Targeted Optogenetics

In cardiomyocytes, cAMP/PKA-dependent phosphorylation of L-type Ca²⁺ channels (LTCC) and Ryanodine receptors type 2 (RyR2) increases contractile force but due to the close vicinity of both proteins, it is unclear if their cAMP/PKA microdomains are functionally separated or cross-talking. To investigate differences from selective phosphorylation, we generated LTCC and RyR2 cAMP microdomains by using a novel optogenetic approach of subcellular targeting the photo-activated adenylate cyclase from Turneriella parva (TpPAC). TpPAC can be targeted to the RyR2 by fusion with the high affinity protein FKBP12.6 and to the LTCC ß subunit by fusing with a specific nanobody. We found an increase of diastolic Ca²⁺ by cAMP in RyR2 microdomains which is highlighting PKA-dependent Ca²⁺ leak from the sarcoplasmic reticulum and might be important to understand cardiac arrythmia mechanisms.