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Regulation and role of ER‐Golgi contact sites
Author(s) -
De Matteis Antonella,
Venditti Rosella,
Masone Maria Chiara,
Rega Laura,
Polishchuk Elena,
Santoro Michele,
Di Tullio Giuseppe,
La Montagna Raffaele
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.104.2
Subject(s) - golgi apparatus , scaffold protein , microbiology and biotechnology , phosphatase , biology , chemistry , phosphorylation , signal transduction , endoplasmic reticulum
Despite their early identification, there are still many unknowns regarding the functions and composition of ER‐TGN membrane contact sites (MCSs) due to the lack of efficient visualization methods at the optical microscopy level. We developed a FRET‐based strategy to follow the ER‐TGN MCSs and used it to run a High Content Screen to identify components and regulators of these structures. We identified, among other components, the VAPA and VAPB proteins as structural determinants for this class of contact sites. Intriguingly, the VAP proteins are not only scaffolding components of ER‐Golgi contact sites but also play an active role in the regulation of Golgi PI4P levels by interacting directly with the Sac1 phosphatase and positioning it at the ER‐TGN MCSs. By contrast, we found that proteins previously described to localize at other MCSs, such as the oxysterol binding proteins OSBP1 and ORP9, are dispensable for the maintenance of the ER‐TGN MCSs. Using a proteomics approach we identified the PH‐domain– containing protein FAPP1 as a novel partner for Sac1 and VAPs at the ER‐Golgi MCSs. We show that FAPP1 depletion results in an increase in PI4P at the Golgi complex, particularly at the trans Golgi network (TGN). Thus FAPP1 acts as a PI4P sensor at the TGN activating the Sac1 phosphatase at the ER‐TGN MCSs.