G1 to S phase transition protein 1 induces apoptosis signal-regulating kinase 1 activation by dissociating 14-3-3 from ASK1

Abstract

Apoptosis signal-regulating kinase 1 (ASK1), a member of the mitogen-activated protein kinase kinase kinase family, plays a critical role in mediating apoptosis signals initiated by a variety of death stimuli such as hydrogen peroxide and tumor necrosis factor-a. Owing to its critical role in inducing apoptosis, the activity of ASK1 is tightly regulated by various mechanisms such as post-translational modifications and protein-protein interactions. Here we describe the identification of G 1 to S phase transition protein 1 (GSPT1), which is associated with protein translation, as a regulator of ASK1. GSPT1 interacts with ASK1 and enhances ASK1-induced apoptotic activity through the activation of caspase-3. In vitro kinase assay data show that GSPT1 enhances ASK1 autophosphorylation and its kinase activity. Cell cycledependent GSPT1 induction and small interfering RNA analyses show that ASK1 autophosphorylation is dependent on the expression level of endogenous GSPT1 in cells. GSPT1 inhibits the binding of ASK1 to the 14-3-3 protein, an ASK1 inhibitor, while GSPT1 has no effect on the interaction between ASK1 and TRAF2, a C-terminalbinding activator of ASK1. Thus, our results reveal a novel role of GSPT1 in the regulation of ASK1-mediated apoptosis.

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

“…The release of serum-starved HEK 293 cells into S phase or cell cycle arrest at the G 2 /M phase in MCF-7 (human breast adenocarcinoma) cells enhanced ASK1 activity without affecting ASK1 protein expression level. 21,34 In order to investigate how ASK1 is regulated during mitosis, we used nocodazole, an antineoplastic agent that interferes with microtubule polymerization, to synchronize cells in prometaphase of mitosis. Both MCF-7 and HEK 293 cells were successfully synchronized in mitosis after 16 h of nocodazole treatment ( Figure 1a).…”

“…Caspase-3 activity was measured as described previously. 21 Briefly, MEF cells (2 × 10 6 /60 mm plate) were transfected with both FLAG-ASK1 and HA-Cdc25C expression plasmids. After 24 h of transfection, cells were transferred to 100 mm plates and grown to 80% confluence.…”

“…ASK1 is regulated either positively or negatively depending on its binding proteins. 12,13,15,[18][19][20][21][22][23][24][25] ASK1 is regulated by phosphorylation at several Ser/Thr/Tyr residues. Phosphorylation at Thr-838 leads to activation of ASK1, whereas phosphorylation at Ser-83, Ser-967, or Ser-1034 inactivates ASK1.…”

“…Although ASK1 phosphorylation is known to be involved in the regulation of apoptosis, only a few reports show that ASK1 phosphorylation or activity is dependent on the cell cycle. 21,34 In this study, we examined the functional relationship between Cdc25C and ASK1 and identified a novel function of Cdc25C phosphatase that can dephosphorylate and inhibit ASK1 in interphase but not in mitosis. Furthermore, we demonstrated that Cdc25C phosphorylation status plays a critical role in the interaction with and the activity of ASK1.…”

Targeting 14-3-3zeta in cancer therapy

“…1 14-3-3 proteins have an important role in a wide range of biologic processes through a variety of regulatory mechanisms by binding to phosphorylatedserine/threonine motifs in diverse partners, such as signal transduction, cell-cycle control, vesicular transport, DNA replication, DNA repair, apoptosis, cellular metabolism, cytoskeleton organization and malignant transformation. [2][3][4][5][6] Meanwhile, a few proteins associate with 14-3-3 proteins independent of serine/threonine sequence motifs. 14-3-3 proteins can interact with 4100 key proteins in cancer.…”