibrils, preferentially at the I-band of the sarcomere, in the sarcoplasm, and in the nuclei. Using transmission electron microscopy and immunogold analysis, we carried out this study on human and rat normal skeletal muscles with the purpose to deepen the ultrastructural localization of HRG in skeletal muscle fibers. The immunogold analysis evidenced the presence of HRG in the sarcomeres, mainly in the I-band and to a less extent in the A-band, in the heterochromatin of nuclei, and in the sarcoplasmic reticulum. The colocalization of HRG and skeletal muscle AMPD1 was also analyzed. A colabeling of HRG and AMPD1 was evident at sarcomeric, sarcoplasmic reticulum, and nuclear levels. The significance of these interesting and new results is discussed in this article.
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Affiliation(s)
- Letizia Mattii
- Dipartimento di Medicina Clinica e Sperimentale, Università di Pisa, Pisa, Italy.,Nutrafood, Centro Interdipartimentale di Ricerca Nutraceutica e Alimentazione per la salute, Pisa, Italy
| | - Francesco Bianchi
- Dipartimento di Medicina Clinica e Sperimentale, Università di Pisa, Pisa, Italy
| | - Alessandra Falleni
- Dipartimento di Medicina Clinica e Sperimentale, Università di Pisa, Pisa, Italy
| | - Sabina Frascarelli
- Dipartimento di Patologia Chirurgica, Medica, Molecolare e dell'Area Critica, Università di Pisa, Pisa, Italy
| | - Matilde Masini
- Dipartimento di Ricerca Traslazionale e delle Nuove Tecnologie in Medicina e Chirurgia, Università di Pisa, Pisa, Italy
| | - Greta Alì
- U.O. Anatomia Patologica III, Azienda Ospedaliero Universitaria Pisana, Pisa, Italy
| | - Grazia Chiellini
- Dipartimento di Patologia Chirurgica, Medica, Molecolare e dell'Area Critica, Università di Pisa, Pisa, Italy
| | - Antonietta R M Sabbatini
- Dipartimento di Patologia Chirurgica, Medica, Molecolare e dell'Area Critica, Università di Pisa, Pisa, Italy
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4
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Nagappa LK, Singh D, Dey S, Kumar KA, Balaram H. Biochemical and physiological investigations on adenosine 5' monophosphate deaminase from Plasmodium spp. Mol Microbiol 2019; 112:699-717. [PMID: 31132185 DOI: 10.1111/mmi.14313] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/22/2019] [Indexed: 11/29/2022]
Abstract
The interplay between ATP generating and utilizing pathways in a cell is responsible for maintaining cellular ATP/energy homeostasis that is reflected by Adenylate Energy Charge (AEC) ratio. Adenylate kinase (AK), that catalyzes inter-conversion of ADP, ATP and AMP, plays a major role in maintaining AEC and is regulated by cellular AMP levels. Hence, the enzymes AMP deaminase (AMPD) and nucleotidases, which catabolize AMP, indirectly regulate AK activity and in-turn affect AEC. Here, we present the first report on AMPD from Plasmodium, the causative agent of malaria. The recombinant enzyme expressed in Saccharomyces cerevisiae was studied using functional complementation assay and residues vital for enzyme activity have been identified. Similarities and differences between Plasmodium falciparum AMPD (PfAMPD) and its homologs from yeast, Arabidopsis and humans are also discussed. The AMPD gene was deleted in the murine malaria parasite P. berghei and was found to be dispensable during all stages of the parasite life cycle. However, when episomal expression was attempted, viable parasites were not obtained, suggesting that perturbing AMP homeostasis by over-expressing AMPD might be lethal. As AMPD is known to be allosterically modulated by ATP, GTP and phosphate, allosteric activators of PfAMPD could be developed as anti-parasitic agents.
