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Żygowska J, Orlikowska M, Zhukov I, Bal W, Szymańska A. Copper interaction with cystatin C: effects on protein structure and oligomerization. FEBS J 2024; 291:1974-1991. [PMID: 38349797 DOI: 10.1111/febs.17092] [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: 06/18/2023] [Revised: 01/09/2024] [Accepted: 02/01/2024] [Indexed: 02/15/2024]
Abstract
Human cystatin C (hCC), a small secretory protein, has gained attention beyond its classical role as a cysteine protease inhibitor owing to its potential involvement in neurodegenerative disorders. This study investigates the interaction between copper(II) ions [Cu(II)] and hCC, specifically targeting histidine residues known to participate in metal binding. Through various analytical techniques, including mutagenesis, circular dichroism, fluorescence assays, gel filtration chromatography, and electron microscopy, we evaluated the impact of Cu(II) ions on the structure and oligomerization of hCC. The results show that Cu(II) does not influence the secondary and tertiary structure of the studied hCC variants but affects their stability. To explore the Cu(II)-binding site, nuclear magnetic resonance (NMR) and X-ray studies were conducted. NMR experiments revealed notable changes in signal intensities and linewidths within the region 86His-Asp-Gln-Pro-His90, suggesting its involvement in Cu(II) coordination. Both histidine residues from this fragment were found to serve as a primary anchor of Cu(II) in solution, depending on the structural context and the presence of other Cu(II)-binding agents. The presence of Cu(II) led to significant destabilization and altered thermal stability of the wild-type and H90A variant, confirming differentiation between His residues in Cu(II) binding. In conclusion, this study provides valuable insights into the interaction between Cu(II) and hCC, elucidating the impact of copper ions on protein stability and identifying potential Cu(II)-binding residues. Understanding these interactions enhances our knowledge of the role of copper in neurodegenerative disorders and may facilitate the development of therapeutic strategies targeting copper-mediated processes in protein aggregation and associated pathologies.
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Affiliation(s)
- Justyna Żygowska
- Department of Biomedical Chemistry, Faculty of Chemistry, University of Gdańsk, Poland
| | - Marta Orlikowska
- Department of Biomedical Chemistry, Faculty of Chemistry, University of Gdańsk, Poland
| | - Igor Zhukov
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Poland
| | - Wojciech Bal
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Poland
| | - Aneta Szymańska
- Department of Biomedical Chemistry, Faculty of Chemistry, University of Gdańsk, Poland
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2
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Jurczak P, Zhukov I, Orlikowska M, Czaplewska P, Sikorska E. Monitoring the interactions between POPG phospholipid bilayer and amyloid-forming protein human cystatin C. Does the bilayer influence the oligomeric state and structure of the protein? BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2024; 1866:184285. [PMID: 38237885 DOI: 10.1016/j.bbamem.2024.184285] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Revised: 11/16/2023] [Accepted: 01/10/2024] [Indexed: 02/02/2024]
Abstract
A biological membrane is a structure characteristic for various cells and organelles present in almost all living organisms. Even though, it is one of the most common structures in organisms, where it serves crucial functions, a phospholipid bilayer may also take part in pathological processes leading to severe diseases. Research indicates that biological membranes have a profound impact on the pathological processes of oligomerization of amyloid-forming proteins. These processes are a hallmark of amyloid diseases, a group of pathological states involving, e.g., Parkinson's or Alzheimer's disease. Even though amyloidogenic diseases reap the harvest in modern societies, especially in elderly patients, the mechanisms governing the amyloid deposition are not clearly described. Therefore, the presented study focuses on the description of interactions between a model biological membrane (POPG) and one of amyloid forming proteins - human cystatin C. For the purpose of the study molecular dynamics simulations were applied to confirm interactions between the protein and POPG membrane. Next the NMR techniques were used to verify how the data obtained in solution compared to MD simulations and determine fragments of the protein responsible for interactions with POPG. Finally, circular dichroism was used to monitor the changes in secondary structure of the protein and size exclusion chromatography was used to monitor its oligomerization process. Obtained data indicates that the protein interacts with POPG submerging itself into the bilayer with the AS region. However, the presence of POPG bilayer does not significantly affect the structure or oligomerization process of human cystatin C.
