| 1. |
- Brännström, Kristoffer, et al.
(författare)
-
A Generic Method for Design of Oligomer-Specific Antibodies
- 2014
-
Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 9:3, s. e90857-
-
Tidskriftsartikel (refereegranskat)abstract
- Antibodies that preferentially and specifically target pathological oligomeric protein and peptide assemblies, as opposed to their monomeric and amyloid counterparts, provide therapeutic and diagnostic opportunities for protein misfolding diseases. Unfortunately, the molecular properties associated with oligomer-specific antibodies are not well understood, and this limits targeted design and development. We present here a generic method that enables the design and optimisation of oligomer-specific antibodies. The method takes a two-step approach where discrimination between oligomers and fibrils is first accomplished through identification of cryptic epitopes exclusively buried within the structure of the fibrillar form. The second step discriminates between monomers and oligomers based on differences in avidity. We show here that a simple divalent mode of interaction, as within e. g. the IgG isotype, can increase the binding strength of the antibody up to 1500 times compared to its monovalent counterpart. We expose how the ability to bind oligomers is affected by the monovalent affinity and the turnover rate of the binding and, importantly, also how oligomer specificity is only valid within a specific concentration range. We provide an example of the method by creating and characterising a spectrum of different monoclonal antibodies against both the A beta peptide and alpha-synuclein that are associated with Alzheimer's and Parkinson's diseases, respectively. The approach is however generic, does not require identification of oligomer-specific architectures, and is, in essence, applicable to all polypeptides that form oligomeric and fibrillar assemblies.
|
|
| 2. |
|
|
| 3. |
- Aguilar, Ximena, 1978-, et al.
(författare)
-
Interaction Studies of the Human and Arabidopsis thaliana Med25-ACID Proteins with the Herpes Simplex Virus VP16-and Plant-Specific Dreb2a Transcription Factors
- 2014
-
Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 9:5, s. e98575-
-
Tidskriftsartikel (refereegranskat)abstract
- Mediator is an evolutionary conserved multi-protein complex present in all eukaryotes. It functions as a transcriptional coregulator by conveying signals from activators and repressors to the RNA polymerase II transcription machinery. The Arabidopsis thaliana Med25 (aMed25) ACtivation Interaction Domain (ACID) interacts with the Dreb2a activator which is involved in plant stress response pathways, while Human Med25-ACID (hMed25) interacts with the herpes simplex virus VP16 activator. Despite low sequence similarity, hMed25-ACID also interacts with the plant-specific Dreb2a transcriptional activator protein. We have used GST pull-down-, surface plasmon resonance-, isothermal titration calorimetry and NMR chemical shift experiments to characterize interactions between Dreb2a and VP16, with the hMed25 and aMed25-ACIDs. We found that VP16 interacts with aMed25-ACID with similar affinity as with hMed25-ACID and that the binding surface on aMed25-ACID overlaps with the binding site for Dreb2a. We also show that the Dreb2a interaction region in hMed25-ACID overlaps with the earlier reported VP16 binding site. In addition, we show that hMed25-ACID/Dreb2a and aMed25-ACID/Dreb2a display similar binding affinities but different binding energetics. Our results therefore indicate that interaction between transcriptional regulators and their target proteins in Mediator are less dependent on the primary sequences in the interaction domains but that these domains fold into similar structures upon interaction.
|
|
| 4. |
- Blomberg, Jeanette, et al.
