Photopharmacology reveals high-specificity linkage of Ca2+ entry at TRPC6 nanodomains to NFAT activation in mast cells

Introduction: Photopharmacology has recently emerged as a strategy for high-precision modulation of immune functions. Here we explored efficiency and specificity of interventions based on light-induced TRPC6 activation in the RBL-2H3 mast cell model. Results: Expression of TRPC6 fusion constructs in RBL-2H3 allowed for generation of temporally well-defined, cytosolic Ca ²⁺ transients in response to photoisomerization of the TRPC6 actuator OptoBI-1. These Ca ²⁺ signals originated exclusively from Ca ²⁺ entry across the plasma membrane. Transient TRPC6 activation in response to UV pulses of 1s duration (3 mW/cm ²) just exceeded the detection threshold for monitoring of Ca ²⁺ signals within the TRPC6-jRGECO1a nano/microdomain. Activation of TRPC6-jRGECO1a by single, 1s UV light pulses was sufficient to trigger maximal cytosolic to nuclear translocation of NFATc1 (NFAT2) equivalent to the level generated by ionomycin (1 µM)-induced Ca ²⁺ entry. TRPC6 photopharmacology enabled control over NFATc1 nuclear translocation devoid of any detectable degranulation responses. Conclusion: We report here the exceptionally efficient and specific modulation of mast cell activity by TRPC6 photopharmacology.