Fluphenazine·HCl and Epigallocatechin Gallate Modulate the Rate of Formation and Structural Properties of Apolipoprotein C-II Amyloid Fibrils

Recognition and release of uridine and hCNT3: From multivariate interactions to molecular design

As a vital target for the development of novel anti-cancer drugs, human concentrative nucleoside transporter 3 (hCNT3) has been widely concerned. Nevertheless, the lack of a comprehensive understanding of molecular interactions and motion mechanism has greatly hindered the development of novel inhibitors against hCNT3. In this paper, molecular recognition of hCNT3 with uridine was investigated with molecular docking, conventional molecular dynamics (CMD) simulations and adaptive steered molecular dynamics (ASMD) simulations; and then, the uridine derivatives with possibly highly inhibitory activity were designed. The result of CMD showed that more water-mediated H-bonds and lower binding free energy both explained higher recognition ability and transported efficiency of hCNT3. While during the ASMD simulation, nucleoside transport process involved the significant side-chain flip of residues F321 and Q142, a typical substrate-induced conformational change. By considering electronegativity, atomic radius, functional group and key H-bonds factors, 25 novel uridine derivatives were constructed. Subsequently, the receptor-ligand binding free energy was predicted by solvated interaction energy (SIE) method to determine the inhibitor c8 with the best potential performance. This work not only revealed molecular recognition and release mechanism of uridine with hCNT3, but also designed a series of uridine derivatives to obtain lead compounds with potential high activity.

Influence of phenothiazine molecules on the interactions between positively charged poly-l-lysine and negatively charged DPPC/DPPG membranes

Phenothiazines are very effective antipsychotic drugs, which also have anticancer and antimicrobial activities. Despite being used in human treatment, the molecular mechanism of the biological actions of these molecules is not yet understood in detail. The role of the interactions between phenothiazines and proteins or lipid membranes has been much discussed. Herein, fourier-transform infrared (FTIR) spectroscopic studies were used to investigate the effect of three phenothiazines: fluphenazine (FPh); chlorpromazine (ChP); and propionylpromazine (PP) on the structures of a positively charged poly-l-lysine (PLL) peptide, a negatively charged dipalmitoylphosphatidylcholine/dipalmitoylphosphatidylglycerol (DPPC/DPPG) membrane, and on the mutual interactions between electrostatically associated PLL molecules and DPPC/DPPG membranes. Phenothiazine-induced alterations in the secondary structure of PLL, the conformational state (trans/gauche) of the hydrocarbon lipid chains, and the hydration of the DPPC/DPPG membrane interface were studied on the basis of amide I' vibrations, antisymmetric and symmetric stretching vibrations of the CH₂ groups of the lipid hydrocarbon chains (ν_sCH₂), and stretching vibrations of the lipid C=O groups (νC = O), respectively. It was shown that in the presence of negatively charged DPPC/DPPG membranes, the phenothiazines were able to modify the secondary structure of charged PLL molecules. Additionally, the effect of PLL on the structure of DPPC/DPPG membranes was also altered by the presence of the phenothiazine molecules.

Effect of phenothiazine compounds on the secondary structure and fibrillogenesis of poly-l-lysine

Phenothiazine molecules are effective and commonly used antipsychotic drugs, especially in the treatment of schizophrenia. However, they produce strong extrapyramidal side-effects manifested by drug-induced parkinsonism. Because Parkinson's disease as a neurodegenerative illness is associated with the formation of amyloid fibrils in neuronal cells, it is postulated that the development of phenothiazine-induced parkinsonism may be related to the phenothiazine-induced formation of fibrillar aggregates. The effect of phenothiazine compounds (fluphenazine (FPh), chlorpromazine (ChP) and propionylpromazine (PP)) on the fibrillogenesis of poly-l-lysine (PLL) was studied using Fourier-transform infrared (FTIR) spectroscopy supported by principal component analysis (PCA), vibrational circular dichroism (VCD), transmission electron microscopy (TEM) and Congo red binding assay. The fibrillogenesis of PLL is accompanied by fibril formation with charged or uncharged polypeptides with PPII (polyproline-like extended helix), α-helix or β-sheet conformations. All of the phenothiazine molecules investigated effectively reduced the temperature required to induce the formation of β-sheet-rich fibrils from α-helix-rich fibrils of PLL.

