Interaction of (−)‐epigallocatechin‐3‐gallate with human serum albumin: Fluorescence, fourier transform infrared, circular dichroism, and docking studies

Maiti, Tushar Kanti; Ghosh, Kalyan Sundar; Dasgupta, Swagata

doi:10.1002/prot.20995

Cited by 147 publications

(113 citation statements)

References 33 publications

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“…EGCG was shown to exert antiamyloid activity by influencing cellular signal transduction pathways and reactive oxygen species (27). However, EGCG also directly binds to hydrophobic protein sequences both by hydrophobic interactions and by hydrogen bonding (28) and has been demonstrated to directly inhibit fibril formation of a wide range of amyloidogenic proteins (2-6). In the past, various small molecules have been shown to inhibit or reverse amyloid formation in vitro (9,26).…”

Section: Resultsmentioning

confidence: 99%

EGCG remodels mature α-synuclein and amyloid-β fibrils and reduces cellular toxicity

Bieschke

Russ

Friedrich

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

898

926

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Protein misfolding and formation of β-sheet-rich amyloid fibrils or aggregates is related to cellular toxicity and decay in various human disorders including Alzheimer's and Parkinson's disease. Recently, we demonstrated that the polyphenol (-)-epi-gallocatechine gallate (EGCG) inhibits α-synuclein and amyloid-β fibrillogenesis. It associates with natively unfolded polypeptides and promotes the self-assembly of unstructured oligomers of a new type. Whether EGCG disassembles preformed amyloid fibrils, however, remained unclear. Here, we show that EGCG has the ability to convert large, mature α-synuclein and amyloid-β fibrils into smaller, amorphous protein aggregates that are nontoxic to mammalian cells. Mechanistic studies revealed that the compound directly binds to β-sheetrich aggregates and mediates the conformational change without their disassembly into monomers or small diffusible oligomers. These findings suggest that EGCG is a potent remodeling agent of mature amyloid fibrils.Alzheimer | Parkinson | catechine | misfolding | oligomer P revious studies have shown that the polyphenol (-)-epi-gallocatechine gallate (EGCG), found in large amounts in green tea, has antiamyloidogenic properties and modulates the misfolding of disease proteins and prions (1-5). EGCG directly binds to unfolded polypeptide chains and inhibits β-sheet formation, an early event in the amyloid formation cascade (6). In the presence of EGCG, the assembly of a new type of unstructured, SDSstable, nontoxic oligomer was observed, instead of the expected formation of β-sheet-rich aggregates. This suggested that the compound redirects aggregation prone polypeptides into offpathway protein assemblies (6), as has since been confirmed for other flavonoids (7).These findings raise the question of whether EGCG might also be able to disassemble preformed, β-sheet-rich structures as well as earlier intermediates of fibrillogenesis. Other small molecules such as curcumin or short β-sheet breaker peptides were described to have this ability; however, their mechanism of action has not been elucidated (8,9). In the present study, we examined the ability of EGCG to alter the structure of mature amyloid fibrils with biochemical and biophysical as well as cell-based assays. Results and DiscussionTo study the effect of EGCG on preformed amyloid aggregates, we first produced α-synuclein (αS) fibrils by incubating natively unfolded monomers (100 μM) at 37°C for 7 d in phosphate buffer. Then aggregates were characterized by EM, atomic force microscopy (AFM), Thioflavin T (ThT) binding assays, and CD spectroscopy (Fig. S1). We observed that the in vitro generated αS aggregates have a β-sheet structure and a fibrillar morphology. Moreover, they efficiently bind the dye ThT, supporting previously published results (10).Next, we added an equimolar concentration of EGCG to the fibrils (50 μM αS monomer equivalent). The effect of the compound was monitored by time-resolved EM and AFM. We found that EGCG very efficiently remodels the ordered, fibrillar morphology ...

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Section: Resultsmentioning

confidence: 99%

EGCG remodels mature α-synuclein and amyloid-β fibrils and reduces cellular toxicity

Bieschke

Russ

Friedrich

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

898

926

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“…A previous report has shown that the hydrophobicity of the catechins obtained for a 1-octanol/PBS binary liquid was increased drastically by the presence of the galloyl moiety (19). On the other hand, studies of serum albumin-polyphenol interactions suggest that binding of polyphenols with serum albumin are stabilized by hydrophobic interactions, hydrogen-bonding forces, and electrostatic forces (20,21). HSA is a globular protein composed of three structurally similar domains (I, II, and III), each containing a number of hydrophobic cavities.…”

Section: Discussionmentioning

confidence: 98%

Influence of the Galloyl Moiety in Tea Catechins on Binding Affinity for Human Serum Albumin

Minoda

Ichikawa

Katsumata

et al. 2010

J Nutr Sci Vitaminol

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SummaryThe major catechins of green tea extract are ( Ϫ )-epicatechin (EC), ( Ϫ )-epigallocatechin (EGC), ( Ϫ )-epicatechin gallate (ECg), and ( Ϫ )-epigallocatechin gallate (EGCg). Recent research has indicated that catechins form complexes with human serum albumin (HSA) in blood, and differences in their binding affinity toward HSA are believed to modulate their bioavailability. In this study, we kinetically investigated the interaction between the catechins and HSA immobilized on a quartz-crystal microbalance (QCM). The association constants obtained from the frequency changes of QCM revealed interactions of ECg and EGCg with HSA that are 100 times stronger than those of EC and EGC. Furthermore, comparisons of these catechins by native-gel electrophoresis/blotting with redox-cycling staining revealed that, in a phosphate buffer, ECg and EGCg have a higher binding affinity toward HSA than EC and EGC. These observations indicate that catechins with a galloyl moiety have higher binding affinities toward HSA than catechins lacking a galloyl moiety.

