Predominant localization of phosphatidylserine at the cytoplasmic leaflet of the ER, and its TMEM16K-dependent redistribution

Takuma Tsuji, Jinglei Cheng, Tsuyako Tatematsu, Aoi Ebata, Hiroki Kamikawa, Akikazu Fujita, Sayuri Gyobu, Katsumori Segawa, Hiroyuki Arai, Tomohiko Taguchi, Shigekazu Nagata, Toyoshi Fujimoto

研究成果: Article査読

40 被引用数 (Scopus)


TMEM16K, a membrane protein carrying 10 transmembrane regions, has phospholipid scramblase activity. TMEM16K is localized to intracellular membranes, but whether it actually scrambles phospholipids inside cells has not been demonstrated, due to technical difficulties in studying intracellular lipid distributions. Here, we developed a freeze-fracture electron microscopy method that enabled us to determine the phosphatidylserine (PtdSer) distribution in the individual leaflets of cellular membranes. Using this method, we found that the endoplasmic reticulum (ER) of mammalian cells harbored abundant PtdSer in its cytoplasmic leaflet and much less in the luminal leaflet, whereas the outer and inner nuclear membranes (NMs) had equivalent amounts of PtdSer in both leaflets. The ER and NMs of budding yeast also harbored PtdSer in their cytoplasmic leaflet, but asymmetrical distribution in the ER was not observed. Treating mouse embryonic fibroblasts with the Ca2+ ionophore A23187 compromised the cytoplasmic leaflet-dominant PtdSer asymmetry in the ER and increased PtdSer in the NMs, especially in the nucleoplasmic leaflet of the inner NM. This Ca2+-induced PtdSer redistribution was not observed in TMEM16K-null fibroblasts, but was recovered in these cells by reexpressing TMEM16K. These results indicate that, similar to the plasma membrane, PtdSer in the ER of mammalian cells is predominantly localized to the cytoplasmic leaflet, and that TMEM16K directly or indirectly mediates Ca2+-dependent phospholipid scrambling in the ER.

ジャーナルProceedings of the National Academy of Sciences of the United States of America
出版ステータスPublished - 2019

ASJC Scopus subject areas

  • 一般


「Predominant localization of phosphatidylserine at the cytoplasmic leaflet of the ER, and its TMEM16K-dependent redistribution」の研究トピックを掘り下げます。これらがまとまってユニークなフィンガープリントを構成します。