Fig. 5: Cortex glia take up hexose through glug specifically for glycolysis-derived alanine synthesis.
From: Glycolysis-derived alanine from glia fuels neuronal mitochondria for memory in Drosophila
a, Immunohistochemistry of nebu-HA (top) and glug-HA (bottom) brains showing a nebu or glug expression pattern (HA, green) within the cortex glia (wrapper, red). The dashed line indicates the MB calyx region. Scale bar, 20 µm. b, Nebu KD in adult cortex glia did not affect memory after single-cycle training (n = 12, F2,33 = 2.21, P = 0.13; after cold shock: n = 12, F2,33 = 0.31, P = 0.73) c, Glug knockdown in adult cortex glia impaired memory after single-cycle training (n = 11, F2,30 = 5.36, P = 0.01) and spaced training (n = 10, F2,27 = 5.92, P = 0.007), but did not affect memory after single-cycle training followed by cold shock (n = 11, F2,30 = 0.84, P = 0.44) or massed training (n = 12, F2,33 = 1.73, P = 0.19). d, The increase in mitochondrial pyruvate flux elicited by single-cycle training (n = 12, t22 = 4.62, P = 0.0001) was impaired by glug KD in adult cortex glia (n = 12, t22 = 0.65, P = 0.52). but not by nebu KD in adult cortex glia (n = 7 (control); n = 9 (1×), t14 = 2.41, P = 0.03). e, Upon MTM formation, hexose sugar, most likely glucose, taken up by cortex glia through glug is routed to glycolysis, to form pyruvate. Pyruvate is then transaminated to alanine by ALAT. Alanine in MB neurons is transaminated back to pyruvate by ALAT. Pyruvate transported into mitochondria through mitochondrial pyruvate carrier 1 (Mpc1) is transformed into acetyl-CoA (ACoA) by PDH, where it is likely integrated into the TCA cycle to produce energy upon oxidative phosphorylation. All data are presented as mean ± s.e.m. Asterisks (*P < 0.05; ***P < 0.001; NS, not significant, P > 0.05) illustrate the significance level of a two-sided t-test or of the least significant pairwise comparison following one-way ANOVA.
