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Goodman SR, Johnson D, Youngentob SL, Kakhniashvili D. The Spectrinome: The Interactome of a Scaffold Protein Creating Nuclear and Cytoplasmic Connectivity and Function. Exp Biol Med (Maywood) 2019; 244:1273-1302. [PMID: 31483159 DOI: 10.1177/1535370219867269] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
We provide a review of Spectrin isoform function in the cytoplasm, the nucleus, the cell surface, and in intracellular signaling. We then discuss the importance of Spectrin’s E2/E3 chimeric ubiquitin conjugating and ligating activity in maintaining cellular homeostasis. Finally we present spectrin isoform subunit specific human diseases. We have created the Spectrinome, from the Human Proteome, Human Reactome and Human Atlas data and demonstrated how it can be a useful tool in visualizing and understanding spectrins myriad of cellular functions.Impact statementSpectrin was for the first 12 years after its discovery thought to be found only in erythrocytes. In 1981, Goodman and colleagues1found that spectrin-like molecules were ubiquitously found in non-erythroid cells leading to a great multitude of publications over the next thirty eight years. The discovery of multiple spectrin isoforms found associated with every cellular compartment, and representing 2-3% of cellular protein, has brought us to today’s understanding that spectrin is a scaffolding protein, with its own E2/E3 chimeric ubiquitin conjugating ligating activity that is involved in virtually every cellular function. We cover the history, localized functions of spectrin isoforms, human diseases caused by mutations, and provide the spectrinome: a useful tool for understanding the myriad of functions for one of the most important proteins in all eukaryotic cells.
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Affiliation(s)
- Steven R Goodman
- Department of Pediatrics, Memphis Institute of Regenerative Medicine, The University of Tennessee Health Science Center, Memphis, TN 38103
| | - Daniel Johnson
- Department of Pediatrics, Memphis Institute of Regenerative Medicine, The University of Tennessee Health Science Center, Memphis, TN 38103
| | - Steven L Youngentob
- Department of Anatomy and Neurobiology, Memphis Institute of Regenerative Medicine, The University of Tennessee Health Science Center, Memphis, TN 38103
| | - David Kakhniashvili
- Department of Pediatrics, Memphis Institute of Regenerative Medicine, The University of Tennessee Health Science Center, Memphis, TN 38103
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2
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Lambert MW. Spectrin and its interacting partners in nuclear structure and function. Exp Biol Med (Maywood) 2019; 243:507-524. [PMID: 29557213 DOI: 10.1177/1535370218763563] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Nonerythroid αII-spectrin is a structural protein whose roles in the nucleus have just begun to be explored. αII-spectrin is an important component of the nucleoskelelton and has both structural and non-structural functions. Its best known role is in repair of DNA ICLs both in genomic and telomeric DNA. αII-spectrin aids in the recruitment of repair proteins to sites of damage and a proposed mechanism of action is presented. It interacts with a number of different groups of proteins in the nucleus, indicating it has roles in additional cellular functions. αII-spectrin, in its structural role, associates/co-purifies with proteins important in maintaining the architecture and mechanical properties of the nucleus such as lamin, emerin, actin, protein 4.1, nuclear myosin, and SUN proteins. It is important for the resilience and elasticity of the nucleus. Thus, αII-spectrin's role in cellular functions is complex due to its structural as well as non-structural roles and understanding the consequences of a loss or deficiency of αII-spectrin in the nucleus is a significant challenge. In the bone marrow failure disorder, Fanconi anemia, there is a deficiency in αII-spectrin and, among other characteristics, there is defective DNA repair, chromosome instability, and congenital abnormalities. One may speculate that a deficiency in αII-spectrin plays an important role not only in the DNA repair defect but also in the congenital anomalies observed in Fanconi anemia , particularly since αII-spectrin has been shown to be important in embryonic development in a mouse model. The dual roles of αII-spectrin in the nucleus in both structural and non-structural functions make this an extremely important protein which needs to be investigated further. Such investigations should help unravel the complexities of αII-spectrin's interactions with other nuclear proteins and enhance our understanding of the pathogenesis of disorders, such as Fanconi anemia , in which there is a deficiency in αII-spectrin. Impact statement The nucleoskeleton is critical for maintaining the architecture and functional integrity of the nucleus. Nonerythroid α-spectrin (αIISp) is an essential nucleoskeletal protein; however, its interactions with other structural and non-structural nuclear proteins and its functional importance in the nucleus have only begun to be explored. This review addresses these issues. It describes αIISp's association with DNA repair proteins and at least one proposed mechanism of action for its role in DNA repair. Specific interactions of αIISp with other nucleoskeletal proteins as well as its important role in the biomechanical properties of the nucleus are reviewed. The consequences of loss of αIISp, in disorders such as Fanconi anemia, are examined, providing insights into the profound impact of this loss on critical processes known to be abnormal in FA, such as development, carcinogenesis, cancer progression and cellular functions dependent upon αIISp's interactions with other nucleoskeletal proteins.
