FFAT motif phosphorylation controls formation and lipid transfer function of inter-organelle contacts

  • EMBO J. 2020 Dec 1;39(23):e104369. doi: 10.15252/embj.2019104369.
Thomas Di Mattia  1  2  3  4 ,  Arthur Martinet  1  2  3  4 ,  Souade Ikhlef  5 ,  Alastair G McEwen  1  2  3  4 ,  Yves Nominé  1  2  3  4 ,  Corinne Wendling  1  2  3  4 ,  Pierre Poussin-Courmontagne  1  2  3  4 ,  Laetitia Voilquin  1  2  3  4 ,  Pascal Eberling  1  2  3  4 ,  Frank Ruffenach  1  2  3  4 ,  Jean Cavarelli  1  2  3  4 ,  John Slee  6 ,  Timothy P Levine  6 ,  Guillaume Drin  5 ,  Catherine Tomasetto  1  2  3  4 ,  Fabien Alpy  1  2  3  4
Affiliations
  • 1. Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Illkirch, France.
  • 2. Institut National de la Santé et de la Recherche Médicale (INSERM), U 1258, Illkirch, France.
  • 3. Centre National de la Recherche Scientifique (CNRS), UMR 7104, Illkirch, France.
  • 4. Université de Strasbourg, Illkirch, France.
  • 5. Institut de Pharmacologie Moléculaire et Cellulaire, Université Côte d'Azur, CNRS, Valbonne, France.
  • 6. UCL Institute of Ophthalmology, London, UK.
PMID: 33124732 DOI: 10.15252/embj.2019104369
Abstract

Organelles are physically connected in membrane contact sites. The endoplasmic reticulum possesses three major receptors, VAP-A, VAP-B, and MOSPD2, which interact with proteins at the surface of Other organelles to build contacts. VAP-A, VAP-B, and MOSPD2 contain an MSP domain, which binds a motif named FFAT (two phenylalanines in an acidic tract). In this study, we identified a non-conventional FFAT motif where a conserved acidic residue is replaced by a serine/threonine. We show that phosphorylation of this serine/threonine is critical for non-conventional FFAT motifs (named Phospho-FFAT) to be recognized by the MSP domain. Moreover, structural analyses of the MSP domain alone or in complex with conventional and Phospho-FFAT peptides revealed new mechanisms of interaction. Based on these new insights, we produced a novel prediction algorithm, which expands the repertoire of candidate proteins with a Phospho-FFAT that are able to create membrane contact sites. Using a prototypical tethering complex made by STARD3 and VAP, we showed that phosphorylation is instrumental for the formation of ER-endosome contacts, and their sterol transfer function. This study reveals that phosphorylation acts as a general switch for inter-organelle contacts.

Keywords
cholesterol; inter-organelle contact; lipid transfer protein; regulation; small linear motif.