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Affiliation(s)
- Lakshmeesha Kempaiah Nagappa
- Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Bengaluru, India
| | - Dipti Singh
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Sandeep Dey
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Kota Arun Kumar
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Hemalatha Balaram
- Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Bengaluru, India
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5
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Role of the HPRG Component of Striated Muscle AMP Deaminase in the Stability and Cellular Behaviour of the Enzyme. Biomolecules 2018; 8:biom8030079. [PMID: 30142952 PMCID: PMC6164516 DOI: 10.3390/biom8030079] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Revised: 08/13/2018] [Accepted: 08/20/2018] [Indexed: 11/16/2022] Open
Abstract
Multiple muscle-specific isoforms of the Zn2+ metalloenzyme AMP deaminase (AMPD) have been identified based on their biochemical and genetic differences. Our previous observations suggested that the metal binding protein histidine-proline-rich glycoprotein (HPRG) participates in the assembly and maintenance of skeletal muscle AMP deaminase (AMPD1) by acting as a zinc chaperone. The evidence of a role of millimolar-strength phosphate in stabilizing the AMPD-HPRG complex of both AMPD1 and cardiac AMP deaminase (AMPD3) is suggestive of a physiological mutual dependence between the two subunit components with regard to the stability of the two isoforms of striated muscle AMPD. The observed influence of the HPRG content on the catalytic behavior of the two enzymes further strengthens this hypothesis. Based on the preferential localization of HPRG at the sarcomeric I-band and on the presence of a Zn2+ binding motif in the N-terminal regions of fast TnT and of the AMPD1 catalytic subunit, we advance the hypothesis that the Zn binding properties of HPRG could promote the association of AMPD1 to the thin filament.
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6
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Immunohistochemical localization of histidine-rich glycoprotein in human skeletal muscle: preferential distribution of the protein at the sarcomeric I-band. Histochem Cell Biol 2017; 148:651-657. [PMID: 28702782 DOI: 10.1007/s00418-017-1594-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/06/2017] [Indexed: 10/19/2022]
Abstract
Histidine-rich glycoprotein (HRG) is a relatively abundant plasma protein that is synthesized by parenchymal liver cells. Using Western blot analysis and immunoperoxidase techniques, we have previously shown the presence of HRG in human skeletal muscle. This paper reports the results of immunofluorescence experiments carried out on sections of human normal skeletal muscle biopsies to investigate the subcellular localization of HRG. The HRG localization was also compared with that of skeletal muscle AMP deaminase (AMPD1), since we have previously described an association of the enzyme with the protein. The obtained results give evidence for a preferential localization of HRG at the I-band level, where it shows the same distribution of actin and where AMPD1 is present in major concentration.
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Philpott CC, Ryu MS, Frey A, Patel S. Cytosolic iron chaperones: Proteins delivering iron cofactors in the cytosol of mammalian cells. J Biol Chem 2017; 292:12764-12771. [PMID: 28615454 DOI: 10.1074/jbc.r117.791962] [Citation(s) in RCA: 88] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Eukaryotic cells contain hundreds of metalloproteins that are supported by intracellular systems coordinating the uptake and distribution of metal cofactors. Iron cofactors include heme, iron-sulfur clusters, and simple iron ions. Poly(rC)-binding proteins are multifunctional adaptors that serve as iron ion chaperones in the cytosolic/nuclear compartment, binding iron at import and delivering it to enzymes, for storage (ferritin) and export (ferroportin). Ferritin iron is mobilized by autophagy through the cargo receptor, nuclear co-activator 4. The monothiol glutaredoxin Glrx3 and BolA2 function as a [2Fe-2S] chaperone complex. These proteins form a core system of cytosolic iron cofactor chaperones in mammalian cells.
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Affiliation(s)
- Caroline C Philpott
- Genetics and Metabolism Section, Liver Diseases Branch, NIDDK, National Institutes of Health, Bethesda, Maryland 20892.
