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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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The relationships among OR length, onset age, and copper binding properties.(A) Onset age for individual cases as a function of extra octarepeat inserts. Note that wild-type corresponds to four repeats, so three inserts corresponds to seven total repeat segments, as in Figures 3 and 4. The horizontal line represents 55.5 years of age and the vertical line separates four and five inserts (separators determined by CART analysis). For all cases with four or fewer inserts (e.g., up to eight total repeats), onset age is more than 55.5 years; for five inserts and longer, 96% of the cases exhibit onset age younger than 55.5 years. (B) Parallel box plot of the data in (A), with the number of individuals in each group given at the top. Blue circles are outliers. (C) F test results for all pairwise comparisons based on disease onset age. Cells in blue correspond to significant pairwise differences, thus establishing groupings in onset age for 1–4 OR inserts (late onset) and for 5–8 inserts (early onset). (D) Average onset age, with standard deviation (blue circles, left axis), and component 1 coordination (orange diamonds and red squares, right axis, for 3.0 and 4.0 equivalents Cu2+, respectively) as a function of extra octarepeat inserts. At both copper concentrations, component 1 coordination drops suddenly at approximately the same OR length threshold as average onset age.
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ppat-1000390-g005: The relationships among OR length, onset age, and copper binding properties.(A) Onset age for individual cases as a function of extra octarepeat inserts. Note that wild-type corresponds to four repeats, so three inserts corresponds to seven total repeat segments, as in Figures 3 and 4. The horizontal line represents 55.5 years of age and the vertical line separates four and five inserts (separators determined by CART analysis). For all cases with four or fewer inserts (e.g., up to eight total repeats), onset age is more than 55.5 years; for five inserts and longer, 96% of the cases exhibit onset age younger than 55.5 years. (B) Parallel box plot of the data in (A), with the number of individuals in each group given at the top. Blue circles are outliers. (C) F test results for all pairwise comparisons based on disease onset age. Cells in blue correspond to significant pairwise differences, thus establishing groupings in onset age for 1–4 OR inserts (late onset) and for 5–8 inserts (early onset). (D) Average onset age, with standard deviation (blue circles, left axis), and component 1 coordination (orange diamonds and red squares, right axis, for 3.0 and 4.0 equivalents Cu2+, respectively) as a function of extra octarepeat inserts. At both copper concentrations, component 1 coordination drops suddenly at approximately the same OR length threshold as average onset age.

Mentions: To examine these data more closely, we plotted the age of onset for each individual case against the number of OR insertions in Figure 5A. The red horizontal line is at 55.5 years (see below). All cases up to four OR inserts are above this line and 96% of the cases of five or more OR inserts are below the line. Although there is significant scatter in reported onset age for each specific OR length, the dramatic shift to early onset disease between four and five inserts is apparent. Figure 5B presents the same data as parallel boxplots, with sample sizes (number of cases) in each boxplot given at the top of the graph. An overall F test provided strong evidence of differences between the mean onset ages for different numbers of repeats (p-value 2.8e-14) [33]. The results for all pairwise comparisons are summarized in Figure 5C; cells in blue correspond to significant pairwise differences at a family-wise error rate of 5%. The results are consistent with the existence of two groups, one made of individuals with 1 to 4 OR inserts and another made of individuals with 5 to 8 inserts. The three patients with 9 repeats did not show a significant difference with any of the other groups; this is due to the small sample size in that group.


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)

The relationships among OR length, onset age, and copper binding properties.(A) Onset age for individual cases as a function of extra octarepeat inserts. Note that wild-type corresponds to four repeats, so three inserts corresponds to seven total repeat segments, as in Figures 3 and 4. The horizontal line represents 55.5 years of age and the vertical line separates four and five inserts (separators determined by CART analysis). For all cases with four or fewer inserts (e.g., up to eight total repeats), onset age is more than 55.5 years; for five inserts and longer, 96% of the cases exhibit onset age younger than 55.5 years. (B) Parallel box plot of the data in (A), with the number of individuals in each group given at the top. Blue circles are outliers. (C) F test results for all pairwise comparisons based on disease onset age. Cells in blue correspond to significant pairwise differences, thus establishing groupings in onset age for 1–4 OR inserts (late onset) and for 5–8 inserts (early onset). (D) Average onset age, with standard deviation (blue circles, left axis), and component 1 coordination (orange diamonds and red squares, right axis, for 3.0 and 4.0 equivalents Cu2+, respectively) as a function of extra octarepeat inserts. At both copper concentrations, component 1 coordination drops suddenly at approximately the same OR length threshold as average onset age.
© Copyright Policy
Related In: Results  -  Collection

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

ppat-1000390-g005: The relationships among OR length, onset age, and copper binding properties.(A) Onset age for individual cases as a function of extra octarepeat inserts. Note that wild-type corresponds to four repeats, so three inserts corresponds to seven total repeat segments, as in Figures 3 and 4. The horizontal line represents 55.5 years of age and the vertical line separates four and five inserts (separators determined by CART analysis). For all cases with four or fewer inserts (e.g., up to eight total repeats), onset age is more than 55.5 years; for five inserts and longer, 96% of the cases exhibit onset age younger than 55.5 years. (B) Parallel box plot of the data in (A), with the number of individuals in each group given at the top. Blue circles are outliers. (C) F test results for all pairwise comparisons based on disease onset age. Cells in blue correspond to significant pairwise differences, thus establishing groupings in onset age for 1–4 OR inserts (late onset) and for 5–8 inserts (early onset). (D) Average onset age, with standard deviation (blue circles, left axis), and component 1 coordination (orange diamonds and red squares, right axis, for 3.0 and 4.0 equivalents Cu2+, respectively) as a function of extra octarepeat inserts. At both copper concentrations, component 1 coordination drops suddenly at approximately the same OR length threshold as average onset age.
Mentions: To examine these data more closely, we plotted the age of onset for each individual case against the number of OR insertions in Figure 5A. The red horizontal line is at 55.5 years (see below). All cases up to four OR inserts are above this line and 96% of the cases of five or more OR inserts are below the line. Although there is significant scatter in reported onset age for each specific OR length, the dramatic shift to early onset disease between four and five inserts is apparent. Figure 5B presents the same data as parallel boxplots, with sample sizes (number of cases) in each boxplot given at the top of the graph. An overall F test provided strong evidence of differences between the mean onset ages for different numbers of repeats (p-value 2.8e-14) [33]. The results for all pairwise comparisons are summarized in Figure 5C; cells in blue correspond to significant pairwise differences at a family-wise error rate of 5%. The results are consistent with the existence of two groups, one made of individuals with 1 to 4 OR inserts and another made of individuals with 5 to 8 inserts. The three patients with 9 repeats did not show a significant difference with any of the other groups; this is due to the small sample size in that group.

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