Maria Georgina Herrera | Ruhr-Universität Bochum (original) (raw)

Papers by Maria Georgina Herrera

Research paper thumbnail of Thin‐Plate Superstructures of the Immunogenic 33‐mer Gliadin Peptide

Research paper thumbnail of Multimodal methods to study protein aggregation and fibrillation

Advances in Protein Molecular and Structural Biology Methods, 2022

Research paper thumbnail of Implementing Complementary Approaches to Shape the Mechanism of α-Synuclein Oligomerization as a Model of Amyloid Aggregation

Molecules

The aggregation of proteins into amyloid fibers is linked to more than forty still incurable cell... more The aggregation of proteins into amyloid fibers is linked to more than forty still incurable cellular and neurodegenerative diseases such as Parkinson’s disease (PD), multiple system atrophy, Alzheimer’s disease and type 2 diabetes, among others. The process of amyloid formation is a main feature of cell degeneration and disease pathogenesis. Despite being methodologically challenging, a complete understanding of the molecular mechanism of aggregation, especially in the early stages, is essential to find new biological targets for innovative therapies. Here, we reviewed selected examples on α-syn showing how complementary approaches, which employ different biophysical techniques and models, can better deal with a comprehensive study of amyloid aggregation. In addition to the monomer aggregation and conformational transition hypothesis, we reported new emerging theories regarding the self-aggregation of α-syn, such as the alpha-helix rich tetramer hypothesis, whose destabilization in...

Research paper thumbnail of Elucidación de la auto-organización de la proteína gliadina y su péptido 33-mer in vitro

Gliadin is a protein present in wheat, rye, and barley that undergoes an incomplete degradation d... more Gliadin is a protein present in wheat, rye, and barley that undergoes an incomplete degradation during digestion, producing several peptides, including 33-mer. This peptide is known to be the most important immunomodulator peptide of celiac disease, producing an imbalance between tolerance and auto-immunity. In this PhD Thesis it is presented a structural and auto-organization elucidation of gliadin and its 33-mer peptide in aqueous medium and on surfaces, in physiological conditions in vitro. Firstly, it was determined that gliadin self-assemble spontaneously at pH 3.0 forming spherical aggregates. When the pH was changed to 7.0 a phase separation, concentration diminution and a change on the composition was observed. However, soluble amorphous aggregates remained in solution. Although no difference in the secondary structure at both pHs were detected, differential exposition of Tyrosine and Tryptophan was observed, which could be caused by a tertiary structure change. By applying ...

Research paper thumbnail of Front Cover: Pepsin Digest of Gliadin Forms Spontaneously Amyloid‐Like Nanostructures Influencing the Expression of Selected Pro‐Inflammatory, Chemoattractant, and Apoptotic Genes in Caco‐2 Cells: Implications for Gluten‐Related Disorders

Molecular Nutrition & Food Research

Research paper thumbnail of Pepsin Digest of Gliadin Forms Spontaneously Amyloid‐Like Nanostructures Influencing the Expression of Selected Pro‐Inflammatory, Chemoattractant, and Apoptotic Genes in Caco‐2 Cells: Implications for Gluten‐Related Disorders

Molecular Nutrition & Food Research

SCOPE Proteolysis-resistant gliadin peptides are intensely investigated in biomedical research re... more SCOPE Proteolysis-resistant gliadin peptides are intensely investigated in biomedical research related to Celiac Disease and gluten-related disorders. Herein, the first integrated supramolecular investigation of pepsin-digested gliadin peptides, p-gliadin, is presented in combination with its functional behavior in Caco-2 cell line. METHODS AND RESULTS First, we investigated gliadin degradation by pepsin at pH 3, and the physicochemical properties of p-gliadin were compared with gliadin. An integrated approach using interfacial, spectroscopic, and microscopic techniques revealed that the p-gliadin forms spontaneously soluble large supramolecular structures, mainly oligomers and fibrils capable of binding amyloid-sensitive dyes. The self-assembly of p-gliadin starts at a concentration of 0.40 μg/ml. Second, we stimulated CaCo-2 cells with the p-gliadin supramolecular system and screened the mRNA expression levels of a panel of genes involved in cellular inflammation, apoptosis, permeability, and chemoattraction of immune cells. Our findings suggest that p-gliadin composed of supramolecular structures triggers significant mRNA up-regulation (p < 0.05) of pro-apoptotic biomarkers (ratio Bcl2/Bak-1), chemokines (CCL2, CCL3, CCL4, CCL5, CXCL8) and the chemokine receptor CXCR3. CONCLUSIONS This work demonstrates that p-gliadin is interfacial active, forming spontaneously amyloid-type structures that trigger genes in the Caco-2 cell line involved in the recruitment of specialized immune cells. This article is protected by copyright. All rights reserved.

