NpHR can be activated by both external light and luciferase-derived bioluminescence in HEK293 cells expressing iLMO2.
(a) Emission spectra and (b) Total luminescence measured from transfected HEK293 cells expressing various luciferases (Nano-lantern, TagRFP-Rluc, Firefly) and iLMO2. (c) Schematic representation of the iLMO2 fusion protein. (d) Fluorescence image showing membrane-localized expression of iLMO2 in transfected HEK293 cells. Scale bar: 50 μm (e) Average peak photocurrent responses to green lamp illumination and CTZ measured from HEK293 cells transfected with NpHR and Nano-lantern separately (NpHR + Nano-lantern), iLMO2 fusion protein, or NpHR alone (n = 5 for each group). Mean responses to CTZ were significantly different (*p < 0.05) but responses to green lamp illumination were not (p > 0.05) by one-way ANOVA with Bonferroni posthoc test. (f) Coupling efficiency (peak photocurrent from CTZ divided by peak photocurrent from lamp) of transfected HEK293 cells expressing NpHR and Nano-lantern separately (NpHR + Nano-lantern) (n = 5) and iLMO2 fusion protein (n = 5). Error bars indicate standard error of the mean.