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Tyrosine phosphorylation of p97 regulates transitional endoplasmic reticulum assembly in vitro

C Lavoie1, E Chevet, L Roy

  • 1Department of Anatomy and Cell Biology, McGill University, Montreal, QC, H3A 2B2, Canada.

Proceedings of the National Academy of Sciences of the United States of America
|November 23, 2000
PubMed

Insights

Protein tyrosine kinase and phosphatase activities regulate transitional endoplasmic reticulum (tER) assembly by controlling the association of p97 ATPase with membranes. This phosphorylation state of p97 coordinates tER assembly in the early secretory pathway.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Transitional endoplasmic reticulum (tER) assembly is crucial for the early secretory pathway.
  • The ATPase p97, p47, and syntaxin 5 are essential for tER reconstitution.
  • Regulation of p97's membrane association is key to tER formation.

Purpose of the Study:

  • To investigate the role of membrane-associated tyrosine kinase and protein-tyrosine phosphatase (PTPase) activities in regulating tER assembly.
  • To identify the specific kinase and PTPase involved in controlling p97's association with membranes.

Main Methods:

  • Cell-free reconstitution of tER from low-density microsomes.
  • Inhibition of PTPase and tyrosine kinase activities.
  • Analysis of p97 tyrosine phosphorylation and membrane association.
  • Purification and identification of endogenous tyrosine kinase and PTPase activities.

Main Results:

  • PTPase activity stabilizes p97 association with membranes, promoting tER assembly, while tyrosine kinase activity destabilizes it.
  • PTPase inhibition enhanced p97 tyrosine phosphorylation and membrane dissociation, inhibiting tER assembly.
  • Tyrosine kinase inhibition promoted tER formation and increased p97 association with syntaxin 5.
  • JAK-2 was identified as the tyrosine kinase and PTPH1 as the PTPase regulating p97.

Conclusions:

  • The tyrosine phosphorylation state of p97 is a critical regulator of tER assembly.
  • JAK-2 and PTPH1 coordinate p97's role in the early secretory pathway through phosphorylation.
  • Understanding this regulation provides insights into the mechanisms of protein trafficking and organelle biogenesis.

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