Charge and Charge-Pair Mutations Alter the Rate of Assembly and Structural Properties of Apolipoprotein C-II Amyloid Fibrils

Mao, Yu; Teoh, Chai Lean; Yang, Shuo; Zlatic, Courtney O.; Rosenes, Zachary; Gooley, Paul R.; Howlett, Geoffrey J.; Griffin, Michael D. W.

doi:10.1021/bi5014535

Cited by 13 publications

(37 citation statements)

References 33 publications

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“…The solution conditions were 100 mM sodium phosphate buffer, pH 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 10 conditions and consistent with previous studies 19 . In contrast, a significant increase in ThT fluorescence was observed for K30D apoC-II at concentrations of 0.8, 1 and 1.5 mg/ml,indicating fibril formation proceeds at higher concentrations.…”

Section: Effect Of Apoc-ii Concentrationsupporting

confidence: 81%

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Solution Conditions Affect the Ability of the K30D Mutation To Prevent Amyloid Fibril Formation by Apolipoprotein C-II: Insights from Experiments and Theoretical Simulations

et al. 2016

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Apolipoproteins form amphipathic helical structures that bind lipid surfaces. Paradoxically, lipid-free apolipoproteins display a strong propensity to form cross-β structure and self-associate into disease-related amyloid fibrils. Studies of apolipoprotein C-II (apoC-II) amyloid fibrils suggest that a K30-D69 ion pair accounts for the dual abilities to form helix and cross-β structure. Consistent with this is the observation that a K30D mutation prevents fibril formation under standard fibril forming conditions. However, we found that fibril formation by K30D apoC-II proceeded readily at low pH and a higher salt or protein concentration. Structural analysis demonstrated that K30D apoC-II fibrils at pH 7 have a structure similar to that of the wild-type fibrils but are less stable. Molecular dynamics simulations of the wild-type apoC-II fibril model at pH 7 and 3 showed that the loss of charge on D69 at pH 3 leads to greater separation between residues K30 and D69 within the fibril with a corresponding reduction in β-strand content around residue 30. In contrast, in simulations of the K30D mutant model at pH 7 and 3, residues D30 and D69 moved closer at pH 3, accompanied by an increase in β-strand content around residue 30. The simulations also demonstrated a strong dominance of inter- over intramolecular contacts between ionic residues of apoC-II and suggested a cooperative mechanism for forming favorable interactions between the individual strands under different conditions. These observations demonstrate the important role of the buried K30-D69 ion pair in the stability and solution properties of apoC-II amyloid fibrils.

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Section: Effect Of Apoc-ii Concentrationsupporting

confidence: 81%

“…Previous studies on the role of the K30-D69 ion-pair in apoC-II fibril formation showed that a D69K mutation reduces the stability of fibrils while increasing the rate of fibril formation 19 . In contrast, a K30D mutation abolished fibril formation under standard fibril forming conditions.…”

Section: Discussionmentioning

confidence: 96%

Solution Conditions Affect the Ability of the K30D Mutation To Prevent Amyloid Fibril Formation by Apolipoprotein C-II: Insights from Experiments and Theoretical Simulations

et al. 2016

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“…show the rate of fibril formation by wild‐type apoC‐II (WT) and three apoC‐II mutants, K30D, D69K, and the double mutant K30D‐D69K (KDDK), in the absence and presence of 500 μ m 1‐Myristoyl‐2‐Hydroxy‐ sn ‐Glycero‐3‐Phosphocholine (LysoMPC). As previously reported, twisted‐ribbon fibril formation by lipid‐free WT, D69K and KDDK apoC‐II is rapid while fibril formation by K30D apoC‐II under these conditions is comparatively slow . The observed differences in the fluorescence yields of WT and mutant apoC‐II are attributable to differences in the net charge of the fibrils .…”

Section: Resultssupporting

confidence: 72%

“…As previously reported, twisted‐ribbon fibril formation by lipid‐free WT, D69K and KDDK apoC‐II is rapid while fibril formation by K30D apoC‐II under these conditions is comparatively slow . The observed differences in the fluorescence yields of WT and mutant apoC‐II are attributable to differences in the net charge of the fibrils . The rates of apoC‐II rod‐like fibril formation in the presence of 500 μ m LysoMPC differed significantly.…”

