Production of biologically active human thioredoxin 1 protein in lettuce chloroplasts
The production of human therapeutic proteins in plants provides opportunities for low-cost production, and minimizes the risk of contamination from potential human pathogens. Chloroplast genetic engineering is a particularly promising strategy, because plant chloroplasts can produce large amounts of foreign target proteins. Oxidative stress is a key factor in various human diseases. Human thioredoxin 1 (hTrx1) is a stress-induced protein that functions as an antioxidant against oxidative stress, and overexpression of hTrx1 has been shown to suppress various diseases in mice. Therefore, hTrx1 is a prospective candidate as a new human therapeutic protein. We created transplastomic lettuce expressing hTrx1 under the control of the psbA promoter. Transplastomic plants grew normally and were fertile. The hTrx1 protein accumulated to approximately 1% of total soluble protein in mature leaves. The hTrx1 protein purified from lettuce leaves was functionally active, and reduced insulin disulfides. The purified protein protected mouse insulinoma line 6 cells from damage by hydrogen peroxide, as reported previously for a recombinant hTrx1 expressed in Escherichia coli. This is the first report of expression of the biologically active hTrx1 protein in plant chloroplasts. This research opens up possibilities for plant-based production of hTrx1. Considering that this expression host is an edible crop plant, this transplastomic lettuce may be suitable for oral delivery of hTrx1.
KeywordsChloroplasts Chloroplast transformation Lettuce Plastome Transplastomic plant Human thioredoxin-1 Therapeutic protein
We thank Dr. Jun-ichi Miyazaki (Osaka University) for the MIN6 cells. We also thank Kazuko Sano, Hanae Sugita, Yaka Ichikawa, and Harumi Sakuyama for technical assistance. This study was conducted as a part of the project of the Development of Fundamental Technologies for Production of High-value Materials using Transgenic Plants (2006–2010) of the Ministry of Economy, Trade, and Industry (METI) of Japan, and the Program for Promotion of Fundamental Studies in Health Sciences of National Institute of Biomedical Innovation (NIBIO).
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