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Role of the fast kinetics of pyroglutamate-modified amyloid-β oligomers in membrane binding and membrane permeability.

Lee J, Gillman AL, Jang H, Ramachandran S, Kagan BL, Nussinov R, Teran Arce F - Biochemistry (2014)

Bottom Line: We find lower concentrations and larger dimensions for both species of membrane-associated AβpE3-42 oligomers.Membrane-inserted AβpE3-42 oligomers were also found to modify the mechanical properties of the membrane.Taken together, our results suggest that membrane-inserted oligomers are the primary species responsible for membrane permeability.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioengineering, University of California at San Diego , La Jolla, California 92093, United States.

ABSTRACT
Membrane permeability to ions and small molecules is believed to be a critical step in the pathology of Alzheimer's disease (AD). Interactions of oligomers formed by amyloid-β (Aβ) peptides with the plasma cell membrane are believed to play a fundamental role in the processes leading to membrane permeability. Among the family of Aβs, pyroglutamate (pE)-modified Aβ peptides constitute the most abundant oligomeric species in the brains of AD patients. Although membrane permeability mechanisms have been studied for full-length Aβ1-40/42 peptides, these have not been sufficiently characterized for the more abundant AβpE3-42 fragment. Here we have compared the adsorbed and membrane-inserted oligomeric species of AβpE3-42 and Aβ1-42 peptides. We find lower concentrations and larger dimensions for both species of membrane-associated AβpE3-42 oligomers. The larger dimensions are attributed to the faster self-assembly kinetics of AβpE3-42, and the lower concentrations are attributed to weaker interactions with zwitterionic lipid headgroups. While adsorbed oligomers produced little or no significant membrane structural damage, increased membrane permeabilization to ionic species is understood in terms of enlarged membrane-inserted oligomers. Membrane-inserted AβpE3-42 oligomers were also found to modify the mechanical properties of the membrane. Taken together, our results suggest that membrane-inserted oligomers are the primary species responsible for membrane permeability.

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Self-assembly kineticsof Aβ1–42 and AβpE3–42 measured by thioflavin-T (ThT) fluorescence at25 °C. The ThT intensity (I) was monitored asa function of time (t) for (A) AβpE3–42 (black) and Aβ1–42 (blue) solutions (fittedcurve shown with a solid blue line) with 20 μM concentrations(a.u., arbitrary units) and (B) 5 μM (dark gray) and 2.5 μM(light gray) solutions of AβpE3–42. Fittedcurves are shown with black lines. tlag and k were obtained from the fitted curves usingeqs 1 and 2.
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fig1: Self-assembly kineticsof Aβ1–42 and AβpE3–42 measured by thioflavin-T (ThT) fluorescence at25 °C. The ThT intensity (I) was monitored asa function of time (t) for (A) AβpE3–42 (black) and Aβ1–42 (blue) solutions (fittedcurve shown with a solid blue line) with 20 μM concentrations(a.u., arbitrary units) and (B) 5 μM (dark gray) and 2.5 μM(light gray) solutions of AβpE3–42. Fittedcurves are shown with black lines. tlag and k were obtained from the fitted curves usingeqs 1 and 2.

Mentions: The ThT fluorescence was used to compare the kineticsof fibril self-assembly for Aβ1–42 and AβpE3–42 peptides (Figure 1). AβpE3–42 peptides have faster self-assembly kinetics,indicated by a considerably shorter lag phase and a faster elongationphase (Figure 1A). The lag phase for AβpE3–42 becomes visible only at the lower concentrations(Figure 1B). Their lag phase times and rateconstants using eqs 1 and 2 are as follows: tlag = 1.14 h and k = 0.51 h–1 for the 5 μM solution,and tlag = 2.01 h and k = 0.31 h–1 for the 2.5 μM solution. Fromthe fitted curves in Figure 1A, we obtaineda tlag of 13.51 h and a k of 0.46 h–1 for Aβ1–42. Our results are in good agreement with previous results for Aβ1–40 and AβpE3–40,52 although those lag phase times are considerablylonger. This is possibly due to the two additional hydrophobic residues(Ile41 and Ala42) at the C-terminus of the Aβ1–42 and AβpE3–42 peptides.


