A Highly Dynamic ER-derived Phosphatidylinositol-Synthesizing Organelle Supplies Phosphoinositides to Cellular Membranes

Dev Cell. 2011 Nov 15;21(5):813-24. doi: 10.1016/j.devcel.2011.09.005.

Abstract

Polyphosphoinositides are lipid signaling molecules generated from phosphatidylinositol (PtdIns) with critical roles in vesicular trafficking and signaling. It is poorly understood where PtdIns is located within cells and how it moves around between membranes. Here we identify a hitherto-unrecognized highly mobile membrane compartment as the site of PtdIns synthesis and a likely source of PtdIns of all membranes. We show that the PtdIns-synthesizing enzyme PIS associates with a rapidly moving compartment of ER origin that makes ample contacts with other membranes. In contrast, CDP-diacylglycerol synthases that provide PIS with its substrate reside in the tubular ER. Expression of a PtdIns-specific bacterial PLC generates diacylglycerol also in rapidly moving cytoplasmic objects. We propose a model in which PtdIns is synthesized in a highly mobile lipid distribution platform and is delivered to other membranes during multiple contacts by yet-to-be-defined lipid transfer mechanisms.

Publication types

  • Research Support, N.I.H., Intramural

MeSH terms

  • Animals
  • COS Cells
  • Cell Membrane / chemistry
  • Cell Membrane / metabolism*
  • Chlorocebus aethiops
  • Diacylglycerol Cholinephosphotransferase / chemistry
  • Diacylglycerol Cholinephosphotransferase / metabolism
  • Endoplasmic Reticulum / chemistry
  • Endoplasmic Reticulum / enzymology
  • Endoplasmic Reticulum / metabolism*
  • HEK293 Cells
  • Humans
  • Organelles / chemistry
  • Organelles / metabolism*
  • Phosphatidylinositols / biosynthesis*
  • Phosphatidylinositols / chemistry
  • Phosphatidylinositols / metabolism*
  • Signal Transduction

Substances

  • Phosphatidylinositols
  • Diacylglycerol Cholinephosphotransferase