In vitro reconstitution of T cell receptor-mediated segregation of the CD45 phosphatase

Significance The T cell receptor (TCR) and PD-1 signaling cascades have been hypothesized to be triggered by the exclusion of the transmembrane phosphatase CD45 from sites of receptor–ligand engagement at the T cell–antigen-presenting cell interface. We reconstituted TCR–pMHC– and PD1–PD-L1–mediated segregation of CD45 with purified proteins and model membranes, demonstrating that this phenomenon can occur in the absence of any active cellular organization. In this minimal system, two developmentally regulated and different size isoforms of CD45 are differently segregated by TCR–pMHC binding, suggesting a possible mechanism for the fine-tuning of signaling. Collectively, our data show that the binding energy of physiological receptor–ligand pairs is sufficient to create spatial organization in membranes.