A sequence cassette encoding 'Cirl-NRS-LexA', tagged at the N-terminal end with Tag:HA and at the C-terminal end with 3xTag:V5, has been inserted into the attP site in TI{TI}Cirl^KO.attP.w-, resulting in its expression under the control of endogenous Cirl regulatory sequences. 'Cirl-NRS-LexA' is a fusion protein composed of the complete Cirl extracellular region (including the autoproteolytically active GAIN domain with its GPCR proteolysis site (GPS)), the juxta- and transmembrane segment of N (JTS) and the lexA::VP16 driver. Upon exposure of the Cirl sequence to activating conditions (ligand and/or mechanical force), autoproteolysis at the GPS exposes the N JTS, allowing its sequential cleavage (at the S2, S3 and S4 cleavage sites). This releases the lexA::VP16 driver, which is then able to translocate to the nucleus and drive expression of a lexAop-driven reporter transgene.