| | - Moon-Suhn Ryu
- Department of Food Science and Nutrition, University of Minnesota, St. Paul, Minnesota 55108
| | | | - Sarju Patel
- Genetics and Metabolism Section, Liver Diseases Branch, NIDDK, National Institutes of Health, Bethesda, Maryland 20892
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Ronca F, Raggi A. Role of troponin T and AMP deaminase in the modulation of skeletal muscle contraction. RENDICONTI LINCEI 2016. [DOI: 10.1007/s12210-016-0586-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Ronca F, Raggi A. Structure-function relationships in mammalian histidine-proline-rich glycoprotein. Biochimie 2015; 118:207-20. [PMID: 26409900 DOI: 10.1016/j.biochi.2015.09.024] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Accepted: 09/22/2015] [Indexed: 02/01/2023]
Abstract
Histidine-proline-rich glycoprotein (HPRG), or histidine-rich glycoprotein (HRG), is a serum protein that is synthesized in the liver and is actively internalised by different cells, including skeletal muscle. The multidomain arrangement of HPRG comprises two modules at the N-terminus that are homologous to cystatin but void of cysteine proteinase inhibitor function, and a second half consisting of a histidine-proline-rich region (HPRR) located between two proline-rich regions (PRR1 and PRR2), and a C-terminus domain. HPRG has been reported to bind various ligands and to modulate angiogenesis via the histidine residues of the HPRR. However, the secondary structure prediction of the HPRR reveals that more than 98% is disordered and the structural basis of the hypothesized functions remains unclear. Comparison of the PRR1 of several mammalian species indicates the presence of a conserved binding site that might coordinate the Zn(2+) ion with an amino acid arrangement compatible with the cysteine-containing site that has been identified experimentally for rabbit HPRG. This observation provides a structural basis to the function of HPRG as an intracellular zinc chaperone which has been suggested by the involvement of the protein in the maintenance of the quaternary structure of skeletal muscle AMP deaminase (AMPD). During Anthropoidea evolution, a change of the primary structure of the PRR1 Zn(2+) binding site took place, giving rise to the sequence M-S-C-S/L-S/R-C that resembles the MxCxxC motif characteristic of metal transporters and metallochaperones.
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Affiliation(s)
- Francesca Ronca
- Laboratory of Biochemistry, Department of Pathology, University of Pisa, Via Roma 55, 56126 Pisa, Italy
| | - Antonio Raggi
- Laboratory of Biochemistry, Department of Pathology, University of Pisa, Via Roma 55, 56126 Pisa, Italy.
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10
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Tierney DL, Schenk G. X-ray absorption spectroscopy of dinuclear metallohydrolases. Biophys J 2015; 107:1263-72. [PMID: 25229134 DOI: 10.1016/j.bpj.2014.07.066] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Revised: 06/14/2014] [Accepted: 07/24/2014] [Indexed: 12/26/2022] Open
Abstract
In this mini-review, we briefly discuss the physical origin of x-ray absorption spectroscopy (XAS) before illustrating its application using dinuclear metallohydrolases as exemplary systems. The systems we have selected for illustrative purposes present a challenging problem for XAS, one that is ideal to demonstrate the potential of this methodology for structure/function studies of metalloenzymes in general. When the metal ion is redox active, XAS provides a sensitive measure of oxidation-state-dependent differences. When the metal ion is zinc, XAS is the only spectroscopic method that will provide easily accessible structural information in solution. In the case of heterodimetallic sites, XAS has the unique ability to interrogate each metal site independently in the same sample. One of the strongest advantages of XAS is its ability to examine metal ion site structures with crystallographic precision, without the need for a crystal. This is key for studying flexible metal ion sites, such as those described in the selected examples, because it allows one to monitor structural changes that occur during substrate turnover.
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Affiliation(s)
- David L Tierney
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio.