Research paper thumbnail of Frataxin Structure and Function

Subcellular Biochemistry

Mammalian frataxin is a small mitochondrial protein involved in iron sulfur cluster assembly. Fra... more Mammalian frataxin is a small mitochondrial protein involved in iron sulfur cluster assembly. Frataxin deficiency causes the neurodegenerative disease Friedreich's Ataxia. Valuable knowledge has been gained on the structural dynamics of frataxin, metal-ion-protein interactions, as well as on the effect of mutations on protein conformation, stability and internal motions. Additionally, laborious studies concerning the enzymatic reactions involved have allowed for understanding the capability of frataxin to modulate Fe-S cluster assembly function. Remarkably, frataxin biological function depends on its interaction with some proteins to form a supercomplex, among them NFS1 desulfurase and ISCU, the scaffolding protein. By combining multiple experimental tools including high resolution techniques like NMR and X-ray, but also SAXS, crosslinking and mass-spectrometry, it was possible to build a reliable model of the structure of the desulfurase supercomplex NFS1/ACP-ISD11/ISCU/frataxin. In this chapter, we explore these issues showing how the scientific view concerning frataxin structure-function relationships has evolved over the last years.

Research paper thumbnail of Evaluation of Peptide/Protein Self-Assembly and Aggregation by Spectroscopic Methods

Molecules

The self-assembly of proteins is an essential process for a variety of cellular functions includi... more The self-assembly of proteins is an essential process for a variety of cellular functions including cell respiration, mobility and division. On the other hand, protein or peptide misfolding and aggregation is related to the development of Parkinson’s disease and Alzheimer’s disease, among other aggregopathies. As a consequence, significant research efforts are directed towards the understanding of this process. In this review, we are focused on the use of UV-Visible Absorption Spectroscopy, Fluorescence Spectroscopy and Circular Dichroism to evaluate the self-organization of proteins and peptides in solution. These spectroscopic techniques are commonly available in most chemistry and biochemistry research laboratories, and together they are a powerful approach for initial as well as routine evaluation of protein and peptide self-assembly and aggregation under different environmental stimulus. Furthermore, these spectroscopic techniques are even suitable for studying complex systems ...

Research paper thumbnail of The Structure of the Human ACP-ISD11 Heterodimer

Research paper thumbnail of Structural conformation and self‐assembly process of p31‐43 gliadin peptide in aqueous solution. Implications for celiac disease

The FEBS Journal

Celiac disease (CeD) is a highly prevalent chronic immune‐mediated enteropathy developed in genet... more Celiac disease (CeD) is a highly prevalent chronic immune‐mediated enteropathy developed in genetically predisposed individuals after ingestion of a group of wheat proteins (called gliadins and glutenins). The 13mer α‐gliadin peptide, p31‐43, induces proinflammatory responses, observed by in vitro assays and animal models, that may contribute to innate immune mechanisms of CeD pathogenesis. Since a cellular receptor for p31‐43 has not been identified, this raises the question of whether this peptide could mediate different biological effects. In this work, we aimed to characterize the p31‐43 secondary structure by different biophysical and in silico techniques. By dynamic light scattering and using an oligomer/fibril‐sensitive fluorescent probe, we showed the presence of oligomers of this peptide in solution. Furthermore, atomic force microscopy analysis showed p31‐43 oligomers with different height distribution. Also, peptide concentration had a very strong influence on peptide self‐organization process. Oligomers gradually increased their size at lower concentration. Whereas, at higher ones, oligomers increased their complexity, forming branched structures. By CD, we observed that p31‐43 self‐organized in a polyproline II conformation in equilibrium with β‐sheets‐like structures, whose pH remained stable in the range of 3–8. In addition, these findings were supported by molecular dynamics simulation. The formation of p31‐43 nanostructures with increased β‐sheet structure may help to explain the molecular etiopathogenesis in the induction of proinflammatory effects and subsequent damage at the intestinal mucosa in CeD.

Research paper thumbnail of Molecular Mechanisms of 33-mer Gliadin Peptide Oligomerisation

Physical Chemistry Chemical Physics

The proteolytical resistant 33-mer gliadin peptide is the immunodominant fragment in gluten and r... more The proteolytical resistant 33-mer gliadin peptide is the immunodominant fragment in gluten and responsible for celiac disease, and other gluten-related disorders. Meanwhile, the primary structure of 33-mer is associated with...

