TNFAIP8: A new effector for Galpha(i) coupling to reduce cell death and induce cell transformation

Abstract

Galpha(i)-coupled receptors comprise a diverse family of receptors that induce transformation by largely unknown mechanisms. We previously found that the Galpha(i)-coupled dopamine-D2short (D2S) receptor transforms Balb-D2S cells via Gαi3. To identify new Gαi effectors, a yeast twohybrid screen was done using constitutively active Gαi3-Q204L as bait, and tumor necrosis factoralpha (TNFα)-induced protein 8 (TNFAIP8, SCC-S2/NDED/GG2-1) was identified. In contrast, TNFAIP8-related TIPE1 and TIPE2 showed a very weak interaction with Gαi3. In yeast mating, in vitro pull-down, co-immunoprecipitation and bioluminescence resonance energy transfer (BRET) assays, TNFAIP8 preferentially interacted with activated Gαi proteins, consistent with direct Gαi-TNFAIP8 coupling. Over-expression or depletion of TNFAIP8 using antisense constructs in Balb-D2S cells did not affect D2S-induced signaling to Gαi-dependent inhibition of cAMP. In contrast, antisense depletion of TNFAIP8 completely inhibited spontaneous and D2S-induced foci formation, consistent with a role for TNFAIP8 in Gαi-dependent transformation. To address possible mechanisms, the effect of D2S signaling via TNFAIP8 on TNFα action was examined. D2S receptor activation inhibited TNFα-induced cell death in Balb-D2S cells, but not in cells depleted of TNFAIP8. However, depletion of TNFAIP8 did not prevent D2S-induced inhibition of TNFα-mediated caspase activation, suggesting that D2S/TNFAIP8-induced protection from TNFα-induced cell death is caspase-independent. The data suggest that Gαi-TNFAIP8-mediated rescue of pre-oncogenic cells enhances progression to oncogenic transformation, providing a selective target to inhibit cellular transformation.Heterotrimeric G proteins (composed of Gα and Gβγ subunits) mediate intracellular signaling of a wide variety of receptors (Bockaert et al., 2002;Fredriksson et al., 2003;Wise et al., 2004), but traditional effectors such as adenylyl cyclase (AC) do not explain all of their actions (Albert and Robillard, 2002;Siderovski and Willard, 2005;Dorsam and Gutkind, 2007;Dave et al., 2009). The "inhibitory" G proteins (Gi1, Gi2, Gi3, and Go) couple to inhibition of AC in nearly all cell types, yet can stimulate cell proliferation and transformation in mesenchymal cell types, but inhibit these processes in neuroendocrine cells (Albert and Robillard, 2002;Dorsam and Gutkind, 2007). In neuroendocrine cells, the Gi/Go-coupled dopamine-D2short (D2S) receptor inhibits AC, phospholipase C (PLC), and mitogen-activated protein kinase (MAPK; ERK1/2), leading to decreased hormone CIHR Author ManuscriptCIHR Author Manuscript CIHR Author Manuscript synthesis, secretion, and reduced cell proliferation (Albert, 1994(Albert, , 2002Albert et al., 1997;Banihashemi and Albert, 2002). Paradoxically, in mesenchymal cells such as Balb/c-3T3 fibroblasts, D2S receptors stimulate calcium mobilization and MAPK activation, leading to increased cell proliferation and transformation (Ghahremani et al., 2000; Albert and Robillard, 2002). These D2S-induced res...

Regulation of inflammation and tumorigenesis by the TIPE family of phospholipid transfer proteins

“…In contrast, TNFAIP8 and TIPE3 appear to be largely anti-apoptotic, pro-proliferative and pro-migratory. 19,36 Accordingly, increases in the expression of the anti-apoptotic and pro-migratory TIPE members are associated with a variety of cancers, whereas the expression of pro-apoptotic and anti-migratory family members is decreased in this setting.…”

“…18,58 It is also a negative regulator of NOD2 inflammatory signaling. 63 Similar to TIPE1, it only weakly interacts with Gαi, 36 Knockdown of TIPE2 in regulatory T cells (Tregs) decreases the expression levels of the cell-surface molecules CTLA-4 and Foxp3 and anti-inflammatory cytokines, such as IL-10 and TGF-β. These modified cells result in the upregulation of IL-2 expression and increased nuclear factor of activated T cells activation as well as T-cell proliferation and differentiation.…”

“…32 In addition, TNFAIP8 has been shown to be directly coupled to Gαi g-proteins; this interaction does not appear to be involved in Gαi3-mediated cAMP inhibition but is involved in Gi-mediated inhibition of cell death, presumably via the Gβγ subunit. 36 TNFAIP8 protein has also been found to associate with activated RAC1-GTP at the cell membrane, 37 and the knockout of this protein resulted in resistance to lethal Listeria monocytogenes infection via decreased RAC1-mediated cell invasion and increased apoptosis. 37 Knocking out the TNFAIP8 gene also exacerbated disease in a dextran sodium sulfate (DSS) model of murine colitis, and the data suggested that this effect was due to decreased epithelial cell survival in the face of the chemical insult.…”

TIPE2 protein serves as a negative regulator of phagocytosis and oxidative burst during infection

“…However, the mechanisms whereby microbes promote them are not well understood. TIPE2, or tumor necrosis factor-α-induced protein 8 (TNFAIP8)-like 2 (TNFAIP8L2), is a member of the TNFAIP8 family, which is preferentially expressed in hematopoietic cells (12)(13)(14)(15)(16)(17)(18). It is significantly down-regulated in patients with infectious or autoimmune disorders (15,19).…”

Expression of tumor necrosis factor-α-induced protein 8 in stage III gastric cancer and the correlation with DcR3 and ERK1/2

“…TIPE is a 21 kDa cytosolic TNF-α-inducible molecule and a member of the Fas-associated death domain-like interleukin-1β-converting enzyme-like inhibitory protein family of cell death inhibitory proteins (5). The overexpression of TIPE contributes to enhanced DNA synthesis, cell proliferation and an inhibition of the activities of the apoptotic enzymes caspase 8 and caspase 3 (6,7). TIPE mRNA expression is induced by the activation of transcription factor nuclear factor (NF)-κB 8 in stage III gastric cancer and the correlation with DcR3 and ERK1/2 and TNF-α in human cancer cells, vascular endothelial cells and primary rheumatoid arthritis synovial fibroblasts.…”