The Impact of Halogenated Phenylalanine Derivatives on NFGAIL Amyloid Formation

The hexapeptide hIAPP(22-27)(NFGAIL) is known as a crucial amyloid core sequence of the human islet amyloid polypeptide (hIAPP) whose aggregates can be used to better understand the wild-type hIAPP ' s toxicity to beta-cell death. In amyloid research, the role of hydrophobic and aromatic-aromatic interactions as potential driving forces during the aggregation process is controversially discussed not only in case of NFGAIL, but also for amyloidogenic peptides in general. We have used halogenation of the aromatic residue as a strategy to modulate hydrophobic and aromatic-aromatic interactions and prepared a library of NFGAIL variants containing fluorinated and iodinated phenylalanine analogues. We used thioflavin T staining, transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) to study the impact of side-chain halogenation on NFGAIL amyloid formation kinetics. Our data revealed a synergy between aggregation behavior and hydrophobicity of the phenylalanine residue. This study introduces systematic fluorination as a toolbox to further investigate the nature of the amyloid self-assembly process

The Impact of Halogenated Phenylalanine Derivatives on NFGAIL Amyloid Formation

The hexapeptide hIAPP22–27 (NFGAIL) is known as a crucial amyloid core sequence of the human islet amyloid polypeptide (hIAPP) whose aggregates can be used to better understand the wild-type hIAPP’s toxicity to β-cell death. In amyloid research, the role of hydrophobic and aromatic-aromatic interactions as potential driving forces during the aggregation process is controversially discussed not only in case of NFGAIL, but also for amyloidogenic peptides in general. We have used halogenation of the aromatic residue as a strategy to modulate hydrophobic and aromatic-aromatic interactions and prepared a library of NFGAIL variants containing fluorinated and iodinated phenylalanine analogues. We used thioflavin T staining, transmission electron microscopy (TEM) and smallangle X-ray scattering (SAXS) to study the impact of side-chain halogenation on NFGAIL amyloid formation kinetics. Our data revealed a synergy between aggregation behavior and hydrophobicity of the phenylalanine residue. This study introduces systematic fluorination as a toolbox to further investigate the nature of the amyloid self-assembly process

Interplay between phosphorylation and palmitoylation mediates plasma membrane targeting and sorting of GAP43.

Phosphorylation and lipidation provide posttranslational mechanisms that contribute to the distribution of cytosolic proteins in growing nerve cells. The growth-associated protein GAP43 is susceptible to both phosphorylation and S-palmitoylation and is enriched in the tips of extending neurites. However, how phosphorylation and lipidation interplay to mediate sorting of GAP43 is unclear. Using a combination of biochemical, genetic, and imaging approaches, we show that palmitoylation is required for membrane association and that phosphorylation at Ser-41 directs palmitoylated GAP43 to the plasma membrane. Plasma membrane association decreased the diffusion constant fourfold in neuritic shafts. Sorting to the neuritic tip required palmitoylation and active transport and was increased by phosphorylation-mediated plasma membrane interaction. Vesicle tracking revealed transient association of a fraction of GAP43 with exocytic vesicles and motion at a fast axonal transport rate. Simulations confirmed that a combination of diffusion, dynamic plasma membrane interaction and active transport of a small fraction of GAP43 suffices for efficient sorting to growth cones. Our data demonstrate a complex interplay between phosphorylation and lipidation in mediating the localization of GAP43 in neuronal cells. Palmitoylation tags GAP43 for global sorting by piggybacking on exocytic vesicles, whereas phosphorylation locally regulates protein mobility and plasma membrane targeting of palmitoylated GAP43

Position-dependent impact of hexafluoroleucine and trifluoroisoleucine on protease digestion

Rapid digestion by proteases limits the application of peptides as therapeutics. One strategy to increase the proteolytic stability of peptides is the modification with fluorinated amino acids. This study presents a systematic investigation of the effects of fluorinated leucine and isoleucine derivatives on the proteolytic stability of a peptide that was designed to comprise substrate specificities of different proteases. Therefore, leucine, isoleucine, and their side-chain fluorinated variants were site-specifically incorporated at different positions of this peptide resulting in a library of 13 distinct peptides. The stability of these peptides towards proteolysis by α-chymotrypsin, pepsin, proteinase K, and elastase was studied, and this process was followed by an FL-RP-HPLC assay in combination with mass spectrometry. In a few cases, we observed an exceptional increase in proteolytic stability upon introduction of the fluorine substituents. The opposite phenomenon was observed in other cases, and this may be explained by specific interactions of fluorinated residues with the respective enzyme binding sites. Noteworthy is that 5,5,5-trifluoroisoleucine is able to significantly protect peptides from proteolysis by all enzymes included in this study when positioned N-terminal to the cleavage site. These results provide valuable information for the application of fluorinated amino acids in the design of proteolytically stable peptide-based pharmaceuticals

eHealth-supported case management for patients with panic disorder or depression in primary care:Study protocol for a cRCT (PREMA)

