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IKK interacts with rictor and regulates mTORC2

Yuanfei Xu1, Eryong Lai, Jun Liu

  • 1Department of Cell Biology, School of Basic Medical Sciences, Southern Medical University, Guangzhou 510515, China.

Cellular Signalling
|July 23, 2013
PubMed

Insights

The inhibitor of nuclear factor κ-B kinase (IKK) interacts with rictor, a component of mTORC2, revealing a novel regulatory mechanism. This interaction impacts AKT phosphorylation and actin cytoskeleton organization, crucial for cell growth and survival.

Area of Science:

  • Cell Biology
  • Molecular Signaling
  • Biochemistry

Background:

  • Mammalian target of rapamycin complex 2 (mTORC2) is crucial for cell growth, survival, and cytoskeletal organization.
  • mTORC2 regulates AKT phosphorylation at Serine 473 and actin cytoskeleton organization.
  • The upstream signaling pathways that activate mTORC2 remain incompletely understood.

Purpose of the Study:

  • To elucidate the mechanism by which upstream signals regulate mTORC2 activity.
  • To investigate the potential interaction between inhibitor of nuclear factor κ-B kinase (IKK) and mTORC2.
  • To determine the functional consequences of IKK interaction with mTORC2 components.

Main Methods:

  • Co-immunoprecipitation assays to detect protein-protein interactions between IKK and rictor.
  • In vitro binding assays to map the interaction domain between rictor and IKK subunits.
  • Kinase assays to measure mTORC2 activity following IKK inhibition or knockdown.
  • Western blotting to assess phosphorylation levels of AKT and protein kinase α (PKCα).
  • siRNA-mediated knockdown and ectopic expression of IKK variants (wild-type and kinase-dead).

Main Results:

  • IKKα and IKKβ physically interact with rictor, a key component of mTORC2.
  • The interaction site between rictor and IKKα/β was mapped to amino acids 999-1397 of rictor.
  • Inhibition or knockdown of IKK significantly reduced mTORC2 activity, evidenced by decreased AKT (S473) phosphorylation.
  • IKK inhibition also affected actin cytoskeleton organization and PKCα (S657) phosphorylation.
  • IKK inhibition increased IKK-rictor interaction while decreasing mTOR-rictor association, suggesting competition for rictor binding.

Conclusions:

  • IKK represents a novel upstream regulator of mTORC2 activity.
  • IKK interacts with rictor, modulating mTORC2's ability to phosphorylate AKT and organize the actin cytoskeleton.
  • Inactivated IKK competes with mTOR for rictor binding, leading to reduced mTORC2 complex stability and activity.
Keywords:
RictorThe IκB kinaseThe mammalian target of rapamycin complex 2

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