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The ORP9-ORP11 dimer promotes sphingomyelin synthesis.

Birol Cabukusta1, Shalom Borst Pauwels1, Jimmy J L L Akkermans1

  • 1Cell and Chemical Biology, Oncode Institute, Leiden University Medical Center, Leiden, Netherlands.

Elife
|August 6, 2024
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Summary

Researchers created a lipid transfer protein (LTP) knockout library to study cellular lipid distribution. The study identified the ORP9-ORP11 heterodimer as crucial for sphingomyelin synthesis in the Golgi apparatus.

Keywords:
LipidomicsORP11ORP9Sphingomyelinbiochemistrycell biologychemical biologyhumanlipid transfer proteinsmembrane contact sites

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Area of Science:

  • Cell Biology
  • Lipid Metabolism
  • Molecular Biology

Background:

  • Lipids are essential for cellular function and are unevenly distributed across organelles.
  • Lipid transfer proteins (LTPs) mediate lipid transport between organelles, but their specific roles are often unclear.
  • The human genome contains numerous intracellular LTPs, necessitating systematic investigation.

Purpose of the Study:

  • To systematically investigate the function of intracellular lipid transfer proteins (LTPs) in cellular lipid homeostasis.
  • To identify novel LTPs involved in regulating cellular lipid levels and distributions.
  • To elucidate the specific roles of ORP9 and ORP11 in lipid metabolism.

Main Methods:

  • Construction of a gene knockout library targeting 90 intracellular LTPs.
  • Comprehensive whole-cell lipidomics analysis of knockout cells.
  • Biochemical characterization of the ORP9-ORP11 heterodimer localization and function.

Main Results:

  • The LTP knockout library revealed known and novel lipid disturbances upon LTP loss.
  • Significant sphingolipid imbalances were observed in ORP9 and ORP11 knockout cells.
  • The ORP9-ORP11 heterodimer was identified to exchange phosphatidylserine (PS) for phosphatidylinositol-4-phosphate (PI(4)P) at ER-Golgi membrane contact sites.

Conclusions:

  • The ORP9-ORP11 heterodimer plays a critical role in sphingomyelin synthesis within the Golgi apparatus.
  • Dysregulation of the ORP9-ORP11 heterodimer leads to phospholipid imbalances and impaired sphingomyelin production.
  • The LTP knockout library is a valuable tool for uncovering novel regulators of cellular lipid metabolism.