RESUMEN
Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by dementia. The most characteristic pathological changes in AD brain include extracellular amyloid-ß (Aß) accumulation and neuronal loss. Particularly, cholinergic neurons in the nucleus basalis of Meynert are some of the first neuronal groups to degenerate; accumulating evidence suggests that Aß oligomers are the primary form of neurotoxicity. Bacopa monniera is a traditional Indian memory enhancer whose extract has shown neuroprotective and Aß-reducing effects. In this study, we explored the low molecular weight compounds from B. monniera extracts with an affinity to Aß aggregates, including its oligomers, using Aß oligomer-conjugated beads and identified plantainoside B. Plantainoside B exhibited evident neuroprotective effects by preventing Aß attachment on the cell surface of human induced pluripotent stem cell (hiPSC)-derived cholinergic neurons. Moreover, it attenuated memory impairment in mice that received intrahippocampal Aß injections. Furthermore, radioisotope experiments revealed that plantainoside B has affinity to Aß aggregates including its oligomers and brain tissue from a mouse model of Aß pathology. In addition, plantainoside B could delay the Aß aggregation rate. Accordingly, plantainoside B may exert neuroprotective effects by binding to Aß oligomers, thus interrupting the binding of Aß oligomers to the cell surface. This suggests its potential application as a theranostics in AD, simultaneously diagnostic and therapeutic drugs.
Asunto(s)
Enfermedad de Alzheimer , Bacopa , Células Madre Pluripotentes Inducidas , Enfermedades Neurodegenerativas , Fármacos Neuroprotectores , Ratones , Humanos , Animales , Bacopa/metabolismo , Fármacos Neuroprotectores/farmacología , Fármacos Neuroprotectores/uso terapéutico , Células Madre Pluripotentes Inducidas/metabolismo , Péptidos beta-Amiloides/toxicidad , Péptidos beta-Amiloides/metabolismo , Enfermedad de Alzheimer/tratamiento farmacológico , Trastornos de la Memoria/inducido químicamente , Trastornos de la Memoria/tratamiento farmacológicoRESUMEN
Sulfated glycosaminoglycans (GAGs) such as heparan sulfate (HS) are heteropolysaccharides implicated in the pathology of protein aggregation diseases including localized and systemic forms of amyloidosis. Among subdomains of sulfated GAGs, highly sulfated domains of HS, called HS S-domains, have been highlighted as being critical for HS function in amyloidoses. Recent studies suggest that the tumor suppressor p53 aggregates to form amyloid fibrils and propagates in a prion-like manner; however, molecules and mechanisms that are involved in the prion-like behavior of p53 aggregates have not been addressed. Here, we identified sulfated GAGs as molecules that mediate prion-like behavior of p53 aggregates. Sulfated GAGs at the cell surface were required for cellular uptake of recombinant and cancer cell-derived p53 aggregates and extracellular release of p53 from cancer cells. We further showed that HS S-domains accumulated within p53 deposits in human ovarian cancer tissues, and enzymatic remodeling of HS S-domains by Sulf-2 extracellular sulfatase down-regulated cellular uptake of p53 aggregates. Finally, sulfated GAG-dependent cellular uptake of p53 aggregates was critical for subsequent extracellular release of the aggregates and gain of oncogenic function in recipient cells. Our work provides a mechanism of prion-like behavior of p53 aggregates and will shed light on sulfated GAGs as a common mediator of prions.
Asunto(s)
Glicosaminoglicanos/metabolismo , Priones/metabolismo , Agregado de Proteínas , Sulfatos/metabolismo , Proteína p53 Supresora de Tumor/química , Proteína p53 Supresora de Tumor/metabolismo , Animales , Células CHO , Membrana Celular/metabolismo , Cricetulus , Endocitosis , Femenino , Heparitina Sulfato/metabolismo , Humanos , Mutación/genética , Neoplasias Ováricas/metabolismo , Neoplasias Ováricas/patología , Proteínas Recombinantes/metabolismo , Proteína p53 Supresora de Tumor/genéticaRESUMEN
Dysregulation of amyloidogenic proteins and their abnormal processing and deposition in tissues cause systemic and localized amyloidosis. Formation of amyloid ß (Aß) fibrils that deposit as amyloid plaques in Alzheimer's disease (AD) brains is an earliest pathological hallmark. The polysulfated heparan sulfate (HS)/heparin (HP) is one of the non-protein components of Aß deposits that not only modulates Aß aggregation, but also acts as a receptor for Aß fibrils to mediate their cytotoxicity. Interfering with the interaction between HS/HP and Aß could be a therapeutic strategy to arrest amyloidosis. Here we have synthesized the 6-O-phosphorylated HS/HP oligosaccharides and reported their competitive effects on the inhibition of HP-mediated Aß fibril formation inâ vitro using a thioflavin T fluorescence assay and a tapping mode atomic force microscopy.
