A conserved, lipid-mediated sorting mechanism of yeast Ist2 and mammalian STIM proteins to the peripheral ER

Traffic. 2009 Dec;10(12):1802-18. doi: 10.1111/j.1600-0854.2009.00995.x. Epub 2009 Oct 5.

Abstract

Sorting of yeast Ist2 to the plasma membrane (PM) or the cortical endoplasmic reticulum (ER) requires a cortical sorting signal (CSS(Ist2)) that interacts with lipids including phosphatidylinositol-4,5-bisphosphate (PI(4,5)P(2)) at the PM. Here, we show that the expression of Ist2 in mammalian cells resulted in a peripheral patch-like localization without any detection of Ist2 at the cell surface. Attached to C-termini of mammalian integral membrane proteins, the CSS(Ist2) targeted these proteins to PM-associated domains of the ER and abolished trafficking via the classical secretory pathway. The interaction of integral membrane proteins with PI(4,5)P(2) at the PM created ER-PM contacts. This process is similar to the regulated coupling of ER domains to the PM via stromal interaction molecule (STIM) proteins during store-operated Ca(2+) entry (SOCE). The CSS(Ist2) and the C-terminus of the ER-located Ca(2+) sensor STIM2 were sufficient to bind PI(4,5)P(2) and PI(3,4,5)P(3) at the PM, showing that an evolutionarily conserved mechanism is involved in the sorting of integral membrane proteins to PM-associated domains of the ER. Yeast Ist2 and STIM2 share a common basic and amphipathic signal at their extreme C-termini. STIM1 showed binding preference for liposomes containing PI(4,5)P(2), suggesting a specific contribution of lipids to the recruitment of ER domains to the PM during SOCE.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Endoplasmic Reticulum / metabolism*
  • Lipids / physiology*
  • Mammals
  • Membrane Proteins / metabolism*
  • Microscopy, Confocal
  • Protein Transport*
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Subcellular Fractions / metabolism

Substances

  • IST2 protein, S cerevisiae
  • Lipids
  • Membrane Proteins
  • Saccharomyces cerevisiae Proteins