Cell cycle-dependent Cdc25C phosphatase determines cell survival by regulating apoptosis signal-regulating kinase 1

Abstract

Cdc25C (cell division cycle 25C) phosphatase triggers entry into mitosis in the cell cycle by dephosphorylating cyclin B-Cdk1. Cdc25C exhibits basal phosphatase activity during interphase and then becomes activated at the G 2 /M transition after hyperphosphorylation on multiple sites and dissociation from 14-3-3. Although the role of Cdc25C in mitosis has been extensively studied, its function in interphase remains elusive. Here, we show that during interphase Cdc25C suppresses apoptosis signal-regulating kinase 1 (ASK1), a member of mitogen-activated protein (MAP) kinase kinase kinase family that mediates apoptosis. Cdc25C phosphatase dephosphorylates phospho-Thr-838 in the activation loop of ASK1 in vitro and in interphase cells. In addition, knockdown of Cdc25C increases the activity of ASK1 and ASK1 downstream targets in interphase cells, and overexpression of Cdc25C inhibits ASK1-mediated apoptosis, suggesting that Cdc25C binds to and negatively regulates ASK1. Furthermore, we showed that ASK1 kinase activity correlated with Cdc25C activation during mitotic arrest and enhanced ASK1 activity in the presence of activated Cdc25C resulted from the weak association between ASK1 and Cdc25C. In cells synchronized in mitosis following nocodazole treatment, phosphorylation of Thr-838 in the activation loop of ASK1 increased. Compared with hypophosphorylated Cdc25C, which exhibited basal phosphatase activity in interphase, hyperphosphorylated Cdc25C exhibited enhanced phosphatase activity during mitotic arrest, but had significantly reduced affinity to ASK1, suggesting that enhanced ASK1 activity in mitosis was due to reduced binding of hyperphosphorylated Cdc25C to ASK1. These findings suggest that Cdc25C negatively regulates proapoptotic ASK1 in a cell cycle-dependent manner and may play a role in G 2 /M checkpointmediated apoptosis.

Ask1 and Akt act synergistically to promote ROS-dependent regeneration in Drosophila

“…2B and S1A Fig. ), as occurs in mammalian cells [36]. We also found low levels of P-Ser83 in wild-type control discs ( Fig.…”

JNK Signaling: Regulation and Functions Based on Complex Protein-Protein Partnerships

“…The inactivation of MAP3Ks can also involve feedback phosphorylation events (42)(43)(44), the association with and phosphorylation by other kinases as reported for MEKK4 (45), or ubiquitin-directed degradation as reported for DLK1 (46,47). Ultimately, following stimulation, phosphatases can remove the activating phosphate groups, as observed for the negative regulation of ASK1 by phosphatases, including PP5, PPM1L (also known previously as PP2C), Cdc25A and Cdc25C (48)(49)(50)(51), or the actions of PP2A or PP6 on TAK1 (52,53), to allow the kinases to return to a monomeric, autoinhibited basal state.…”

Activation of PERK Contributes to Apoptosis and G2/M Arrest by Microtubule Disruptors in Human Colorectal Carcinoma Cells

“…Previous studies indicated that overexpression of Cdc25C promotes phosphatase activity during the interphase and is activated at the G 2 /M transition after hyperphosphorylation [35,36]. Cho et al [37] indicated that NOC-induced hyperphosphorylation of the Cdc25C protein contributed to M-phase arrest in HEK-293 cells. In the present study, expression levels of phosphorylated Cdc25C and cycB1 proteins increased after TAX and NOC stimulation with the occurrence of G 2 /M arrest in human CRC cells, and those events were inhibited by adding the PERK inhibitor GSK.…”