Glycogen synthase kinase 3β induces apoptosis in cancer cells through increase of survivin nuclear localization

Abstract

Glycogen synthase kinase 3β (GSK3β) regulates numerous signaling pathways that control a wide range of cellular processes, including cell proliferation, differentiation, apoptosis and metabolism. We report a novel function of GSK3β: It interacts with the inhibitor-of-apoptosis protein (IAP) survivin to modulate its expression, thus regulating apoptosis in human lung cancer cells. A coimmunoprecipitation assay revealed that GSK3β can bind survivin. Activation of GSK3β induced translocation of survivin from the cytoplasm to the nucleus, resulting in G1 cell-cycle arrest and apoptosis, as well as sensitization to the chemotherapeutic drug doxorubicin. In contrast, inactivation of GSK3β, either by transfection of a dominant-negative mutant inhibitor DN-GSK3β or with selective inhibitor LiCl, increased cytoplasmic survivin expression, leading to cell cycle progression and resistance to apoptosis. These results identify a pro-apoptotic role for GSK3β in cancer cells, through its modulation of survivin in subcellular redistribution. This new role suggests that there is a potential for pharmacologic activation of GSK3β to enhance treatment of cancer patients, including those with resistance.

RNA interference against SPARC promotes the growth of U-87MG human malignant glioma cells

“…As a core component of certain pathways involved in a number of cancers, such as the Wnt and Hedgehog pathways, GSK-3β plays a role in multiple cell processes including cell growth, differentiation, cell survival, and proliferation (24)(25)(26). Decreased GSK-3β expression may promote mammary tumorigenesis and increase the number of cells in the S phase (27,28). Our results showed that the increased phosphorylation of GSK-3β at Ser9 in U-87MG/ SPARC shRNA, which in turn inactivates GSK-3β enzymatic activity (29), may be another signal molecule associated with growth promotion.…”

Nuclear Survivin: Cellular Consequences and Therapeutic Implications

“…This is somewhat surprising given that borealin interacts with survivin at its homodimerisation interface and could potentially mask part of the central NES ( Figure 2B), nevertheless, it points to the subtleties lying within the structure of this tiny protein. As mentioned above redistribution of survivin into the nucleus is promoted by activation of GSK3B, and although it is not yet known whether survivin is a substrate of this kinase, GSK3B can bind survivin directly and has a bipartite NLS (Li et al, 2008).…”

“…Survivin acetylation, which occurs at K129, and is facilitated by the acetyl transferase CREB-binding protein (CBP), has been implicated in aiding survivin transit out of the nucleus (Wang et al, 2010), presumably by affecting the activity of the C-terminal NES (Engelsma et al, 2007). Glucogen synthase kinase 3β (GSK3β) facilitates translocation of survivin into the nucleus, but whether phosphorylation of survivin by GSK3β is involved is not yet known (Li et al, 2008). Work from my lab has recently provided two lines of evidence that suggest that casein kinase 2 (CK2) phosphorylation helps to maintain survivin within the cytoplasm, as treatment with the CK2 specific inhibitor, TBB (4,5,6,7-tetrabromobenzotriazole), or mutation of threonine 48 (T48), the unique site targeted by CK2 in survivin, causes its accumulation in the nucleus (Barrett et al, 2011).…”

“…A second consequence of nuclear residence of survivin is the loss of its cytoprotective activity. Converging data from analysis of NES mutants , NLS fusions (Connell et al, 2008a), LMB treatment , GSK3β-activated cells (Li et al, 2008), and the response of cells in which nuclear survivin naturally occurs (Temme et al, 2007), have clearly demonstrated that nuclear survivin can no longer inhibit cell death, invoked by either the intrinsic or extrinsic apoptotic pathways. An apparent paradox here is that while cytoplasmic localisation of survivin is a requirement for it to protect cells from irradiation (IR), irradiation itself induces translocation of survivin to the nucleus (Chakravarti et al, 2004).…”

Protective Effects of Estrogen Against Reperfusion Arrhythmias Following Severe Myocardial Ischemia in Rats

“…After being washed with PBS, the cells were incubated with a fluorescein isothiocyanate-tagged anti-biotin monoclonal antibody (1:500) at 37°C for 1 h and then observed by fluorescent microscopy. 18 Peroxidase was transformed with substrate at 37°C for 30 min; finally, slices were stained with DAB and counterstained lightly with hematoxylin. The samples without the addition of enzyme were regarded as positive controls.…”