Fig. 1

Signal transduction mechanism and detection principle of the BWZ reporter assays. In the BWZ cells, TREM2 (shown in blue) is expressed in a single chimeric protein containing CD8 transmembrane domain (shown in green) and a CD3ζ domain (shown in purple and pink), with an extracellular FLAG-tag (shown in brown). When a TREM2 ligand, here ApoE, binds to TREM2 (a), the CD3ζ ITAM motifs (shown in purple) are phosphorylated (b), which leads to an intracellular signaling cascade resulting in an increased intracellular Ca²⁺ concentration. This induces the NFAT promoter, so that β-galactosidase is expressed from the lacZ gene (c). β-galactosidase is released from the cells using a lysis buffer containing saponin (d). The yellow β-galactosidase substrate, CPRG, is also present in the lysis buffer, and when cleaved by β-galactosidase, it forms a red product which is measured by absorbance (e)