lexAop and UAS regulatory sequences and a minimal Hsp70 promoter (derived from the pUASTLOTattB vector) are fused upstream of a fusion protein that consists of the mCherry fluorescent tag, a transmembrane domain (Tag:M(mCd8a) and the GFP-binding VHH(GFP4) nanobody. The VHH(GFP4) nanobody is intracellular, while the mCherry tag is extracellular. The lexAop and UAS regulatory sequences are flanked by loxP and lox2272 recombinase target sites respectively (meaning that the P1cre recombinase can be used to excise one of the enhancers in a mutually exclusive manner if desired).