Research paper thumbnail of Exploring iron-binding to human frataxin and to selected Friedreich ataxia mutants by means of NMR and EPR spectroscopies

Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics

The neurodegenerative disease Friedreich ataxia results from a deficiency of frataxin, a mitochon... more The neurodegenerative disease Friedreich ataxia results from a deficiency of frataxin, a mitochondrial protein. Most patients have a GAA expansion in the first intron of both alleles of frataxin gene, whereas a minority of them are heterozygous for the expansion and contain a mutation in the other allele. Frataxin has been claimed to participate in iron homeostasis and biosynthesis of FeS clusters, however its role in both pathways is not unequivocally defined. In this work we combined different advanced spectroscopic analyses to explore the iron-binding properties of human frataxin, as isolated and at the FeS clusters assembly machinery. For the first time we used EPR spectroscopy to address this key issue providing clear evidence of the formation of a complex with a low symmetry coordination of the metal ion. By 2D NMR, we confirmed that iron can be bound in both oxidation states, a controversial issue, and, in addition, we were able to point out a transient interaction of frataxin with a N-terminal 6his-tagged variant of ISCU, the scaffold protein of the FeS clusters assembly machinery. To obtain insights on structure/function relationships relevant to understand the disease molecular mechanism(s), we extended our studies to four clinical frataxin mutants. All variants showed a moderate to strong impairment in their ability to activate the FeS cluster assembly machinery in vitro, while keeping the same iron-binding features of the wild type protein. This supports the multifunctional nature of frataxin and the complex biochemical consequences of its mutations.

Research paper thumbnail of Modulating the amyloid fibrillation in a minimalist model peptide by intermolecular disulfide chemical reduction

Physical Chemistry Chemical Physics

Peptide structural transformation and aggregation is associated with a large number of outsider a... more Peptide structural transformation and aggregation is associated with a large number of outsider aetiology diseases, and it is intrinsically linked to amyloid peptide aggregation. Diphenylalanine self-assembled structures are used as...

Research paper thumbnail of p31-43 Gliadin Peptide Forms Oligomers and Induces NLRP3 Inflammasome/Caspase 1- Dependent Mucosal Damage in Small Intestine

Frontiers in Immunology

Celiac disease (CD) is a chronic enteropathy elicited by a Th1 response to gluten peptides in the... more Celiac disease (CD) is a chronic enteropathy elicited by a Th1 response to gluten peptides in the small intestine of genetically susceptible individuals. However, it remains unclear what drives the induction of inflammatory responses of this kind against harmless antigens in food. In a recent work, we have shown that the p31-43 peptide (p31-43) from α-gliadin can induce an innate immune response in the intestine and that this may initiate pathological adaptive immunity. The receptors and mechanisms responsible for the induction of innate immunity by p31-43 are unknown and here we present evidence that this may reflect conformational changes in the peptide that allow it to activate the NLRP3 inflammasome. Administration of p31-43, but not scrambled or inverted peptides, to normal mice induced enteropathy in the proximal small intestine, associated with increased production of type I interferon and mature IL-1β. P31-43 showed a sequence-specific spontaneous ability to form structured oligomers and aggregates in vitro and induced activation of the ASC speck complex. In parallel, the enteropathy induced by p31-43 in vivo did not occur in the absence of NLRP3 or caspase 1 and was inhibited by administration of the caspase 1 inhibitor Ac-YVAD-cmk. Collectively, these findings show that p31-43 gliadin has an intrinsic propensity to form oligomers which trigger the NLRP3 inflammasome and that this pathway is required for intestinal inflammation and pathology when p31-43 is administered orally to mice. This innate activation of the inflammasome may have important implications in the initial stages of CD pathogenesis.

Research paper thumbnail of Rescuing the Rescuer: On the Protein Complex between the Human Mitochondrial Acyl Carrier Protein and ISD11

ACS chemical biology, Jan 16, 2018

Iron-sulfur clusters are essential cofactors in many biochemical processes. ISD11, one of the sub... more Iron-sulfur clusters are essential cofactors in many biochemical processes. ISD11, one of the subunits of the protein complex that carries out the cluster assembly in mitochondria, is necessary for cysteine desulfurase NFS1 stability and function. Several authors have recently provided evidence showing that ISD11 interacts with the acyl carrier protein (ACP). We carried out the coexpression of human mitochondrial ACP and ISD11 in E. coli. This work shows that ACP and ISD11 form a soluble, structured, and stable complex able to bind to the human NFS1 subunit modulating its activity. Results suggest that ACP plays a key-role in ISD11 folding and stability in vitro. These findings offer the opportunity to study the mechanism of interaction between ISD11 and NFS1.

Research paper thumbnail of Insights on the conformational dynamics of human frataxin through modifications of loop-1

Archives of biochemistry and biophysics, Dec 30, 2017

Human frataxin (FXN) is a highly conserved mitochondrial protein involved in iron homeostasis and... more Human frataxin (FXN) is a highly conserved mitochondrial protein involved in iron homeostasis and activation of the iron-sulfur cluster assembly. FXN deficiency causes the neurodegenerative disease Friedreich's Ataxia. Here, we investigated the effect of alterations in loop-1, a stretch presumably essential for FXN function, on the conformational stability and dynamics of the native state. We generated four loop-1 variants, carrying substitutions, insertions and deletions. All of them were stable and well-folded proteins. Fast local motions (ps-ns) and slower long-range conformational dynamics (μs-ms) were altered in some mutants as judged by NMR. Particularly, loop-1 modifications impact on the dynamics of a distant region that includes residues from the β-sheet, helix α1 and the C-terminal. Remarkably, all the mutants retain the ability to activate cysteine desulfurase, even when two of them exhibit a strong decrease in iron binding, revealing a differential sensitivity of the...