Asunto(s)
Enfermedad de Alzheimer , Amiloidosis , Enfermedad de Alzheimer/metabolismo , Amiloide , Péptidos beta-Amiloides/metabolismo , Heparina/metabolismo , Heparitina Sulfato , Humanos , Oligosacáridos , Fragmentos de Péptidos/metabolismoRESUMEN
The present review discusses the current status and difficulties of the analytical methods used to evaluate size and surface modifications of nanoparticle-based pharmaceutical products (NPs) such as liposomal drugs and new SARS-CoV-2 vaccines. We identified the challenges in the development of methods for (1) measurement of a wide range of solid-state NPs, (2) evaluation of the sizes of polydisperse NPs, and (3) measurement of non-spherical NPs. Although a few methods have been established to analyze surface modifications of NPs, the feasibility of their application to NPs is unknown. The present review also examined the trends in standardization required to validate the size and surface measurements of NPs. It was determined that there is a lack of available reference materials and it is difficult to select appropriate ones for modified NP surface characterization. Research and development are in progress on innovative surface-modified NP-based cancer and gene therapies targeting cells, tissues, and organs. Next-generation nanomedicine should compile studies on the practice and standardization of the measurement methods for NPs to design surface modifications and ensure the quality of NPs.
Asunto(s)
COVID-19 , Nanopartículas , Vacunas contra la COVID-19 , Composición de Medicamentos , Humanos , Tamaño de la Partícula , SARS-CoV-2RESUMEN
The N-terminal (1-83) fragment of the major constituent of plasma high-density lipoprotein, apolipoprotein A-I (apoA-I), strongly tends to form amyloid fibrils, leading to systemic amyloidosis. Here, using a series of deletion variants, we examined the roles of two major amyloidogenic segments (residues 14-22 and 50-58) in the aggregation and fibril formation of an amyloidogenic G26R variant of the apoA-I 1-83 fragment (apoA-I 1-83/G26R). Thioflavin T fluorescence assays and atomic force microscopy revealed that elimination of residues 14-22 completely inhibits fibril formation of apoA-I 1-83/G26R, whereas Δ32-40 and Δ50-58 variants formed fibrils with markedly reduced nucleation and fibril growth rates. CD measurements revealed structural transitions from random coil to ß-sheet structures in all deletion variants except for the Δ14-22 variant, indicating that residues 14-22 are critical for the ß-transition and fibril formation. Thermodynamic analysis of the kinetics of fibril formation by apoA-I 1-83/G26R indicated that both nucleation and fibril growth are enthalpically unfavorable, whereas entropically, nucleation is favorable, but fibril growth is unfavorable. Interestingly, the nucleation of the Δ50-58 variant was entropically unfavorable, indicating that residues 50-58 entropically promote the nucleation step in fibril formation of apoA-I 1-83/G26R. Moreover, a residue-level structural investigation of apoA-I 1-83/G26R fibrils with site-specific pyrene labeling indicated that the two amyloidogenic segments are in close proximity to form an amyloid core structure, whereas the N- and C-terminal tail regions are excluded from the amyloid core. These results provide critical insights into the aggregation mechanism and fibril structure of the amyloidogenic N-terminal fragment of apoA-I.
