Natàlia Carulla

IRB Barcelona Institute for Research in Biomedicine, Barcino, Catalonia, Spain

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Publications (24)155.72 Total impact

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    ABSTRACT: The characterization of amyloid-beta peptide (Aβ) oligomer forms and structures is crucial to the advancement in the field of Alzheimer´s disease (AD). Here we report a critical evaluation of two methods used for this purpose, namely sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), extensively used in the field, and ion mobility coupled to electrospray ionization mass spectrometry (ESI-IM-MS), an emerging technique with great potential for oligomer characterization. To evaluate their performance, we first obtained pure cross-linked Aβ40 and Aβ42 oligomers of well-defined order. Analysis of these samples by SDS-PAGE revealed that SDS affects the oligomerization state of Aβ42 oligomers, thus providing flawed information on their order and distribution. In contrast, ESI-IM-MS provided accurate information, while also reported on the chemical nature and on the structure of the oligomers. Our findings have important implications as they challenge scientific paradigms in the AD field built upon SDS-PAGE characterization of Aβ oligomer samples.
    Scientific Reports 10/2015; 5. DOI:10.1038/srep14809 · 5.58 Impact Factor
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    DESCRIPTION: The characterization of amyloid-beta peptide (Aβ) oligomer samples is crucial to advance in the field of Alzheimer´s disease (AD). Here we report a critical evaluation of two methods used for this purpose, namely sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), extensively used in the field, and ion mobility coupled to electrospray ionization mass spectrometry (ESI-IM-MS), an emerging technique with great potential for oligomer characterization. Our findings have important implications as they challenge scientific paradigms in the AD field built upon SDS-PAGE characterization of Aβ oligomer samples.
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    ABSTRACT: The aggregation of the amyloid-β peptide (Aβ) to form fibrils and plaques is strongly associated with Alzheimer's disease (AD). Although it is well established that this process generates neurotoxicity, it is also heterogeneous with a variety of species being formed during the conversion process. This heterogeneity makes it difficult to detect and characterize each of the aggregates formed, which precludes establishing the specific features responsible for the neurotoxicity observed. Here we use pulse-labeling hydrogen-deuterium exchange experiments analyzed by electrospray ionization mass spectrometry (PL-HDX-ESI-MS) to distinguish three ensembles populated during the aggregation of the 40 and 42 residue forms of the Aβ peptide, Aβ40 and Aβ42, on the basis of differences in their persistent structure. Noticeably, two of them are more abundant at the beginning and at the end of the lag phase and are therefore not detectable by conventional assays such as Thioflavin T (ThT). The ensembles populated at different stages of the aggregation process have a surprisingly consistent average degree of exchange, indicating that there are definite structural transitions between the different stages of aggregation. To determine whether an ensemble of species with a given hydrogen exchange pattern correlates with neurotoxicity, we combined PL-HDX-ESI-MS experiments with parallel measurements of the neurotoxicity of the samples under study. The results of this dual approach show that the maximum toxicity correlates with the ensemble comprising HDX protected oligomers, indicating that development of persistent structure within Aβ oligomers is a determinant of neurotoxicity.
    ACS Chemical Biology 09/2014; 9(11). DOI:10.1021/cb500621x · 5.33 Impact Factor

