Designed protein logic to target cells with precise combinations of surface antigens

Logic at the cell surface A major challenge in medical interventions is to target only diseased cells. Although there are biomarkers characteristic of certain cancers, for example, it is unlikely that a single marker can specify a particular cell type. Lajoie et al. addressed this problem by designing protein switches called Co-LOCKR that bind to antigens on the cell surface and activate through a conformational change only when there is a precise combination of antigens. They designed switches that can perform AND, OR, and NOT logic. On the path toward applying this technology, they used Co-LOCKR to direct chimeric antigen receptor T cells to tumor cells expressing specific antigens. Science, this issue p. 1637 Designed proteins compute logic on the cell surface by transforming multiple binding events into a single biological output. Precise cell targeting is challenging because most mammalian cell types lack a single surface marker that distinguishes them from other cells. A solution would be to target cells using specific combinations of proteins present on their surfaces. In this study, we design colocalization-dependent protein switches (Co-LOCKR) that perform AND, OR, and NOT Boolean logic operations. These switches activate through a conformational change only when all conditions are met, generating rapid, transcription-independent responses at single-cell resolution within complex cell populations. We implement AND gates to redirect T cell specificity against tumor cells expressing two surface antigens while avoiding off-target recognition of single-antigen cells, and three-input switches that add NOT or OR logic to avoid or include cells expressing a third antigen. Thus, de novo designed proteins can perform computations on the surface of cells, integrating multiple distinct binding interactions into a single output.