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Affiliation(s)
- Przemyslaw Jurczak
- Mossakowski Medical Research Centre Polish Academy of Sciences, Laboratory of Molecular and Cellular Nephrology, Gdansk, Poland; Department of Biomedical Chemistry, Faculty of Chemistry, University of Gdansk, Gdansk, Poland.
| | - Igor Zhukov
- Biological NMR Facility, Institute of Biochemistry and Bioscience, Polish Academy of Science, Warsaw, Poland
| | - Marta Orlikowska
- Department of Biomedical Chemistry, Faculty of Chemistry, University of Gdansk, Gdansk, Poland
| | - Paulina Czaplewska
- Specialist Laboratories, Intercollegiate Faculty of Biotechnology UG&MUG, Gdansk, Poland.
| | - Emilia Sikorska
- Department of Organic Chemistry, Faculty of Chemistry, University of Gdansk, Gdansk, Poland.
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Niedziałkowski P, Jurczak P, Orlikowska M, Wcisło A, Ryl J, Ossowski T, Czaplewska P. Phospholipid-functionalized gold electrode for cellular membrane interface studies - interactions between DMPC bilayer and human cystatin C. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2024; 1866:184266. [PMID: 38151198 DOI: 10.1016/j.bbamem.2023.184266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2023] [Revised: 12/14/2023] [Accepted: 12/20/2023] [Indexed: 12/29/2023]
Abstract
This work describes the electrochemical studies on the interactions between V57G mutant of human cystatin C (hCC V57G) and membrane bilayer immobilized on the surface of a gold electrode. The electrode was modified with 6-mercaptohexan-1-ol (MCH) and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). DMPC was used as a membrane mimetic for monitoring electrochemical changes resulting from the interactions between the functionalized electrode surface and human cystatin C. The interactions between the modified electrode and hCC V57G were investigated by cyclic voltammetry and electrochemical impedance spectroscopy in a phosphate buffered saline (PBS) containing Fe(CN)63-/4- as a redox probe. The electrochemical measurements confirm that fabricated electrode is sensitive to hCC V57G at the concentration of 1 × 10-14 M. The incubation studies carried out at higher concentrations resulted in insignificant changes observed in cyclic voltammetry and electrochemical impedance spectroscopy measurements. The calculated values of surface coverage θR confirm that the electrode is equally covered at higher concentrations of hCC V57G. Measurements of wettability and surface free energy made it possible to determine the influence of individual structural elements of the modified gold electrode on its properties, and thus allowed to understand the nature of the interactions. Contact angle values confirmed the results obtained during electrochemical measurements, indicating the sensitivity of the electrode towards hCC V57G at the concentration of 1 × 10-14 M. In addition, the XPS spectra confirmed the successful anchoring of hCC V57G to the DMPC-functionalized surface.
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Affiliation(s)
- Paweł Niedziałkowski
- Department of Analytical Chemistry, Faculty of Chemistry, University of Gdansk, Wita Stwosza 63, Gdańsk 80-308, Poland.
| | - Przemysław Jurczak
- Department of Biomedical Chemistry, Faculty of Chemistry, University of Gdansk, Wita Stwosza 63, Gdańsk 80-308, Poland; Specialist Laboratories, Intercollegiate Faculty of Biotechnology UG&MUG, Abrahama 58, Gdańsk 80-307, Poland.
