Abstract

The human complement component 3a receptor (C3aR) is a G protein-coupled receptor (GPCR) that plays a critical role in the inflammatory response and is a significant therapeutic target for immune-related diseases. However, the study of C3aR structure and function is often hampered by the inherent instability of membrane proteins upon extraction and purification. This manuscript addresses this challenge by focusing on the **Expression and Stabilization of Recombinant Human C3aR Receptor**. We successfully developed a robust expression system using the *Spodoptera frugiperda* (Sf9) insect cell line to produce high yields of the full-length human C3aR. Following detergent-based solubilization, various stabilizing agents and purification strategies, including affinity chromatography and size-exclusion chromatography, were systematically screened. Our key finding is the identification of a novel stabilizing cocktail that significantly enhances the thermal and conformational stability of the purified recombinant C3aR, as confirmed by circular dichroism and ligand-binding assays. This stabilized, functional recombinant C3aR protein provides an essential tool for high-resolution structural studies, such as cryo-electron microscopy, and for the development of novel therapeutic modulators.