Section: Resultssupporting

confidence: 68%

Polymorphism in disease‐related apolipoprotein C‐II amyloid fibrils: a structural model for rod‐like fibrils

et al. 2018

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Human apolipoprotein (apo) C-II is one of several plasma apolipoproteins that form amyloid deposits in vivo and is an independent risk factor for cardiovascular disease. Lipid-free apoC-II readily self-assembles into twisted-ribbon amyloid fibrils but forms straight, rod-like amyloid fibrils in the presence of low concentrations of micellar phospholipids. Charge mutations exerted significantly different effects on rod-like fibril formation compared to their effects on twisted-ribbon fibril formation. For instance, the double mutant, K30D-D69K apoC-II, readily formed twisted-ribbon fibrils, while the rate of rod-like fibril formation in the presence of micellar phospholipid was negligible. Structural analysis of rod-like apoC-II fibrils, using hydrogen-deuterium exchange and NMR analysis showed exchange protection consistent with a core cross-β structure comprising the C-terminal 58-76 region. Molecular dynamics simulations of fibril arrangements for this region favoured a parallel cross-β structure. X-ray fibre diffraction data for aligned rod-like fibrils showed a major meridional spacing at 4.6 Å and equatorial spacings at 9.7, 23.8 and 46.6 Å. The latter two equatorial spacings are not observed for aligned twisted-ribbon fibrils and are predicted for a model involving two cross-β fibrils in an off-set antiparallel structure with four apoC-II units per rise of the β-sheet. This model is consistent with the mutational effects on rod-like apoC-II fibril formation. The lipid-dependent polymorphisms exhibited by apoC-II fibrils could determine the properties of apoC-II in renal amyloid deposits and their potential role in the development of cardiovascular disease.

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“…To explore the role of the K30-D69 charge pair, we have previously studied the fibril forming ability of a D69K charge-pair mutant of apoC-II. 16 This study describes the effects of this mutation on the structural properties of apoC-II amyloid fibrils.…”

mentioning

confidence: 99%

Hydrogen/Deuterium Exchange and Molecular Dynamics Analysis of Amyloid Fibrils Formed by a D69K Charge-Pair Mutant of Human Apolipoprotein C-II

et al. 2015

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Plasma apolipoproteins form amphipathic α helices in lipid environments but in the lipid-free state show a high propensity to form β structure and self-associate into amyloid fibrils. The widespread occurrence of apolipoproteins in amyloid plaques suggests disease-related roles, specifically in atherosclerosis. To reconcile the dual abilities of apolipoproteins to form either α helices or cross-β sheet structures, we examined fibrils formed by human apolipoprotein C-II (apoC-II). A structural model for apoC-II fibrils shows a cross-β core with parallel β strands, including a buried K30-D69 charge pair. We investigated the effect of abolishing this charge pair in mutant D69K apoC-II. Fluorescence studies indicated more rapid fibril formation and less solvent accessibility of tryptophan (W26) in D69K apoC-II fibrils than in wild-type (WT) fibrils. X-ray diffraction data of aligned D69K apoC-II fibrils yielded a typical cross-β structure with increased β sheet spacing compared to that of WT fibrils. Hydrogen/deuterium (H/D) exchange patterns were similar for D69K apoC-II fibrils compared to WT fibrils, albeit with an overall reduction in the level of slow H/D exchange, particularly around residues 29-32. Molecular dynamics simulations indicated reduced β strand content for a model D69K apoC-II tetramer compared to the WT tetramer and confirmed an expansion of the cross-β spacing that contributed to the formation of a stable charge pair between K69 and E27. The results highlight the importance of charge-pair interactions within the apoC-II fibril core, which together with numerous salt bridges in the flexible connecting loop play a major role in the ability of lipid-free apoC-II to form stable cross-β fibrils.

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Charge and Charge-Pair Mutations Alter the Rate of Assembly and Structural Properties of Apolipoprotein C-II Amyloid Fibrils

Cited by 13 publications

References 33 publications

Solution Conditions Affect the Ability of the K30D Mutation To Prevent Amyloid Fibril Formation by Apolipoprotein C-II: Insights from Experiments and Theoretical Simulations

Solution Conditions Affect the Ability of the K30D Mutation To Prevent Amyloid Fibril Formation by Apolipoprotein C-II: Insights from Experiments and Theoretical Simulations

Polymorphism in disease‐related apolipoprotein C‐II amyloid fibrils: a structural model for rod‐like fibrils

Hydrogen/Deuterium Exchange and Molecular Dynamics Analysis of Amyloid Fibrils Formed by a D69K Charge-Pair Mutant of Human Apolipoprotein C-II

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