| | - Marta Orlikowska
- Department of Biomedical Chemistry, Faculty of Chemistry, University of Gdansk, Wita Stwosza 63, Gdańsk 80-308, Poland
| | - Anna Wcisło
- Department of Analytical Chemistry, Faculty of Chemistry, University of Gdansk, Wita Stwosza 63, Gdańsk 80-308, Poland
| | - Jacek Ryl
- Division of Electrochemistry and Surface Physical Chemistry, Institute of Nanotechnology and Materials Engineering and Advanced Materials Center, Gdańsk University of Technology, Narutowicza 11/12, Gdańsk 80-233, Poland
| | - Tadeusz Ossowski
- Department of Analytical Chemistry, Faculty of Chemistry, University of Gdansk, Wita Stwosza 63, Gdańsk 80-308, Poland
| | - Paulina Czaplewska
- Specialist Laboratories, Intercollegiate Faculty of Biotechnology UG&MUG, Abrahama 58, Gdańsk 80-307, Poland
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Żyła A, Martel A, Jurczak P, Moliński A, Szymańska A, Kozak M. Human cystatin C induces the disaggregation process of selected amyloid beta peptides: a structural and kinetic view. Sci Rep 2023; 13:20833. [PMID: 38012338 PMCID: PMC10682421 DOI: 10.1038/s41598-023-47514-w] [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: 09/20/2023] [Accepted: 11/14/2023] [Indexed: 11/29/2023] Open
Abstract
Neurodegenerative diseases, such as Alzheimer's disease (AD) and various types of amyloidosis, are incurable; therefore, understanding the mechanisms of amyloid decomposition is crucial to develop an effective drug against them for future therapies. It has been reported that one out of three people over the age of 85 are suffering from dementia as a comorbidity to AD. Amyloid beta (Aβ), the hallmark of AD, transforms structurally from monomers into β-stranded aggregates (fibrils) via multiple oligomeric states. Astrocytes in the central nervous system secrete the human cystatin C protein (HCC) in response to various proteases and cytokines. The codeposition of Aβ and HCC in the brains of patients with AD led to the hypothesis that cystatin C is implicated in the disease process. In this study, we investigate the intermolecular interactions between different atomic structures of fibrils formed by Aβ peptides and HCC to understand the pathological aggregation of these polypeptides into neurotoxic oligomers and then amyloid plaques. To characterize the interactions between Aβ and HCC, we used a complementary approach based on the combination of small-angle neutron scattering analysis, atomic force microscopy and computational modelling, allowing the exploration of the structures of multicomponent protein complexes. We report here an optimized protocol to study that interaction. The results show a dependency of the sequence length of the Aβ peptide on the ability of the associated HCC to disaggregate it.
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Affiliation(s)
- Adriana Żyła
- Department of Biomedical Physics, Faculty of Physics, Adam Mickiewicz University, Poznań, Poland
- NanoBioMedical Centre, Adam Mickiewicz University, Poznań, Poland
| | - Anne Martel
- Large Scale Structures, ILL Neutrons for Society, Institute Laue-Langevin, Grenoble, France
| | - Przemysław Jurczak
- Laboratory of Medical Chemistry, Department of Biomedical Chemistry, Faculty of Chemistry, University of Gdańsk, Gdańsk, Poland
| | - Augustyn Moliński
- Department of Biomedical Physics, Faculty of Physics, Adam Mickiewicz University, Poznań, Poland
- NanoBioMedical Centre, Adam Mickiewicz University, Poznań, Poland
| | - Aneta Szymańska
- Laboratory of Medical Chemistry, Department of Biomedical Chemistry, Faculty of Chemistry, University of Gdańsk, Gdańsk, Poland
| | - Maciej Kozak
- Department of Biomedical Physics, Faculty of Physics, Adam Mickiewicz University, Poznań, Poland.
- SOLARIS National Synchrotron Radiation Centre, Jagiellonian University, Kraków, Poland.