(författare)
-
Interactions between DNA, transcriptional regulator Dreb2a and the Med25 mediator subunit from Arabidopsis thaliana involve conformational changes
- 2012
-
Ingår i: Nucleic Acids Research. - Oxford : Oxford University Press. - 0305-1048 .- 1362-4962. ; 40:13, s. 5938-5950
-
Tidskriftsartikel (refereegranskat)abstract
- Mediator is a multiprotein coregulatory complex that conveys signals from DNA-bound transcriptional regulators to the RNA polymerase II transcription machinery in eukaryotes. The molecular mechanisms for how these signals are transmitted are still elusive. By using purified transcription factor Dreb2a, mediator subunit Med25 from Arabidopsis thaliana, and a combination of biochemical and biophysical methods, we show that binding of Dreb2a to its canonical DNA sequence leads to an increase in secondary structure of the transcription factor. Similarly, interaction between the Dreb2a and Med25 in the absence of DNA results in conformational changes. However, the presence of the canonical Dreb2a DNA-binding site reduces the affinity between Dreb2a and Med25. We conclude that transcription regulation is facilitated by small but distinct changes in energetic and structural parameters of the involved proteins.
|
|
| 5. |
- Brännström, Jonas, et al.
(författare)
-
The initial evaluation of an Internet-based support system for audiologists and first-time hearing aid clients
- 2016
-
Ingår i: Internet Interventions. - : Elsevier BV. - 2214-7829. ; 4, s. 82-91
-
Tidskriftsartikel (refereegranskat)abstract
- Objectives: Audiologists provide professional contact and support between appointments to clients with hearing impairment using telephone and e-mail, but more advanced and flexible technological platforms are also possible. The present study aimed to evaluate the clinical application of an Internet-based support system for audiologists and their first-time hearing aid clients. Design: An Internet-based support system developed by Månsson et al. (2013) for psychologists and their clients was adapted for audiologic purposes. Three audiologic clinics in Sweden tested the support system with their clients. Study sample: Twenty-three clients managed by four audiologists used and evaluated the support system. In addition, five of the clients and all four audiologists were interviewed and their responses were analyzed using content analysis. Results: The clients and the audiologists reported positive experiences and overall satisfaction but audiologists reported that the support system did not address the needs of all clients. More positive experiences and greater satisfaction with the support system were associated with reductions on self-reported consequences of hearing loss and positive hearing aids outcomes. Conclusions: An Internet-based support system can be used in audiologic rehabilitation. Both audiologists and clients recognized the system's potential value to offer an online support to the provision of audiologic services.
|
|
| 6. |
|
|
| 7. |
- Brännström, Jonas, et al.
(författare)
-
The Process of Developing an Internet-Based Support System for Audiologists and First-Time Hearing Aid Clients
- 2015
-
Ingår i: American Journal of Audiology. - : American Speech-Language-Hearing Association. - 1059-0889 .- 1558-9137. ; 24:3, s. 320-324
-
Tidskriftsartikel (refereegranskat)abstract
- Background: In audiologic practice, complementary information sources and access to the clinician between appointments improve information retention and facilitate adjustment behaviors. An Internet-based support system is a novel way to support information sharing and clinician access. Purpose: This research forum article describes the process of developing an Internet-based support system for audiologists and their first-time hearing aid clients. Method: The iterative development process, including revisions by 4 research audiologists and 4 clinical audiologists, is described. The final system is exemplified. Conclusion: An Internet-based support system was successfully developed for audiologic practice.
|
|
| 8. |
- Brännström, Kristoffer, et al.
(författare)
-
Aβ peptide fibrillar architectures controlled by conformational constraints of the monomer
- 2011
-
Ingår i: PLOS ONE. - San Francisco, CA : Public Library of Science. - 1932-6203. ; 6:9, s. e25157-
-
Tidskriftsartikel (refereegranskat)abstract
- Anomalous self-assembly of the Aβ peptide into fibrillar amyloid deposits is strongly correlated with the development of Alzheimer's disease. Aβ fibril extension follows a template guided "dock and lock" mechanism where polymerisation is catalysed by the fibrillar ends. Using surface plasmon resonance (SPR) and quenched hydrogen-deuterium exchange NMR (H/D-exchange NMR), we have analysed the fibrillar structure and polymerisation properties of both the highly aggregation prone Aβ1-40 Glu22Gly (Aβ(40Arc)) and wild type Aβ1-40 (Aβ(40WT)). The solvent protection patterns from H/D exchange experiments suggest very similar structures of the fibrillar forms. However, through cross-seeding experiments monitored by SPR, we found that the monomeric form of Aβ(40WT) is significantly impaired to acquire the fibrillar architecture of Aβ(40Arc). A detailed characterisation demonstrated that Aβ(40WT) has a restricted ability to dock and isomerise with high binding affinity onto Aβ(40Arc) fibrils. These results have general implications for the process of fibril assembly, where the rate of polymerisation, and consequently the architecture of the formed fibrils, is restricted by conformational constraints of the monomers. Interestingly, we also found that the kinetic rate of fibril formation rather than the thermodynamically lowest energy state determines the overall fibrillar structure.
