Autocrine activation of GPR34. Isogenic Flp-InTRex293 cell lines that stably express a single copy of GPR34 or its truncated variant, together with the parental cell lines (control), were transfected with AP1 firefly and Renilla reporter plasmids, cultured overnight, and then incubated with 16:0-18:1 PS or LysoPS for indicated times before measuring reporter activities. The data (mean ± standard deviation) presented are from 3 independent experiments. Statistical differences among different cell lines were analyzed by using a linear regression model, with significant differences indicated. WT, wild type.