A general approach for engineering RTKs optically controlled with far-red light.
                            
                                red
                            
                            
                                DrBphP
                            
                            
                                
                                    HEK293
                                
                            
                                
                                    mouse in vivo
                                
                            
                                
                                    Neuro-2a
                                
                            
                                
                                    PC6-3
                                
                            
                                
                                    rat cortical neurons
                                
                            
                            
                                Signaling cascade control
                            
                                Immediate control of second messengers
                            
                                Neuronal activity control
                            
                            
                            
                            
                            
                        
                        
                        
                        
                            Abstract:
                            Regulation of receptor tyrosine kinase (RTK) activity is necessary for studying cell signaling pathways in health and disease. We developed a generalized approach for engineering RTKs optically controlled with far-red light. We targeted the bacterial phytochrome DrBphP to the cell surface and allowed its light-induced conformational changes to be transmitted across the plasma membrane via transmembrane helices to intracellular RTK domains. Systematic optimization of these constructs has resulted in optically regulated epidermal growth factor receptor, HER2, TrkA, TrkB, FGFR1, IR1, cKIT and cMet, named eDrRTKs. eDrRTKs induced downstream signaling in mammalian cells in tens of seconds. The ability to activate eDrRTKs with far-red light enabled spectral multiplexing with fluorescent probes operating in a shorter spectral range, allowing for all-optical assays. We validated eDrTrkB performance in mice and found that minimally invasive stimulation in the neocortex with penetrating via skull far-red light-induced neural activity, early immediate gene expression and affected sleep patterns.