Figure 5. STK3/STK4 phosphorylation of LC3 at threonine 50 is essential for autophagic flux.
(A) Representative confocal fluorescence micrographs of wild-type (WT) and Stk3+/−;Stk4−/− MEFs transiently expressing GFP-tagged WT LC3, LC3-T50A (phospho null), or LC3-T50E (phosphomimetic). Nuclei were stained with DAPI and are false colored red. Scale bar = 10 µm.
(B) Quantification of GFP::LC3-positive puncta in cells represented in (A). Data are representative of 4 independent experiments.
(C-E) Quantification of GFP::LC3–positive puncta in WT and Stk3+/−;Stk4−/− MEFs expressing WT LC3 (C), LC3-T50A (D), or LC3-T50E (E) incubated in basal-, starvation-, or basal medium containing 50 nM BafA. Note that the y-axis scale for C, D, and E differs. Data are representative of 3 independent experiments.
For B-E, ****P < 0.0001, ***P < 0.001, **P < 0.01, one-way ANOVA. Black and red asterisks indicate comparisons to WT and Stk3+/−;Stk4−/− cells expressing WT LC3 under basal conditions, respectively. Mean ± SEM from at least 15 cells per condition.
See also Figure S5.