Background: Panic disorder (PD), frequently occurring with agoraphobia (AG), and depression are common mental disorders in primary care and associated with considerable individual and societal costs. Early detection and effective treatment of depression and PD/AG are of major importance. Cognitive behavioural exposure exercises have been shown to be effective in reducing anxiety and depressive symptoms. Practice team-based case management can improve clinical outcomes for patients with chronic diseases in primary care. The present study aims at evaluating the effects and cost-effectiveness of a primary care team-based intervention using behavioural therapy elements and case management supported by eHealth components in patients with PD/AG or depression compared to treatment as usual.Methods/design: This is a two-arm cluster-randomized, controlled trial (cRCT). General practices represent the units of randomisation. General practitioners recruit adult patients with depression and PD +/- AG according to the International Classification of Diseases, version 10 (ICD-10). In the intervention group, patients receive cognitive behaviour therapy-oriented psychoeducation and instructions to self-managed exposure exercises in four manualbased appointments with the general practitioner. A trained health care assistant from the practice team delivers case management and is continuously monitoring symptoms and treatment progress in ten protocol-based telephone contacts with patients. Practice teams and patients are supported by eHealth components. In the control group, patients receive usual care from general practitioners. Outcomes are measured at baseline (T0), at follow-up after 6 months (T1), and at follow-up after 12 months (T2). The primary outcome is the mental health status of patients as measured by the Mental Health Index (MHI-5). Effect sizes of 0.2 standard deviation (SD) are regarded as relevant. Assuming a drop-out rate of 20% of practices and patients each, we aim at recruiting 1844 patients in 148 primary care practices. This corresponds to 12.5 patients on average per primary care practice. Secondary outcomes include depression and anxiety-related clinical parameters and health-economic costs.Discussion: If the intervention is more effective than treatment as usual, the three-component (cognitive behaviour therapy, case-management, eHealth) primary care-based intervention for patients suffering from PD/AG or depression could be a valuable low-threshold option that benefits patients and primary care practice teams.Trial registration: German clinical trials register, DRKS00016622. Registered on February 22nd, 2019.</p

The Impact of Halogenated Phenylalanine Derivatives on NFGAIL Amyloid Formation

The hexapeptide hIAPP22–27 (NFGAIL) is known as a crucial amyloid core sequence of the human islet amyloid polypeptide (hIAPP) whose aggregates can be used to better understand the wild-type hIAPP’s toxicity to β-cell death. In amyloid research, the role of hydrophobic and aromatic-aromatic interactions as potential driving forces during the aggregation process is controversially discussed not only in case of NFGAIL, but also for amyloidogenic peptides in general. We have used halogenation of the aromatic residue as a strategy to modulate hydrophobic and aromatic-aromatic interactions and prepared a library of NFGAIL variants containing fluorinated and iodinated phenylalanine analogues. We used thioflavin T staining, transmission electron microscopy (TEM) and smallangle X-ray scattering (SAXS) to study the impact of side-chain halogenation on NFGAIL amyloid formation kinetics. Our data revealed a synergy between aggregation behavior and hydrophobicity of the phenylalanine residue. This study introduces systematic fluorination as a toolbox to further investigate the nature of the amyloid self-assembly process

eHealth-supported case management for patients with panic disorder or depression in primary care: Study protocol for a cRCT (PREMA)

BACKGROUND: Panic disorder (PD), frequently occurring with agoraphobia (AG), and depression are common mental disorders in primary care and associated with considerable individual and societal costs. Early detection and effective treatment of depression and PD/AG are of major importance. Cognitive behavioural exposure exercises have been shown to be effective in reducing anxiety and depressive symptoms. Practice team-based case management can improve clinical outcomes for patients with chronic diseases in primary care. The present study aims at evaluating the effects and cost-effectiveness of a primary care team-based intervention using behavioural therapy elements and case management supported by eHealth components in patients with PD/AG or depression compared to treatment as usual. METHODS/DESIGN: This is a two-arm cluster-randomized, controlled trial (cRCT). General practices represent the units of randomisation. General practitioners recruit adult patients with depression and PD ± AG according to the International Classification of Diseases, version 10 (ICD-10). In the intervention group, patients receive cognitive behaviour therapy-oriented psychoeducation and instructions to self-managed exposure exercises in four manual-based appointments with the general practitioner. A trained health care assistant from the practice team delivers case management and is continuously monitoring symptoms and treatment progress in ten protocol-based telephone contacts with patients. Practice teams and patients are supported by eHealth components. In the control group, patients receive usual care from general practitioners. Outcomes are measured at baseline (T0), at follow-up after 6 months (T1), and at follow-up after 12 months (T2). The primary outcome is the mental health status of patients as measured by the Mental Health Index (MHI-5). Effect sizes of 0.2 standard deviation (SD) are regarded as relevant. Assuming a drop-out rate of 20% of practices and patients each, we aim at recruiting 1844 patients in 148 primary care practices. This corresponds to 12.5 patients on average per primary care practice. Secondary outcomes include depression and anxiety-related clinical parameters and health-economic costs. DISCUSSION: If the intervention is more effective than treatment as usual, the three-component (cognitive behaviour therapy, case-management, eHealth) primary care-based intervention for patients suffering from PD/AG or depression could be a valuable low-threshold option that benefits patients and primary care practice teams. TRIAL REGISTRATION: German clinical trials register, DRKS00016622. Registered on February 22nd, 2019.status: publishe