Crosstalk Between NDP52 and LUBAC in Innate Immune Responses, Cell Death, and Xenophagy

Front Immunol. 2021 Mar 19;12:635475. doi: 10.3389/fimmu.2021.635475. eCollection 2021.

Abstract

Nuclear dot protein 52 kDa (NDP52, also known as CALCOCO2) functions as a selective autophagy receptor. The linear ubiquitin chain assembly complex (LUBAC) specifically generates the N-terminal Met1-linked linear ubiquitin chain, and regulates innate immune responses, such as nuclear factor-κB (NF-κB), interferon (IFN) antiviral, and apoptotic pathways. Although NDP52 and LUBAC cooperatively regulate bacterial invasion-induced xenophagy, their functional crosstalk remains enigmatic. Here we show that NDP52 suppresses canonical NF-κB signaling through the broad specificity of ubiquitin-binding at the C-terminal UBZ domain. Upon TNF-α-stimulation, NDP52 associates with LUBAC through the HOIP subunit, but does not disturb its ubiquitin ligase activity, and has a modest suppressive effect on NF-κB activation by functioning as a component of TNF-α receptor signaling complex I. NDP52 also regulates the TNF-α-induced apoptotic pathway, but not doxorubicin-induced intrinsic apoptosis. A chemical inhibitor of LUBAC (HOIPIN-8) cancelled the increased activation of the NF-κB and IFN antiviral pathways, and enhanced apoptosis in NDP52-knockout and -knockdown HeLa cells. Upon Salmonella-infection, colocalization of Salmonella, LC3, and linear ubiquitin was detected in parental HeLa cells to induce xenophagy. Treatment with HOIPIN-8 disturbed the colocalization and facilitated Salmonella expansion. In contrast, HOIPIN-8 showed little effect on the colocalization of LC3 and Salmonella in NDP52-knockout cells, suggesting that NDP52 is a weak regulator in LUBAC-mediated xenophagy. These results indicate that the crosstalk between NDP52 and LUBAC regulates innate immune responses, apoptosis, and xenophagy.

Keywords: LUBAC; NDP52; NF-κB; apoptosis; ubiquitin; xenophagy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • A549 Cells
  • Apoptosis* / drug effects
  • Enzyme Inhibitors / pharmacology
  • HEK293 Cells
  • HeLa Cells
  • Humans
  • Hydrocarbons, Aromatic / pharmacology
  • Immunity, Innate* / drug effects
  • Macroautophagy* / drug effects
  • NF-kappa B / genetics
  • NF-kappa B / metabolism
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Protein Binding
  • Salmonella enterica
  • Signal Transduction
  • Tumor Necrosis Factor-alpha / pharmacology
  • Ubiquitin / metabolism*
  • Ubiquitin-Protein Ligase Complexes / antagonists & inhibitors
  • Ubiquitin-Protein Ligase Complexes / genetics
  • Ubiquitin-Protein Ligase Complexes / metabolism*
  • Ubiquitination

Substances

  • CALCOCO2 protein, human
  • Enzyme Inhibitors
  • HOIPIN-8
  • Hydrocarbons, Aromatic
  • NF-kappa B
  • Nuclear Proteins
  • Tumor Necrosis Factor-alpha
  • Ubiquitin
  • Ubiquitin-Protein Ligase Complexes