Recombinant expression of IGF-1 and LR3 IGF-1 fused with xylanase in Pichia pastoris

Insulin-like growth factor-1 (IGF-1) is a pleiotropic protein hormone and has become an attractive therapeutic target because of its multiple roles in various physiological processes, including growth, development, and metabolism. However, its production is hindered by low heterogenous protein expression levels in various expression systems and hard to meet the needs of clinical and scientific research. Here, we report that human IGF-1 and its analog Long R3 IGF-1 (LR3 IGF-1) are recombinant expressed and produced in the Pichia pastoris (P. pastoris) expression system through being fused with highly expressed xylanase XynCDBFV. Furthermore, purified IGF-1 and LR3 IGF-1 display excellent bioactivity of cell proliferation compared to the standard IGF-1. Moreover, higher heterologous expression levels of the fusion proteins XynCDBFV-IGF-1 and XynCDBFV-LR3 IGF-1 are achieved by fermentation in a 15-L bioreactor, reaching up to about 0.5 g/L XynCDBFV-IGF-1 and 1 g/L XynCDBFV-TEV-LR3 IGF-1. Taken together, high recombinant expression of bioactive IGF-1 and LR3 IGF-1 is acquired with the assistance of xylanase as a fusion partner in P. pastoris, which could be used for both clinical and scientific applications. KEY POINTS: • Human IGF-1 and LR3 IGF-1 are produced in the P. pastoris expression system. • Purified IGF-1 and LR3 IGF-1 show bioactivity comparable to the standard IGF-1. • High heterologous expression of IGF-1 and LR3 IGF-1 is achieved by fermentation in a bioreactor.