SENP1 mediates TNF-induced desumoylation and cytoplasmic translocation of HIPK1 to enhance ASK1-dependent apoptosis

Abstract

We have previously shown that tumor necrosis factor (TNF)-induced desumoylation and subsequent cytoplasmic translocation of HIPK1 are critical for ASK1-JNK activation. However, the mechanism by which TNF induces desumoylation of HIPK1 is unclear. Here, we show that SENP1, a SUMO-specific protease, specifically deconjugates SUMO from HIPK1 in vitro and in vivo. In resting endothelial cells (ECs), SENP1 is localized in the cytoplasm where it is complexed with an antioxidant protein thioredoxin. TNF induces the release of SENP1 from thioredoxin as well as nuclear translocation of SENP1. TNF-induced SENP1 nuclear translocation is specifically blocked by antioxidants such as N-acetyl-cysteine, suggesting that TNF-induced translocation of SENP1 is ROS dependent. TNF-induced nuclear import of SENP1 kinetically correlates with HIPK1 desumoylation and cytoplasmic translocation. Furthermore, the wild-type form of SENP1 enhances, whereas the catalyticinactive mutant form or siRNA of SENP1 blocks, TNF-induced desumoylation and cytoplasmic translocation of HIPK1 as well as TNF-induced ASK1-JNK activation. More importantly, these critical functions of SENP1 in TNF signaling were further confirmed in mouse embryonic fibroblast cells derived from SENP1-knockout mice. We conclude that SENP1 mediates TNF-induced desumoylation and translocation of HIPK1, leading to an enhanced ASK1-dependent apoptosis. The small ubiquitin-like modifier (SUMO) can be covalently attached to a large number of proteins through the formation of isopeptide bonds with specific lysine residues of target proteins. 1,2 A large number of sumoylated proteins, including RanGAP1, PML, homeodomain-interacting protein kinases (HIPKs), IkB, p53, c-Jun, Sp3, Elk-1, p300 histone acetyltransferase, histone deacetylase (HDAC), and many nuclear receptors, have been identified. 1-3 Sumoylation is a dynamic process that is mediated by activating, conjugating, and ligating enzymes and that is readily reversed by a family of SUMO-specific proteases. 4 Several members of SUMOspecific proteases have been reported in the mammalian system. 5-10 SENP1 is a protease that appears to deconjugate a large number of sumoylated proteins. 5 Different members of these SUMO-specific proteases appear to localize in different cellular compartments where they regulate protein function by modifying the protein stability, cellular localization, and protein-protein interactions. 5,6,[8][9][10][11][12] However, it is not known how these SUMO-specific proteases are regulated.HIPK1 is one of three closely related serine/threonine protein kinases that are primarily localized in the nucleus where it is sumoylated. 13,14 The HIPKs were originally identified as nuclear protein kinases that function as co-repressors for various homeodomain-containing transcription factors. 15 Recently, HIPKs have been shown to interact with other proteins involved in apoptosis and signal transduction in a cellular localization-dependent manner. In nucleus, HIPK2 phosphorylates p53 on Ser 46, resulting in the activatio...

Covalent Small Ubiquitin-like Modifier (SUMO) Modification of Maf1 Protein Controls RNA Polymerase III-dependent Transcription Repression

“…The pcDNA3-Maf1HA expression vector was previously described (6). Ubc9 and SENP1 siRNAs were previously described (14,15). COS7 and 293T cells were transfected using F1 transfection reagent (Targeting Systems) as per the manufacturer's protocol.…”

SUMOylation and De-SUMOylation: Wrestling with Life's Processes

“…Thus, SENP1 plays a critical role in stress-induced apoptosis through de-SUMOylation of SIRT1, which regulates members of the p53 family. In another study, it was shown that SENP1 can be trapped in the cytosol by thioredoxin and that TNF induces the release of SENP1 from thioredoxin through a reactive oxygen species-dependent mechanism (40). TNF-induced nuclear transport of SENP1 correlates with de-SUMOylation of HIPK1 (homeodomain-interacting protein kinase 1) and cytoplasmic translocation of HIPK1, leading to an increase in ASK-1 (apoptosis signal-regulating kinase 1)-dependent apoptosis.…”

“…In fact, the SENPs can be dynamically regulated by their import and export signals through environmental influences. A good example is the regulation of cytosolic and nuclear localization of SENP1 by TNF (40).…”

HIPK1 drives p53 activation to limit colorectal cancer cell growth

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