期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 102, 期 26, 页码 9394-9399出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0502352102
关键词
thiopurine toxicity; protein aggregation; pharmacogenomics; protein degradation
资金
- NIGMS NIH HHS [R01GM35720, R01GM28157, R01 GM035720, U01GM61388, U01 GM061388, R01 GM028157] Funding Source: Medline
Thiopurine S-methyltransferase (TPMT) catalyzes the S-methylation of thiopurine drugs. TPMT genetic polymorphisms represent a striking example of the potential clinical value of pharmacogenetics. Subjects homozygous for TPMT*3A, the most common variant allele for low activity, an allele that encodes a protein with two changes in amino acid sequence, are at greatly increased risk for life-threatening toxicity when treated with standard doses of thiopurines. These subjects have virtually undetectable levels of TPMT protein. In this study, we tested the hypothesis that TPMT*3A might result in protein misfolding and aggregation. We observed that TPMT*3A forms aggresomes in cultured cells and that it aggregates in vitro, functional mechanisms not previously described in pharmacogenetics. Furthermore, there was a correlation among TPMT half-life values in rabbit reticulocyte lysate, aggresome formation in COS-1 cells, and protein aggregation in vitro for the three variant allozymes encoded by alleles that include the two TPMT*3A single-nucleotide polymorphisms. These observations were compatible with a common structural explanation for all of these effects, a conclusion supported by size-exclusion chromatography and CD spectroscopy. The results of these experiments provide insight into a unique pharmacogenetic mechanism by which common polymorphisms affect TPMT protein function and, as a result, therapeutic response to thiopurine drugs.
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