  • Barcelona BioMed Conferences, barcelona , spain; 07/2014
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    ABSTRACT: Reelin is an extracellular matrix protein that is crucial for neural development and adult brain plasticity. While the Reelin signalling cascade has been reported to be associated with Alzheimer's disease (AD), the role of Reelin in this pathology is not understood. Here we use an in vitro approach to show that Reelin interacts with amyloid-β (Aβ42) soluble species, delays Aβ42 fibril formation and is recruited into amyloid fibrils. Furthermore, Reelin protects against both the neuronal death and dendritic spine loss induced by Aβ42 oligomers. In mice carrying the APPSwe/Ind mutation (J20 mice), Reelin overexpression delays amyloid plaque formation and rescues the recognition memory deficits. Our results indicate that by interacting with Aβ42 soluble species, delaying Aβ plaque formation, protecting against neuronal death and dendritic spine loss and preventing AD cognitive deficits, the Reelin pathway deserves consideration as a therapeutic target for the treatment of AD pathogenesis.
    Nature Communications 03/2014; 5:3443. DOI:10.1038/ncomms4443 · 11.47 Impact Factor
  • Muriel Arimon · Fausto Sanz · Ernest Giralt · Natàlia Carulla ·
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    ABSTRACT: Amyloid-β protein (Aβ) aggregation into amyloid fibrils is central to the origin and development of Alzheimer's disease (AD), yet this highly complex process is poorly understood at the molecular level. Extensive studies have shown that Aβ fibril growth occurs through fibril elongation, whereby soluble molecules add to the fibril ends. Nevertheless, fibril morphology strongly depends on aggregation conditions. For example, at high ionic strength, Aβ fibrils laterally associate into bundles. To further study the mechanisms leading to fibril growth, we developed a single-fibril growth assay based on differential labeling of two Aβ42 variants with gold nanoparticles. We used this assay to study Aβ42 fibril growth under different conditions and observed that bundle formation is preceded by lateral interaction of soluble Aβ42 molecules with pre-existing fibrils. Based on this data, we propose template-assisted lateral fibril growth as an additional mechanism to elongation for Aβ42 fibril growth.
    Bioconjugate Chemistry 11/2011; 23(1):27-32. DOI:10.1021/bc200077s · 4.51 Impact Factor
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    ABSTRACT: A critical aspect to understanding the molecular basis of Alzheimer's disease (AD) is the characterization of the kinetics of interconversion between the different species present during amyloid-β protein (Aβ) aggregation. By monitoring hydrogen/deuterium exchange in Aβ fibrils using electrospray ionization mass spectrometry, we demonstrate that the Aβ molecules comprising the fibril continuously dissociate and reassociate, resulting in molecular recycling within the fibril population. Investigations on Aβ40 and Aβ42 amyloid fibrils reveal that molecules making up Aβ40 fibrils recycle to a much greater extent than those of Aβ42. By examining factors that could influence molecular recycling and by running simulations, we show that the rate constant for dissociation of molecules from the fibril (k(off)) is much greater for Aβ40 than that for Aβ42. Importantly, the k(off) values obtained for Aβ40 and Aβ42 reveal that recycling occurs on biologically relevant time scales. These results have implications for understanding the role of Aβ fibrils in neurotoxicity and for designing therapeutic strategies against AD.
    Journal of the American Chemical Society 05/2011; 133(17):6505-8. DOI:10.1021/ja1117123 · 12.11 Impact Factor
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    ABSTRACT: The aggregation of proteins into amyloid fibrils is a complex and fascinating process associated with debilitating clinical disorders such as Alzheimer’s and Parkinson’s diseases. The process of aggregation involves a series of steps during which many intermediate aggregation states are populated. Recent evidence points to these intermediate states as the toxic moieties primarily responsible for cell damage or cell death, which are critical steps in the origin and progression of these disorders. To understand the molecular basis of these diseases, it is crucial to investigate and define the details of the aggregation process, and to achieve this objective, researchers need the tools to characterize the structure and kinetics of interconversion of the various species present during amyloid fibril formation. Hydrogen−deuterium (HD) exchange experiments are based on solvent accessibilities and provide one means by which this kind of information may be acquired. In this Account, we describe research based on HD exchange processes that is directed toward better understanding the dynamics and structural reorganizations involved in the formation of amyloid fibrils.
    Accounts of Chemical Research 08/2010; 43(8):1072-9. DOI:10.1021/ar9002784 · 22.32 Impact Factor
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 06/2010; 28(24). DOI:10.1002/chin.199724206
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 05/2010; 28(20). DOI:10.1002/chin.199720163
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    Muriel Arimon · Fausto Sanz · Ernest Giralt · Natàlia Carulla ·