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Wojciechowska D, Taube M, Rucińska K, Maksim J, Kozak M. Oligomerization of Human Cystatin C—An Amyloidogenic Protein: An Analysis of Small Oligomeric Subspecies. Int J Mol Sci 2022; 23:ijms232113441. [PMID: 36362228 PMCID: PMC9656228 DOI: 10.3390/ijms232113441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 10/27/2022] [Accepted: 11/01/2022] [Indexed: 11/06/2022] Open
Abstract
Human cystatin C (HCC), an amyloidogenic protein, forms dimers and higher oligomers (trimers, tetramers and donut like large oligomers) via a domain-swapping mechanism. The aim of this study was the characterization of the HCC oligomeric states observed within the pH range from 2.2 to 10.0 and also in conditions promoting oligomerization. The HCC oligomeric forms obtained in different conditions were characterized using size exclusion chromatography, dynamic light scattering and small-angle X-ray scattering. The marked ability of HCC to form tetramers at low pH (2.3 or 3.0) and dimers at pH 4.0–5.0 was observed. HCC remains monomeric at pH levels above 6.0. Based on the SAXS data, the structure of the HCC tetramer was proposed. Changes in the environment (from acid to neutral) induced a breakdown of the HCC tetramers to dimers. The tetrameric forms of human cystatin C are formed by the association of the dimers without a domain-swapping mechanism. These observations were confirmed by their dissociation to dimers at pH 7.4.
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Affiliation(s)
- Daria Wojciechowska
- Department of Biomedical Physics, Faculty of Physics, Adam Mickiewicz University, 61-614 Poznań, Poland
| | - Michał Taube
- Department of Biomedical Physics, Faculty of Physics, Adam Mickiewicz University, 61-614 Poznań, Poland
| | - Karolina Rucińska
- Department of Biomedical Physics, Faculty of Physics, Adam Mickiewicz University, 61-614 Poznań, Poland
| | - Joanna Maksim
- Department of Biomedical Physics, Faculty of Physics, Adam Mickiewicz University, 61-614 Poznań, Poland
| | - Maciej Kozak
- Department of Biomedical Physics, Faculty of Physics, Adam Mickiewicz University, 61-614 Poznań, Poland
- National Synchrotron Radiation Centre SOLARIS, Jagiellonian University, 30-392 Kraków, Poland
- Correspondence:
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Identification of a Steric Zipper Motif in the Amyloidogenic Core of Human Cystatin C and Its Use for the Design of Self-Assembling Peptides. Int J Mol Sci 2022; 23:ijms23105800. [PMID: 35628610 PMCID: PMC9147961 DOI: 10.3390/ijms23105800] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2022] [Revised: 05/14/2022] [Accepted: 05/20/2022] [Indexed: 02/05/2023] Open
Abstract
Amyloid fibrils have been known for many years. Unfortunately, their fame stems from negative aspects related to amyloid diseases. Nevertheless, due to their properties, they can be used as interesting nanomaterials. Apart from their remarkable stability, amyloid fibrils may be regarded as a kind of a storage medium and as a source of active peptides. In many cases, their structure may guarantee a controlled and slow release of peptides in their active form; therefore, they can be used as a potential nanomaterial in drug delivery systems. In addition, amyloid fibrils display controllable stiffness, flexibility, and satisfactory mechanical strength. In addition, they can be modified and functionalized very easily. Understanding the structure and genesis of amyloid assemblies derived from a broad range of amyloidogenic proteins could help to better understand and use this unique material. One of the factors responsible for amyloid aggregation is the steric zipper. Here, we report the discovery of steric zipper-forming peptides in the sequence of the amyloidogenic protein, human cystatin C (HCC). The ability of short peptides derived from this fragment of HCC to form fibrillar structures with defined self-association characteristics and the factors influencing this aggregation are also presented in this paper.
