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J Cell Biol. 2016 Apr 11;213(1):33-48. doi: 10.1083/jcb.201508106. Epub 2016 Apr 4.

Dynamic formation of ER-PM junctions presents a lipid phosphatase to regulate phosphoinositides.

Author information

1
Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, WA 98195 dickson2@uw.edu.
2
Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, WA 98195.

Abstract

Endoplasmic reticulum-plasma membrane (ER-PM) contact sites play an integral role in cellular processes such as excitation-contraction coupling and store-operated calcium entry (SOCE). Another ER-PM assembly is one tethered by the extended synaptotagmins (E-Syt). We have discovered that at steady state, E-Syt2 positions the ER and Sac1, an integral ER membrane lipid phosphatase, in discrete ER-PM junctions. Here, Sac1 participates in phosphoinositide homeostasis by limiting PM phosphatidylinositol 4-phosphate (PI(4)P), the precursor of PI(4,5)P2 Activation of G protein-coupled receptors that deplete PM PI(4,5)P2disrupts E-Syt2-mediated ER-PM junctions, reducing Sac1's access to the PM and permitting PM PI(4)P and PI(4,5)P2to recover. Conversely, depletion of ER luminal calcium and subsequent activation of SOCE increases the amount of Sac1 in contact with the PM, depleting PM PI(4)P. Thus, the dynamic presence of Sac1 at ER-PM contact sites allows it to act as a cellular sensor and controller of PM phosphoinositides, thereby influencing many PM processes.

PMID:
27044890
PMCID:
PMC4828688
DOI:
10.1083/jcb.201508106
[Indexed for MEDLINE]
Free PMC Article

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