Low-burden and precursor-free cell-cell communication in mammalian cells enabled by denovo design of super-sensitive...

Mammalian cells utilize intercellular signals to regulate physiological processes such as development and homeostasis. Synthetic signaling systems emulate these processes using orthogonal signals like small molecules, which offer benefits including rapid diffusion, controllability, and reduced immunogenicity compared with proteins. However, prior synthetic small molecule systems exhibited limited sensitivity (50% effective concentrations [EC₅₀] > 10^-7 mol/L) and imposed high metabolic burdens due to precursor biosynthesis. To address this, we engineered a super-sensitive (EC₅₀ ∼10^-9 mol/L) and low-burden cell-cell communication platform comprising de novo designed sender, receiver, and degrader modules. The sender produces signal molecules from the endogenous amino acid phenylalanine, the receiver integrates cis-regulatory elements from genomic data and AI-assisted trans-regulatory factor optimization to minimize leakage, and the degrader employs screened enzymes for highly efficient signal control. Finally, this precursor-free system facilitates robust, long-range morphogen gradient formation. The intercellular communication system reported herein holds great potential for future applications in tissue engineering.