|
|
| 9. |
- Brännström, Kristoffer, et al.
(författare)
-
Ca2+ enhances Aβ polymerization rate and fibrillar stability in a dynamic manner
- 2013
-
Ingår i: Biochemical Journal. - : Portland Press. - 0264-6021 .- 1470-8728. ; 450, s. 189-197
-
Tidskriftsartikel (refereegranskat)abstract
- Identifying factors that affect the self-assembly of the amyloid-β peptide (Aβ) is of utmost importance in the quest to understand the molecular mechanisms causing Alzheimer's disease (AD). Ca2+ has previously been shown to accelerate both Aβ fibril nucleation and maturation, and a dysregulated Ca2+ homeostasis frequently correlates with development of AD. The mechanisms regarding Ca2+ binding as well as its effect on fibril kinetics are not fully understood. Using a polymerization assay we show that Ca2+ in a dynamic and reversible manner enhances both the elongation rate and fibrillar stability, where specifically the "dock and lock" phase mechanism is enhanced. Through NMR analysis we found that Ca2+ affects the fibrillar architecture. In addition, and unexpectedly, we found that Ca2+ does not bind the free Aβ monomer. This implies that Ca2+ binding requires an architecture adopted by assembled peptides, and consequently is mediated through intermolecular interactions between adjacent peptides. This gives a mechanistic explanation to the enhancing effect on fibril maturation and indicates structural similarities between prefibrillar structures and mature amyloid. Taken together we expose how Ca2+ levels affect the delicate equilibrium between the monomeric and assembled Aβ and how fluctuations in vivo may contribute to development and progression of the disease.
|
|
| 10. |
- Brännström, Kristoffer, et al.
(författare)
-
Characterization of SPINK9, a KLK5-specific inhibitor expressed in palmo-plantar epidermis
- 2012
-
Ingår i: Biological chemistry (Print). - : Walter de Gruyter. - 1431-6730 .- 1437-4315. ; 393:5, s. 369-377
-
Tidskriftsartikel (refereegranskat)abstract
- SPINK9, a Kazal-type serine protease inhibitor, is almost exclusively expressed in the palmo-plantar epidermis. SPINK9 selectively inhibits kallikrein-related peptidase 5 (KLK5), no other target enzyme is known at present. In this study, we defined the reactive loop to residues 48 and 49 of SPINK9 and characterized the inhibition and binding of different SPINK9 variants towards KLK5, KLK7, KLK8 and KLK14. Substitutions of single amino acids in the reactive loop had a large impact on both inhibitory efficiency and specificity. Binding studies showed that it is mainly the dissociation rate that is affected by the amino acid substitutions. The inhibitory effect of wild-type SPINK9 was clearly pH-dependent with an improved effect at a pH similar to that of the outer layers of the skin. Modeling of the enzyme-inhibitor complexes showed that the reactive loop of SPINK9 fits very well into the deep negatively charged binding pocket of KLK5. A decrease in pH protonates His48 of the wild-type protein resulting in a positively charged residue, thereby explaining the observed decreased dissociation rate. Interestingly, substitution with a positively charged amino acid at position 48 resulted in a more efficient inhibitor at higher pH.
|
|
