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Lim CM, González Díaz A, Fuxreiter M, Pun FW, Zhavoronkov A, Vendruscolo M. Multiomic prediction of therapeutic targets for human diseases associated with protein phase separation. Proc Natl Acad Sci U S A 2023; 120:e2300215120. [PMID: 37774095 PMCID: PMC10556643 DOI: 10.1073/pnas.2300215120] [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: 01/05/2023] [Accepted: 08/02/2023] [Indexed: 10/01/2023] Open
Abstract
The phenomenon of protein phase separation (PPS) underlies a wide range of cellular functions. Correspondingly, the dysregulation of the PPS process has been associated with numerous human diseases. To enable therapeutic interventions based on the regulation of this association, possible targets should be identified. For this purpose, we present an approach that combines the multiomic PandaOmics platform with the FuzDrop method to identify PPS-prone disease-associated proteins. Using this approach, we prioritize candidates with high PandaOmics and FuzDrop scores using a profiling method that accounts for a wide range of parameters relevant for disease mechanism and pharmacological intervention. We validate the differential phase separation behaviors of three predicted Alzheimer's disease targets (MARCKS, CAMKK2, and p62) in two cell models of this disease. Overall, the approach that we present generates a list of possible therapeutic targets for human diseases associated with the dysregulation of the PPS process.
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Affiliation(s)
- Christine M. Lim
- Yusuf Hamied Department of Chemistry, Centre for Misfolding Diseases, University of Cambridge, CambridgeCB2 1EW, United Kingdom
| | - Alicia González Díaz
- Yusuf Hamied Department of Chemistry, Centre for Misfolding Diseases, University of Cambridge, CambridgeCB2 1EW, United Kingdom
| | - Monika Fuxreiter
- Department of Biomedical Sciences, University of Padova, Padova35131, Italy
| | - Frank W. Pun
- Insilico Medicine, Hong Kong Science and Technology Park, Hong Kong, China
| | - Alex Zhavoronkov
- Insilico Medicine, Hong Kong Science and Technology Park, Hong Kong, China
| | - Michele Vendruscolo
- Yusuf Hamied Department of Chemistry, Centre for Misfolding Diseases, University of Cambridge, CambridgeCB2 1EW, United Kingdom
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Iqbal S, Walsh TR, Rodger A, Packer NH. Interaction between Polysialic Acid and the MARCKS-ED Peptide at the Molecular Level. ACS Chem Neurosci 2020; 11:1944-1954. [PMID: 32412743 DOI: 10.1021/acschemneuro.0c00139] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Polysialic acid (polySia) is a highly negatively charged linear homopolymer comprising α-2,8-linked sialic acids. It is abundant in the embryonic brain and modulates various functions such as differentiation and synaptic plasticity in the adult central nervous system by direct binding to its protein partners. One such example is the binding of polySia to myristoylated-alanine rich C-kinase substrate (MARCKS) to modulate neuritogenesis. To understand their interaction mechanism at the molecular level, we performed a binding assay which showed a direct binding of the MARCKS-ED peptide (KKKKKRFSFKKSFKLSGFSFKKNKK) with polySia in a concentration-dependent manner. Molecular dynamics simulations revealed that this binding is not exclusively dominated by electrostatics but can in part be attributed to the presence of near-regularly spaced Phe residues, that confer a compact 3D conformation based on pseudoglycine loop structures supported by Phe-Phe interactions. Our simulations, which are confirmed by circular dichroism measurements, also indicate that the peptide-polySia binding induces large-scale conformational rearrangement of polySia into coils at the binding site, whereas the peptide conformation is relatively unperturbed. As a consequence, we predict that each peptide can bind to a domain extending ∼14 polySia repeat units. Using the fluorescently tagged MARCKS-ED peptide on rat brainstem tissue sections, we demonstrate the ability of the peptide to detect polySia, similarly to polySia-specific antibody mAb735, especially in the spinal trigeminal nucleus and the dorsal vagal complex. This study provides information about the interaction between polySia and its CNS protein binding partner, MARCKS, and provides a fundamental platform for further studies to explore the prospect of the MARCKS-ED as an effective polySia-binding peptide for bioimaging and drug delivery applications.
