| 1. |
- Abelein, Axel, et al.
(författare)
-
Molecular Structure of Cu(II)-Bound Amyloid-β Monomer Implicated in Inhibition of Peptide Self-Assembly in Alzheimer’s Disease
- 2022
-
Ingår i: JACS Au. - : American Chemical Society (ACS). - 2691-3704. ; 2:11, s. 2571-2584
-
Tidskriftsartikel (refereegranskat)abstract
- Metal ions, such as copper and zinc ions, have been shown to strongly modulate the self-assembly of the amyloid-β (Aβ) peptide into insoluble fibrils, and elevated concentrations of metal ions have been found in amyloid plaques of Alzheimer’s patients. Among the physiological transition metal ions, Cu(II) ions play an outstanding role since they can trigger production of neurotoxic reactive oxygen species. In contrast, structural insights into Cu(II) coordination of Aβ have been challenging due to the paramagnetic nature of Cu(II). Here, we employed specifically tailored paramagnetic NMR experiments to determine NMR structures of Cu(II) bound to monomeric Aβ. We found that monomeric Aβ binds Cu(II) in the N-terminus and combined with molecular dynamics simulations, we could identify two prevalent coordination modes of Cu(II). For these, we report here the NMR structures of the Cu(II)–bound Aβ complex, exhibiting heavy backbone RMSD values of 1.9 and 2.1 Å, respectively. Further, applying aggregation kinetics assays, we identified the specific effect of Cu(II) binding on the Aβ nucleation process. Our results show that Cu(II) efficiently retards Aβ fibrillization by predominately reducing the rate of fibril-end elongation at substoichiometric ratios. A detailed kinetic analysis suggests that this specific effect results in enhanced Aβ oligomer generation promoted by Cu(II). These results can quantitatively be understood by Cu(II) interaction with the Aβ monomer, forming an aggregation inert complex. In fact, this mechanism is strikingly similar to other transition metal ions, suggesting a common mechanism of action of retarding Aβ self-assembly, where the metal ion binding to monomeric Aβ is a key determinant.
|
|
| 2. |
- Al Adwani, Salma, et al.
(författare)
-
Citrullination Alters the Antibacterial and Anti-Inflammatory Functions of the Host Defense Peptide Canine Cathelicidin K9CATH In Vitro
- 2021
-
Ingår i: Journal of Immunology. - : The American Association of Immunologists. - 0022-1767 .- 1550-6606. ; 207:3, s. 974-984
-
Tidskriftsartikel (refereegranskat)abstract
- K9CATH is the sole cathelicidin in canines (dogs) and exhibits broad antimicrobial activity against both Gram-positive and Gram-negative bacteria. K9CATH also modulates inflammatory responses and binds to LPS. These activities depend on the secondary structure and a net-positive charge of the peptide. Peptidylarginine deiminases (PAD) convert cationic peptidyl arginine to neutral citrulline. Thus, we hypothesized that citrullination is a biologically relevant modification of the peptide that would reduce the antibacterial and LPS-binding activities of K9CATH. Recombinant PAD2 and PAD4 citrullinated K9CATH to various extents and circular dichroism spectroscopy revealed that both native and citrullinated K9CATH exhibited similar α-helical secondary structures. Notably, citrullination of K9CATH reduced its bactericidal activity, abolished its ability to permeabilize the membrane of Gram-negative bacteria and reduced the hemolytic capacity. Electron microscopy showed that citrullinated K9CATH did not cause any morphological changes of Gram-negative bacteria, whereas the native peptide caused clear alterations of membrane integrity, concordant with a rapid bactericidal effect. Finally, citrullination of K9CATH impaired its capacity to inhibit LPS-mediated release of proinflammatory molecules from mouse and canine macrophages. In conclusion, citrullination attenuates the antibacterial and the LPS-binding properties of K9CATH, demonstrating the importance of a net positive charge for antibacterial lysis of bacteria and LPS-binding effects and suggests that citrullination is a means to regulate cathelicidin activities.
|
|
| 3. |
- Król, Sylwia, et al.
