A conserved, lipid-mediated sorting mechanism of yeast Ist2 and mammalian STIM proteins to the peripheral ER.
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.
Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Alliance, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany.
Ebru
E
Ercan
Frank
F
Momburg
Ulrike
U
Engel
Koen
K
Temmerman
Walter
W
Nickel
Matthias
M
Seedorf
D000818:Animals; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D008055:Lipids / Q000502:physiology*; D008322:Mammals; D008565:Membrane Proteins / Q000378:metabolism*; D018613:Microscopy, Confocal; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism
C477782:IST2 protein, S cerevisiae; D008055:Lipids; D008565:Membrane Proteins; D029701:Saccharomyces cerevisiae Proteins