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Affiliation(s)
- Sameera Iqbal
- Department of Molecular Sciences, Macquarie University, Sydney, New South Wales 2109, Australia
- ARC Centre of Excellence for Nanoscale Biophotonics, Macquarie University, Sydney, New South Wales 2109, Australia
| | - Tiffany R. Walsh
- Institute for Frontier Materials, Deakin University, Geelong, Victoria 3216, Australia
| | - Alison Rodger
- Department of Molecular Sciences, Macquarie University, Sydney, New South Wales 2109, Australia
| | - Nicolle H. Packer
- Department of Molecular Sciences, Macquarie University, Sydney, New South Wales 2109, Australia
- ARC Centre of Excellence for Nanoscale Biophotonics, Macquarie University, Sydney, New South Wales 2109, Australia
- Institute for Glycomics, Griffith University, Gold Coast, Queensland 4222, Australia
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Pradhan G, Raj Abraham P, Shrivastava R, Mukhopadhyay S. Calcium Signaling Commands Phagosome Maturation Process. Int Rev Immunol 2020; 38:57-69. [PMID: 31117900 DOI: 10.1080/08830185.2019.1592169] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Phagosome-lysosome (P-L) fusion is one of the central immune-effector responses of host. It is known that phagosome maturation process is associated with numerous signaling cascades and among these, important role of calcium (Ca2+) signaling has been realized recently. Ca2+ plays key roles in actin rearrangement, activation of NADPH oxidase and protein kinase C (PKC). Involvement of Ca2+ in these cellular processes directs phagosomal maturation process. Some of the intracellular pathogens have acquired the strategies to modulate Ca2+ associated pathways to block P-L fusion process. In this review we have described the mechanism of Ca2+ signals that influence P-L fusion by controlling ROS, actin and PKC signaling cascades. We have also discussed the strategies implemented by the intracellular pathogens to manipulate Ca2+ signaling to consequently subvert P-L fusion. A detail study of factors associated in manipulating Ca2+ signaling may provide new insights for the development of therapeutic tools for more effective treatment options against infectious diseases.
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Affiliation(s)
- Gourango Pradhan
- a Laboratory of Molecular Cell Biology , Centre for DNA Fingerprinting and Diagnostics (CDFD) , Hyderabad , India.,b Graduate Studies , Manipal Academy of Higher Education , Manipal , Karnataka , India
| | - Philip Raj Abraham
- a Laboratory of Molecular Cell Biology , Centre for DNA Fingerprinting and Diagnostics (CDFD) , Hyderabad , India
| | - Rohini Shrivastava
- a Laboratory of Molecular Cell Biology , Centre for DNA Fingerprinting and Diagnostics (CDFD) , Hyderabad , India.,b Graduate Studies , Manipal Academy of Higher Education , Manipal , Karnataka , India
| | - Sangita Mukhopadhyay
- a Laboratory of Molecular Cell Biology , Centre for DNA Fingerprinting and Diagnostics (CDFD) , Hyderabad , India
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Aparicio G, Arruti C, Zolessi FR. MARCKS phosphorylation by PKC strongly impairs cell polarity in the chick neural plate. Genesis 2018; 56:e23104. [PMID: 29603589 DOI: 10.1002/dvg.23104] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Revised: 03/23/2018] [Accepted: 03/25/2018] [Indexed: 12/26/2022]
Abstract
Neurulation involves a complex coordination of cellular movements that are in great part based on the modulation of the actin cytoskeleton. MARCKS, an F-actin-binding protein and the major substrate for PKC, is necessary for gastrulation and neurulation morphogenetic movements in mice, frogs, and fish. We previously showed that this protein accumulates at the apical region of the closing neural plate in chick embryos, and here further explore its role in this process and how it is regulated by PKC phosphorylation. PKC activation by PMA caused extensive neural tube closure defects in cultured chick embryos, together with MARCKS phosphorylation and redistribution to the cytoplasm. This was concomitant with an evident disruption of neural plate cell polarity and extensive apical cell extrusion. This effect was not due to actomyosin hypercontractility, but it was reproduced upon MARCKS knockdown. Interestingly, the overexpression of a nonphosphorylatable form of MARCKS was able to revert the cellular defects observed in the neural plate after PKC activation. Altogether, these results suggest that MARCKS function during neurulation would be to maintain neuroepithelial polarity through the stabilization of subapical F-actin, a function that appears to be counteracted by PKC activation.
