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Early onset prion disease from octarepeat expansion correlates with copper binding properties.

Stevens DJ, Walter ED, Rodríguez A, Draper D, Davies P, Brown DR, Millhauser GL - PLoS Pathog. (2009)

Bottom Line: With up to four extra octarepeats, the average onset age is above 60 years, whereas five to nine extra octarepeats results in an average onset age between 30 and 40 years, a difference of almost three decades.We find that there is little change in affinity or coordination mode populations for octarepeat domains with up to seven segments (three inserts).However, domains with eight or nine total repeats (four or five inserts) become energetically arrested in the multi-histidine coordination mode, as dictated by higher copper uptake capacity and also by increased binding affinity.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry and Biochemistry, University of California Santa Cruz, Santa Cruz, California, USA.

ABSTRACT
Insertional mutations leading to expansion of the octarepeat domain of the prion protein (PrP) are directly linked to prion disease. While normal PrP has four PHGGGWGQ octapeptide segments in its flexible N-terminal domain, expanded forms may have up to nine additional octapeptide inserts. The type of prion disease segregates with the degree of expansion. With up to four extra octarepeats, the average onset age is above 60 years, whereas five to nine extra octarepeats results in an average onset age between 30 and 40 years, a difference of almost three decades. In wild-type PrP, the octarepeat domain takes up copper (Cu(2+)) and is considered essential for in vivo function. Work from our lab demonstrates that the copper coordination mode depends on the precise ratio of Cu(2+) to protein. At low Cu(2+) levels, coordination involves histidine side chains from adjacent octarepeats, whereas at high levels each repeat takes up a single copper ion through interactions with the histidine side chain and neighboring backbone amides. Here we use both octarepeat constructs and recombinant PrP to examine how copper coordination modes are influenced by octarepeat expansion. We find that there is little change in affinity or coordination mode populations for octarepeat domains with up to seven segments (three inserts). However, domains with eight or nine total repeats (four or five inserts) become energetically arrested in the multi-histidine coordination mode, as dictated by higher copper uptake capacity and also by increased binding affinity. We next pooled all published cases of human prion disease resulting from octarepeat expansion and find remarkable agreement between the sudden length-dependent change in copper coordination and onset age. Together, these findings suggest that either loss of PrP copper-dependent function or loss of copper-mediated protection against PrP polymerization makes a significant contribution to early onset prion disease.

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Related in: MedlinePlus

Three-dimensional model of PrP with eight total repeats (four inserts) coordinated to two equivalents of Cu2+ in the component 3 mode.(Note that N-terminal residues 23–59 are not shown.) Results presented here demonstrate that this structure is persistent and, in contrast to wild-type PrP, resists transitioning to component 1 coordination (Figure 1).
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ppat-1000390-g006: Three-dimensional model of PrP with eight total repeats (four inserts) coordinated to two equivalents of Cu2+ in the component 3 mode.(Note that N-terminal residues 23–59 are not shown.) Results presented here demonstrate that this structure is persistent and, in contrast to wild-type PrP, resists transitioning to component 1 coordination (Figure 1).

Mentions: To gain insight into the three-dimensional characteristics of PrP with an expanded OR domain interacting with Cu2+, we performed structure calculations using distance restraints tethering four adjacent repeat His side chains to a single copper ion. We examined PrP with eight repeats and two copper equivalents. The C-terminal domain coordinates are from NMR studies. Other than Cu2+-imidazole distances, the OR domain was left unrestrained during energy minimization. The resulting structure is shown in Figure 6. (Non-octarepeat Cu2+ are omitted and approximately 40 residues on the N-terminal side of the first repeat are not shown.) His imidazoles arrange with an approximate tetrahedral geometry around each copper center. As expected, the expanded OR domain readily takes up two Cu2+ with a relaxed backbone conformation. Also, with eight total repeat segments, the OR domain comprises a significant fraction of the total protein. Although each copper center carries a divalent positive charge, the rest of the 64 amino acids within the expanded OR domain are uncharged and thus comprise a significant hydrophobic domain. PrP with OR inserts show a strong propensity to form aggregates and amyloid. The enhanced hydrophobicity of the N-terminal domain may facilitate interactions between PrPC copies, thus promoting the amyloid assembly process.


