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Studying RNA Interactors of Protein Kinase RNA-Activated during the Mammalian Cell Cycle
10:05

Studying RNA Interactors of Protein Kinase RNA-Activated during the Mammalian Cell Cycle

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Akt phosphorylation and nuclear phosphoinositide association mediate mRNA export and cell proliferation activities by

Masashi Okada1, Sang-Wuk Jang, Keqiang Ye

  • 1Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA.

Proceedings of the National Academy of Sciences of the United States of America
|June 20, 2008
PubMed

Insights

Nuclear phosphoinositide 3-kinase (PI3K) signaling regulates the nuclear protein Aly, impacting cell proliferation and mRNA export via Akt phosphorylation and phosphoinositide binding. This pathway is crucial for Aly

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • Nuclear phosphoinositide 3-kinase (PI3K) and its effectors are vital for cellular processes like proliferation, survival, differentiation, and pre-mRNA splicing.
  • Aly, a nuclear speckle protein, is known to be involved in messenger RNA (mRNA) export.

Purpose of the Study:

  • To investigate Aly as a physiological target of nuclear PI3K signaling.
  • To elucidate the mechanisms by which PI3K signaling regulates Aly's subnuclear residency, cell proliferation, and mRNA export functions.

Main Methods:

  • Investigated the interaction between nuclear Akt and Aly.
  • Analyzed the role of Akt-mediated phosphorylation of Aly at threonine-219.
  • Studied Aly's binding to phosphoinositides and how this is regulated by Akt.
  • Assessed the impact of Aly depletion and phosphorylation inhibition on cell proliferation and mRNA export.
  • Examined the effect of disrupting Aly-phosphoinositide association on these cellular activities.

Main Results:

  • Nuclear Akt phosphorylates Aly on threonine-219, a modification essential for Aly-Akt interaction.
  • Aly binds phosphoinositides, and this binding is modulated by Akt-mediated phosphorylation.
  • Aly's nuclear speckle residency is determined by phosphoinositide binding, not Akt phosphorylation.
  • Depletion of Aly leads to suppressed cell growth and reduced mRNA export.
  • Inhibition of Aly phosphorylation or disruption of its phosphoinositide association significantly impairs cell proliferation and mRNA export.

Conclusions:

  • Nuclear PI3K signaling directly targets Aly, regulating its function in both cell proliferation and mRNA export.
  • Akt-mediated phosphorylation and phosphoinositide binding are key mechanisms through which PI3K signaling controls Aly's activities.
  • Aly plays a critical role in mediating PI3K-dependent cell proliferation and mRNA export.

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