Design and characterization of a FGF1‐FGF21 chimeric protein with increased stability and enhanced antidiabetic activities

Abstract

Fibroblast growth factor (FGF) family is consisted of 22 proteins that regulate a wide variety of biological functions such as wound healing, tissue repairs, and angiogenesis. FGF family follows three main modes of action: paracrine, intracrine or endocrine. One member of the paracrine FGFs is FGF1, which works locally through interaction with heparin or heparin sulfate (HS). With its mitogenic and cell survival activities, FGF1 participates in many developmental processes, cell growth and differentiation, tissue repairs, and tumor growth and invasion. A representative of endocrine FGFs is FGF21, which is often used in long range physiological processes, but does not require HS. FGF21 engages in many functions across various organs like liver, pancreas, adipose tissues. One of FGF21’s abilities is the regulation of glucose uptake in adipocytes through upregulating the transcription of glucose transporter‐1. Thus, FGF21 is a potential treatment for metabolic diseases such as Type‐2 Diabetes. However, FGF21 has been reported to possess an inherently unstable core with low thermal stability and receptor affinity. Herein, we designed a structure‐based chimera protein by replacing the core of FGF21 with a thermally stable paracrine FGF1 (sFGF1). Using techniques such as fluorescence spectroscopy, and circular dichroism, we show that the chimera protein sFGF1‐FGF21 adopts a β‐trefoil core. Intrinsic fluorescence spectra of the chimera protein shows an emission maximum centered at 307 nm indicating that the emission of the conserved tryptophan is quenched similar to wildtype FGF1. Differential calorimetry data suggests that chimera sFGF1‐FGF21 is significantly more stable than wild type FGF21. The findings of this study provide valuable clues for the rational design of FGF21‐based therapeutic against hyperglycemia and obesity.