Research paper thumbnail of Gliadin proteolytical resistant peptides: the interplay between structure and self-assembly in gluten-related disorders

Biophysical Reviews

In recent years, the evaluation of the structural properties of food has become of crucial import... more In recent years, the evaluation of the structural properties of food has become of crucial importance in the understanding of food-related disorders. One of the most exciting systems is gliadin, a protein in wheat gluten, that plays a protagonist role in gluten-related disorders with a worldwide prevalence of 5%, including autoimmune celiac disease (CeD) (1%) and non-celiac wheat sensitivity (0.5–13%). It is accepted that gliadin is not fully digested by humans, producing large peptides that reach the gut mucosa. The gliadin peptides cross the lamina propria eliciting different immune responses in susceptible patients. Many clinical and biomedical efforts aim to diagnose and understand gluten-related disorders; meanwhile, the early stages of the inflammatory events remain elusive. Interestingly, although the primary sequence of many gliadin peptides is well known, it was only recently revealed the self-assembly capability of two pathogenic gliadin fragments and their connection to t...

Research paper thumbnail of Large supramolecular structures of 33-mer gliadin peptide activate toll-like receptors in macrophages

Nanomedicine : nanotechnology, biology, and medicine, Jan 22, 2018

Gliadin, an immunogenic protein present in wheat, is not fully degraded by humans and after the n... more Gliadin, an immunogenic protein present in wheat, is not fully degraded by humans and after the normal gastric and pancreatic digestion, the immunodominant 33-mer gliadin peptide remains unprocessed. The 33-mer gliadin peptide is found in human faeces and urine, proving not only its proteolytic resistance in vivo but more importantly its transport through the entire human body. Here, we demonstrate that 33-mer supramolecular structures larger than 220 nm induce the overexpression of nuclear factor kappa B (NF-κB) via a specific Toll-like Receptor (TLR) 2 and (TLR) 4 dependent pathway and the secretion of pro-inflammatory cytokines such as IP-10/CXCL10 and TNF-α. Using helium ion microscopy, we elucidated the initial stages of oligomerisation of 33-mer gliadin peptide, showing that rod-like oligomers are nucleation sites for protofilament formation. The relevance of the 33-mer supramolecular structures in the early stages of the disease is paving new perspectives in the understanding...

Research paper thumbnail of Circular dichroism and electron microscopy studies in vitro of 33‐mer gliadin peptide revealed secondary structure transition and supramolecular organization

Biopolymers, 2014

Gliadin, a protein present in wheat, rye, and barley, undergoes incomplete enzymatic degradation ... more Gliadin, a protein present in wheat, rye, and barley, undergoes incomplete enzymatic degradation during digestion, producing an immunogenic 33-mer peptide, LQLQPF(PQPQLPY)3 PQPQPF. The special features of 33-mer that provoke a break in its tolerance leading to gliadin sensitivity and celiac disease remains elusive. Herein, it is reported that 33-mer gliadin peptide was not only able to fold into polyproline II secondary structure but also depending on concentration resulted in conformational transition and self-assembly under aqueous condition, pH 7.0. A 33-mer dimer is presented as one initial possible step in the self-assembling process obtained by partial electrostatics charge distribution calculation and molecular dynamics. In addition, electron microscopy experiments revealed supramolecular organization of 33-mer into colloidal nanospheres. In the presence of 1 mM sodium citrate, 1 mM sodium borate, 1 mM sodium phosphate buffer, 15 mM NaCl, the nanospheres were stabilized, whereas in water, a linear organization and formation of fibrils were observed. It is hypothesized that the self-assembling process could be the result of the combination of hydrophobic effect, intramolecular hydrogen bonding, and electrostatic complementarity due to 33-mer&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s high content of proline and glutamine amino acids and its calculated nonionic amphiphilic character. Although, performed in vitro, these experiments have revealed new features of the 33-mer gliadin peptide that could represent an important and unprecedented event in the early stage of 33-mer interaction with the gut mucosa prior to onset of inflammation. Moreover, these findings may open new perspectives for the understanding and treatment of gliadin intolerance disorders. © 2013 Wiley Periodicals, Inc. Biopolymers 101: 96-106, 2014.

Research paper thumbnail of Self-assembly of 33-mer gliadin peptide oligomers

Soft Matter, 2015

The 33-mer gliadin peptide, is a highly immunogenic peptide involved in celiac disease and probab... more The 33-mer gliadin peptide, is a highly immunogenic peptide involved in celiac disease and probably in other immune pathologies associated to gliadin. The spontaneous self-assembly of 33-mer in water is reported, providing a better insight into oligomers morphology and secondary structure.

