Abstract
Membrane contact sites are cellular structures that mediate interorganelle exchange and communication. The two major tether proteins of the endoplasmic reticulum (ER), VAP-A and VAP-B, interact with proteins from other organelles that possess a small VAP-interacting motif, named FFAT [two phenylalanines (FF) in an acidic track (AT)]. In this study, using an unbiased proteomic approach, we identify a novel ER tether named motile sperm domain-containing protein 2 (MOSPD2). We show that MOSPD2 possesses a Major Sperm Protein (MSP) domain which binds FFAT motifs and consequently allows membrane tethering in vitro MOSPD2 is an ER-anchored protein, and it interacts with several FFAT-containing tether proteins from endosomes, mitochondria, or Golgi. Consequently, MOSPD2 and these organelle-bound proteins mediate the formation of contact sites between the ER and endosomes, mitochondria, or Golgi. Thus, we characterized here MOSPD2, a novel tethering component related to VAP proteins, bridging the ER with a variety of distinct organelles.