We sought to endow T cell autonomous regulation of cell surface protein expression by exploiting the conditional proteolytic activity of ADAM17 following T cell activation. Screening of canonical ADAM17 substrates yielded a minimal 15-aa CD62L-derived motif that confers rapid and reversible cleavage of a receptor following T cell activation-termed activation-induced release (AIR). Embedding AIR into tonic-signaling CARs reduced basal CAR expression proportional to the degree of tonic signaling induced, curtailing exhaustion and improving antitumor potency. In non-tonic signaling CARs, AIR decreased activation-induced cell death and enhanced T cell expansion after stimulation. AIR's modularity supports higher-order logic-gating; AIR-regulated peptide masks enable antigen-dependent unmasking of an EGFR-targeting CAR. Finally, CRISPR knockin of AIR into endogenous FAS or TGFBR2 endowed them with activation-induced shedding, which enhanced tumor clearance while preserving signaling in non-activating conditions. AIR is a compact switch that provides fast, autonomous regulation of surface proteins for next-generation cell therapies.
Bjelajac et al. (Fri,) studied this question.