Research paper thumbnail of Thin‐Plate Superstructures of the Immunogenic 33‐mer Gliadin Peptide

Research paper thumbnail of Multimodal methods to study protein aggregation and fibrillation

Advances in Protein Molecular and Structural Biology Methods, 2022

Research paper thumbnail of Implementing Complementary Approaches to Shape the Mechanism of α-Synuclein Oligomerization as a Model of Amyloid Aggregation

Molecules

The aggregation of proteins into amyloid fibers is linked to more than forty still incurable cell... more The aggregation of proteins into amyloid fibers is linked to more than forty still incurable cellular and neurodegenerative diseases such as Parkinson’s disease (PD), multiple system atrophy, Alzheimer’s disease and type 2 diabetes, among others. The process of amyloid formation is a main feature of cell degeneration and disease pathogenesis. Despite being methodologically challenging, a complete understanding of the molecular mechanism of aggregation, especially in the early stages, is essential to find new biological targets for innovative therapies. Here, we reviewed selected examples on α-syn showing how complementary approaches, which employ different biophysical techniques and models, can better deal with a comprehensive study of amyloid aggregation. In addition to the monomer aggregation and conformational transition hypothesis, we reported new emerging theories regarding the self-aggregation of α-syn, such as the alpha-helix rich tetramer hypothesis, whose destabilization in...

Research paper thumbnail of Elucidación de la auto-organización de la proteína gliadina y su péptido 33-mer in vitro

Gliadin is a protein present in wheat, rye, and barley that undergoes an incomplete degradation d... more Gliadin is a protein present in wheat, rye, and barley that undergoes an incomplete degradation during digestion, producing several peptides, including 33-mer. This peptide is known to be the most important immunomodulator peptide of celiac disease, producing an imbalance between tolerance and auto-immunity. In this PhD Thesis it is presented a structural and auto-organization elucidation of gliadin and its 33-mer peptide in aqueous medium and on surfaces, in physiological conditions in vitro. Firstly, it was determined that gliadin self-assemble spontaneously at pH 3.0 forming spherical aggregates. When the pH was changed to 7.0 a phase separation, concentration diminution and a change on the composition was observed. However, soluble amorphous aggregates remained in solution. Although no difference in the secondary structure at both pHs were detected, differential exposition of Tyrosine and Tryptophan was observed, which could be caused by a tertiary structure change. By applying ...

Research paper thumbnail of Front Cover: Pepsin Digest of Gliadin Forms Spontaneously Amyloid‐Like Nanostructures Influencing the Expression of Selected Pro‐Inflammatory, Chemoattractant, and Apoptotic Genes in Caco‐2 Cells: Implications for Gluten‐Related Disorders

Molecular Nutrition & Food Research

Research paper thumbnail of Pepsin Digest of Gliadin Forms Spontaneously Amyloid‐Like Nanostructures Influencing the Expression of Selected Pro‐Inflammatory, Chemoattractant, and Apoptotic Genes in Caco‐2 Cells: Implications for Gluten‐Related Disorders

Molecular Nutrition & Food Research

SCOPE Proteolysis-resistant gliadin peptides are intensely investigated in biomedical research re... more SCOPE Proteolysis-resistant gliadin peptides are intensely investigated in biomedical research related to Celiac Disease and gluten-related disorders. Herein, the first integrated supramolecular investigation of pepsin-digested gliadin peptides, p-gliadin, is presented in combination with its functional behavior in Caco-2 cell line. METHODS AND RESULTS First, we investigated gliadin degradation by pepsin at pH 3, and the physicochemical properties of p-gliadin were compared with gliadin. An integrated approach using interfacial, spectroscopic, and microscopic techniques revealed that the p-gliadin forms spontaneously soluble large supramolecular structures, mainly oligomers and fibrils capable of binding amyloid-sensitive dyes. The self-assembly of p-gliadin starts at a concentration of 0.40 μg/ml. Second, we stimulated CaCo-2 cells with the p-gliadin supramolecular system and screened the mRNA expression levels of a panel of genes involved in cellular inflammation, apoptosis, permeability, and chemoattraction of immune cells. Our findings suggest that p-gliadin composed of supramolecular structures triggers significant mRNA up-regulation (p < 0.05) of pro-apoptotic biomarkers (ratio Bcl2/Bak-1), chemokines (CCL2, CCL3, CCL4, CCL5, CXCL8) and the chemokine receptor CXCR3. CONCLUSIONS This work demonstrates that p-gliadin is interfacial active, forming spontaneously amyloid-type structures that trigger genes in the Caco-2 cell line involved in the recruitment of specialized immune cells. This article is protected by copyright. All rights reserved.

