Induced proximity at the cell surface

Molecular proximity is a governing principle of biology that is essential to normal and disease-related biochemical pathways. At the cell surface, protein–protein proximity regulates receptor activation, inhibition and protein recycling and degradation. Induced proximity is a molecular engineering principle in which bifunctional molecules are designed to bring two protein targets into close contact, inducing a desired biological outcome. Researchers use this engineering principle for therapeutic purposes and to interrogate fundamental biological mechanisms. This Review focuses on the use of induced proximity at the cell surface for diverse applications, such as targeted protein degradation, receptor inhibition and activating intracellular signaling cascades. We see a rich future for proximity-based modulation of cell surface protein activity both in basic and translational science. Technologies to modulate induced proximity at the cell surface advance the manipulation of diverse biological responses.