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Affiliation(s)
- Gonzalo Aparicio
- Laboratorio de Cultivo de Tejidos, Sección Biología Celular, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay.,Cell Biology of Neural Development Laboratory, Institut Pasteur de Montevideo, Montevideo, Uruguay
| | - Cristina Arruti
- Laboratorio de Cultivo de Tejidos, Sección Biología Celular, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay
| | - Flavio R Zolessi
- Laboratorio de Cultivo de Tejidos, Sección Biología Celular, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay.,Cell Biology of Neural Development Laboratory, Institut Pasteur de Montevideo, Montevideo, Uruguay
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El Amri M, Fitzgerald U, Schlosser G. MARCKS and MARCKS-like proteins in development and regeneration. J Biomed Sci 2018; 25:43. [PMID: 29788979 PMCID: PMC5964646 DOI: 10.1186/s12929-018-0445-1] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Accepted: 05/07/2018] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The Myristoylated Alanine-Rich C-kinase Substrate (MARCKS) and MARCKS-like protein 1 (MARCKSL1) have a wide range of functions, ranging from roles in embryonic development to adult brain plasticity and the inflammatory response. Recently, both proteins have also been identified as important players in regeneration. Upon phosphorylation by protein kinase C (PKC) or calcium-dependent calmodulin-binding, MARCKS and MARCKSL1 translocate from the membrane into the cytosol, modulating cytoskeletal actin dynamics and vesicular trafficking and activating various signal transduction pathways. As a consequence, the two proteins are involved in the regulation of cell migration, secretion, proliferation and differentiation in many different tissues. MAIN BODY Throughout vertebrate development, MARCKS and MARCKSL1 are widely expressed in tissues derived from all germ layers, with particularly strong expression in the nervous system. They have been implicated in the regulation of gastrulation, myogenesis, brain development, and other developmental processes. Mice carrying loss of function mutations in either Marcks or Marcksl1 genes die shortly after birth due to multiple deficiencies including detrimental neural tube closure defects. In adult vertebrates, MARCKS and MARCKL1 continue to be important for multiple regenerative processes including peripheral nerve, appendage, and tail regeneration, making them promising targets for regenerative medicine. CONCLUSION This review briefly summarizes the molecular interactions and cellular functions of MARCKS and MARCKSL1 proteins and outlines their vital roles in development and regeneration.
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Affiliation(s)
- Mohamed El Amri
- Centre for Research in Medical Devices (CÚRAM), National University of Ireland, Galway, Biomedical Sciences Building, Newcastle Road, Galway, Ireland
| | - Una Fitzgerald
- Galway Neuroscience Centre, School of Natural Sciences, Biomedical Sciences Building, National University of Ireland, Newcastle Road, Galway, Ireland
| | - Gerhard Schlosser
- Centre for Research in Medical Devices (CÚRAM), National University of Ireland, Galway, Biomedical Sciences Building, Newcastle Road, Galway, Ireland. .,School of Natural Sciences and Regenerative Medicine Institute (REMEDI), National University of Ireland, Galway, Biomedical Sciences Building, Newcastle Road, Galway, Ireland.
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Prieto D, Zolessi FR. Functional Diversification of the Four MARCKS Family Members in Zebrafish Neural Development. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2016; 328:119-138. [PMID: 27554589 DOI: 10.1002/jez.b.22691] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Revised: 06/01/2016] [Accepted: 06/20/2016] [Indexed: 12/25/2022]
Abstract
Myristoylated alanin-rich C-kinase substrate (MARCKS) and MARCKS-like 1, each encoded by a different gene, comprise a very small family of actin-modulating proteins with essential roles in mammalian neural development. We show here that four genes (two marcks and two marcksl1) are present in teleosts including zebrafish, while ancient actinopterigians, sarcopterigian fishes, and chondrichtyans only have two. No marcks genes were found in agnaths or invertebrates. All four zebrafish genes are expressed during development, and we show here how their early knockdown causes defects in neural development, with some phenotypical differences. Knockdown of marcksa generated embryos with smaller brain and eyes, while marcksb caused different morphogenetic defects, such as larger hindbrain ventricle and folded retina. marcksl1a and marcksl1b morpholinos also caused smaller eyes and brain, although marcksl1a alone generated larger brain ventricles. At 24 hpf, marcksb caused a wider angle of the hindbrain walls, while marcksl1a showed a "T-shaped" neural tube and alterations in neuroepithelium organization. The double knockdown surprisingly produced new features, which included an increased neuroepithelial disorganization and partial neural tube duplications evident at 48 hpf, suggesting defects in convergent extension. This disorganization was also evident in the retina, although retinal ganglion cells were still able to differentiate. marcksl1b morphants presented a unique retinal phenotype characterized by the occurrence of sporadic ectopic neuronal differentiation. Although only marcksl1a morphant had a clear "ciliary phenotype," all presented significantly shorter cilia. Altogether, our data show that all marcks genes have functions in zebrafish neural development, with some differences that suggest the onset of protein diversification.