Research paper thumbnail of Frataxin Structure and Function

Subcellular Biochemistry

Mammalian frataxin is a small mitochondrial protein involved in iron sulfur cluster assembly. Fra... more Mammalian frataxin is a small mitochondrial protein involved in iron sulfur cluster assembly. Frataxin deficiency causes the neurodegenerative disease Friedreich's Ataxia. Valuable knowledge has been gained on the structural dynamics of frataxin, metal-ion-protein interactions, as well as on the effect of mutations on protein conformation, stability and internal motions. Additionally, laborious studies concerning the enzymatic reactions involved have allowed for understanding the capability of frataxin to modulate Fe-S cluster assembly function. Remarkably, frataxin biological function depends on its interaction with some proteins to form a supercomplex, among them NFS1 desulfurase and ISCU, the scaffolding protein. By combining multiple experimental tools including high resolution techniques like NMR and X-ray, but also SAXS, crosslinking and mass-spectrometry, it was possible to build a reliable model of the structure of the desulfurase supercomplex NFS1/ACP-ISD11/ISCU/frataxin. In this chapter, we explore these issues showing how the scientific view concerning frataxin structure-function relationships has evolved over the last years.

Research paper thumbnail of Evaluation of Peptide/Protein Self-Assembly and Aggregation by Spectroscopic Methods

Molecules

The self-assembly of proteins is an essential process for a variety of cellular functions includi... more The self-assembly of proteins is an essential process for a variety of cellular functions including cell respiration, mobility and division. On the other hand, protein or peptide misfolding and aggregation is related to the development of Parkinson’s disease and Alzheimer’s disease, among other aggregopathies. As a consequence, significant research efforts are directed towards the understanding of this process. In this review, we are focused on the use of UV-Visible Absorption Spectroscopy, Fluorescence Spectroscopy and Circular Dichroism to evaluate the self-organization of proteins and peptides in solution. These spectroscopic techniques are commonly available in most chemistry and biochemistry research laboratories, and together they are a powerful approach for initial as well as routine evaluation of protein and peptide self-assembly and aggregation under different environmental stimulus. Furthermore, these spectroscopic techniques are even suitable for studying complex systems ...

Research paper thumbnail of The Structure of the Human ACP-ISD11 Heterodimer

Research paper thumbnail of Structural conformation and self‐assembly process of p31‐43 gliadin peptide in aqueous solution. Implications for celiac disease

The FEBS Journal

Celiac disease (CeD) is a highly prevalent chronic immune‐mediated enteropathy developed in genet... more Celiac disease (CeD) is a highly prevalent chronic immune‐mediated enteropathy developed in genetically predisposed individuals after ingestion of a group of wheat proteins (called gliadins and glutenins). The 13mer α‐gliadin peptide, p31‐43, induces proinflammatory responses, observed by in vitro assays and animal models, that may contribute to innate immune mechanisms of CeD pathogenesis. Since a cellular receptor for p31‐43 has not been identified, this raises the question of whether this peptide could mediate different biological effects. In this work, we aimed to characterize the p31‐43 secondary structure by different biophysical and in silico techniques. By dynamic light scattering and using an oligomer/fibril‐sensitive fluorescent probe, we showed the presence of oligomers of this peptide in solution. Furthermore, atomic force microscopy analysis showed p31‐43 oligomers with different height distribution. Also, peptide concentration had a very strong influence on peptide self‐organization process. Oligomers gradually increased their size at lower concentration. Whereas, at higher ones, oligomers increased their complexity, forming branched structures. By CD, we observed that p31‐43 self‐organized in a polyproline II conformation in equilibrium with β‐sheets‐like structures, whose pH remained stable in the range of 3–8. In addition, these findings were supported by molecular dynamics simulation. The formation of p31‐43 nanostructures with increased β‐sheet structure may help to explain the molecular etiopathogenesis in the induction of proinflammatory effects and subsequent damage at the intestinal mucosa in CeD.

Research paper thumbnail of Molecular Mechanisms of 33-mer Gliadin Peptide Oligomerisation

Physical Chemistry Chemical Physics

The proteolytical resistant 33-mer gliadin peptide is the immunodominant fragment in gluten and r... more The proteolytical resistant 33-mer gliadin peptide is the immunodominant fragment in gluten and responsible for celiac disease, and other gluten-related disorders. Meanwhile, the primary structure of 33-mer is associated with...

