Calcium-dependent changes in intracellular phosphatidylserine distribution

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K07265
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 48010:Anatomy-related
• Research Institution: Juntendo University
• Principal Investigator: Tsuji Takuma 順天堂大学, 大学院医学研究科, 特任助教 (40725628)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: ホスファチジルセリン / スクランブラーゼ / 電子顕微鏡 / 凍結割断レプリカ標識法 / 小胞体

Outline of Final Research Achievements

Phosphatidylserine (PS) is a major anionic phospholipid. Asymmetric distribution of PS in the plasma membrane is well established, and Ca2+-activated TMEM16F-dependent scrambling of PtdSer has been shown. In the present study, we developed a freeze-fracture electron microscopy method that can define the PS distribution in the individual leaflets of cellular membranes. Using this method, we found that the ER of mouse embryonic fibroblasts harbored abundant PS in the cytoplasmic leaflet and much less in the luminal leaflet. Significant amount of PS appeared in the luminal side of the ER upon treatment with the Ca2+ ionophore A23187 for 10 min. Interestingly, the A23187 treatment also increased PS in the nuclear membrane. This Ca2+-induced PS redistribution was not observed in TMEM16K KO cells, but was recovered in cells re-expressing Flag-TMEM16K. The results indicate that TMEM16K mediates Ca2+-dependent phospholipid scrambling in the ER.

Free Research Field

細胞生物学

Academic Significance and Societal Importance of the Research Achievements

細胞膜スクランブラーゼTMEM16F/ANO6は細胞内カルシウム濃度の上昇により活性化し、細胞質側のPSを細胞外側に輸送する。細胞内にもTMEM16ファミリー分子が存在し、全身性に発現するTMEM16K/ANO10は脊髄小脳変性症の原因遺伝子である。本研究で得られた成果は基礎生物学分野のみならず、医学的にも重要性が高いと言える。