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Zhang X, Liu X, Su G, Li M, Liu J, Wang C, Xu D. pH-dependent and dynamic interactions of cystatin C with heparan sulfate. Commun Biol 2021; 4:198. [PMID: 33580179 PMCID: PMC7881039 DOI: 10.1038/s42003-021-01737-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2020] [Accepted: 01/20/2021] [Indexed: 01/27/2023] Open
Abstract
Cystatin C (Cst-3) is a potent inhibitor of cysteine proteases with diverse biological functions. As a secreted protein, the potential interaction between Cst-3 and extracellular matrix components has not been well studied. Here we investigated the interaction between Cst-3 and heparan sulfate (HS), a major component of extracellular matrix. We discovered that Cst-3 is a HS-binding protein only at acidic pH. By NMR and site-directed mutagenesis, we identified two HS binding regions in Cst-3: the highly dynamic N-terminal segment and a flexible region located between residue 70-94. The composition of the HS-binding site by two highly dynamic halves is unique in known HS-binding proteins. We further discovered that HS-binding severely impairs the inhibitory activity of Cst-3 towards papain, suggesting the interaction could actively regulate Cst-3 activity. Using murine bone tissues, we showed that Cst-3 interacts with bone matrix HS at low pH, again highlighting the physiological relevance of our discovery.
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Affiliation(s)
- Xiaoxiao Zhang
- Department of Oral Biology, The University at Buffalo, Buffalo, NY, USA
| | - Xinyue Liu
- Department of Biology, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY, USA
| | - Guowei Su
- Division of Chemical Biology and Natural Product, School of Pharmacy, The University of North Carolina, Chapel Hill, NC, USA
| | - Miaomiao Li
- Department of Oral Biology, The University at Buffalo, Buffalo, NY, USA
| | - Jian Liu
- Division of Chemical Biology and Natural Product, School of Pharmacy, The University of North Carolina, Chapel Hill, NC, USA
| | - Chunyu Wang
- Department of Biology, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY, USA.
| | - Ding Xu
- Department of Oral Biology, The University at Buffalo, Buffalo, NY, USA.
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Jurczak P, Sikorska E, Czaplewska P, Rodziewicz-Motowidlo S, Zhukov I, Szymanska A. The Influence of the Mixed DPC:SDS Micelle on the Structure and Oligomerization Process of the Human Cystatin C. MEMBRANES 2020; 11:17. [PMID: 33374409 PMCID: PMC7824358 DOI: 10.3390/membranes11010017] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/06/2020] [Revised: 12/19/2020] [Accepted: 12/21/2020] [Indexed: 11/23/2022]
Abstract
Human cystatin C (hCC), a member of the superfamily of papain-like cysteine protease inhibitors, is the most widespread cystatin in human body fluids. Physiologically active hCC is a monomer, which dimerization and oligomerization lead to the formation of the inactive, insoluble amyloid form of the protein, strictly associated with cerebral amyloid angiopathy, a severe state causing death among young patients. It is known, that biological membranes may accelerate the oligomerization processes of amyloidogenic proteins. Therefore, in this study, we describe an influence of membrane mimetic environment-mixed dodecylphosphocholine:sodium dodecyl sulfate (DPC:SDS) micelle (molar ratio 5:1)-on the effect of the hCC oligomerization. The hCC-micelle interactions were analyzed with size exclusion chromatography, circular dichroism, and nuclear magnetic resonance spectroscopy. The experiments were performed on the wild-type (WT) cystatin C, and two hCC variants-V57P and V57G. Collected experimental data were supplemented with molecular dynamic simulations, making it possible to highlight the binding interface and select the residues involved in interactions with the micelle. Obtained data shows that the mixed DPC:SDS micelle does not accelerate the oligomerization of protein and even reverses the hCC dimerization process.
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Affiliation(s)
- Przemyslaw Jurczak
- Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland; (E.S.); (S.R.-M.)
| | - Emilia Sikorska
- Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland; (E.S.); (S.R.-M.)
| | - Paulina Czaplewska
- Intercollegiate Faculty of Biotechnology UG & MUG, University of Gdańsk, Gdańsk, Abrahama 58, 80-307 Gdańsk, Poland;
| | | | - Igor Zhukov
- NanoBioMedical Centre, Adam Mickiewicz University, Wszechnicy Piastowskiej 3, 61-614 Poznań, Poland
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Adolfa Pawińskiego 5A, 02-106 Warszawa, Poland
| | - Aneta Szymanska
- Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland; (E.S.); (S.R.-M.)