Asunto(s)
Amiloide/química , Apolipoproteína A-I/química , Amiloide/metabolismo , Apolipoproteína A-I/metabolismo , Supervivencia Celular , Células HEK293 , Humanos , Agregado de Proteínas , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Termodinámica , Liposomas Unilamelares/síntesis química , Liposomas Unilamelares/químicaRESUMEN
The highly sulfated domains of heparan sulfate (HS), alias HS S-domains, are made up of repeated trisulfated disaccharide units [iduronic acid (2S)-glucosamine (NS, 6S)] and are selectively remodeled by extracellular endoglucosamine 6-sulfatases (Sulfs). Although HS S-domains are critical for signal transduction of several growth factors, their roles in amyloidoses are not yet fully understood. Herein, we found HS S-domains in the kidney of a patient with transthyretin amyloidosis. In in vitro assays with cells stably expressing human Sulfs, heparin, a structural analog of HS S-domains, promoted aggregation of transthyretin in an HS S-domain-dependent manner. Interactions of cells with transthyretin fibrils and cytotoxicity of these fibrils also depended on HS S-domains at the cell surface. Furthermore, glypican-5, encoded by the susceptibility gene for nephrotic syndrome GPC5, was found to be accumulated in the transthyretin amyloidosis kidney. Our study, thus, provides a novel insight into the pathologic roles of HS S-domains in amyloidoses, and we propose that enzymatic remodeling of HS chains by Sulfs may offer an effective approach to inhibiting formation and cytotoxicity of amyloid fibrils.
Asunto(s)
Neuropatías Amiloides Familiares/metabolismo , Amiloide/metabolismo , Heparitina Sulfato/metabolismo , Riñón/metabolismo , Síndrome Nefrótico/metabolismo , Prealbúmina/metabolismo , Adulto , Anciano , Neuropatías Amiloides Familiares/patología , Femenino , Glipicanos/metabolismo , Humanos , Riñón/patología , Masculino , Persona de Mediana Edad , Síndrome Nefrótico/patología , Sulfotransferasas/metabolismoRESUMEN
Type III secretion system (T3SS) is a protein injection nano-machine consisting of syringe and needle-like structure spanning bacterial inner and outer membranes. Bacteria insert the tip of T3SS needle to host cell membranes, and deliver effector proteins directly into host cells via T3SS to prime the host cell environment for infection. Thus inhibition of T3SS would be a potent strategy for suppressing bacterial infection. We previously demonstrated that T3SS needle rotates by proton-motive force (PMF) with the same mechanism as two evolutionally related rotary protein motors, flagellum and ATP synthase (FASEB J., 27, 2013, Ohgita et al.). Inhibition of needle rotation resulted in suppression of effector secretion, indicating the requirement of needle rotation for effector export. Simulation analysis of protein export by the T3SS needle suggests the importance of a hydrophobic helical groove formed by the conserved aromatic residue in the needle components. Based on these results, we have proposed a novel model of protein export by the T3SS needle, in which effector proteins are exported by PMF-dependent needle rotation oppositely to the hydrophobic helical groove in the needle. Quantitative examinations of the correlation between the speeds of T3SS rotation and the amount of effector export support this model. In this review, we summarize our current understanding of T3SS, and discuss our novel model of the protein export mechanism of T3SS based on the needle rotation.
Asunto(s)
Bacterias/metabolismo , Sistemas de Secreción Tipo III/metabolismo , Complejos de ATP Sintetasa/metabolismo , Proteínas Bacterianas/metabolismo , Flagelos/metabolismo , Transporte de ProteínasRESUMEN
Liposomes are closed-membrane vesicles comprised of lipid bilayers, in which the inside of the vesicles is isolated from the external environment. Liposomes are therefore often used as models for biomembranes and as drug delivery carriers. However, materials encapsulated within liposomes often cannot respond to changes in the external environment. The ability of enclosed materials to maintain their responsiveness to changes in the external environment following encapsulation into liposomes would greatly expand the applicability of such systems. We hypothesize that embedding pore-like "access points" into the liposomal membrane could allow for the transmission of information between the internal and external liposomal environments and thus overcome this inherent limitation of conventional liposomes. To investigate this, we evaluated whether a change in the pH of an external solution could be transmitted to the inside of liposomes through the pore-forming protein, yeast voltage-dependent anion channel (VDAC). Transmission of a pH change via VDAC was evaluated using a polyglutamic acid/doxorubicin complex (PGA/Dox) as an internal pH sensor. Upon encapsulation into conventional liposomes, PGA/Dox exhibits no pH sensitivity due to isolation from the external environment. On the other hand, PGA/Dox was found to retain its pH sensitivity upon encapsulation into VDAC-reconstituted liposomes, suggesting that VDAC facilitated the transmission of information on the pH of the external environment to the inside of the liposomes. In conclusion, we successfully demonstrated the transmission of information between the external and internal liposomal environments by a stable pore-like structure embedded into the liposomal membranes, which serve as access points.