| | - Gerhard Schenk
- School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, Queensland, Australia
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11
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Ranieri-Raggi M, Moir AJG, Raggi A. The role of histidine-proline-rich glycoprotein as zinc chaperone for skeletal muscle AMP deaminase. Biomolecules 2014; 4:474-97. [PMID: 24970226 PMCID: PMC4101493 DOI: 10.3390/biom4020474] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Revised: 04/08/2014] [Accepted: 04/10/2014] [Indexed: 11/19/2022] Open
Abstract
Metallochaperones function as intracellular shuttles for metal ions. At present, no evidence for the existence of any eukaryotic zinc-chaperone has been provided although metallochaperones could be critical for the physiological functions of Zn2+ metalloenzymes. We propose that the complex formed in skeletal muscle by the Zn2+ metalloenzyme AMP deaminase (AMPD) and the metal binding protein histidine-proline-rich glycoprotein (HPRG) acts in this manner. HPRG is a major plasma protein. Recent investigations have reported that skeletal muscle cells do not synthesize HPRG but instead actively internalize plasma HPRG. X-ray absorption spectroscopy (XAS) performed on fresh preparations of rabbit skeletal muscle AMPD provided evidence for a dinuclear zinc site in the enzyme compatible with a (μ-aqua)(μ-carboxylato)dizinc(II) core with two histidine residues at each metal site. XAS on HPRG isolated from the AMPD complex showed that zinc is bound to the protein in a dinuclear cluster where each Zn2+ ion is coordinated by three histidine and one heavier ligand, likely sulfur from cysteine. We describe the existence in mammalian HPRG of a specific zinc binding site distinct from the His-Pro-rich region. The participation of HPRG in the assembly and maintenance of skeletal muscle AMPD by acting as a zinc chaperone is also demonstrated.
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Affiliation(s)
- Maria Ranieri-Raggi
- Laboratory of Biochemistry, Department of Pathology, University of Pisa, via Roma 55, Pisa 56126, Italy.
| | - Arthur J G Moir
- Department of Molecular Biology and Biotechnology, Krebs Institute, University of Sheffield, Sheffield S10 2UH, UK.
| | - Antonio Raggi
- Laboratory of Biochemistry, Department of Pathology, University of Pisa, via Roma 55, Pisa 56126, Italy.
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12
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La Mendola D, Magrì A, Santoro AM, Nicoletti VG, Rizzarelli E. Copper(II) interaction with peptide fragments of histidine–proline-rich glycoprotein: Speciation, stability and binding details. J Inorg Biochem 2012; 111:59-69. [DOI: 10.1016/j.jinorgbio.2012.02.027] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2011] [Revised: 02/17/2012] [Accepted: 02/20/2012] [Indexed: 12/23/2022]
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Sabbatini ARM, Mattii L, Battolla B, Polizzi E, Martini D, Ranieri-Raggi M, Moir AJG, Raggi A. Evidence that muscle cells do not express the histidine-rich glycoprotein associated with AMP deaminase but can internalise the plasma protein. Eur J Histochem 2011; 55:e6. [PMID: 21556121 PMCID: PMC3167348 DOI: 10.4081/ejh.2011.e6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2010] [Revised: 11/30/2010] [Accepted: 01/12/2011] [Indexed: 11/25/2022] Open
Abstract
Histidine-rich glycoprotein (HRG) is synthesized by liver and is present at relatively high concentration in the plasma of vertebrates. We have previously described the association of a HRG-like molecule to purified rabbit skeletal muscle AMP deaminase (AMPD). We also provided the first evidence for the presence of a HRG-like protein in human skeletal muscle where a positive correlation between HRG content and total determined AMPD activity has been shown. In the present paper we investigate the origin of skeletal muscle HRG. The screening of a human skeletal muscle cDNA expression library using an anti-HRG antibody failed to reveal any positive clone. The RT-PCR analysis, performed on human skeletal muscle RNA as well as on RNA from the rhabdomyosarcoma (RD) cell line, failed to show any mRNA specific for the plasma HRG or for the putative muscle variant. When the RD cells were incubated with human plasma HRG, a time-dependent increase of the HRG immunoreactivity was detected both at the plasma membrane level and intracellularly. The internalisation of HRG was inhibited by the addition of heparin. The above data strongly suggest that skeletal muscle cells do not synthesize the muscle variant of HRG but instead can actively internalise it from plasma.
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Affiliation(s)
- A R M Sabbatini
- Dipartimento di Scienze dell’Uomo edell’Ambiente, Chimica e Biochimica Medica, University of Pisa.