The amyloidogenicity of a C-terminal region of TDP-43 implicated in Amyotrophic Lateral Sclerosis can be affected by anions, acetylation and homodimerization

Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disease associated with accumulation of hyper-phosphorylated, and ubiquitinated TAR DNA-binding protein-43 (TDP-43) as inclusion deposits in neuronal cells. Recently, amyloid-like fibrillar aggregates of TDP-43 have been reported from several ALS patients. The C-terminal region of TDP-43 is central to TDP-43's pathological aggregation and most of the familial ALS mutations in the encoding TARDBP gene are located in this domain. Also, aberrant proteolytic cleavages of TDP-43 produce cytotoxic C-terminal fragments of ∼15-35 kDa. The C-terminal end harbours a glycine-rich region and a Q/N rich prion-like aggregation-prone domain which has been shown to form amyloid-like fibrillar aggregates in vitro. Previously, TDP-43 protein has also been shown to undergo several other post-translational modifications such as acetylation and dimerization, however, their effects on TDP-43's amyloid-like in vitro aggregation have not been examined. Towards this, we have here examined effects of anions, acetylation and homodimerization on the in vitro aggregation of a C-terminal fragment (amino acid: 193-414) of TDP-43 termed TDP-43^2C. We find that kosmotropic anions greatly accelerate whereas chaotropic anions impede its aggregation. Also, we show that acetylation of certain lysines in C-terminal fragments significantly reduces the TDP-43^2C's amyloid-like aggregation. Furthermore, we separated spontaneously formed cysteine-linked homodimers of the recombinantly purified TDP-43^2C using size-exclusion chromatography and found that these dimers retain amyloidogenicity. These findings would be of significance to the TDP-43 aggregation-induced pathology in ALS.

An acridine derivative, [4,5-bis{(N-carboxy methyl imidazolium)methyl}acridine] dibromide, shows anti-TDP-43 aggregation effect in ALS disease models

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease associated with aggregation of TAR DNA-binding protein-43 (TDP-43) in neuronal cells and manifests as motor neuron dysfunction & muscle atrophy. The carboxyl-terminal prion-like domain of TDP-43 can aggregate in vitro into toxic β-sheet rich amyloid-like structures. So far, treatment options for ALS are very limited and Riluzole, which targets glutamate receptors, is the only but highly ineffective drug. Therefore, great interest exists in developing molecules for ALS treatment. Here, we have examined certain derivatives of acridine containing same side chains at position 4 & 5, for inhibitory potential against TDP-43 aggregation. Among several acridine derivatives examined, AIM4, which contains polar carboxyl groups in the side arms, significantly reduces TDP-43-YFP aggregation in the powerful yeast model cell and also abolishes in vitro amyloid-like aggregation of carboxyl terminal domain of TDP-43, as observed by AFM imaging. Thus, AIM4 can be a lead molecule potentiating further therapeutic research for ALS.

Copper dyshomoeostasis in Parkinson's disease: implications for pathogenesis and indications for novel therapeutics

Copper is a biometal essential for normal brain development and function, thus copper deficiency or excess results in central nervous system disease. Well-characterized disorders of disrupted copper homoeostasis with neuronal degeneration include Menkes disease and Wilson's disease but a large body of evidence also implicates disrupted copper pathways in other neurodegenerative disorders, including Parkinson's disease, Alzheimer's disease, Amyotrophic lateral sclerosis, Huntington's disease and prion diseases. In this short review we critically evaluate the data regarding changes in systemic and brain copper levels in Parkinson's disease, where alterations in brain copper are associated with regional neuronal cell death and disease pathology. We review copper regulating mechanisms in the human brain and the effects of dysfunction within these systems. We then examine the evidence for a role for copper in pathogenic processes in Parkinson's disease and consider reports of diverse copper-modulating strategies in in vitro and in vivo models of this disorder. Copper-modulating therapies are currently advancing through clinical trials for Alzheimer's and Huntington's disease and may also hold promise as disease modifying agents in Parkinson's disease.