Asunto(s)
Liposomas/química , Liposomas/metabolismo , Canales Aniónicos Dependientes del Voltaje/metabolismo , Doxorrubicina/química , Doxorrubicina/metabolismo , Concentración de Iones de Hidrógeno , Ácido Poliglutámico/química , Ácido Poliglutámico/metabolismo , Porosidad , Saccharomyces cerevisiae , Canales Aniónicos Dependientes del Voltaje/químicaRESUMEN
An intelligent shRNA expression device (iRed) contains the minimum essential components needed for shRNA production in cells, and could be a novel tool to regulate target genes. However, general delivery carriers consisting of cationic polymers/lipids could impede function of a newly generated shRNA via electrostatic interaction in the cytoplasm. Recently, we found that faint electric treatment (fET) of cells enhanced delivery of siRNA and functional nucleic acids into the cytoplasm in the absence of delivery carriers. Here, we examined fET of cells stably expressing luciferase in the presence of iRed encoding anti-luciferase shRNA. Transfection of lipofectamine 2000 (LFN)/iRed lipoplexes showed an RNAi effect, but fET-mediated iRed transfection did not, likely because of the endosomal localization of iRed after delivery. However, fET in the presence of lysosomotropic agent chloroquine significantly improved the RNAi effect of iRed/fET to levels that were higher than those for the LFN/iRed lipoplexes. Furthermore, the amount of lipid droplets in adipocytes significantly decreased following fET with iRed against resistin in the presence of chloroquine. Thus, iRed could be a useful tool to regulate target genes following fET-mediated cytoplasmic delivery with endosomal escape devices.
RESUMEN
The type III secretion apparatus (T3SA) participates in the secretion of bacterial proteins called effectors, although the detailed mechanism of effector secretion remains unclear. T3SA and flagellum were shown to branch from a common ancestor and also show structural similarity. In addition, both T3SA-dependent effector secretion and flagellar rotation were reported to require proton-motive force (PMF) for activity. From these reports, we hypothesized that T3SA, like the flagellum, would rotate via PMF and that this rotation is responsible for effector secretion. To observe T3SA rotation, we constructed a novel observation system by modifying the tip of T3SA on bacterial cell membranes with an observation probe, which allowed documentation of T3SA rotation for the first time. T3SA rotation was stopped by the addition of a protonophore that decreases PMF. Moreover, increased viscosity of the observation medium inhibited both rotation of T3SA associated with beads and effector secretion. These results suggested that effector secretion would follow the PMF-dependent rotation of T3SA and could be inhibited by preventing T3SA rotation. Moreover, the motion-track analysis of bead rotation suggested that the T3SA needle might be flexible. Consequently, we propose a "rotational secretion model" as a novel effector secretion mechanism of T3SA.