Research paper thumbnail of Exploring iron-binding to human frataxin and to selected Friedreich ataxia mutants by means of NMR and EPR spectroscopies

Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics

The neurodegenerative disease Friedreich ataxia results from a deficiency of frataxin, a mitochon... more The neurodegenerative disease Friedreich ataxia results from a deficiency of frataxin, a mitochondrial protein. Most patients have a GAA expansion in the first intron of both alleles of frataxin gene, whereas a minority of them are heterozygous for the expansion and contain a mutation in the other allele. Frataxin has been claimed to participate in iron homeostasis and biosynthesis of FeS clusters, however its role in both pathways is not unequivocally defined. In this work we combined different advanced spectroscopic analyses to explore the iron-binding properties of human frataxin, as isolated and at the FeS clusters assembly machinery. For the first time we used EPR spectroscopy to address this key issue providing clear evidence of the formation of a complex with a low symmetry coordination of the metal ion. By 2D NMR, we confirmed that iron can be bound in both oxidation states, a controversial issue, and, in addition, we were able to point out a transient interaction of frataxin with a N-terminal 6his-tagged variant of ISCU, the scaffold protein of the FeS clusters assembly machinery. To obtain insights on structure/function relationships relevant to understand the disease molecular mechanism(s), we extended our studies to four clinical frataxin mutants. All variants showed a moderate to strong impairment in their ability to activate the FeS cluster assembly machinery in vitro, while keeping the same iron-binding features of the wild type protein. This supports the multifunctional nature of frataxin and the complex biochemical consequences of its mutations.

Research paper thumbnail of Modulating the amyloid fibrillation in a minimalist model peptide by intermolecular disulfide chemical reduction

Physical Chemistry Chemical Physics

Peptide structural transformation and aggregation is associated with a large number of outsider a... more Peptide structural transformation and aggregation is associated with a large number of outsider aetiology diseases, and it is intrinsically linked to amyloid peptide aggregation. Diphenylalanine self-assembled structures are used as...

Research paper thumbnail of p31-43 Gliadin Peptide Forms Oligomers and Induces NLRP3 Inflammasome/Caspase 1- Dependent Mucosal Damage in Small Intestine

Frontiers in Immunology

Celiac disease (CD) is a chronic enteropathy elicited by a Th1 response to gluten peptides in the... more Celiac disease (CD) is a chronic enteropathy elicited by a Th1 response to gluten peptides in the small intestine of genetically susceptible individuals. However, it remains unclear what drives the induction of inflammatory responses of this kind against harmless antigens in food. In a recent work, we have shown that the p31-43 peptide (p31-43) from α-gliadin can induce an innate immune response in the intestine and that this may initiate pathological adaptive immunity. The receptors and mechanisms responsible for the induction of innate immunity by p31-43 are unknown and here we present evidence that this may reflect conformational changes in the peptide that allow it to activate the NLRP3 inflammasome. Administration of p31-43, but not scrambled or inverted peptides, to normal mice induced enteropathy in the proximal small intestine, associated with increased production of type I interferon and mature IL-1β. P31-43 showed a sequence-specific spontaneous ability to form structured oligomers and aggregates in vitro and induced activation of the ASC speck complex. In parallel, the enteropathy induced by p31-43 in vivo did not occur in the absence of NLRP3 or caspase 1 and was inhibited by administration of the caspase 1 inhibitor Ac-YVAD-cmk. Collectively, these findings show that p31-43 gliadin has an intrinsic propensity to form oligomers which trigger the NLRP3 inflammasome and that this pathway is required for intestinal inflammation and pathology when p31-43 is administered orally to mice. This innate activation of the inflammasome may have important implications in the initial stages of CD pathogenesis.

Research paper thumbnail of Rescuing the Rescuer: On the Protein Complex between the Human Mitochondrial Acyl Carrier Protein and ISD11

ACS chemical biology, Jan 16, 2018

Iron-sulfur clusters are essential cofactors in many biochemical processes. ISD11, one of the sub... more Iron-sulfur clusters are essential cofactors in many biochemical processes. ISD11, one of the subunits of the protein complex that carries out the cluster assembly in mitochondria, is necessary for cysteine desulfurase NFS1 stability and function. Several authors have recently provided evidence showing that ISD11 interacts with the acyl carrier protein (ACP). We carried out the coexpression of human mitochondrial ACP and ISD11 in E. coli. This work shows that ACP and ISD11 form a soluble, structured, and stable complex able to bind to the human NFS1 subunit modulating its activity. Results suggest that ACP plays a key-role in ISD11 folding and stability in vitro. These findings offer the opportunity to study the mechanism of interaction between ISD11 and NFS1.

Research paper thumbnail of Insights on the conformational dynamics of human frataxin through modifications of loop-1

Archives of biochemistry and biophysics, Dec 30, 2017

Human frataxin (FXN) is a highly conserved mitochondrial protein involved in iron homeostasis and... more Human frataxin (FXN) is a highly conserved mitochondrial protein involved in iron homeostasis and activation of the iron-sulfur cluster assembly. FXN deficiency causes the neurodegenerative disease Friedreich's Ataxia. Here, we investigated the effect of alterations in loop-1, a stretch presumably essential for FXN function, on the conformational stability and dynamics of the native state. We generated four loop-1 variants, carrying substitutions, insertions and deletions. All of them were stable and well-folded proteins. Fast local motions (ps-ns) and slower long-range conformational dynamics (μs-ms) were altered in some mutants as judged by NMR. Particularly, loop-1 modifications impact on the dynamics of a distant region that includes residues from the β-sheet, helix α1 and the C-terminal. Remarkably, all the mutants retain the ability to activate cysteine desulfurase, even when two of them exhibit a strong decrease in iron binding, revealing a differential sensitivity of the...