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Affiliation(s)
- Muriel W Lambert
- Department of Pathology and Laboratory Medicine, Rutgers New Jersey Medical School, The State University of New Jersey, Newark, NJ 07103, USA
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3
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Méndez-Hernández LE, Robledo-Rivera AY, Macías-Silva M, Calera MR, Sánchez-Olea R. Gpn3 is polyubiquitinated on lysine 216 and degraded by the proteasome in the cell nucleus in a Gpn1-inhibitable manner. FEBS Lett 2017; 591:3757-3770. [DOI: 10.1002/1873-3468.12883] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 10/04/2017] [Accepted: 10/05/2017] [Indexed: 11/09/2022]
Affiliation(s)
| | | | - Marina Macías-Silva
- Instituto de Fisiología Celular; Universidad Nacional Autónoma de México; México
| | - Mónica R. Calera
- Instituto de Física; Universidad Autónoma de San Luis Potosí; México
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4
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Abstract
In this minireview, we cover the discovery of the human erythrocyte α spectrin E2/E3 ubiquitin conjugating/ligating enzymatic activity and the specific cysteines involved. We then discuss the consequences when this activity is partially inhibited in sickle cell disease and the possibility that the same attenuation is occurring in multiple organ dysfunction syndrome. We finish by discussing the reasons for believing that nonerythroid α spectrin isoforms (I and II) also have this activity and the importance of testing this hypothesis. If correct, this would suggest that the nonerythroid spectrin isoforms play a major role in protein ubiquitination in all cell types. This would open new fields in experimental biology focused on uncovering the impact that this enzymatic activity has upon protein-protein interactions, protein turnover, cellular signaling, and many other functions impacted by spectrin, including DNA repair.
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Affiliation(s)
- Steven R Goodman
- Department of Biochemistry and Molecular Biology, Department of Pediatrics, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Rachel Petrofes Chapa
- Department of Medical Physiology, College of Medicine, Texas A&M Health Science Center, College Station, TX 77843, USA
| | - Warren E Zimmer
- Department of Medical Physiology, College of Medicine, Texas A&M Health Science Center, College Station, TX 77843, USA
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5
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Jadhav TS, Wooten MW, Wooten MC. Mining the TRAF6/p62 interactome for a selective ubiquitination motif. BMC Proc 2011; 5 Suppl 2:S4. [PMID: 21554762 PMCID: PMC3090762 DOI: 10.1186/1753-6561-5-s2-s4] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
A new approach is described here to predict ubiquitinated substrates of the E3 ubiquitin ligase, TRAF6, which takes into account its interaction with the scaffold protein SQSTM1/p62. A novel TRAF6 ubiquitination motif defined as [–(hydrophobic)–k–(hydrophobic)–x–x–(hydrophobic)– (polar)–(hydrophobic)–(polar)–(hydrophobic)] was identified and used to screen the TRAF6/p62 interactome composed of 155 proteins, that were either TRAF6 or p62 interactors, or a negative dataset, composed of 54 proteins with no known association to either TRAF6 or p62. NRIF (K19), TrkA (K485), TrkB (K811), TrkC (K602 and K815), NTRK2 (K828), NTRK3 (K829) and MBP (K169) were found to possess a perfect match for the amino acid consensus motif for TRAF6/p62 ubiquitination. Subsequent analyses revealed that this motif was biased to the C-terminal regions of the protein (nearly 50% the sites), and had preference for loops (~50%) and helices (~37%) over beta-strands (15% or less). In addition, the motif was observed to be in regions that were highly solvent accessible (nearly 90%). Our findings suggest that specific Lysines may be selected for ubiquitination based upon an embedded code defined by a specific amino acid motif with structural determinants. Collectively, our results reveal an unappreciated role for the scaffold protein in targeting ubiquitination. The findings described herein could be used to aid in identification of other E3/scaffold ubiquitination sites.
