重组rHSA-hFGF21融合蛋白在毕赤酵母中的表达纯化及活性分析

Expression, purification and bioactivity analysis of a recombinant fusion protein rHSA-hFGF21 in Pichia pastoris

摘要:

人成纤维细胞生长因子21(human fibroblast growth factor 21,hFGF21)已成为改善血糖和脂质代谢的候选药物，但却存在半衰期短和易被体内代谢等缺点，导致靶组织利用率低，限制了其临床应用。本研究通过柔性连接肽(GGGGS)₃将hFGF21的N端连接至人血清白蛋白（human serum albumin,HSA）的C端，经过毕赤酵母密码子优化后，将重组基因片段rHSA-hFGF21连入pPIC9k和pPICZαA两种载体，并转化到X33、GS115和SMD1168三种不同酵母菌株中。通过加压筛选得到高表达的X33-pPIC9K-rHSA-hFGF21工程菌株，并优化摇瓶诱导条件如OD值、甲醇浓度和诱导时间进一步提高rHSA-hFGF21的表达效率。培养上清经中空纤维膜切向流技术粗分离、Blue亲和层析和Q离子交换层析纯化获得纯度约98.18%的rHSA-hFGF21蛋白。与hFGF21相比，rHSA-hFGF21具有更好的热稳定性和抗胰蛋白酶降解的能力，其血浆半衰期也延长了约27.6倍；中高浓度条件下rHSA-hFGF21刺激HepG2细胞摄取葡萄糖的能力优于hFGF21；在2型糖尿病动物中rHSA-hFGF21比hFGF21具有更好的长效降糖效果。本研究将为FGF21蛋白的大规模生产奠定基础。

Abstract:

Human fibroblast growth factor 21 (hFGF21) has become a candidate drug for regulating blood glucose and lipid metabolism. The poor stability and short half-life of hFGF21 resulted in low target tissue availability, which hampers its clinical application. In this study, the hFGF21 was fused with a recombinant human serum albumin (HSA), and the resulted fusion protein rHSA-hFGF21 was expressed in Pichia pastoris. After codon optimization, the recombinant gene fragment rHSA-hFGF21 was inserted into two different vectors (pPIC9k and pPICZaA) and transformed into three different strains (X33, GS115 and SMD1168), respectively. We investigated the rHSA-hFGF21 expression levels in three different strains and screened an engineered strain X33-pPIC9K-rHSA-hFGF21 with the highest expression level. To improve the production efficiency of rHSA-hFGF21, we optimized the shake flask fermentation conditions, such as the OD value, methanol concentration and induction time. After purification by hollow fiber membrane separation, Blue affinity chromatography and Q ion exchange chromatography, the purity of the rHSA-hFGF21 protein obtained was 98.18%. Compared to hFGF21, the biostabilities of rHSA-hFGF21, including their resistance to temperature and trypsinization were significantly enhanced, and its plasma half-life was extended by about 27.6 times. Moreover, the fusion protein rHSA-hFGF21 at medium and high concentration showed a better ability to promote glucose uptake after 24 h of stimulation in vitro. In vivo animal studies showed that rHSA-hFGF21 exhibited a better long-term hypoglycemic effect than hFGF21 in type 2 diabetic mice. Our results demonstrated a small-scale production of rHSA-hFGF21, which is important for large-scale production and clinical application in the future.