Phosphorylation of TPL-2 on Serine 400 is Essential for Lipopolysaccharide Activation of Extracellular Signal-regulated Kinase in Macrophages
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Tumor progression locus 2 (TPL-2) kinase is essential for Toll-like receptor 4 activation of the mitogen-activated protein kinase extracellular signal-regulated kinase (ERK) and for upregulation of the inflammatory cytokine tumor necrosis factor (TNF) in lipopolysaccharide (LPS)-stimulated macrophages. LPS activation of ERK requires TPL-2 release from associated NF-kappaB1 p105, which blocks TPL-2 access to its substrate, the ERK kinase MEK. Here we demonstrate that TPL-2 activity is also regulated independently of p105, since LPS stimulation was still needed for TPL-2-dependent activation of ERK in Nfkb1(-/-) macrophages. In wild-type macrophages, LPS induced the rapid phosphorylation of serine (S) 400 in the TPL-2 C-terminal tail. Mutation of this conserved residue to alanine (A) blocked the ability of retrovirally expressed TPL-2 to induce the activation of ERK in LPS-stimulated Nfkb1(-/-) macrophages. TPL-2(S400A) expression also failed to reconstitute LPS activation of ERK and induction of TNF in Map3k8(-/-) macrophages, which lack endogenous TPL-2. Consistently, the S400A mutation was found to block LPS stimulation of TPL-2 MEK kinase activity. Thus, induction of TPL-2 MEK kinase activity by LPS stimulation of macrophages requires TPL-2 phosphorylation on S400, in addition to its release from NF-kappaB1 p105. Oncogenic C-terminal truncations of TPL-2 that remove S400 could promote its transforming potential by eliminating this critical control step.
Zhao T, Li R, Qian M, Wang M, Zhang X, Wang Y Toxins (Basel). 2023; 15(2).
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IKBKE-driven TPL2 and MEK1 phosphorylations sustain constitutive ERK1/2 activation in tumor cells.
Goktuna S EXCLI J. 2022; 21:436-453.
PMID: 35391917 PMC: 8983855. DOI: 10.17179/excli2021-4578.
Cell adhesion tunes inflammatory TPL2 kinase signal transduction.
Vougioukalaki M, Georgila K, Athanasiadis E, Eliopoulos A Cell Mol Life Sci. 2022; 79(3):156.
PMID: 35218437 PMC: 11072766. DOI: 10.1007/s00018-022-04130-7.
Latha K, Jamison K, Watford W Front Immunol. 2021; 12:738490.
PMID: 34691044 PMC: 8529111. DOI: 10.3389/fimmu.2021.738490.
Hao J, Shen C, Wei N, Yan M, Zhang X, Xu G Front Immunol. 2021; 11:580334.
PMID: 33488582 PMC: 7821752. DOI: 10.3389/fimmu.2020.580334.