Fig. 1: APC/C transiently inactivates during the G0/G1 transition.
From: Transient APC/C inactivation by mTOR boosts glycolysis during cell cycle entry
a, Cells need mitogens and glycolysis to enter the cell cycle (1); APC/C inhibits glycolysis (2); and APC/C is reportedly fully active during quiescence and remains active until the G1/S transition (3). b, Test to determine whether glycolysis is required for cell cycle entry. CDK2 activity traces of single MCF-10A cells after mitogen stimulation with or without 2-DG after 48 h starvation-induced quiescence. Green, cells entering the cell cycle; grey, quiescent cells. n = 100 cells per condition. c, Test to determine whether APC/C inhibits glycolysis. The ECAR levels in quiescent cells or 4 h after mitogen treatment in cells expressing empty vector or CDH1 are shown. Data are mean ± s.d. n = 5. Statistical analysis was performed using one-way analysis of variance (ANOVA). d, Test to determine APC/C activity during the G1/S transition. Time-lapse images of a quiescent MCF-10A cell expressing an APC/C biosensor as it re-enters the cell cycle. Transient biosensor accumulation (red) occurs between 1 and 6 h, with sustained accumulation at G1/S. Bottom, higher exposure of the same cell. Exp, exposure. e, Representative trace of APC/C biosensor levels (red) and APC/C activity (black) in a single MCF-10A cell re-entering the cycle after 48 h starvation and mitogen stimulation. f, Single-cell traces of APC/C biosensor levels (left) and APC/C activity (right) of cells entering the cell cycle. Cells were starved for 48 h to induce quiescence, followed by mitogen stimulation at time 0 h to promote cell cycle entry. n = 200 cells for each condition. g, Median APC/C biosensor traces from cells with or without MG132 at the indicated times. MCF-10A cells were starved for 48 h, then stimulated (stim.) with mitogens (mit.). The pre-MG132 slope reflects APC/C inactivation; the post-MG132 slope reflects blocked biosensor degradation. h, APC/C biosensor-accumulation slopes from single cells before and after MG132 treatment from g. i, The percentage APC/C inactivation as measured by the ratio of APC/C biosensor-accumulation slopes before and after MG132 treatment from g and h. j, Updated model of cell cycle entry from a. Full growth medium promotes transient APC/C inactivation during cell cycle entry.
