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Cot/tpl2 activity is required for TLR-induced activation of the Akt p70 S6k pathway in macrophages: Implications for

Marta López-Peláez1, Irene Soria-Castro, Lisardo Boscá

  • 1Instituto de Investigaciones Biomédicas Alberto Sols, CSIC-UAM, Madrid, Spain.

European Journal of Immunology
|April 7, 2011
PubMed

Insights

The Cot/tpl2 pathway fine-tunes Toll-like receptor (TLR) signaling by regulating Akt-mTOR-p70 S6k phosphorylation, impacting inflammatory responses in macrophages. This MAP3K controls key signaling events and nitric oxide synthase 2 expression.

Area of Science:

  • Immunology
  • Cellular Signaling
  • Molecular Biology

Background:

  • Lipopolysaccharide (LPS) stimulation activates multiple signaling pathways, including IKK, MAP kinases, and PI3K-Akt-mTOR-p70 S6k.
  • The PI3K-Akt-mTOR-p70 S6k pathway acts as a negative regulator of MyD88-dependent intracellular signals.
  • Understanding the precise roles of specific kinases in modulating these pathways is crucial for deciphering immune responses.

Purpose of the Study:

  • To investigate the role of Cot/tpl2, a MAP3K, in regulating intracellular signaling pathways upon LPS stimulation in macrophages.
  • To determine how Cot/tpl2 deficiency affects key signaling events and inflammatory mediator expression.
  • To elucidate the interplay between Cot/tpl2 and the PI3K-Akt-mTOR-p70 S6k pathway in TLR signaling.

Main Methods:

  • Utilized knockout (KO) macrophages lacking Cot/tpl2 and compared them with wild-type (WT) macrophages.
  • Stimulated macrophages with LPS, zymosan, and polyI:C.
  • Analyzed intracellular signaling by measuring phosphorylation of Akt, p70 S6k, JNK, p38α, and IκBα recovery.
  • Assessed the expression of nitric oxide synthase 2 (NOS2).
  • Employed PI3K pathway inhibition to dissect signaling crosstalk.

Main Results:

  • Cot/tpl2 deficiency led to reduced IκBα recovery and increased JNK and p38α phosphorylation after LPS stimulation.
  • Cot/tpl2 knockout macrophages exhibited higher LPS-induced nitric oxide synthase 2 (NOS2) expression.
  • Cot/tpl2 mediated Akt (P-Ser473) and p70 S6k (P-Thr389) phosphorylation in LPS-stimulated macrophages.
  • Inhibition of the PI3K pathway normalized differences in IκBα and NOS2 expression between Cot/tpl2 KO and WT macrophages.
  • Cot/tpl2 also mediated Akt phosphorylation and affected IκBα and NOS2 expression in response to zymosan and polyI:C stimulation.

Conclusions:

  • Cot/tpl2 plays a significant role in Toll-like receptor (TLR) signaling by controlling the activation of the Akt-mTOR-p70 S6k pathway.
  • Cot/tpl2 acts as a critical regulator, fine-tuning the balance of other signaling pathways, including those involving JNK and p38α.
  • These findings reveal a novel function for Cot/tpl2 in modulating macrophage inflammatory responses, particularly NOS2 expression, through its interaction with the PI3K-Akt pathway.

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