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Affiliation(s)
- Trafina S Jadhav
- Program in Cellular and Molecular Biosciences, Department of Biological Sciences, 331 Funchess Hall, Auburn University, Auburn, AL, 36849, USA.
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6
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Xu G, Paige JS, Jaffrey SR. Global analysis of lysine ubiquitination by ubiquitin remnant immunoaffinity profiling. Nat Biotechnol 2010; 28:868-73. [PMID: 20639865 PMCID: PMC2946519 DOI: 10.1038/nbt.1654] [Citation(s) in RCA: 414] [Impact Index Per Article: 29.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2010] [Accepted: 06/11/2010] [Indexed: 11/09/2022]
Abstract
Protein ubiquitination is a post-translational modification (PTM) that regulates various aspects of protein function by different mechanisms. Characterization of ubiquitination has lagged behind that of smaller PTMs, such as phosphorylation, largely because of the difficulty of isolating and identifying peptides derived from the ubiquitinated portion of proteins. To address this issue, we generated a monoclonal antibody that enriches for peptides containing lysine residues modified by diglycine, an adduct left at sites of ubiquitination after trypsin digestion. We use mass spectrometry to identify 374 diglycine-modified lysines on 236 ubiquitinated proteins from HEK293 cells, including 80 proteins containing multiple sites of ubiquitination. Seventy-two percent of these proteins and 92% of the ubiquitination sites do not appear to have been reported previously. Ubiquitin remnant profiling of the multi-ubiquitinated proteins proliferating cell nuclear antigen (PCNA) and tubulin alpha-1A reveals differential regulation of ubiquitination at specific sites by microtubule inhibitors, demonstrating the effectiveness of our method to characterize the dynamics of lysine ubiquitination.
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Affiliation(s)
- Guoqiang Xu
- Department of Pharmacology, Weill Medical College, Cornell University, New York, New York, USA
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7
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Wu J, Zhang YC, Suo WH, Liu XB, Shen WW, Tian H, Fu GH. Induction of anion exchanger-1 translation and its opposite roles in the carcinogenesis of gastric cancer cells and differentiation of K562 cells. Oncogene 2010; 29:1987-96. [PMID: 20062076 DOI: 10.1038/onc.2009.481] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Anion exchanger-1 (AE1), an erythroid-specific membrane protein, mediates the Cl(-)/HCO(-)(3) exchange across the plasma membrane and regulates intracellular pH. We have found that AE1 was unexpectedly expressed in gastric cancer cells and participated in the tumorigenesis of the cancer. Here, we focus on the induction of AE1 expression and its role in gastric carcinogenesis as well as in the differentiation of K562 cells. The results show that expression of AE1 is not related to genetic mutation or the mRNA level, but rather, that it is modulated by miR-24. miR-24 decreases the expression of AE1 through binding to the 3'UTR of AE1 mRNA. Transfection of an miR-24 into gastric cancer cells reduced the elevation of the AE1 protein, which resulted in return of AE1-sequestrated p16 to the nucleus, thereby inhibiting proliferation of the cells. Furthermore, the miR-24 inhibitor cooperated with hemin to induce the expression of AE1 in K562 cells and differentiation of the cells, which is consistent with results obtained from the cells cultured at pH 7.6 or from forced stable expression of AE1. These findings establish a novel regulation of miR-24-related AE1 expression in gastric carcinogenesis and erythropoiesis.
