TY - JOUR
T1 - Pathogenic polyglutamine expansion length correlates with polarity of the flanking sequences
AU - Kim, Meewhi
N1 - Funding Information:
I thank to Leah Taylor for administrative assistance, members of Bezprozvanny and Kim laboratories for helpful discussions and Drs Ilya Bezprozvanny (I.B.) and George De Martino for comments on the paper. MWK is a Young Investigator of the National Ataxia Foundation and supported by the Hereditary Disease Foundation. This work was also supported by the contract with the Russian Ministry of Science 11. G34.31.0056 (I.B), by the Russian Scientific Fund grant 14-25-00024 (IB), and by the NIH grants R01NS074376 and R01NS056224 (I.B.).
PY - 2014
Y1 - 2014
N2 - BACKGROUND: Polyglutamine (polyQ) repeat expansion within coding sequence of a soluble protein is responsible for eight autosomal-dominant genetic neurodegenerative disorders. These disorders affect cerebellum, striatum, basal ganglia and other brain regions. The pathogenic polyQ-expansion threshold in these proteins varies from 32Q to 54Q. Understanding the reasons for variability in pathogenic polyQ threshold may provide insights into pathogenic mechanisms responsible for development of these disorders.FINDINGS: Here we established a quantitative correlation between the polarity of the flanking sequences and pathogenic polyQ-expansion threshold in this protein family. We introduced an "edge polarity index" (EPI) to quantify polarity effects of the flanking regions and established a strong correlation between EPI index and critical polyQ expansion length in this protein family. Based on this analysis we subdivided polyQ-expanded proteins into 2 groups - with strong and weak dependence of polyQ threshold on EPI index. The main difference between members of the first and the second group is a polarity profile of these proteins outside of polyQ and flanking regions. PolyQ proteins are known substrates for proteasome and most likely mechanistic explanation for the observed correlation is that proteasome may have an impaired ability to process continuous non-polar regions of proteins.CONCLUSIONS: The proposed hypothesis provides a quantitative explanation for variability in pathogenic threshold among polyQ-expansion disorders, which we established to correlate with polarity of flanking regions. To explain these results we propose that proteasome is not efficient in processing continuous non-polar regions of proteins, resulting in release of undigested and partially digested fragments. If supported experimentally, our hypothesis may have wide implications for further understanding the pathogensis of polyglutamine expansion disorders.
AB - BACKGROUND: Polyglutamine (polyQ) repeat expansion within coding sequence of a soluble protein is responsible for eight autosomal-dominant genetic neurodegenerative disorders. These disorders affect cerebellum, striatum, basal ganglia and other brain regions. The pathogenic polyQ-expansion threshold in these proteins varies from 32Q to 54Q. Understanding the reasons for variability in pathogenic polyQ threshold may provide insights into pathogenic mechanisms responsible for development of these disorders.FINDINGS: Here we established a quantitative correlation between the polarity of the flanking sequences and pathogenic polyQ-expansion threshold in this protein family. We introduced an "edge polarity index" (EPI) to quantify polarity effects of the flanking regions and established a strong correlation between EPI index and critical polyQ expansion length in this protein family. Based on this analysis we subdivided polyQ-expanded proteins into 2 groups - with strong and weak dependence of polyQ threshold on EPI index. The main difference between members of the first and the second group is a polarity profile of these proteins outside of polyQ and flanking regions. PolyQ proteins are known substrates for proteasome and most likely mechanistic explanation for the observed correlation is that proteasome may have an impaired ability to process continuous non-polar regions of proteins.CONCLUSIONS: The proposed hypothesis provides a quantitative explanation for variability in pathogenic threshold among polyQ-expansion disorders, which we established to correlate with polarity of flanking regions. To explain these results we propose that proteasome is not efficient in processing continuous non-polar regions of proteins, resulting in release of undigested and partially digested fragments. If supported experimentally, our hypothesis may have wide implications for further understanding the pathogensis of polyglutamine expansion disorders.
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U2 - 10.1186/1750-1326-9-45
DO - 10.1186/1750-1326-9-45
M3 - Article
C2 - 25377768
AN - SCOPUS:84920768668
SN - 1750-1326
VL - 9
SP - 45
JO - Molecular neurodegeneration
JF - Molecular neurodegeneration
ER -