Asunto(s)
Proteínas Bacterianas/metabolismo , Membrana Celular/fisiología , Fuerza Protón-Motriz/fisiología , Pseudomonas aeruginosa/fisiología , ADP Ribosa Transferasas/metabolismo , Antígenos Bacterianos/genética , Antígenos Bacterianos/metabolismo , Toxinas Bacterianas/genética , Toxinas Bacterianas/metabolismo , Western Blotting , Carbonil Cianuro m-Clorofenil Hidrazona/farmacología , Membrana Celular/efectos de los fármacos , Membrana Celular/metabolismo , Flagelos/metabolismo , Flagelos/fisiología , Proteínas Activadoras de GTPasa/metabolismo , Microscopía de Fuerza Atómica , Modelos Biológicos , Modelos Moleculares , Mutación , Oligopéptidos/genética , Oligopéptidos/metabolismo , Polietilenglicoles/farmacología , Proteínas Citotóxicas Formadoras de Poros/genética , Proteínas Citotóxicas Formadoras de Poros/metabolismo , Ionóforos de Protónes/farmacología , Fuerza Protón-Motriz/efectos de los fármacos , Pseudomonas aeruginosa/genética , Pseudomonas aeruginosa/metabolismo , RotaciónRESUMEN
Deposition and accumulation of amyloid fibrils is a hallmark of a group of diseases called amyloidosis and neurodegenerative disorders. Although polypeptides potentially have a fibril-forming propensity, native proteins have evolved into proper functional conformations to avoid aggregation and fibril formation. Understanding the mechanism for regulation of fibril formation of native proteins provides clues for the rational design of molecules for inhibiting fibril formation. Although fibril formation is a complex multistep reaction, experimentally obtained fibril formation curves can be fitted with the Finke-Watzky (F-W) two-step model for homogeneous nucleation followed by autocatalytic fibril growth. The resultant F-W rate constants for nucleation and fibril formation provide information on the chemical kinetics of fibril formation. Using the F-W two-step model analysis, we investigated the physicochemical mechanisms of fibril formation of a Parkinson's disease protein α-synuclein (αS) and a systemic amyloidosis protein apolipoprotein A-I (apoA-I). The results indicate that the C-terminal region of αS enthalpically and entropically suppresses nucleation through the intramolecular interaction with the N-terminal region and the intermolecular interaction with existing fibrils. In contrast, the nucleation of the N-terminal fragment of apoA-I is entropically driven likely due to dehydration of large hydrophobic segments in the molecule. Based on our recent findings, we discuss the similarity and difference of the fibril formation mechanisms of αS and the N-terminal fragment of apoA-I from the physicochemical viewpoints.
RESUMEN
Introduction: Cell therapeutic clinical trials using fetal mesencephalic tissue provided a proof-of-concept for regenerative therapy in patients with Parkinson's disease. Postmortem studies of patients with fetal grafts revealed that α-synuclein+ Lewy body (LB)-like inclusions emerged in long-term transplantation and might worsen clinical outcomes even if the grafts survived and innervated in the recipients. Various studies aimed at addressing whether host-derived α-synuclein could be transferred to the grafted neurons to assess α-synuclein+ inclusion appearance in the grafts. However, determining whether α-synuclein in the grafted neurons has been propagated from the host is difficult due to the intrinsic α-synuclein expression. Methods: We induced midbrain dopaminergic (mDA) neurons from human induced pluripotent stem cells (hiPSCs) and transplanted them into the striatum of immunodeficient rats. The recombinant human α-synuclein preformed fibrils (PFFs) were inoculated into the cerebral cortex after transplantation of SNCA-/- hiPSC-derived mDA neural progenitors into the striatum of immunodeficient rats to evaluate the host-to-graft propagation of human α-synuclein PFFs. Additionally, we examined the incorporation of human α-synuclein PFFs into SNCA-/- hiPSC-derived mDA neurons using in vitro culture system. Results: We detected human α-synuclein-immunoreactivity in SNCA-/- hiPSC-derived mDA neurons that lacked endogenous α-synuclein expression in vitro. Additionally, we observed host-to-graft α-synuclein propagation into the grafted SNCA-/- hiPSC-derived mDA neurons. Conclusion: We have successfully proven that intracerebral inoculated α-synuclein PFFs are propagated and incorporated from the host into grafted SNCA-/- hiPSC-derived mDA neurons. Our results contribute toward the basic understanding of the molecular mechanisms related to LB-like α-synuclein deposit formation in grafted mDA neurons.
RESUMEN
Apolipoprotein E (apoE) is a regulator of lipid metabolism, cholesterol transport, and the clearance and aggregation of amyloid ß in the brain. The three human apoE isoforms apoE2, apoE3, and apoE4 only differ in one or two residues. Nevertheless, the functions highly depend on the isoform types and lipidated states. Here, we generated novel anti-apoE monoclonal antibodies (mAbs) and obtained an apoE4-selective mAb whose epitope is within residues 110-117. ELISA and bio-layer interferometry measurements demonstrated that the dissociation constants of mAbs are within the nanomolar range. Using the generated antibodies, we successfully constructed sandwich ELISA systems, which can detect all apoE isoforms or selectively detect apoE4. These results suggest the usability of the generated anti-apoE mAbs for selective detection of apoE isoforms.