    Biophysical Journal 01/2010; 98(3):456-. DOI:10.1016/j.bpj.2009.12.2480 · 3.97 Impact Factor
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    ABSTRACT: An emerging and attractive target for the treatment of Alzheimer's disease is to inhibit the aggregation of beta-amyloid protein (Abeta). We applied the retro-enantio concept to design an N-methylated peptidic inhibitor of the Abeta42 aggregation process. This inhibitor, inrD, as well as the corresponding all-L (inL) and all-D (inD) analogues were assayed for inhibition of Abeta42 aggregation. They were also screened in neuroblastoma cell cultures to assess their capacity to inhibit Abeta42 cytotoxicity and evaluated for proteolytic stability. The results reveal that inrD and inD inhibit Abeta42 aggregation more effectively than inL, that inrD decreases Abeta42 cytotoxicity to a greater extent than inL and inD, and that as expected, both inD and inrD are stable to proteases. Based on these results, we propose that the retro-enantio approach should be considered in future designs of peptide inhibitors of protein aggregation.
    ChemMedChem 09/2009; 4(9):1488-94. DOI:10.1002/cmdc.200900191 · 2.97 Impact Factor
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    ABSTRACT: Recent experimental evidence points to intermediates populated during the process of amyloid fibril formation as the toxic moieties primarily responsible for the development of increasingly common disorders such as Alzheimer's disease and type II diabetes. We describe here the application of a pulse-labeling hydrogen-deuterium (HD) exchange strategy monitored by mass spectrometry (MS) and NMR spectroscopy (NMR) to characterize the aggregation process of an SH3 domain under 2 different conditions, both of which ultimately lead to well-defined amyloid fibrils. Under one condition, the intermediates appear to be largely amorphous in nature, whereas under the other condition protofibrillar species are clearly evident. Under the conditions favoring amorphous-like intermediates, only species having no protection against HD exchange can be detected in addition to the mature fibrils that show a high degree of protection. By contrast, under the conditions favoring protofibrillar-like intermediates, MS reveals that multiple species are present with different degrees of HD exchange protection, indicating that aggregation occurs initially through relatively disordered species that subsequently evolve to form ordered aggregates that eventually lead to amyloid fibrils. Further analysis using NMR provides residue-specific information on the structural reorganizations that take place during aggregation, as well as on the time scales by which they occur.
    Proceedings of the National Academy of Sciences 06/2009; 106(19):7828-33. DOI:10.1073/pnas.0812227106 · 9.67 Impact Factor
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    ABSTRACT: A novel combinatorial strategy for the redesign of proteins based on the strength and specificity of intra- and interprotein interactions is described. The strategy has been used to redesign the hydrophobic core of the B domain of protein A. Using one-bead-one-compound combinatorial chemistry, 300 analogues of the C-terminal alpha-helix of the B domain, H3x, have been synthesized using a biocompatible resin and the HMFS linker, allowing the screening to occur while the peptides were bound to the resin. The screening was based on the ability of the H3x analogues to interact with the N-terminal helices of the B domain, H1-H2, and retain the native B domain activity, that is binding to IgG. Eight different analogues containing some nonconservative mutations were obtained from the library, the two most frequent of which, H3P1 and H3P2, were studied in detail. CD analysis revealed that the active analogues interact with H1-H2. To validate the redesign strategy the covalent modified domains H1-H2-H3P1 and H1-H2-H3P2 were synthesized and characterized. CD and NMR analysis revealed that they had a unique, stable, and well-defined three-dimensional structure similar to that for the wild-type B domain. This combinatorial strategy allows us to select for redesigned proteins with the desired activity or the desired physicochemical properties provided the right screening test is used. Furthermore, it is rich in potential for the chemical modification of proteins overcoming the drawbacks associated with the total synthesis of large protein domains.
    Journal of the American Chemical Society 01/2008; 129(48):14922-32. DOI:10.1021/ja073969x · 12.11 Impact Factor
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    ABSTRACT: Amyloid fibrils are thread-like protein aggregates with a core region formed from repetitive arrays of beta-sheets oriented parallel to the fibril axis. Such structures were first recognized in clinical disorders, but more recently have also been linked to a variety of non-pathogenic phenomena ranging from the transfer of genetic information to synaptic changes associated with memory. The observation that many proteins can convert into similar structures in vitro has suggested that this ability is a generic feature of polypeptide chains. Here we have probed the nature of the amyloid structure by monitoring hydrogen/deuterium exchange in fibrils formed from an SH3 domain using a combination of nuclear magnetic resonance spectroscopy and electrospray ionization mass spectrometry. The results reveal that under the conditions used in this study, exchange is dominated by a mechanism of dissociation and re-association that results in the recycling of molecules within the fibril population. This insight into the dynamic nature of amyloid fibrils, and the ability to determine the parameters that define this behaviour, have important implications for the design of therapeutic strategies directed against amyloid disease.
    Nature 08/2005; 436(7050):554-8. DOI:10.1038/nature03986 · 41.46 Impact Factor
  • Clare Woodward · Natàlia Carulla · George Barany ·