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“…Moreover, by first allowing for the formation of amyloid fibrils or inhibition thereof in a controlled environment in vitro, we avoid interference by active molecular chaperones, such as clusterin and BSA, which are readily present as nutrients in cell medium. 44,64,65 After incubation of the treated cells for 48 h, the treatment mixture was removed and 100 μL of serum-free medium containing MTT (0.6 mM) was added to each well. The cells were then incubated for an additional 2 h, and the MTT-containing medium was replaced with 100 μL of DMSO.…”

Section: Solution-state 1 H Nmr Spectroscopymentioning

confidence: 99%

(−)-Epigallocatechin-3-Gallate (EGCG) Maintains κ-Casein in Its Pre-Fibrillar State without Redirecting Its Aggregation Pathway

Hudson

Ecroyd

Dehle

et al. 2009

Journal of Molecular Biology

133

120

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The polyphenol (-)-epigallocatechin-3-gallate (EGCG) has recently attracted much research interest in the field of protein-misfolding diseases because of its potent anti-amyloid activity against amyloid-beta, alphasynuclein and huntingtin, the amyloid-fibril-forming proteins involved in Alzheimer's, Parkinson's and Huntington's diseases, respectively. EGCG redirects the aggregation of these polypeptides to a disordered offfolding pathway that results in the formation of non-toxic amorphous aggregates. whether this anti-fibril activity is specific to these disease-related target proteins or ismore generic remains to be established. In addition, the mechanism by which EGCG exerts its effects, as with all anti-amyloidogenic polyphenols, remains unclear. To address these aspects, we have investigated the ability of EGCG to inhibit amyloidogenesis of the generic model fibril-forming protein RCMkappa-CN (reduced and carboxymethylated kappa-casein) and thereby protect pheochromocytoma-12 cells from RCMkappa-CN amyloid-induced toxicity. We found that EGCG potently inhibits in vitro fibril formation byRCMkappa-CN [the IC50 for 50 uM RCMkappa-CN is 1 uM]. Biophysical studies reveal that EGCG prevents RCMkappa-CN fibril formation by stabilising RCMkappa-CN in its nativelike state rather than by redirecting its aggregation to the disordered, amorphous aggregation pathway. Thus, while it appears that EGCG is a generic inhibitor of amyloid-fibril formation, the mechanism by which it achieves this inhibition is specific to the target fibril-forming polypeptide. It is proposed that EGCG is directed to the amyloidogenic sheet-turn-sheet motif of monomeric RCMkappa-CN with high affinity by strong non-specific hydrophobic associations. Additional non-covalent pi-pi stacking interactions between the polyphenolic and aromatic residues common to the amyloidogenic sequence are also implicated. The polyphenol (−)-epigallocatechin-3-gallate (EGCG) has recently attracted much research interest in the field of protein-misfolding diseases because of its potent anti-amyloid activity against amyloid-β, α-synuclein and huntingtin, the amyloid-fibril-forming proteins involved in Alzheimer's, Parkinson's and Huntington's diseases, respectively. EGCG redirects the aggregation of these polypeptides to a disordered off-folding pathway that results in the formation of non-toxic amorphous aggregates. Whether this anti-fibril activity is specific to these disease-related target proteins or is more generic remains to be established. In addition, the mechanism by which EGCG exerts its effects, as with all anti-amyloidogenic polyphenols, remains unclear. To address these aspects, we have investigated the ability of EGCG to inhibit amyloidogenesis of the generic model fibril-forming protein RCMκ-CN (reduced and carboxymethylated κ-casein) and thereby protect pheochromocytoma-12 cells from RCMκ-CN amyloid-induced toxicity. We found that EGCG potently inhibits in vitro fibril formation by RCMκ-CN [the IC 50 for 50 μM RCMκ-CN is 13 ± 1 μM]. Biophys...

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Interaction of (−)‐epigallocatechin‐3‐gallate with human serum albumin: Fluorescence, fourier transform infrared, circular dichroism, and docking studies

Cited by 147 publications

References 33 publications

EGCG remodels mature α-synuclein and amyloid-β fibrils and reduces cellular toxicity

EGCG remodels mature α-synuclein and amyloid-β fibrils and reduces cellular toxicity

Influence of the Galloyl Moiety in Tea Catechins on Binding Affinity for Human Serum Albumin

(−)-Epigallocatechin-3-Gallate (EGCG) Maintains κ-Casein in Its Pre-Fibrillar State without Redirecting Its Aggregation Pathway

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