Asunto(s)
Anticuerpos Monoclonales , Apolipoproteínas E , Isoformas de Proteínas , Anticuerpos Monoclonales/inmunología , Anticuerpos Monoclonales/química , Humanos , Isoformas de Proteínas/inmunología , Apolipoproteínas E/metabolismo , Apolipoproteínas E/genética , Apolipoproteínas E/química , Apolipoproteínas E/inmunología , Animales , Epítopos/inmunología , Epítopos/química , Ensayo de Inmunoadsorción Enzimática/métodos , Ratones , Apolipoproteína E4/genética , Apolipoproteína E4/inmunología , Apolipoproteína E4/metabolismo , Ratones Endogámicos BALB C , Apolipoproteína E3/inmunología , Apolipoproteína E3/genética , Apolipoproteína E3/química , Apolipoproteína E3/metabolismoRESUMEN
Development of novel devices for effective nucleotide release from nanoparticles is required to improve the functionality of nonviral delivery systems, because decondensation of nucleotide/polycation complexes is considered as a key step for cytoplasmic delivery of nucleotides. Previously, PepFect6 (PF6) comprised chloroquine analog moieties and a stearylated cell-penetrating peptide to facilitate endosomal escape and cellular uptake, respectively, was developed as a device for efficient siRNA delivery. As PF6 contains bulky chloroquine analog moieties, the polyplexes are expected to be loose structure, which facilitates decondensation. In the present study, siRNA was electrostatically condensed by PF6, and the PF6/siRNA complexes were coated with lipid membranes. The surface of the nanoparticles encapsulating the PF6/siRNA core (PF6-NP) was modified with PF6 for endosomal escape (PF6/PF6-NP). The RNAi effect of PF6/PF6-NP was compared with those of stearylated cell-penetrating peptide octaarginine (R8)-modified PF6-NP, R8-modified nanoparticles encapsulating the R8/siRNA core (R8-NP) and PF6-modified R8-NP. Nanoparticles encapsulating the PF6 polyplex, especially PF/PF-NP, showed a significant knockdown effect on luciferase activity of B16-F1 cells stably expressing luciferase. siRNA was widely distributed within the cytoplasm after transfection of the nanoparticles encapsulating the PF6 polyplex, while siRNA encapsulated in the R8-presenting nanoparticles was localized within the nuclei. Thus, the siRNA distribution was dependent on the manner of peptide-modification. In conclusion, we have successfully developed PF6/PF6-NP exhibiting a potent RNAi effect resulting from high cellular uptake, efficient endosomal escape and decondensation of the polyplexes based on the multifunctional cell penetrating peptide PF6. PF6 is therefore a useful pluripotential device for siRNA delivery.
Asunto(s)
Péptidos de Penetración Celular , ARN Interferente Pequeño , Péptidos de Penetración Celular/química , Endosomas , Humanos , Nanopartículas/química , TransfecciónRESUMEN
The N-terminal fragment of apolipoprotein A-I (apoA-I), comprising residues 1-83, contains three segments prone to aggregation: residues 14-22, 53-58, and 67-72. We previously demonstrated that residues 14-22 are critical in apoA-I fibril formation while residues 53-58 entropically drove the nucleation process. Here, we investigated the impact of amyloidogenic mutations (Δ60-71/VT, Δ70-72, and F71Y) located around residues 67-72 on fibril formation by the apoA-I 1-83 fragment. Thioflavin T fluorescence assay demonstrated that the Δ60-71/VT mutation significantly enhances both nucleation and fibril elongation rates, whereas the Δ70-72 and F71Y mutations had minimal effects. Circular dichroism measurements and microscopic observations revealed that all variant fragments formed straight fibrils, transitioning from random coils to ß-sheet structures. Kinetic analysis demonstrated that primary nucleation is the dominant step in fibril formation, with fibril elongation reaching saturation at high protein concentrations. Thermodynamically, both nucleation and fibril elongation were enthalpically and entropically unfavorable in all apoA-I 1-83 variants, in which the entropic barrier of nucleation was almost eliminated for the Δ60-71/VT variant. Taken together, our results suggest the presence of new aggregation-prone segment in the Δ60-71/VT variant that promotes nucleation through entropic effects.