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Affiliation(s)
- J Wu
- Department of Pathology, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Institutes of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai, PR China
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Abstract
It has been more than 30 years since the initial report of the discovery of ubiquitin as an 8.5 kDa protein of unknown function expressed universally in living cells. And still, protein modification by covalent conjugation of the ubiquitin molecule is one of the most dynamic posttranslational modifications studied in terms of biochemistry and cell physiology. Ubiquitination plays a central regulatory role in number of eukaryotic cellular processes such as receptor endocytosis, growth-factor signaling, cell-cycle control, transcription, DNA repair, gene silencing, and stress response. Ubiquitin conjugation is a three step concerted action of the E1-E2-E3 enzymes that produces a modified protein. In this review we investigate studies undertaken to identify both ubiquitin and SUMO (small ubiquitin-related modifier) substrates with the goal of understanding how lysine selectivity is achieved. The SUMOylation pathway though distinct from that of ubiquitination, draws many parallels. Based upon the recent findings, we present a model to explain how an individual ubiquitin ligase may target specific lysine residue(s) with the co-operation from a scaffold protein.
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Affiliation(s)
- Trafina Jadhav
- Program in Cellular and Molecular Biosciences, Department of Biological Sciences, Auburn University, Auburn, AL, 36849, USA
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9
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Jadhav T, Geetha T, Jiang J, Wooten MW. Identification of a consensus site for TRAF6/p62 polyubiquitination. Biochem Biophys Res Commun 2008; 371:521-4. [PMID: 18457658 DOI: 10.1016/j.bbrc.2008.04.138] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2008] [Accepted: 04/19/2008] [Indexed: 11/26/2022]
Abstract
Tumor necrosis factor receptor-associated factor 6 (TRAF6) is an ubiquitin ligase that regulates a diverse array of physiological processes via forming Lys-63 linked polyubiquitin chains. In this study, the lysine selection process for TRAF6/p62 ubiquitination was examined. The protein sequence of two characterized TRAF6/p62 substrates, NRIF and TrkA, revealed a conserved consensus pattern for the ubiquitination site of these two TRAF6 substrates. The consensus pattern established in the verified substrates was common to the other Trk receptor family members, TrkB and TrkC. Interestingly, Lysine 811 in TrkB was selected for ubiquination, and mutation of Lysine 811 diminished the formation of TRAF6/p62 complex that is necessary for effective ubiquination. Moreover, downstream signaling was affected upon binding of BDNF to the mutant TrkB receptor. These findings reveal a possible selection process for targeting a specific lysine residue by a single E3 ligase and underscore the role of the scaffold, p62, in this process.
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Affiliation(s)
- Trafina Jadhav
- Program in Cellular and Molecular Biosciences, Department of Biological Sciences, Auburn University, 331 Funchess Hall, Auburn, AL 36849, USA
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10
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Hülsmeier J, Pielage J, Rickert C, Technau GM, Klämbt C, Stork T. Distinct functions of alpha-Spectrin and beta-Spectrin during axonal pathfinding. Development 2007; 134:713-22. [PMID: 17215305 DOI: 10.1242/dev.02758] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Cell-shape changes during development require a precise coupling of the cytoskeleton with proteins situated in the plasma membrane. Important elements controlling the shape of cells are the Spectrin proteins that are expressed as a subcortical cytoskeletal meshwork linking specific membrane receptors with F-actin fibers. Here, we demonstrate that Drosophila karussell mutations affect beta-spectrin and lead to distinct axonal patterning defects in the embryonic CNS. karussell mutants display a slit-sensitive axonal phenotype characterized by axonal looping in stage-13 embryos. Further analyses of individual, labeled neuroblast lineages revealed abnormally structured growth cones in these animals. Cell-type-specific rescue experiments demonstrate that beta-Spectrin is required autonomously and non-autonomously in cortical neurons to allow normal axonal patterning. Within the cell, beta-Spectrin is associated with alpha-Spectrin. We show that expression of the two genes is tightly regulated by post-translational mechanisms. Loss of beta-Spectrin significantly reduces levels of neuronal alpha-Spectrin expression, whereas gain of beta-Spectrin leads to an increase in alpha-Spectrin protein expression. Because the loss of alpha-spectrin does not result in an embryonic nervous system phenotype, beta-Spectrin appears to act at least partially independent of alpha-Spectrin to control axonal patterning.