Role of the fast kinetics of pyroglutamate-modified amyloid-β oligomers in membrane binding and membrane permeability.

Lee J, Gillman AL, Jang H, Ramachandran S, Kagan BL, Nussinov R, Teran Arce F - Biochemistry (2014)

Self-assembly kineticsof Aβ1–42 and AβpE3–42 measured by thioflavin-T (ThT) fluorescence at25 °C. The ThT intensity (I) was monitored asa function of time (t) for (A) AβpE3–42 (black) and Aβ1–42 (blue) solutions (fittedcurve shown with a solid blue line) with 20 μM concentrations(a.u., arbitrary units) and (B) 5 μM (dark gray) and 2.5 μM(light gray) solutions of AβpE3–42. Fittedcurves are shown with black lines. tlag and k were obtained from the fitted curves usingeqs 1 and 2.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4215883&req=5

fig1: Self-assembly kineticsof Aβ1–42 and AβpE3–42 measured by thioflavin-T (ThT) fluorescence at25 °C. The ThT intensity (I) was monitored asa function of time (t) for (A) AβpE3–42 (black) and Aβ1–42 (blue) solutions (fittedcurve shown with a solid blue line) with 20 μM concentrations(a.u., arbitrary units) and (B) 5 μM (dark gray) and 2.5 μM(light gray) solutions of AβpE3–42. Fittedcurves are shown with black lines. tlag and k were obtained from the fitted curves usingeqs 1 and 2.
Mentions: The ThT fluorescence was used to compare the kineticsof fibril self-assembly for Aβ1–42 and AβpE3–42 peptides (Figure 1). AβpE3–42 peptides have faster self-assembly kinetics,indicated by a considerably shorter lag phase and a faster elongationphase (Figure 1A). The lag phase for AβpE3–42 becomes visible only at the lower concentrations(Figure 1B). Their lag phase times and rateconstants using eqs 1 and 2 are as follows: tlag = 1.14 h and k = 0.51 h–1 for the 5 μM solution,and tlag = 2.01 h and k = 0.31 h–1 for the 2.5 μM solution. Fromthe fitted curves in Figure 1A, we obtaineda tlag of 13.51 h and a k of 0.46 h–1 for Aβ1–42. Our results are in good agreement with previous results for Aβ1–40 and AβpE3–40,52 although those lag phase times are considerablylonger. This is possibly due to the two additional hydrophobic residues(Ile41 and Ala42) at the C-terminus of the Aβ1–42 and AβpE3–42 peptides.

Bottom Line: We find lower concentrations and larger dimensions for both species of membrane-associated AβpE3-42 oligomers.Membrane-inserted AβpE3-42 oligomers were also found to modify the mechanical properties of the membrane.Taken together, our results suggest that membrane-inserted oligomers are the primary species responsible for membrane permeability.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioengineering, University of California at San Diego , La Jolla, California 92093, United States.

ABSTRACT
Membrane permeability to ions and small molecules is believed to be a critical step in the pathology of Alzheimer's disease (AD). Interactions of oligomers formed by amyloid-β (Aβ) peptides with the plasma cell membrane are believed to play a fundamental role in the processes leading to membrane permeability. Among the family of Aβs, pyroglutamate (pE)-modified Aβ peptides constitute the most abundant oligomeric species in the brains of AD patients. Although membrane permeability mechanisms have been studied for full-length Aβ1-40/42 peptides, these have not been sufficiently characterized for the more abundant AβpE3-42 fragment. Here we have compared the adsorbed and membrane-inserted oligomeric species of AβpE3-42 and Aβ1-42 peptides. We find lower concentrations and larger dimensions for both species of membrane-associated AβpE3-42 oligomers. The larger dimensions are attributed to the faster self-assembly kinetics of AβpE3-42, and the lower concentrations are attributed to weaker interactions with zwitterionic lipid headgroups. While adsorbed oligomers produced little or no significant membrane structural damage, increased membrane permeabilization to ionic species is understood in terms of enlarged membrane-inserted oligomers. Membrane-inserted AβpE3-42 oligomers were also found to modify the mechanical properties of the membrane. Taken together, our results suggest that membrane-inserted oligomers are the primary species responsible for membrane permeability.

Show MeSH
Related in: MedlinePlus