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Affiliation(s)
- Daniel Prieto
- Facultad de Ciencias, Sección Biología Celular, Universidad de la República, Montevideo, Uruguay
| | - Flavio R Zolessi
- Facultad de Ciencias, Sección Biología Celular, Universidad de la República, Montevideo, Uruguay.,Cell Biology of Neural Development Lab, Institut Pasteur de Montevideo, Montevideo, Uruguay
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Synthesis and dephosphorylation of MARCKS in the late stages of megakaryocyte maturation drive proplatelet formation. Blood 2016; 127:1468-80. [PMID: 26744461 DOI: 10.1182/blood-2015-08-663146] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Accepted: 12/23/2015] [Indexed: 12/12/2022] Open
Abstract
Platelets are essential for hemostasis, and thrombocytopenia is a major clinical problem. Megakaryocytes (MKs) generate platelets by extending long processes, proplatelets, into sinusoidal blood vessels. However, very little is known about what regulates proplatelet formation. To uncover which proteins were dynamically changing during this process, we compared the proteome and transcriptome of round vs proplatelet-producing MKs by 2D difference gel electrophoresis (DIGE) and polysome profiling, respectively. Our data revealed a significant increase in a poorly-characterized MK protein, myristoylated alanine-rich C-kinase substrate (MARCKS), which was upregulated 3.4- and 5.7-fold in proplatelet-producing MKs in 2D DIGE and polysome profiling analyses, respectively. MARCKS is a protein kinase C (PKC) substrate that binds PIP2. In MKs, it localized to both the plasma and demarcation membranes. MARCKS inhibition by peptide significantly decreased proplatelet formation 53%. To examine the role of MARCKS in the PKC pathway, we treated MKs with polymethacrylate (PMA), which markedly increased MARCKS phosphorylation while significantly inhibiting proplatelet formation 84%, suggesting that MARCKS phosphorylation reduces proplatelet formation. We hypothesized that MARCKS phosphorylation promotes Arp2/3 phosphorylation, which subsequently downregulates proplatelet formation; both MARCKS and Arp2 were dephosphorylated in MKs making proplatelets, and Arp2 inhibition enhanced proplatelet formation. Finally, we used MARCKS knockout (KO) mice to probe the direct role of MARCKS in proplatelet formation; MARCKS KO MKs displayed significantly decreased proplatelet levels. MARCKS expression and signaling in primary MKs is a novel finding. We propose that MARCKS acts as a "molecular switch," binding to and regulating PIP2 signaling to regulate processes like proplatelet extension (microtubule-driven) vs proplatelet branching (Arp2/3 and actin polymerization-driven).
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Brudvig JJ, Weimer JM. X MARCKS the spot: myristoylated alanine-rich C kinase substrate in neuronal function and disease. Front Cell Neurosci 2015; 9:407. [PMID: 26528135 PMCID: PMC4602126 DOI: 10.3389/fncel.2015.00407] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Accepted: 09/25/2015] [Indexed: 11/18/2022] Open
Abstract
Intracellular protein-protein interactions are dynamic events requiring tightly regulated spatial and temporal checkpoints. But how are these spatial and temporal cues integrated to produce highly specific molecular response patterns? A helpful analogy to this process is that of a cellular map, one based on the fleeting localization and activity of various coordinating proteins that direct a wide array of interactions between key molecules. One such protein, myristoylated alanine-rich C-kinase substrate (MARCKS) has recently emerged as an important component of this cellular map, governing a wide variety of protein interactions in every cell type within the brain. In addition to its well-documented interactions with the actin cytoskeleton, MARCKS has been found to interact with a number of other proteins involved in processes ranging from intracellular signaling to process outgrowth. Here, we will explore these diverse interactions and their role in an array of brain-specific functions that have important implications for many neurological conditions.
