Figure 5

Noradrenaline- and isoprenaline-induced increase in [lactate]_i in astrocytes expressing RFP-TDP-43^208–414 versus RFP-TDP-43^wt. (A,B) panels i Representative (left) and average (right) time-dependent changes in the Laconic FRET signal increase (ΔFRET; mTFP/Venus) after the addition of 100 µM NA (A,i) and 100 µM Iso (B,i; black lines) in astrocytes co-expressing RFP-TDP-43^wt (black line/circles; n = 9 (NA), n = 16 (Iso)) or RFP-TDP-43^208–414 (grey line/circles; n = 7 (NA), n = 9 (Iso)). Data are expressed as percentages of the inverse FRET signal (mTFP/Venus), denoting an increase in [lactate]_i, relative to the baseline FRET signal. Each data point in the right panel represents the mean ± SEM. (A,B) panels ii, iii Mean changes in the Laconic FRET signal increase (Mean ΔFRET; (A,B) panels ii) and the mean initial rates of the FRET signal increase (ΔFRET/Δt; (A,B) panels iii) after the addition of NA (A) and Iso (B) for RFP-TDP-43^wt and RFP-TDP-43^208–414 experimental groups. Numbers adjacent to the error bars depict the number of cells analysed. Data are presented as means ± SEM and acquired from at least two different animals (one cell was recorded per coverslip). The Student’s t-test, used to test significant differences between astrocytes expressing RFP-TDP-43^208–414 and RFP-TDP-43^wt, revealed the similarity of the responses, however, in Iso-treated astrocytes expressing RFP-TDP-43^208–414 there was a trend towards the reduction in the [lactate]_i increase. (C,D) Pie graphs showing the responsiveness of astrocytes to (C) noradrenaline- and (D) isoprenaline-induced changes in intracellular lactate levels. Note that the probability of observing a response to NA with production of lactate in RFP-TDP-43^208–414-expressing astrocytes was 1.6-fold higher compared to RFP-TDP-43^wt-expressing astrocytes, but not in Iso-treated cells (see also Table 2).