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A Mass Spectrometry-Based Approach to Identify Phosphoprotein Phosphatases and their Interactors
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A Mass Spectrometry-Based Approach to Identify Phosphoprotein Phosphatases and their Interactors

Published on: April 29, 2022

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The pseudophosphatase MK-STYX physically and genetically interacts with the mitochondrial phosphatase PTPMT1

Natalie M Niemi1, Juliana L Sacoman1, Laura M Westrate1

  • 1Laboratory of Systems Biology, Van Andel Research Institute, Grand Rapids, Michigan, United States of America.

Plos One
|April 9, 2014
PubMed

Insights

MK-STYX, a phosphatase, prevents apoptosis and chemoresistance by suppressing PTPMT1 activity. Restoring PTPMT1 function re-sensitizes cells to chemotherapy, revealing a novel mechanism in mitochondrial cell death and chemoresistance.

Area of Science:

  • Cell Biology
  • Biochemistry
  • Molecular Oncology

Background:

  • Mitogen-activated protein kinase (MAPK) phospho-serine/threonine/tyrosine-binding protein (MK-STYX) is a catalytically inactive phosphatase.
  • MK-STYX knockdown confers chemoresistance by inhibiting apoptosis and cytochrome c release.
  • The precise molecular mechanism of MK-STYX in regulating apoptosis remains undefined.

Purpose of the Study:

  • To elucidate the molecular mechanism by which MK-STYX regulates apoptosis and chemoresistance.
  • To identify proteins interacting with MK-STYX using an unbiased proteomics approach.
  • To investigate the functional relationship between MK-STYX and its interaction partners in mitochondrial cell death.

Main Methods:

  • RNA interference (RNAi) screening to identify genes involved in chemoresistance.
  • Unbiased proteomics to identify MK-STYX interacting proteins.
  • Co-immunoprecipitation to confirm protein interactions.
  • Assessment of apoptosis, cytochrome c release, and chemosensitivity.
  • Enzyme activity assays to determine the effect of MK-STYX on PTPMT1.

Main Results:

  • Proteomics identified the mitochondrial phosphatase PTPMT1 (PTP localized to mitochondrion 1) as a key interaction partner of MK-STYX.
  • MK-STYX and PTPMT1 interact in cells, and MK-STYX suppresses PTPMT1 catalytic activity.
  • Knockdown of PTPMT1 in MK-STYX knockdown cells restored chemosensitivity and cytochrome c release.
  • MK-STYX negatively regulates PTPMT1, impacting mitochondrial-dependent cell death.

Conclusions:

  • MK-STYX controls apoptosis and chemoresistance by inhibiting the catalytic activity of PTPMT1.
  • This interaction suggests a novel regulatory axis in mitochondrial cell death pathways.
  • Dysregulation of mitochondrial lipid metabolism, influenced by PTPMT1, may contribute to chemoresistance, offering potential therapeutic targets.

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