Cold-sensitive phenotypes of a yeast null mutant of ARV1 support its role as a GPI flippase

Glycosylphosphatidylinositol (GPI) is synthesized in the endoplasmic reticulum (ER) and added onto proteins to form GPI-anchored proteins. Among the many proteins involved in this process, ACAT-related enzyme-2 required for viability 1 (Arv1) is a candidate, functioning as a flippase that translocates GPI intermediates from the cytoplasmic side into the luminal side of the ER membranes. Here, we show that the deletion of theARV1gene in yeast leads to cold-sensitive defects in cell growth and GPI anchor synthesis. Furthermore, complementation assays show that the overexpression of a missense humanARV1-G189R mutant does not completely restore the cold-sensitive phenotypes of the yeastarv1mutant. Our results support the proposed role of Arv1 in GPI anchor synthesis and suggest thatARV1-linked human diseases result from defective GPI anchor synthesis.