Early onset prion disease from octarepeat expansion correlates with copper binding properties.

Stevens DJ, Walter ED, Rodríguez A, Draper D, Davies P, Brown DR, Millhauser GL - PLoS Pathog. (2009)

Three-dimensional model of PrP with eight total repeats (four inserts) coordinated to two equivalents of Cu2+ in the component 3 mode.(Note that N-terminal residues 23–59 are not shown.) Results presented here demonstrate that this structure is persistent and, in contrast to wild-type PrP, resists transitioning to component 1 coordination (Figure 1).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2663819&req=5

ppat-1000390-g006: Three-dimensional model of PrP with eight total repeats (four inserts) coordinated to two equivalents of Cu2+ in the component 3 mode.(Note that N-terminal residues 23–59 are not shown.) Results presented here demonstrate that this structure is persistent and, in contrast to wild-type PrP, resists transitioning to component 1 coordination (Figure 1).
Mentions: To gain insight into the three-dimensional characteristics of PrP with an expanded OR domain interacting with Cu2+, we performed structure calculations using distance restraints tethering four adjacent repeat His side chains to a single copper ion. We examined PrP with eight repeats and two copper equivalents. The C-terminal domain coordinates are from NMR studies. Other than Cu2+-imidazole distances, the OR domain was left unrestrained during energy minimization. The resulting structure is shown in Figure 6. (Non-octarepeat Cu2+ are omitted and approximately 40 residues on the N-terminal side of the first repeat are not shown.) His imidazoles arrange with an approximate tetrahedral geometry around each copper center. As expected, the expanded OR domain readily takes up two Cu2+ with a relaxed backbone conformation. Also, with eight total repeat segments, the OR domain comprises a significant fraction of the total protein. Although each copper center carries a divalent positive charge, the rest of the 64 amino acids within the expanded OR domain are uncharged and thus comprise a significant hydrophobic domain. PrP with OR inserts show a strong propensity to form aggregates and amyloid. The enhanced hydrophobicity of the N-terminal domain may facilitate interactions between PrPC copies, thus promoting the amyloid assembly process.

Bottom Line: With up to four extra octarepeats, the average onset age is above 60 years, whereas five to nine extra octarepeats results in an average onset age between 30 and 40 years, a difference of almost three decades.We find that there is little change in affinity or coordination mode populations for octarepeat domains with up to seven segments (three inserts).However, domains with eight or nine total repeats (four or five inserts) become energetically arrested in the multi-histidine coordination mode, as dictated by higher copper uptake capacity and also by increased binding affinity.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry and Biochemistry, University of California Santa Cruz, Santa Cruz, California, USA.

ABSTRACT
Insertional mutations leading to expansion of the octarepeat domain of the prion protein (PrP) are directly linked to prion disease. While normal PrP has four PHGGGWGQ octapeptide segments in its flexible N-terminal domain, expanded forms may have up to nine additional octapeptide inserts. The type of prion disease segregates with the degree of expansion. With up to four extra octarepeats, the average onset age is above 60 years, whereas five to nine extra octarepeats results in an average onset age between 30 and 40 years, a difference of almost three decades. In wild-type PrP, the octarepeat domain takes up copper (Cu(2+)) and is considered essential for in vivo function. Work from our lab demonstrates that the copper coordination mode depends on the precise ratio of Cu(2+) to protein. At low Cu(2+) levels, coordination involves histidine side chains from adjacent octarepeats, whereas at high levels each repeat takes up a single copper ion through interactions with the histidine side chain and neighboring backbone amides. Here we use both octarepeat constructs and recombinant PrP to examine how copper coordination modes are influenced by octarepeat expansion. We find that there is little change in affinity or coordination mode populations for octarepeat domains with up to seven segments (three inserts). However, domains with eight or nine total repeats (four or five inserts) become energetically arrested in the multi-histidine coordination mode, as dictated by higher copper uptake capacity and also by increased binding affinity. We next pooled all published cases of human prion disease resulting from octarepeat expansion and find remarkable agreement between the sudden length-dependent change in copper coordination and onset age. Together, these findings suggest that either loss of PrP copper-dependent function or loss of copper-mediated protection against PrP polymerization makes a significant contribution to early onset prion disease.

Show MeSH
Related in: MedlinePlus