    Methods in Enzymology 02/2004; 380:379-400. DOI:10.1016/S0076-6879(04)80017-X · 2.09 Impact Factor
  • Natàlia Carulla · George Barany · Clare Woodward ·
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    ABSTRACT: A strategy for design of new proteins that mimic folding properties of native proteins is based on peptides modeled on the slow exchange cores of natural proteins. We have synthesized peptides, called core modules, that correspond to the elements of secondary structure that carry the very slowest exchanging amides in a protein. The expectation is that, if soluble in water, core modules will form conformational ensembles that favor native-like structure. Core modules modeled on natural bovine pancreatic trypsin inhibitor have been shown by NMR studies to meet this expectation. The next step toward production of a native state mimic is to further shift the conformational bias of a core module toward more ordered structure by promoting module-module interactions that are mutually stabilizing. For this, two core modules were incorporated into a single molecule by means of a long cross-link. From a panel of several two-module peptides, one very promising lead emerged; it is called BetaCore. BetaCore is monomeric in water and forms a new fold composed of a four-stranded, antiparallel beta-sheet. The single, dominant conformation of BetaCore is characterized by various NMR experiments. Here we compare the individual core module to the two-module BetaCore and discuss the progressive stabilization of intramodule structure and the formation of new intermodule interactions.
    Biophysical Chemistry 01/2003; 101-102:67-79. DOI:10.1016/S0301-4622(02)00149-7 · 1.99 Impact Factor
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    Natàlia Carulla · Clare Woodward · George Barany ·
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    ABSTRACT: BetaCore is a designed approximately 50-residue protein in which two BPTI-derived core modules, CM I and CM II, are connected by a 22-atom cross-link. At low temperature and pH 3, homo- and heteronuclear NMR data report a dominant folded ('f') conformation with well-dispersed chemical shifts, i, i+1 periodicity, numerous long-range NOEs, and slowed amide hydrogen isotope exchange patterns that is a four-stranded antiparallel beta-sheet with nonsymmetrical and specific association of CM I and CM II. BetaCore 'f' conformations undergo reversible, global, moderately cooperative, non-two-state thermal transitions to an equilibrium ensemble of unfolded 'u' conformations. There is a significant energy barrier between 'f' and 'u' conformations. This is the first designed four-stranded antiparallel beta-sheet that folds in water.
    Protein Science 07/2002; 11(6):1539-51. DOI:10.1110/ps.4440102 · 2.85 Impact Factor
  • Natàlia Carulla · Clare Woodward · George Barany ·
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    ABSTRACT: A 25-residue disulfide-cross-linked peptide, termed 'oxidized core module' (OxCM), that includes essentially all of the secondary structural elements of bovine pancreatic trypsin inhibitor (BPTI) most refractory to hydrogen exchange, was shown previously to favor nativelike beta-sheet structure [Carulla, N., Woodward, C., and Barany, G. (2000) Synthesis and Characterization of a beta-Hairpin Peptide That Represents a 'Core Module' of Bovine Pancreatic Trypsin Inhibitor (BPTI). Biochemistry 39, 7927-7937]. The present work prepares to explore the hypothesis that the energies of nativelike conformations, relative to other possible conformations, could be decreased further by covalent linkage of two OxCMs. Optimized syntheses of six approximately 50-residue OxCM dimers are reported herein, featuring appropriate monomer modifications followed by oxime-forming ligation chemistry to create covalent cross-links at various positions and with differing lengths. Several side reactions were recognized through this work, and modified procedures to lessen or mitigate their occurrence were developed. Particularly noteworthy, guanidine or urea denaturants that were included as peptide-solubilizing components for some reaction mixtures were proven to form adducts with glyoxylyl moieties, thus affecting rates and outcomes. All six synthetic OxCM dimers were characterized by 1D (1)H NMR; three of them showed considerable chemical shift dispersion suggestive of self-association and mutual stabilization between the monomer units.
    Bioconjugate Chemistry 09/2001; 12(5):726-41. DOI:10.1021/bc015518m · 4.51 Impact Factor
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    Clare Woodward · Elisar Barbar · Natalia Carulla · John Battiste · George Barany ·
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    ABSTRACT: In a review of protein hydrogen exchange, we concluded that the slow exchange core is the folding core. By this we mean that the elements of secondary structure carrying the slowest exchanging backbone amides will tend to be the elements of secondary structure to fold first, that partially folded proteins will tend to be most organized in the core, and that peptides made to mimic the slow exchange core will tend to show nativelike structure. These generalizations have led us to ask several experimental questions that will be examined here: (1) In partially folded and unfolded proteins, how do the dynamics and structure of core regions differ from noncore regions? (2) Can we make protein 'core modules' as peptides corresponding to the slow exchange core? Can core modules be covalently linked to make a native state in which one conformation is significantly more stable than all other accessible conformations? (3) In a mutant perturbed outside the core, what are the effects on hydrogen exchange and folding?
    Journal of Molecular Graphics and Modelling 02/2001; 19(1):94-101. DOI:10.1016/S1093-3263(00)00131-5 · 1.72 Impact Factor

Publication Stats

530 Citations
155.72 Total Impact Points


  • 2010-2015
    • IRB Barcelona Institute for Research in Biomedicine
      Barcino, Catalonia, Spain
    • Parc de recerca biomedica de barcelona
      Barcino, Catalonia, Spain
  • 1997-2010
    • University of Barcelona
      • Department of Organic Chemistry
      Barcino, Catalonia, Spain
  • 2009
    • Catalan Institution for Research and Advanced Studies
      Barcino, Catalonia, Spain
  • 2003-2005
    • University of Cambridge
      • Department of Chemistry
      Cambridge, England, United Kingdom
  • 2001-2002
    • University of Minnesota Duluth
      • Department of Chemistry and Biochemistry
      Duluth, Minnesota, United States
  • 2000
    • Saint Mary's University of Minnesota
      Minneapolis, Minnesota, United States