GSK-3: A Bifunctional Role in Cell Death Pathways

Joe

The Journal of Immunology

et al. 2015

126

114

IL-1β and TNF-α are important proinflammatory cytokines that respond to mutated self-antigens of tissue damage and exogenous pathogens. The endoplasmic reticulum (ER) stress and unfolded protein responses are related to the induction of proinflammatory cytokines. However, the detailed molecular pathways by which ER stress mediates cytokine gene expression have not been investigated. In this study, we found that ER stress–induced inositol-requiring enzyme (IRE)1α activation differentially regulates proinflammatory cytokine gene expression via activation of glycogen synthase kinase (GSK)-3β and X-box binding protein (XBP)-1. Surprisingly, IL-1β gene expression was modulated by IRE1α-mediated GSK-3β activation, but not by XBP-1. However, IRE1α-mediated XBP-1 splicing regulated TNF-α gene expression. SB216763, a GSK-3 inhibitor, selectively inhibited IL-1β gene expression, whereas the IRE1α RNase inhibitor STF083010 suppressed only TNF-α production. Additionally, inhibition of GSK-3β greatly increased IRE1α-dependent XBP-1 splicing. Our results identify an unsuspected differential role of downstream mediators GSK-3β and XBP-1 in ER stress–induced IRE1α activation that regulates cytokine production through signaling cross-talk. These results have important implications in the regulation of inflammatory pathways during ER stress, and they suggest novel therapeutic targets for diseases in which meta-inflammation plays a key role.

Section: Discussionmentioning

confidence: 66%

Endoplasmic Reticulum Stress–Induced IRE1α Activation Mediates Cross-Talk of GSK-3β and XBP-1 To Regulate Inflammatory Cytokine Production

Joe

The Journal of Immunology

et al. 2015

126

114

“…It is reported that GSK-3β regulates apoptotic pathways directly or indirectly. It directly triggers the mitochondrial apoptosis cascade by promoting Bax translocation to mitochondria [49] and indirectly leads to canonical Wnt pathway-mediated apoptosis through phosphorylation of β-catenin [50] . Here, we also investigated the regulatory effects of LX2343-mediated GSK-3β inhibition against apoptosis.…”

Section: Discussionmentioning

confidence: 99%

LX2343 alleviates cognitive impairments in AD model rats by inhibiting oxidative stress-induced neuronal apoptosis and tauopathy

et al. 2017

alzheimer's disease (aD) is a progressive neurodegenerative disease leading to the irreversible loss of brain neurons and cognitive abilities, and the vicious interplay between oxidative stress (OS) and tauopathy is believed to be one of the major players in aD development. Here, we demonstrated the capability of the small molecule N-(1,3-benzodioxol-5-yl)-2-[5-chloro-2-methoxy(phenylsulfonyl)anilino]acetamide (LX2343) to ameliorate the cognitive dysfunction of aD model rats by inhibiting OS-induced neuronal apoptosis and tauopathy. Streptozotocin (STZ) was used to induce OS in neuronal cells in vitro and in aD model rats that were made by intracerebroventricular injection of STZ (3 mg/kg, bilaterally), and Morris water maze test was used to evaluate the cognitive dysfunction in ICV-STZ rats. Treatment with LX2343 (5-20 μmol/L) significantly attenuated STZ-induced apoptosis in SH-SY5Y cells and mouse primary cortical neurons by alleviating OS and inhibiting the JNK/p38 and pro-apoptotic pathways. LX2343 was able to restore the integrity of mitochondrial function and morphology, increase aTP biosynthesis, and reduce ROS accumulation in the neuronal cells. In addition, LX2343 was found to be a non-ATP competitive GSK-3β inhibitor with IC 50 of 1.84±0.07 μmol/L, and it potently inhibited tau hyperphosphorylation in the neuronal cells. In ICV-STZ rats, administration of LX2343 (7, 21 mg·kg -1 ·d -1 , ip, for 5 weeks) efficiently improved their cognitive deficits. LX2343 ameliorates the cognitive dysfunction in the AD model rats by suppressing OS-induced neuronal apoptosis and tauopathy, thus highlighting the potential of LX2343 for the treatment of aD.

“…4,5,30,31 GSK-3β was found to be inhibited by activation of AKT in L. donovani-infected condition as upon use of dominant negative AKT, phosphorylation-mediated inhibition of GSK-3β was not seen. As GSK-3β is known to inhibit or induce apoptosis depending on the stimulus, 32 we transfected cells with constitutively active GSK-3β constructs which in infection resulted in significant drop in parasite burden and anti-inflammatory responses while increasing the overall proinflammatory responses and mitochondrial membrane permeabilization, indicating that GSK-3β works as a pro-apoptotic protein in Leishmania infection. This increase, however, was not at par with that seen in AKT-inactivated infected cells indicating the possible role of multiple targets working downstream of AKT.…”

Section: Discussionmentioning

confidence: 99%

Leishmania donovani inhibits macrophage apoptosis and pro-inflammatory response through AKT-mediated regulation of β-catenin and FOXO-1

et al. 2016

In order to establish infection, intra-macrophage parasite Leishmania donovani needs to inhibit host defense parameters like inflammatory cytokine production and apoptosis. In the present study, we demonstrate that the parasite achieves both by exploiting a single host regulator AKT for modulating its downstream transcription factors, β-catenin and FOXO-1. L. donovaniinfected RAW264.7 and bone marrow-derived macrophages (BMDM) treated with AKT inhibitor or dominant negative AKT constructs showed decreased anti-inflammatory cytokine production and increased host cell apoptosis resulting in reduced parasite survival. Infection-induced activated AKT triggered phosphorylation-mediated deactivation of its downstream target, GSK-3β. Inactivated GSK-3β, in turn, could no longer sequester cytosolic β-catenin, an anti-apoptotic transcriptional regulator, as evidenced from its nuclear translocation during infection. Constitutively active GSK-3β-transfected L. donovani-infected cells mimicked the effects of AKT inhibition and siRNA-mediated silencing of β-catenin led to disruption of mitochondrial potential along with increased caspase-3 activity and IL-12 production leading to decreased parasite survival. In addition to activating antiapoptotic β-catenin, phospho-AKT inhibits activation of FOXO-1, a pro-apoptotic transcriptional regulator. Nuclear retention of FOXO-1, inhibited during infection, was reversed when infected cells were transfected with dominant negative AKT constructs. Overexpression of FOXO-1 in infected macrophages not only documented increased apoptosis but promoted enhanced TLR4 expression and NF-κB activity along with an increase in IL-1β and decrease in IL-10 secretion. In vivo administration of AKT inhibitor significantly decreased liver and spleen parasite burden and switched cytokine balance in favor of host. In contrast, GSK-3β inhibitor did not result in any significant change in infectivity parameters. Collectively our findings revealed that L. donovani triggered AKT activation to regulate GSK-3β/β-catenin/FOXO-1 axis, thus ensuring inhibition of both host cell apoptosis and immune response essential for its intra-macrophage survival.