Asunto(s)
Amiloide , Apolipoproteína A-I , Apolipoproteína A-I/metabolismo , Cinética , Mutagénesis Insercional , Amiloide/metabolismo , Mutación , Dicroismo CircularRESUMEN
Regulation of α-synuclein (αS) fibril formation is a potent therapeutic strategy for αS-related neurodegenerative disorders. αS, an intrinsically disordered 140-residue intraneural protein, comprises positively charged N-terminal, hydrophobic non-amyloid ß component (NAC), and negatively charged C-terminal regions. Although mouse and human αS share 95% sequence identity, mouse αS forms amyloid fibrils faster than human αS. To evaluate the kinetic regulation of αS fibrillation, we examined the effects of mismatched residues in human and mouse αS on fibril formation and intramolecular interactions. Thioflavin T fluorescence assay using domain-swapped or C-terminal-truncated αS variants revealed that mouse αS exhibited higher nucleation and fibril elongation than human αS. In mouse αS, S87N substitution in the NAC region rather than A53T substitution is dominant for enhanced fibril formation. FÓ§rester resonance energy transfer analysis demonstrated that the intramolecular interaction of the C-terminal region with the N-terminal and NAC regions observed in human αS is perturbed in mouse αS. In mouse αS, S87N substitution is responsible for the perturbed interaction. These results indicate that the interaction of the C-terminal region with the N-terminal and NAC regions suppresses αS fibril formation and that the human-to-mouse S87N substitution in the NAC region accelerates αS fibril formation by perturbing intramolecular interaction.
Asunto(s)
Enfermedad de Parkinson , alfa-Sinucleína , Animales , Humanos , Ratones , alfa-Sinucleína/metabolismo , Enfermedad de Parkinson/metabolismoRESUMEN
Amphipathic arginine-rich peptide, A2-17, exhibits moderate perturbation of lipid membranes and the highest cell penetration among its structural isomers. We investigated the direct cell-membrane penetration mechanism of the A2-17 peptide while focusing on structural flexibility. We designed conformationally constrained versions of A2-17, stapled (StpA2-17) and stitched (StchA2-17), whose α-helical conformations were stabilized by chemical crosslinking. Circular dichroism confirmed that StpA2-17 and StchA2-17 had higher α-helix content than A2-17 in aqueous solution. Upon liposome binding, only A2-17 exhibited a coil-to-helix transition. Confocal microscopy revealed that A2-17 had higher cell penetration efficiency than StpA2-17, whereas StchA2-17 remained on the cell membrane without cell penetration. Although the tryptophan fluorescence analysis suggested that A2-17 and its analogs had similar membrane-insertion positions between the interface and hydrophobic core, StchA2-17 exhibited a higher membrane affinity than A2-17 or StpA2-17. Atomic force microscopy demonstrated that A2-17 reduced the mechanical rigidity of liposomes to a greater extent than StpA2-17 and StchA2-17. Finally, electrophysiological analysis showed that A2-17 induced a higher charge influx through transient pores in a planer lipid bilayer than StpA2-17 and StchA2-17. These findings indicate that structural flexibility, which enables diverse conformations of A2-17, leads to a membrane perturbation mode that contributes to cell membrane penetration.
Asunto(s)
Apolipoproteínas E , Arginina , Péptidos , Membrana Celular , Dicroismo Circular , Liposomas , Péptidos/químicaRESUMEN
Astaxanthin (Asx) is known to be a potent quencher of singlet oxygen and an efficient scavenger of superoxide anion. Therefore, Asx would be expected to be a useful antioxidant for the prevention of oxidative stress, a causative factor in severe diseases such as ischemic reperfusion injury. However, it is still unclear whether Asx has scavenging capability against the most potent reactive oxygen species (ROS), hydroxyl radical, because the hydrophobicity of Asx prevents analysis of hydroxyl radical scavenging ability in aqueous solution. In this study, to solve this problem, liposomes containing Asx (Asx-lipo), which could be dispersed in water, were prepared, and the scavenging ability of Asx-lipo for the hydroxyl radical was examined. The liposomal formulation enabled encapsulation of a high concentration of Asx. Asx-lipo gave a dose-dependent reduction of chemiluminescence intensity induced by hydroxyl radical in aqueous solution. Hydroxyl radical scavenging of Asx was more potent than α-tocopherol. The absorbance of Asx in the liposome decreased after reduction of hydroxyl radicals, indicating the direct hydroxyl radical scavenging by Asx. Moreover, Asx-lipo prevented hydroxyl radical-induced cytotoxicity in cultured NIH-3T3 cells. In conclusion, Asx has potent scavenging capability against hydroxyl radicals in aqueous solution, and this paper is the first report regarding hydroxyl radial scavenging by Asx.
