Alpha-protein kinase 1 signaling pathway

Stable Identifier
Homo sapiens
ALPK1 signaling pathway
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Immune recognition of pathogen-associated molecular patterns (PAMPs) by pattern recognition receptors (PRR) often activates proinflammatory nuclear factor kappa B (NF-κB) signalling. Lipopolysaccharide (LPS) is a well-known PAMP produced by gram-negative bacteria. LPS is recognized by toll like receptor 4 (TLR4) and is a strong activator of NF-κB inflammatory responses (Akashi S et al. 2003). LPS is also recognized in the cytosol by mouse caspase-11 and related human caspase-4 and caspase-5, which stimulate pyroptosis, a proinflammatory form of cell death (Kayagaki N et al. 2011; Shi J et al. 2015). Key metabolic intermediates in LPS biosynthesis, d-glycero-β-d-manno-heptose 1,7-bisphosphate (HBP) and ADP L-glycero-β-d-manno-heptose (ADP-heptose) were reported to activate the NF-κB pathway and trigger the innate immune responses (Milivojevic M et al. 2017; Zimmermann S et al. 2017; Zhou P et al. 2018; García-Weber D; 2018). ADP-heptose but not HBP can enter host cells autonomously (Zhou P et al. 2018). During infection, ADP-heptose or HBP translocate into the host cytosol where their presence is sensed by alpha-protein kinase 1 (ALPK1) (Zimmermann S et al. 2017; Zhou P et al. 2018). ADP-heptose directly binds and activates ALPK1 (Garcia-Weber D et al. 2018; Zhou P et al. 2018); instead, HBP is converted by host-derived adenylyltransferases, such as nicotinamide nucleotide adenylyltransferases, to ADP-heptose 7-P, a substrate which can then activate ALPK1 (Zhou P et al. 2018). The ADP-heptose binding to ALPK1 is thought to trigger conformational changes and stimulate the kinase domain of ALPK1 (Zhou P et al. 2018). ALPK1 kinase activity in turn leads to the phosphorylation-dependent oligomerization of the tumor necrosis factor (TNF-α) receptor–associated factor (TRAF)–interacting protein with the forkhead-associated domain (TIFA) (Zimmermann S et al. 2017; Zhou P et al. 2018). This process activates TRAF6 oligomerization and ubiquitination, and the recruitment of transforming growth factor β-activated kinase 1 (TAK1)-binding protein 2 (TAB2), a component of the TAK1 (MAP3K7) complex (Ea CK et al. 2004; Gaudet RG et al. 2017). This TIFA oligomer signaling platform was given the term: TIFAsome. TIFAsome-activated TAK1 induces NF-κB nuclear translocation and proinflammatory gene expression. The ALPK1-TIFA signaling pathway has been identified in human embryonic kidney cells, intestinal epithelial cells, gastric cells and cervical cancer cells (Gaudet RG et al. 2015, 2017; Stein SC et al. 2017; Gall A et al. 2017; Zimmermann S et al. 2017; Milivojevic M et al. 2017; Zhou P et al. 2018). In vivo studies demonstrate that ADP-heptose and Burkholderia cenocepacia trigger massive inflammatory responses with increased production of several NF-κB-dependent cytokines and chemokines in wild type (WT), but not in Alpk1-/- mice (Zhou P et al. 2018).

This Reactome module describes ALPK1 as a cytosolic innate immune receptor for bacterial ADP-heptose.

Literature References
PubMed ID Title Journal Year
30684847 ADP-heptose: A new innate immune modulator

Hu, X, Zhang, GL, Wang, PG, Yang, C

Carbohydr. Res. 2019
30111836 Alpha-kinase 1 is a cytosolic innate immune receptor for bacterial ADP-heptose

Wang, DC, Lu, S, Li, P, Dong, N, Zamyatina, A, Borio, A, She, Y, Wu, Q, He, H, Zhou, P, Ding, J, Ding, X, Shao, F, Cao, Y, Dong, M, Gao, W, Xu, Y

Nature 2018
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