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Affiliation(s)
- Jon J Brudvig
- Children's Health Research Center, Sanford Research Sioux Falls, SD, USA ; Basic Biomedical Sciences, University of South Dakota Vermillion, SD, USA
| | - Jill M Weimer
- Children's Health Research Center, Sanford Research Sioux Falls, SD, USA ; Department of Pediatrics, Sanford School of Medicine, University of South Dakota Vermillion, SD, USA
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Contreras-Vallejos E, Utreras E, Bórquez DA, Prochazkova M, Terse A, Jaffe H, Toledo A, Arruti C, Pant HC, Kulkarni AB, González-Billault C. Searching for novel Cdk5 substrates in brain by comparative phosphoproteomics of wild type and Cdk5-/- mice. PLoS One 2014; 9:e90363. [PMID: 24658276 PMCID: PMC3962345 DOI: 10.1371/journal.pone.0090363] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Accepted: 01/28/2014] [Indexed: 01/07/2023] Open
Abstract
Protein phosphorylation is the most common post-translational modification that regulates several pivotal functions in cells. Cyclin-dependent kinase 5 (Cdk5) is a proline-directed serine/threonine kinase which is mostly active in the nervous system. It regulates several biological processes such as neuronal migration, cytoskeletal dynamics, axonal guidance and synaptic plasticity among others. In search for novel substrates of Cdk5 in the brain we performed quantitative phosphoproteomics analysis, isolating phosphoproteins from whole brain derived from E18.5 Cdk5+/+ and Cdk5−/− embryos, using an Immobilized Metal-Ion Affinity Chromatography (IMAC), which specifically binds to phosphorylated proteins. The isolated phosphoproteins were eluted and isotopically labeled for relative and absolute quantitation (iTRAQ) and mass spectrometry identification. We found 40 proteins that showed decreased phosphorylation at Cdk5−/− brains. In addition, out of these 40 hypophosphorylated proteins we characterized two proteins, :MARCKS (Myristoylated Alanine-Rich protein Kinase C substrate) and Grin1 (G protein regulated inducer of neurite outgrowth 1). MARCKS is known to be phosphorylated by Cdk5 in chick neural cells while Grin1 has not been reported to be phosphorylated by Cdk5. When these proteins were overexpressed in N2A neuroblastoma cell line along with p35, serine phosphorylation in their Cdk5 motifs was found to be increased. In contrast, treatments with roscovitine, the Cdk5 inhibitor, resulted in an opposite effect on serine phosphorylation in N2A cells and primary hippocampal neurons transfected with MARCKS. In summary, the results presented here identify Grin 1 as novel Cdk5 substrate and confirm previously identified MARCKS as a a bona fide Cdk5 substrate.