Research paper thumbnail of Gliadin proteolytical resistant peptides: the interplay between structure and self-assembly in gluten-related disorders

Biophysical Reviews

In recent years, the evaluation of the structural properties of food has become of crucial import... more In recent years, the evaluation of the structural properties of food has become of crucial importance in the understanding of food-related disorders. One of the most exciting systems is gliadin, a protein in wheat gluten, that plays a protagonist role in gluten-related disorders with a worldwide prevalence of 5%, including autoimmune celiac disease (CeD) (1%) and non-celiac wheat sensitivity (0.5–13%). It is accepted that gliadin is not fully digested by humans, producing large peptides that reach the gut mucosa. The gliadin peptides cross the lamina propria eliciting different immune responses in susceptible patients. Many clinical and biomedical efforts aim to diagnose and understand gluten-related disorders; meanwhile, the early stages of the inflammatory events remain elusive. Interestingly, although the primary sequence of many gliadin peptides is well known, it was only recently revealed the self-assembly capability of two pathogenic gliadin fragments and their connection to t...

Research paper thumbnail of Large supramolecular structures of 33-mer gliadin peptide activate toll-like receptors in macrophages

Nanomedicine : nanotechnology, biology, and medicine, Jan 22, 2018

Gliadin, an immunogenic protein present in wheat, is not fully degraded by humans and after the n... more Gliadin, an immunogenic protein present in wheat, is not fully degraded by humans and after the normal gastric and pancreatic digestion, the immunodominant 33-mer gliadin peptide remains unprocessed. The 33-mer gliadin peptide is found in human faeces and urine, proving not only its proteolytic resistance in vivo but more importantly its transport through the entire human body. Here, we demonstrate that 33-mer supramolecular structures larger than 220 nm induce the overexpression of nuclear factor kappa B (NF-κB) via a specific Toll-like Receptor (TLR) 2 and (TLR) 4 dependent pathway and the secretion of pro-inflammatory cytokines such as IP-10/CXCL10 and TNF-α. Using helium ion microscopy, we elucidated the initial stages of oligomerisation of 33-mer gliadin peptide, showing that rod-like oligomers are nucleation sites for protofilament formation. The relevance of the 33-mer supramolecular structures in the early stages of the disease is paving new perspectives in the understanding...

Research paper thumbnail of Circular dichroism and electron microscopy studies in vitro of 33‐mer gliadin peptide revealed secondary structure transition and supramolecular organization

Biopolymers, 2014

Gliadin, a protein present in wheat, rye, and barley, undergoes incomplete enzymatic degradation ... more Gliadin, a protein present in wheat, rye, and barley, undergoes incomplete enzymatic degradation during digestion, producing an immunogenic 33-mer peptide, LQLQPF(PQPQLPY)3 PQPQPF. The special features of 33-mer that provoke a break in its tolerance leading to gliadin sensitivity and celiac disease remains elusive. Herein, it is reported that 33-mer gliadin peptide was not only able to fold into polyproline II secondary structure but also depending on concentration resulted in conformational transition and self-assembly under aqueous condition, pH 7.0. A 33-mer dimer is presented as one initial possible step in the self-assembling process obtained by partial electrostatics charge distribution calculation and molecular dynamics. In addition, electron microscopy experiments revealed supramolecular organization of 33-mer into colloidal nanospheres. In the presence of 1 mM sodium citrate, 1 mM sodium borate, 1 mM sodium phosphate buffer, 15 mM NaCl, the nanospheres were stabilized, whereas in water, a linear organization and formation of fibrils were observed. It is hypothesized that the self-assembling process could be the result of the combination of hydrophobic effect, intramolecular hydrogen bonding, and electrostatic complementarity due to 33-mer&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s high content of proline and glutamine amino acids and its calculated nonionic amphiphilic character. Although, performed in vitro, these experiments have revealed new features of the 33-mer gliadin peptide that could represent an important and unprecedented event in the early stage of 33-mer interaction with the gut mucosa prior to onset of inflammation. Moreover, these findings may open new perspectives for the understanding and treatment of gliadin intolerance disorders. © 2013 Wiley Periodicals, Inc. Biopolymers 101: 96-106, 2014.

Research paper thumbnail of Self-assembly of 33-mer gliadin peptide oligomers

Soft Matter, 2015

The 33-mer gliadin peptide, is a highly immunogenic peptide involved in celiac disease and probab... more The 33-mer gliadin peptide, is a highly immunogenic peptide involved in celiac disease and probably in other immune pathologies associated to gliadin. The spontaneous self-assembly of 33-mer in water is reported, providing a better insight into oligomers morphology and secondary structure.