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

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Di Mattia, Thomas | Martinet, Arthur | Ikhlef, Souade | Mcewen, Alastair, G | Nominé, Yves | Wendling, Corinne | Poussin‐courmontagne, Pierre | Voilquin, Laetitia | Eberling, Pascal | Ruffenach, Frank | Cavarelli, Jean | Slee, John | Levine, Timothy, P | Drin, Guillaume | Tomasetto, Catherine | Alpy, Fabien

Edité par CCSD ; EMBO Press -

International audience. Organelles are physically connected by 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 nonconventional 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 form 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.

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