Abstract
Membrane asymmetry is a key organizational feature of the plasma membrane. Type IV P-type ATPases (P4-ATPases) are phospholipid flippases that establish membrane asymmetry by translocating phospholipids, such as phosphatidylserine (PS) and phospatidylethanolamine, from the exofacial leaflet to the cytosolic leaflet. Saccharomyces cerevisiae expresses five P4-ATPases: Drs2, Neo1, Dnf1, Dnf2, and Dnf3. The inactivation of Neo1 is lethal, suggesting Neo1 mediates an essential function not exerted by the other P4-ATPases. However, the disruption of ANY1, which encodes a PQ-loop membrane protein, allows the growth of neo1Δ and reveals functional redundancy between Golgi-localized Neo1 and Drs2. Here we show Drs2 PS flippase activity is required to support neo1Δ any1Δ viability. Additionally, a Dnf1 variant with enhanced PS flipping ability can replace Drs2 and Neo1 function in any1Δ cells. any1Δ also suppresses drs2Δ growth defects but not the loss of membrane asymmetry. Any1 overexpression perturbs the growth of cells but does not disrupt membrane asymmetry. Any1 coimmunoprecipitates with Neo1, an association prevented by the Any1-inactivating mutation D84G. These results indicate a critical role for PS flippase activity in Golgi membranes to sustain viability and suggests Any1 regulates Golgi membrane remodeling through protein-protein interactions rather than a previously proposed scramblase activity.
Highlights
Membrane asymmetry is a key organizational feature of the plasma membrane
PS flippase activity is required in any1-deficient Golgi membranes
Regulating membrane asymmetry requires a complex network of membrane remodeling machineries (Fig. 1A)
Summary
Membrane asymmetry is a key organizational feature of the plasma membrane. Type IV P-type ATPases (P4ATPases) are phospholipid flippases that establish membrane asymmetry by translocating phospholipids, such as phosphatidylserine (PS) and phospatidylethanolamine, from the exofacial leaflet to the cytosolic leaflet. Any coimmunoprecipitates with Neo, an association prevented by the Any1-inactivating mutation D84G These results indicate a critical role for PS flippase activity in Golgi membranes to sustain viability and suggests Any regulates Golgi membrane remodeling through protein-protein interactions rather than a previously proposed scramblase activity.—Takar, M., Y. The PQ-loop protein Any segregates Drs and Neo functions required for viability and plasma membrane phospholipid asymmetry. Scramblases in the TMEM16F and Xkr protein families are phospholipid channels that open in response to a Ca2+ influx (TMEM16F) or caspase cleavage (Xkr8) to dissipate the phospholipid gradient [14,15,16,17] These scramblases play important roles in blood clotting and the removal of apoptotic cell corpses, respectively.
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