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Jurczak P, Szutkowski K, Lach S, Jurga S, Czaplewska P, Szymanska A, Zhukov I. DMPC Phospholipid Bilayer as a Potential Interface for Human Cystatin C Oligomerization: Analysis of Protein-Liposome Interactions Using NMR Spectroscopy. MEMBRANES 2020; 11:membranes11010013. [PMID: 33374166 PMCID: PMC7824490 DOI: 10.3390/membranes11010013] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Revised: 12/14/2020] [Accepted: 12/18/2020] [Indexed: 12/13/2022]
Abstract
Studies revolving around mechanisms responsible for the development of amyloid-based diseases lay the foundations for the recognition of molecular targets of future to-be-developed treatments. However, the vast number of peptides and proteins known to be responsible for fibril formation, combined with their complexity and complexity of their interactions with various cellular components, renders this task extremely difficult and time-consuming. One of these proteins, human cystatin C (hCC), is a well-known and studied cysteine-protease inhibitor. While being a monomer in physiological conditions, under the necessary stimulus—usually a mutation, it tends to form fibrils, which later participate in the disease development. This process can potentially be regulated (in several ways) by many cellular components and it is being hypothesized that the cell membrane might play a key role in the oligomerization pathway. Studies involving cell membranes pose several difficulties; therefore, an alternative in the form of membrane mimetics is a very attractive solution. Here, we would like to present the first study on hCC oligomerization under the influence of phospholipid liposomes, acting as a membrane mimetic. The protein–mimetic interactions are studied utilizing circular dichroism, nuclear magnetic resonance, and size exclusion chromatography.
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Affiliation(s)
- Przemyslaw Jurczak
- Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland; (P.J.); (S.L.); (A.S.)
| | - Kosma Szutkowski
- NanoBioMedical Centre, Adam Mickiewicz University, Wszechnicy Piastowskiej 3, 61-614 Poznań, Poland; (K.S.); (S.J.)
| | - Slawomir Lach
- Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland; (P.J.); (S.L.); (A.S.)
| | - Stefan Jurga
- NanoBioMedical Centre, Adam Mickiewicz University, Wszechnicy Piastowskiej 3, 61-614 Poznań, Poland; (K.S.); (S.J.)
| | - Paulina Czaplewska
- Intercollegiate Faculty of Biotechnology UG & MUG, University of Gdańsk, Gdańsk, Abrahama 58, 80-307 Gdańsk, Poland;
| | - Aneta Szymanska
- Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland; (P.J.); (S.L.); (A.S.)
| | - Igor Zhukov
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Adolfa Pawińskiego 5A, 02-106 Warszawa, Poland
- Correspondence: ; Tel.: +48-22-592-2038
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Abstract
The epididymal lumen contains a complex cystatin-rich nonpathological amyloid matrix with putative roles in sperm maturation and sperm protection. Given our growing understanding for the biological function of this and other functional amyloids, the problem still remains: how functional amyloids assemble including their initial transition to early oligomeric forms. To examine this, we developed a protocol for the purification of nondenatured mouse CRES, a component of the epididymal amyloid matrix, allowing us to examine its assembly to amyloid under conditions that may mimic those in vivo. Herein we use X-ray crystallography, solution-state NMR, and solid-state NMR to follow at the atomic level the assembly of the CRES amyloidogenic precursor as it progressed from monomeric folded protein to an advanced amyloid. We show the CRES monomer has a typical cystatin fold that assembles into highly branched amyloid matrices, comparable to those in vivo, by forming β-sheet assemblies that our data suggest occur via two distinct mechanisms: a unique conformational switch of a highly flexible disulfide-anchored loop to a rigid β-strand and by traditional cystatin domain swapping. Our results provide key insight into our understanding of functional amyloid assembly by revealing the earliest structural transitions from monomer to oligomer and by showing that some functional amyloid structures may be built by multiple and distinctive assembly mechanisms.
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