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Updated: May 21, 2026

Identification of Inositol Phosphate or Phosphoinositide Interacting Proteins by Affinity Chromatography Coupled to Western Blot or Mass Spectrometry
08:07

Identification of Inositol Phosphate or Phosphoinositide Interacting Proteins by Affinity Chromatography Coupled to Western Blot or Mass Spectrometry

Published on: July 26, 2019

Nucleocytoplasmic shuttling of human inositol phosphate multikinase is influenced by CK2 phosphorylation

Rüdiger Meyer1, Marcus M Nalaskowski, Patrick Ehm

  • 1Institute of Biochemistry and Signal Transduction, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, D-20246 Hamburg, Germany.

Biological Chemistry
|June 22, 2012
PubMed

Insights

Human inositol phosphate multikinase (IPMK) shuttles between the nucleus and cytoplasm. Protein kinase CK2 phosphorylation of IPMK regulates its nuclear import, influencing cellular signaling pathways.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Human inositol phosphate multikinase (IPMK) is a key multifunctional protein involved in cellular signal transduction.
  • IPMK acts as a multispecific inositol phosphate kinase, phosphatidylinositol 3-kinase, and a scaffold protein in the mTOR-raptor complex.
  • Proper intracellular localization of IPMK is crucial for its diverse nuclear and cytoplasmic functions.

Purpose of the Study:

  • To investigate the intracellular localization dynamics of human inositol phosphate multikinase (IPMK).
  • To identify the mechanisms regulating IPMK's nucleocytoplasmic shuttling and its functional implications.

Main Methods:

  • Identification and characterization of a functional nuclear export signal (NES) in IPMK.
  • Analysis of the interaction between protein kinase CK2 and IPMK.
  • Phosphorylation site mapping (Serine 284) and assessment of its impact on IPMK localization.

Main Results:

  • IPMK is demonstrated to be a nucleocytoplasmic shuttling protein, not exclusively nuclear as previously thought.
  • Nuclear export of IPMK is mediated by the CRM1 receptor, facilitated by a functional NES.
  • Protein kinase CK2 phosphorylates IPMK at Serine 284, a modification that can decrease nuclear localization in a cell-type-specific manner.

Conclusions:

  • The nucleocytoplasmic shuttling of IPMK is regulated by a CRM1-dependent NES and a CK2-mediated phosphorylation mechanism.
  • Controlled nuclear import of IPMK allows for distinct functional roles in nuclear inositol phosphate metabolism and cytoplasmic signaling pathways.
  • This regulatory mechanism fine-tunes IPMK's involvement in cellular signal transduction, including phosphatidylinositol-4,5-bisphosphate metabolism and mTOR signaling.

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