Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong.
BMC Biotechnol. 2011 Apr 12;11:37. doi: 10.1186/1472-6750-11-37.
Human insulin-like growth factor-I (hIGF-I) is a growth factor which is highly resemble to insulin. It is essential for cell proliferation and has been proposed for treatment of various endocrine-associated diseases including growth hormone insensitivity syndrome and diabetes mellitus. In the present study, an efficient plant expression system was developed to produce biologically active recombinant hIGF-I (rhIGF-I) in transgenic rice grains.
The plant-codon-optimized hIGF-I was introduced into rice via Agrobacterium-mediated transformation. To enhance the stability and yield of rhIGF-I, the endoplasmic reticulum-retention signal and glutelin signal peptide were used to deliver rhIGF-I to endoplasmic reticulum for stable accumulation. We found that only glutelin signal peptide could lead to successful expression of hIGF-I and one gram of hIGF-I rice grain possessed the maximum activity level equivalent to 3.2 micro molar of commercial rhIGF-I. In vitro functional analysis showed that the rice-derived rhIGF-I was effective in inducing membrane ruffling and glucose uptake on rat skeletal muscle cells. Oral meal test with rice-containing rhIGF-I acutely reduced blood glucose levels in streptozotocin-induced and Zucker diabetic rats, whereas it had no effect in normal rats.
Our findings provided an alternative expression system to produce large quantities of biologically active rhIGF-I. The provision of large quantity of recombinant proteins will promote further research on the therapeutic potential of rhIGF-I.
人胰岛素样生长因子-I（hIGF-I）是一种与胰岛素高度相似的生长因子。它对细胞增殖至关重要，已被提议用于治疗各种与内分泌相关的疾病，包括生长激素不敏感综合征和糖尿病。在本研究中，开发了一种高效的植物表达系统，用于在转基因稻米中生产具有生物活性的重组 hIGF-I（rhIGF-I）。
通过农杆菌介导的转化将植物密码子优化的 hIGF-I 引入水稻。为了提高 rhIGF-I 的稳定性和产量，使用内质网保留信号和谷蛋白信号肽将 rhIGF-I 递送到内质网中以进行稳定积累。我们发现只有谷蛋白信号肽才能导致 hIGF-I 的成功表达，一克 hIGF-I 稻米颗粒具有相当于 3.2 微摩尔商业 rhIGF-I 的最大活性水平。体外功能分析表明，稻米衍生的 rhIGF-I 可有效诱导大鼠骨骼肌细胞的膜皱襞和葡萄糖摄取。含 rhIGF-I 的稻米口服餐试验可使链脲佐菌素诱导的和 Zucker 糖尿病大鼠的血糖水平急性降低，而对正常大鼠则没有影响。
我们的研究结果提供了一种替代的表达系统来大量生产具有生物活性的 rhIGF-I。大量重组蛋白的提供将促进对 rhIGF-I 治疗潜力的进一步研究。
