PEDS Advance Access published online on June 23, 2009
Protein Engineering Design and Selection, doi:10.1093/protein/gzp025
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Differential modification of Cys10 alters transthyretin's effect on beta-amyloid aggregation and toxicity
1Department of Chemical and Biological Engineering, University of Wisconsin, 1415 Engineering Drive, Madison, WI 53706 2Cellular and Molecular Biology Program and McArdle Laboratory for Cancer Research, University of Wisconsin, 1400 University Ave., Madison, WI 53706 3Human Proteomics Program, School of Medicine and Public Health, University of Wisconsin, 1300 University Ave., Madison, WI 53706 4Division of Pharmaceutical Sciences, School of Pharmacy, University of Wisconsin, 777 Highland Ave., Madison, WI 53705, USA 5Present address: Wyeth Pharmaceutical, 100 Academy St., Rouses Point, NY 12979, USA 6Present address: Shire PLC, 700 Main St., Cambridge, MA 02139, USA
7 To whom correspondence should be addressed. E-mail: regina{at}engr.wisc.edu
Tg2576 mice produce high levels of beta-amyloid (Aβ) and develop amyloid deposits, but lack neurofibrillary tangles and do not suffer the extensive neuronal cell loss characteristic of Alzheimer's disease. Protection from Aβ toxicity has been attributed to up-regulation of transthyretin (TTR), a normal component of plasma and cerebrospinal fluid. We compared the effect of TTR purified from human plasma (pTTR) with that produced recombinantly (rTTR) on Aβ aggregation and toxicity. pTTR slowed Aβ aggregation but failed to protect primary cortical neurons from Aβ toxicity. In contrast, rTTR accelerated aggregation, while effectively protecting neurons. This inverse correlation between Aβ aggregation kinetics and toxicity is consistent with the hypothesis that soluble intermediates rather than insoluble fibrils are the most toxic Aβ species. We carried out a detailed comparison of pTTR with rTTR to ascertain the probable cause of these different effects. No differences in secondary, tertiary or quaternary structure were detected. However, pTTR differed from rTTR in the extent and nature of modification at Cys10. We hypothesize that differential modification at Cys10 regulates TTR's effect on Aβ aggregation and toxicity.
Keywords: Alzheimer's disease/beta-amyloid/post-translational modification/transthyretin
Received May 20, 2009; revised May 20, 2009; accepted May 23, 2009.