The present invention relates to a nucleic acid molecule encoding a fusion protein, wherein the nucleic acid molecule comprises: (a) a first nucleic acid sequence encoding a first biosensor, wherein said first biosensor is a first molecule capable of interacting with a second molecule; (b) a second nucleic acid sequence encoding an effector-activating module, wherein the effector-activating module comprises a nucleic acid sequence encoding a first part of a protease, wherein said first part of the protease is capable of interacting with a second part of said protease to form an active form of said protease; (c) a third nucleic acid sequence encoding a third biosensor comprising a protease cleavage site, wherein the protease cleavage site is sterically occluded in the absence of a stimulus for said third biosensor and wherein the protease cleavage site becomes accessible in the presence of said stimulus.