(författare)
-
The amyloid-inhibiting NCAM-PrP peptide targets Aβ peptide aggregation in membrane-mimetic environments
- 2021
-
Ingår i: iScience. - : Elsevier BV. - 2589-0042. ; 24:8
-
Tidskriftsartikel (refereegranskat)abstract
- Substantial research efforts have gone into elucidating the role of protein misfolding and self-assembly in the onset and progression of Alzheimer’s disease (AD). Aggregation of the Amyloid-β (Aβ) peptide into insoluble fibrils is closely associated with AD. Here, we use biophysical techniques to study a peptide-based approach to target Aβ amyloid aggregation. A peptide construct, NCAM-PrP, consists of a largely hydrophobic signal sequence linked to a positively charged hexapeptide. The NCAM-PrP peptide inhibits Aβ amyloid formation by forming aggregates which are unavailable for further amyloid aggregation. In a membrane-mimetic environment, Aβ and NCAM-PrP form specific heterooligomeric complexes, which are of lower aggregation states compared to Aβ homooligomers. The Aβ:NCAM-PrP interaction appears to take place on different aggregation states depending on the absence or presence of a membrane-mimicking environment. These insights can be useful for the development of potential future therapeutic strategies targeting Aβ at several aggregation states.
|
|
| 4. |
- Mörman, Cecilia, 1988-
(författare)
-
Self-assembly of amyloid-β peptides in the presence of metal ions and interacting molecules – a detour of amyloid building blocks
- 2020
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Misfolding of proteins into amyloid structures is implicated as a pathological feature in several neurodegenerative diseases and the molecular causes are still unclear. One typical characteristic of Alzheimer’s disease is self-assembly and accumulation of soluble amyloid-β (Aβ) peptides into insoluble fibrils and plaques. One way to provide fundamental knowledge about the underlying fibrillization processes is to perturb the aggregation by varying the experimental conditions. Two main aspects are included in this thesis work: interactions with the Aβ peptide, and modulation of the Aβ peptide aggregation kinetics. The interplay between the Aβ peptide and three different types of aggregation modulators was studied mainly in vitro by biophysical techniques such as NMR, circular dichroism, and fluorescence spectroscopy.Metal ions, such as Ag(I), Cu(II), Hg(II), and Zn(II), at sub-stoichiometric concentrations with specific binding to monomeric Aβ peptides modulate and attenuate the Aβ self-assembly process. The bound (metal:Aβ) state removes Aβ monomers from the monomeric pool of amyloid building blocks used for fibril formation. In contrast, designed peptide constructs with cell-penetrating properties do not interact with monomeric Aβ, but exhibit an inhibitory effect on the Aβ oligomerization and fibrillization in vitro and in cells, via interactions with multimeric Aβ structures. The designed peptide constructs rescue Aβ-induced neurotoxicity and target both intracellular and extracellular Aβ. Full-length and native Tau protein, another protein implicated in Alzheimer’s disease, prevents the Aβ peptide fibrillization. The Aβ fibrillization process is not prevented by Tau interactions with the Aβ monomeric species, but rather with fibrils and oligomeric species of Aβ.Here we showed that the Aβ peptide interacts with various metal ions and molecules, both at the monomeric stage and as larger assemblies, with resulting perturbation of the Aβ aggregation kinetics. The interactions and aggregation modulators can be used to learn more about the underlying fibrillization processes and for the development of potential therapeutic strategies.
|
|
| 5. |
- Paul, Suman, et al.
(författare)
-
13C- and 15N-labeling of amyloid-β and inhibitory peptides to study their interaction via nanoscale infrared spectroscopy
- 2023
-
Ingår i: Communications Chemistry. - 2399-3669. ; 6:1
-
Tidskriftsartikel (refereegranskat)abstract
- Interactions between molecules are fundamental in biology. They occur also between amyloidogenic peptides or proteins that are associated with different amyloid diseases, which makes it important to study the mutual influence of two polypeptides on each other's properties in mixed samples. However, addressing this research question with imaging techniques faces the challenge to distinguish different polypeptides without adding artificial probes for detection. Here, we show that nanoscale infrared spectroscopy in combination with C-13, N-15-labeling solves this problem. We studied aggregated amyloid-& beta; peptide (A & beta;) and its interaction with an inhibitory peptide (NCAM1-PrP) using scattering-type scanning near-field optical microscopy. Although having similar secondary structure, labeled and unlabeled peptides could be distinguished by comparing optical phase images taken at wavenumbers characteristic for either the labeled or the unlabeled peptide. NCAM1-PrP seems to be able to associate with or to dissolve existing A & beta; fibrils because pure A & beta; fibrils were not detected after mixing. Interactions of proteins or polypeptides with different secondary structures can be studied in a mixture by nanoscale infrared spectroscopy, however, this technique remains challenging for polypeptides with similar secondary structures. Here, the authors demonstrate clear discrimination of two polypeptides from a mixture by scattering-type scanning near-field optical microscopy when one of the components is labeled with C-13- and N-15-isotopes.
|
|
