ATP11C mutation is responsible for the defect in phosphatidylserine uptake in UPS-1 cells

• Published in: Journal of lipid research Vol. 56; no. 11; pp. 2151 - 2157
• Main Authors: Takada, Naoto, Takatsu, Hiroyuki, Miyano, Rie, Nakayama, Kazuhisa, Shin, Hye-Won
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.11.2015; The American Society for Biochemistry and Molecular Biology; Elsevier
• Subjects: adenosine triphosphatases; Adenosine Triphosphatases - physiology; Animals; Cell Membrane - enzymology; CHO Cells; Cricetinae; Cricetulus; flippase; Humans; membrane bilayer; Membrane Transport Proteins - physiology; Phosphatidylserines - metabolism; phospholipid; plasma membrane; uptake of fluorescent phosphatidylserine analogs; flippase; adenosine triphosphatases; phospholipid; plasma membrane; uptake of fluorescent phosphatidylserine analogs; membrane bilayer
• ISSN: 0022-2275; 1539-7262
• DOI: 10.1194/jlr.M062547

Type IV P-type ATPases (P4-ATPases) translocate phospholipids from the exoplasmic to the cytoplasmic leaflets of cellular membranes. We and others previously showed that ATP11C, a member of the P4-ATPases, translocates phosphatidylserine (PS) at the plasma membrane. Twenty years ago, the UPS-1 (uptake of fluorescent PS analogs) cell line was isolated from mutagenized Chinese hamster ovary (CHO)-K1 cells with a defect in nonendocytic uptake of nitrobenzoxadiazole PS. Due to its defect in PS uptake, the UPS-1 cell line has been used in an assay for PS-flipping activity; however, the gene(s) responsible for the defect have not been identified to date. Here, we found that the mRNA level of ATP11C was dramatically reduced in UPS-1 cells relative to parental CHO-K1 cells. By contrast, the level of ATP11A, another PS-flipping P4-ATPase at the plasma membrane, or CDC50A, which is essential for delivery of most P4-ATPases to the plasma membrane, was not affected in UPS-1 cells. Importantly, we identified a nonsense mutation in the ATP11C gene in UPS-1 cells, indicating that the intact ATP11C protein is not expressed. Moreover, exogenous expression of ATP11C can restore PS uptake in UPS-1 cells. These results indicate that lack of the functional ATP11C protein is responsible for the defect in PS uptake in UPS-1 cells and ATP11C is crucial for PS flipping in CHO-K1 cells.