Asunto(s)
Depuradores de Radicales Libres/farmacología , Radical Hidroxilo/metabolismo , Estrés Oxidativo/efectos de los fármacos , Animales , Cápsulas , Relación Dosis-Respuesta a Droga , Depuradores de Radicales Libres/administración & dosificación , Interacciones Hidrofóbicas e Hidrofílicas , Liposomas , Ratones , Células 3T3 NIH , Xantófilas/administración & dosificación , Xantófilas/farmacología , alfa-Tocoferol/farmacologíaRESUMEN
Aggregation of α-synuclein (α-syn) into amyloid fibrils is closely associated with Parkinson's disease (PD). Familial mutations or posttranslational truncations in α-syn are known as risk factor for PD. Here, we examined the effects of the PD-related A30P or A53T point mutation and C-terminal 123-140 or 104-140 truncation on the aggregating property of α-syn based on the kinetic and thermodynamic analyses. Thioflavin T fluorescence measurements indicated that A53T, Δ123â140, and Δ104-140 variants aggregated faster than WT α-syn, in which the A53T mutation markedly increases nucleation rate whereas the Δ123â140 or Δ104â140 truncation significantly increases both nucleation and fibril elongation rates. Ultracentrifugation and western blotting analyses demonstrated that these mutations or truncations promote the conversion of monomer to aggregated forms of α-syn. Analysis of the dependence of aggregation reaction of α-syn variants on the monomer concentration suggested that the A53T mutation enhances conversion of monomers to amyloid nuclei whereas the C-terminal truncations, especially the Δ104-140, enhance autocatalytic aggregation on existing fibrils. In addition, thermodynamic analysis of the kinetics of nucleation and fibril elongation of α-syn variants indicated that both nucleation and fibril elongation of WT α-syn are enthalpically and entropically unfavorable. Interestingly, the unfavorable activation enthalpy of nucleation greatly decreases for the A53T and becomes reversed in sign for the C-terminally truncated variants. Taken together, our results indicate that the A53T mutation and the C-terminal truncation enhance α-syn aggregation by reducing unfavorable activation enthalpy of nucleation, and the C-terminal truncation further triggers the autocatalytic fibril elongation on the fibril surfaces.
Asunto(s)
Enfermedad de Parkinson , alfa-Sinucleína , Amiloide/genética , Humanos , Mutación , Enfermedad de Parkinson/genética , Mutación Puntual , alfa-Sinucleína/genéticaRESUMEN
Owing to the relatively high molecular weight of macrocyclic peptides, investigation of the cellular uptake mechanism is required for the efficient design of macrocyclic peptides as potential drugs. We have previously reported, using HPLC, that cyclosporine A, a model macrocyclic peptide, and its congeners B, C, and D had different lipophilicity despite differing by only one amino acid. In the present study, we investigated how this difference in lipophilicity affected the interaction of the congeners with cell membranes. The circular dichroism spectra showed that the secondary structures were similar between the four congeners even at high temperature. The molar ellipticity of the four congeners in the presence of liposomes, as a cell membrane model, differed, and cyclosporines D and A showed lower molar ellipticity, while cyclosporine C exhibited higher molar ellipticity. Fluorescent spectra analysis using Laurdan indicated that liposome hydration was decreased in the presence of the cyclosporines, especially cyclosporines D and A. HPLC analysis also quantitatively showed that the amount of cyclosporine molecules internalized in HpG2 cells was the largest for cyclosporine D. We determined, using spectroscopy and HPLC, that the intensity of the interaction of the congeners with cell membranes was overall correlated with the lipophilicity derived from the side chains of each congener. Our results will contribute to the design of new macrocyclic peptides with favorable drug properties.