Pseudohyphal growth in Saccharomyces cerevisiae involves protein kinase-regulated lipid flippases

Abstract

Lipid flippases of the P4 ATPase family establish phospholipid asymmetry in eukaryotic cell membranes and are involved in many essential cellular processes. The yeast Saccharomyces cerevisiae contains five P4 ATPases, among which Dnf3p is poorly characterized. Here, we demonstrate that Dnf3p is a flippase that catalyzes translocation of major glycerophospholipids, including phosphatidylserine, towards the cytosolic membrane leaflet. Deletion of the genes encoding Dnf3p and the distantly related P4 ATPases Dnf1p and Dnf2p results in yeast mutants with aberrant formation of pseudohyphae, suggesting that the Dnf1p-3p proteins have partly redundant functions in the control of this specialized form of polarized growth. Furthermore, as previously demonstrated for Dnf1-2p, the phospholipid flipping activity of Dnf3p is positively regulated by Flippase Kinase1 (Fpk1p) and Fpk2p. Phylogenetic analyses demonstrate that Dnf3p belongs to a subfamily of P4 ATPases specific for fungi and likely to represent a hallmark of fungal evolution.