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Affiliation(s)
- Erick Contreras-Vallejos
- Laboratory of Cellular and Neuronal Dynamics, Department of Biology, Faculty of Sciences, Universidad de Chile, Santiago, Chile
| | - Elías Utreras
- Laboratory of Cellular and Neuronal Dynamics, Department of Biology, Faculty of Sciences, Universidad de Chile, Santiago, Chile
| | - Daniel A. Bórquez
- Laboratory of Cellular and Neuronal Dynamics, Department of Biology, Faculty of Sciences, Universidad de Chile, Santiago, Chile
| | - Michaela Prochazkova
- Functional Genomics Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda MD, USA
| | - Anita Terse
- Functional Genomics Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda MD, USA
| | - Howard Jaffe
- Protein and Peptide Facility, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda MD, USA
| | - Andrea Toledo
- Laboratorio de Cultivo de Tejidos, Sección Biología Celular, Departamento de Biología Celular y Molecular, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay
| | - Cristina Arruti
- Laboratorio de Cultivo de Tejidos, Sección Biología Celular, Departamento de Biología Celular y Molecular, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay
| | - Harish C. Pant
- Laboratory of Neurochemistry, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda MD, USA
| | - Ashok B. Kulkarni
- Functional Genomics Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda MD, USA
- * E-mail: (CGB); (ABK)
| | - Christian González-Billault
- Laboratory of Cellular and Neuronal Dynamics, Department of Biology, Faculty of Sciences, Universidad de Chile, Santiago, Chile
- * E-mail: (CGB); (ABK)
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Tinoco LW, Fraga JL, Anobom CD, Zolessi FR, Obal G, Toledo A, Pritsch O, Arruti C. Structural characterization of a neuroblast-specific phosphorylated region of MARCKS. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2014; 1844:837-49. [PMID: 24590112 DOI: 10.1016/j.bbapap.2014.02.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Revised: 02/07/2014] [Accepted: 02/20/2014] [Indexed: 11/19/2022]
Abstract
MARCKS (Myristoylated Alanine-Rich C Kinase substrate) is a natively unfolded protein that interacts with actin, Ca(2+)-Calmodulin, and some plasma membrane lipids. Such interactions occur at a highly conserved region that is specifically phosphorylated by PKC: the Effector Domain. There are two other conserved domains, MH1 (including a myristoylation site) and MH2, also located in the amino terminal region and whose structure and putative protein binding capabilities are currently unknown. MH2 sequence contains a serine that we described as being phosphorylated only in differentiating neurons (S25 in chick). Here, Circular Dichroism (CD) and Nuclear Magnetic Resonance (NMR) spectroscopy were used to characterize the phosphorylated and unphosphorylated forms of a peptide with the MARCKS sequence surrounding S25. The peptide phosphorylated at this residue is recognized by monoclonal antibody 3C3 (mAb 3C3). CD and NMR data indicated that S25 phosphorylation does not cause extensive modifications in the peptide structure. However, the sharper lines, the absence of multiple spin systems and relaxation dispersion data observed for the phosphorylated peptide suggested a more ordered structure. Surface Plasmon Resonance was employed to compare the binding properties of mAb 3C3 to MARCKS protein and peptide. SPR showed that mAb 3C3 binds to the whole protein and the peptide with a similar affinity, albeit different kinetics. The slightly ordered structure of the phosphorylated peptide might be at the origin of its ability to interact with mAb 3C3 antibody, but this binding did not noticeably modify the peptide structure.
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Affiliation(s)
- Luzineide W Tinoco
- Instituto de Pesquisas de Produtos Naturais, Universidade Federal do Rio de Janeiro, Cidade Universitária, CCS, Bloco H, Rio de Janeiro 21941-902, RJ, Brazil.
| | - Jully L Fraga
- Instituto de Pesquisas de Produtos Naturais, Universidade Federal do Rio de Janeiro, Cidade Universitária, CCS, Bloco H, Rio de Janeiro 21941-902, RJ, Brazil.
| | - Cristiane D Anobom
- Departamento de Bioquímica, Instituto de Química, Universidade Federal do Rio de Janeiro, Cidade Universitária, CT, Bloco A, Rio de Janeiro 21941-909, RJ, Brazil.
| | - Flavio R Zolessi
- Laboratorio de Cultivo de Tejidos, Sección Biología Celular, DBCM, Facultad de Ciencias, Universidad de la República, Iguá 4225, 11400 Montevideo, Uruguay.
| | - Gonzalo Obal
- Unidad de Biofísica de Proteínas, Institut Pasteur de Montevideo, Mataojo 2020, 11400 Montevideo, Uruguay.
| | - Andrea Toledo
- Laboratorio de Cultivo de Tejidos, Sección Biología Celular, DBCM, Facultad de Ciencias, Universidad de la República, Iguá 4225, 11400 Montevideo, Uruguay.
| | - Otto Pritsch
- Unidad de Biofísica de Proteínas, Institut Pasteur de Montevideo, Mataojo 2020, 11400 Montevideo, Uruguay.
| | - Cristina Arruti
- Laboratorio de Cultivo de Tejidos, Sección Biología Celular, DBCM, Facultad de Ciencias, Universidad de la República, Iguá 4225, 11400 Montevideo, Uruguay.
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