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14
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Dimakis N, Farooqi MJ, Garza ES, Bunker G. Zinc cysteine active sites of metalloproteins: A density functional theory and x-ray absorption fine structure study. J Chem Phys 2008; 128:115104. [DOI: 10.1063/1.2835601] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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15
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Martini D, Ranieri-Raggi M, Sabbatini ARM, Moir AJG, Polizzi E, Mangani S, Raggi A. Characterization of the metallocenter of rabbit skeletal muscle AMP deaminase. A new model for substrate interactions at a dinuclear cocatalytic Zn site. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2007; 1774:1508-18. [PMID: 17991449 DOI: 10.1016/j.bbapap.2007.10.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2007] [Revised: 09/19/2007] [Accepted: 10/03/2007] [Indexed: 11/28/2022]
Abstract
We have previously provided evidence for a dinuclear zinc site in rabbit skeletal muscle AMPD compatible with a (micro-aqua)(micro-carboxylato)dizinc(II) core with an average of two histidine residues at each metal site. XAS of the zinc binding site of the enzyme in the presence of PRN favors a model where PRN is added to the coordination sphere of one of the two zinc ions increasing its coordination number to five. The uncompetitive nature of the inhibition of AMPD by fluoride reveals that the anion probably displaces the nucleophile water molecule terminally coordinated to the catalytic Zn(1) ion at the enzyme C-terminus, following the binding of AMP at the Zn(2) ion located at N-terminus of the enzyme. Thus, the two Zn ions in the AMPD metallocenter operate together as a single catalytic unit, but have independent function, one of them (Zn(1)) acting to polarize the nucleophile water molecule, whilst the other (Zn(2)) acts transiently as a receptor for an activating substrate molecule. The addition of fluoride to AMPD also abolishes the cooperative behaviour induced in the enzyme by the inhibitory effect of ATP at acidic pH that probably resides in the competition with the substrate for an adenine nucleotide specific regulatory site located in the Zn(2) ion binding region and which is responsible for the positive homotropic cooperativity behaviour of AMPD.
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Affiliation(s)
- Daniela Martini
- Dipartimento di Scienze dell'Uomo e dell'Ambiente, Chimica e Biochimica Medica, Università di Pisa, Via Roma 55, 56126 Pisa, Italy
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16
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Mangani S, Benvenuti M, Moir AJG, Ranieri-Raggi M, Martini D, Sabbatini ARM, Raggi A. Characterization of the metallocenter of rabbit skeletal muscle AMP deaminase. Evidence for a dinuclear zinc site. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2006; 1774:312-22. [PMID: 17254852 DOI: 10.1016/j.bbapap.2006.12.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2006] [Revised: 12/06/2006] [Accepted: 12/18/2006] [Indexed: 11/29/2022]
Abstract
XAS of Zn-peptide binary and ternary complexes prepared using peptides mimicking the potential metal binding sites of rabbit skeletal muscle AMP deaminase (AMPD) strongly suggest that the region 48-61 of the enzyme contains a zinc binding site, whilst the region 360-372 of the enzyme is not able to form 1:1 complexes with zinc, in contrast with what has been suggested for the corresponding region of yeast AMPD. XAS performed on fresh preparations of rabbit skeletal muscle AMPD provides evidence for a dinuclear zinc site in the enzyme compatible with a (mu-aqua)(mu-carboxylato)dizinc(II) core with an average of two histidine residues at each metal site and a Zn-Zn distance of about 3.3 Angstrom. The data indicate that zinc is not required for HPRG/AMPD interaction, both zinc ions being bound to the catalytic subunit of the enzyme, one to the three conserved amino acid residues among those four assumed to be in contact with zinc in yeast AMPD, and the other at the N-terminal region, probably to His-52, Glu-53 and His-57. Tryptic digests of different enzyme preparations demonstrate the existence of two different protein conformations and of a zinc ion connecting the N-terminal and C-terminal regions of AMPD.
