Programming cell-surface signaling by phase-separation-controlled compartmentalization.

The landscape of cell-surface signaling is formidably complex. Robust tools capable of manipulating the spatiotemporal distribution of cell-surface proteins (CSPs) for dissecting signaling are in high demand. Some CSPs are regulated via multivalency-driven liquid-liquid phase separation (LLPS). Employing the robustness and versatility of LLPS, we decided to engineer LLPS-based tools for precisely manipulating CSPs. We generated membrane-tethering LLPS systems by fusing multivalent modular phase-separation scaffold pairs with CSP binders. Phase separation of the scaffold pairs, concomitant compartmentalization of CSPs on membranes, and cluster-dependent signaling outputs of CSPs require membrane recruitment of one or both scaffolds. We also engineered orthogonal phase-separation systems to segregate CSPs into mutually exclusive compartments. The engineered phase-separation systems can robustly cluster individual CSPs, co-cluster two or more CSPs, or segregate different CSPs into distinct compartments on cell surfaces. These tools will enable the dissection of complicated cell-signaling landscapes with high precision.