Regulation of enzymatic activities of P4-ATPases and its physiological function

2019 Fiscal Year Final Research Report

• Project/Area Number: 17H03655
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Functional biochemistry
• Research Institution: Kyoto University
• Principal Investigator: Shin Hye-Won 京都大学, 薬学研究科, 准教授 (10345598)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 生体膜 / フリッパーゼ / 脂質二重層 / P4-ATPase

Outline of Final Research Achievements

In this study, I demonstrated the regulation mechanism of ATP11C flippase activity. ATP11C is a member of P4-ATPase family and flips phosphatidylserine (PS) from the exoplasmic to the cytosolic leaflet at the plasma membrane. ATP11C-a isoform was downregulated by the Ca2+-mediated PKC activation. The C-terminal cytoplasmic region of ATP11C-a was phosphorylated by PKC and subsequently allowed to form a di-leucine-like sorting motif, which serve as an endocytic signal. Endocytosis of ATP11C-a caused the decrease of phosphatidylserine flipping activity at the plasma membrane. Therefore, the PS flipping activity can be regulated by Ca-signal-mediated ATP11C-a endocytosis. Moreover, I discovered that a C-terminal splicing variant ATP11C-b localized to the restricted region of the plasma membrane while ATP11C-a to the entire plasma membrane. Moreover, the critical motif for the polarized localization of ATP11C-b was identified and a mechanism of the specific localization was elucidated.

Free Research Field

分子細胞生物学

Academic Significance and Societal Importance of the Research Achievements

定常状態の細胞膜において内葉に限局しているホスファチジルセリン（PS)は、アポトーシスを起こした細胞や活性化された血小板の表面に露出し、細胞除去や血液凝固のシグナルとなる。このように死にゆく細胞だけではなく、生細胞においても一過性にPSが露出されることが示されていた（例、免疫細胞や分泌細胞）。しかし、シグナル依存的なPSの一過的な露出と回復の制御メカニズムは不明だった。本研究では、シグナル依存的なPSフリッパーゼの活性調節メカニズムを初めて明らかにし、生細胞の一過的なPSの露出と回復のメカニズムを示唆した。本研究成果は、PS露出の制御による様々な生理現象を理解するための基盤となる。