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Affiliation(s)
- Stefano Mangani
- Dipartimento di Chimica, Università di Siena, Via Aldo Moro, 53100-Siena, Italy; CERM, Università di Firenze, Via Luigi Sacconi 6, 50019 Firenze, Italy
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Sabbatini ARM, Toscano A, Aguennouz M, Martini D, Polizzi E, Ranieri-Raggi M, Moir AJG, Migliorato A, Musumeci O, Vita G, Raggi A. Immunohistochemical analysis of human skeletal muscle AMP deaminase deficiency. Evidence of a correlation between the muscle HPRG content and the level of the residual AMP deaminase activity. J Muscle Res Cell Motil 2006; 27:83-92. [PMID: 16570231 DOI: 10.1007/s10974-006-9059-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2005] [Accepted: 02/09/2006] [Indexed: 10/24/2022]
Abstract
We have previously described that, in healthy human skeletal muscle, an anti-histidine-proline-rich-glycoprotein (HPRG) antibody selectively binds to type IIB fibers that are well known to contain the highest level of AMP deaminase (AMPD) activity, suggesting an association of the HPRG-like protein to the enzyme isoform M. The present paper reports an immunohistochemical study performed on human skeletal muscle biopsies from patients with AMPD deficiency and carried out utilizing both the anti-HPRG antibody and an anti-AMPD antibody specific for the isoform M. A correlation between the muscle content of the HPRG-like protein and the level of AMPD activity was demonstrated. In the specimens from patients with Acquired AMPD deficiency the HPRG-immunoreactivity was less intense than that shown by the control subjects and was related to the residual AMPD activity. The patients affected by Primary and Coincidental AMPD deficiency, which were characterized by an absence of enzyme activity and AMPD immunoreactivity, showed the lowest HPRG immunoreactivity that was clearly detectable by Western blot analysis, but not by immunohistochemistry. The interpretation of the significance of these observations suggests a physiological mutual dependence between skeletal muscle HPRG and AMPD polypeptides with regard to their stability.
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Affiliation(s)
- Antonietta R M Sabbatini
- Dipartimento di Scienze dell'Uomo e dell'Ambiente, Chimica e Biochimica Medica, Università di Pisa, Via Roma 55, 56126 Pisa, Italy.
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Martini D, Montali U, Ranieri-Raggi M, Sabbatini ARM, Thorpe SJ, Moir AJG, Raggi A. A calpain-like proteolytic activity produces the limited cleavage at the N-terminal regulatory domain of rabbit skeletal muscle AMP deaminase: evidence of a protective molecular mechanism. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2004; 1702:191-8. [PMID: 15488771 DOI: 10.1016/j.bbapap.2004.08.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2004] [Revised: 08/23/2004] [Accepted: 08/25/2004] [Indexed: 11/19/2022]
Abstract
On storage at 4 degrees C, rabbit skeletal muscle AMP deaminase undergoes limited proteolysis with the conversion of the native 85-kDa enzyme subunit to a 75-kDa core that is resistant to further proteolysis. Further studies have shown that limited proteolysis of AMP deaminase with trypsin, removing the 95-residue N-terminal fragment, converts the native enzyme to a species that exhibits hyperbolic kinetics even at low K+ concentration. The results of this report show that a 21-residue synthetic peptide, when incubated with the purified enzyme, is cleaved with a specificity identical to that reported for ubiquitous calpains. In addition, the cleavage of a specific fluorogenic peptide substrate by rabbit m-calpain is inhibited by a synthetic peptide that corresponds to residues 10-17 of rabbit skeletal muscle AMP deaminase; this peptide contains a sequence (K-E-L-D-D-A) that is present in the fourth subdomain A of rabbit calpastatin, suggesting that the N-terminus of AMP deaminase shares with calpastatin a regulatory sequence that might exert a protective role against the fragmentation-induced activation of AMP deaminase. These observations suggest that a calpain-like proteinase present in muscle removes from AMP deaminase a domain that holds the enzyme in an inactive conformation and which also contains a regulatory region that protects against unregulated proteolysis. We conclude that proteolysis of AMP deaminase is the basis of the large ammonia accumulation that occurs in skeletal muscle subjected to strong tetanic contraction or passing into rigor mortis.
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Affiliation(s)
- D Martini
- Dipartimento di Scienze dell'Uomo e dell'Ambiente, Chimica e Biochimica Medica, Università di Pisa, Via Roma 55, 56126 Pisa Italy
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