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Affiliation(s)
- Jörn Hülsmeier
- Institut für Neurobiologie, Badestr. 9, 48149 Münster, Germany
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11
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Mollah S, Wertz IE, Phung Q, Arnott D, Dixit VM, Lill JR. Targeted mass spectrometric strategy for global mapping of ubiquitination on proteins. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2007; 21:3357-64. [PMID: 17883243 DOI: 10.1002/rcm.3227] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Post-translational modifications of proteins including phosphorylation, glycosylation, acetylation and ubiquitination facilitate the regulation of many cellular processes and intracellular signaling events. Ubiquitination plays a key role in the functional regulation and degradation of many classes of proteins, and the study of ubiquitination and poly-ubiquitination has emerged as one of the most active areas in proteomic research. A variety of mass spectrometric methods have been described for the identification of ubiquitination sites, the study of poly-ubiquitin topology and the identification of ubiquitin substrates. The most popular workflow for both ubiquitination site mapping and poly-ubiquitination chain topology characterization is to take advantage of the Gly-Gly signature on the substrate's lysine residue observed after tryptic digestion. Although a number of protocols have been described for the mapping of ubiquitination sites, one major challenge is that ubiquitination is typically heterogeneous, and several lysine residues may be ubiquitinated within a protein. When multiple ubiquitination sites are present, multiple analyses are often required to cover all of the potential modification sites which in turn can necessitate the usage of larger quantities of material. In addition, the level of ubiquitination on endogenous and recombinant proteins may be of low intensity, adding further analytical challenges in the identification of this modification. The use of the multiple reaction monitoring (MRM)-initiated detection and sequencing workflow (MIDAS) for the identification of phosphorylation sites has previously been described. Here, we explore the use of an MRM workflow for ubiquitination site mapping on the substrate protein, receptor interacting protein (RIP).
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12
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Chang TL, Kakhniashvili DG, Goodman SR. Spectrin's E2/E3 ubiquitin conjugating/ligating activity is diminished in sickle cells. Am J Hematol 2005; 79:89-96. [PMID: 15929114 DOI: 10.1002/ajh.20351] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Erythrocyte spectrin contains E2/E3 ubiquitin conjugating/ligating activity in its alpha subunit. Ankyrin is a target of spectrin's E2/E3 ubiquitin conjugating/ligating activity in vitro and in vivo. We compare the ubiquitination levels of ankyrin mediated by control and sickle cell spectrin using a biotinylated ubiquitin cell-free assay. Sickle cell spectrin has diminished ability to transfer ubiquitin from an intermediate spectrin-ubiquitin thioester adduct (alpha' spectrin) to ankyrin, which may be due to glutathiolation of spectrin's E2 and/or E3 active site cysteines. There is also a diminished ability of the sickle cell ankyrin to serve as target of spectrin's E2/E3 activity, probably due to oxidative damage to ankyrin. A direct correlation exists between the alpha'/alpha spectrin ratio and spectrin's ability to ubiquitinate ankyrin. There is also an inverse correlation between severity of the disease and the alpha'/alpha spectrin ratio in SS erythrocytes. These results suggest that reduced spectrin E2/E3 activity is an important determinant of sickle cell severity.
