Engineering a Transmembrane Receptor for Coacervate-Based Artificial Cells

Cell-surface receptors enable cells to sense physical or chemical stimuli and respond accordingly. Such a responsivity is key for almost all biochemical processes inside cells. Because of the importance of membrane-mediated signaling for the proper functioning of cells, mimicking this process with membrane-incorporating receptors in artificial cells is gaining interest. Here, we report on the engineering of a modular transmembrane receptor in copolymer-membrane-decorated coacervates that enables synthetic signal transduction. We have designed a heterodimerizing receptor that is dimerized via coiled-coil peptide interactions on the extracellular side upon binding to a soluble ditopic ligand. The receptor subunits are fused via a transmembrane domain to two split luciferase domains that generate bioluminescence upon receptor dimerization. The transmembrane domain is based on an elastin-like polypeptide (ELP) domain that undergoes hydrophobic interactions with the membrane-forming copolymer. Membrane insertion of the engineered proteins is dependent on the ELP sequence, and their protein diffusivity in the membrane is retained. Dose-dependent receptor activation is achieved by input ligand addition, resulting in a 5-fold increase in receptor activation. This modular system could be applied to engineer other synthetic receptors with different sensing and enzymatic output domains.