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Affiliation(s)
- Tsui-Ling Chang
- Department of Molecular and Cell Biology, UTD Sickle Cell Disease Research Center, Institute of Biomedical Sciences and Technology, The University of Texas at Dallas, Richardson, Texas, USA
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Qin X, Soulard J, Laublin G, Morse D, Cappadocia M. Molecular analysis of the conserved C4 region of the S11-RNase of Solanum chacoense. PLANTA 2005; 221:531-537. [PMID: 15650838 DOI: 10.1007/s00425-004-1470-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2004] [Accepted: 12/01/2004] [Indexed: 05/24/2023]
Abstract
The stylar component to gametophytic self-incompatibility in Solanaceae is an S-RNase. Its primary structure has a characteristic pattern of two hypervariable regions, involved in pollen recognition, and five constant regions. Two of the latter (C2 and C3) constitute the active site, while the highly hydrophobic C1 and C5 are believed to be involved in protein stability. We analyzed the role of the C4 region by site-directed mutagenesis. A GGGG mutant, in which the four charged residues in the C4 region were replaced with glycine, did not accumulate the protein to detectable levels in styles, suggestive of a role in protein stability. A R115G mutant, in which a charged amino acid was eliminated to reduce the potential binding affinity, had no effect on the pollen rejection phenotype. This suggests the C4 does not interact with partners such as potential pollen tube receptors facilitating S-RNase uptake. Finally, a K113R mutant replaced a potential ubiquitination target with arginine. However, this RNase acted as the wild type in both incompatible and compatible crosses. The latter crosses rule out the role of the conserved C4 lysine in ubiquitination.
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Affiliation(s)
- Xike Qin
- IRBV, Biology Department, University of Montreal, 4101 rue Sherbrooke est, Montreal, Canada, H1X 2B2
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Riahi MH, Kakhniashvili DG, Goodman SR. Ubiquitination of red blood cell alpha-spectrin does not affect heterodimer formation. Am J Hematol 2005; 78:281-7. [PMID: 15795915 DOI: 10.1002/ajh.20282] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Erythrocyte alpha-spectrin is ubiquitinated in repeats alpha20/alpha21, which also represents the nucleation site for contact with the beta subunit which leads to heterodimer formation by a zippering mechanism. In this study we have determined the second-order rate constant for association of ubiquitinated alpha'-spectrin, nonubiquitinated alpha-spectrin, and beta-spectrin into the alpha'beta or alphabeta heterodimer. The rate constant for incorporation of monomers into heterodimers at 37 degrees C were (5.181 +/- 0.001) x 10(5) M(-1) sec(-1) for total alpha-spectrin (alpha + alpha'), (5.121 +/- 0.001) x 10(5) M(-1) sec(-1) for alpha'-spectrin, and (5.178 +/- 0.003) x 10(5) M(-1) sec(-1) for beta-spectrin. We conclude that ubiquitination of alpha-spectrin does not regulate heterodimer formation.
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Affiliation(s)
- Mahnoush H Riahi
- Department of Molecular and Cell Biology, University of Texas at Dallas, Richardson, Texas 75083-0688, USA
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15
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Hopkins LM, Schall M, Leykam JF, Gerlach JA. Characterization of major histocompatibility complex-associated peptides from a small volume of whole blood. Anal Biochem 2004; 328:155-61. [PMID: 15113691 DOI: 10.1016/j.ab.2004.02.011] [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] [Received: 10/31/2003] [Indexed: 11/18/2022]
Abstract
Class I major histocompatibility complex (MHC) presents intracellular-derived peptides on the majority of cells within the human body. Intracellular proteins are degraded into peptides of 8-11 amino acids, allowing them to fit into the groove of an empty MHC class I molecule. Detection of MHC-associated peptides can be challenging with the major difficulty being the ability to obtain peptides in adequate concentration. Published protocols require a large sample size that is unrealistic for a clinically available sample. Based on calculations, it should be possible to characterize MHC-associated peptides from cells obtained from 30 ml of whole blood. A citric acid wash of whole platelets was implemented to release the peptides with sample cleanup by reversed-phase high-performance liquid chromatography on a peptide trap. Peptides were analyzed by liquid chromatography tandem mass spectrometry. Four peptides were identified from an individual's platelets. The binding motifs of the peptides were consistent with the published MHC binding motif of the individual. Since red blood cells do not express MHC, they were used as a negative control. Using citric acid wash of whole cells and a peptide trap, the more abundant MHC-associated peptides can be identified. This report demonstrates the identification of peptides from a sample volume compatible with reasonable clinical availability.
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Affiliation(s)
- Leann M Hopkins
- Department of Pathobiology and Diagnostic Investigation, Michigan State University, East Lansing, MI 48824, USA
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