アポプトティックなフォスファティジルセリンの被曝のために,フォスフォリピド・フリッパースのカスパーゼ媒介分裂
Katsumori Segawa1, Sachiko Kurata1, Yuichi Yanagihashi1
1Department of Medical Chemistry, Graduate School of Medicine, Kyoto University, Yoshida-Konoe, Kyoto 606-8501, Japan.
まとめ
ある研究では,ATP11CとCDC50Aが,細胞膜におけるフォスフォリピドの非対称性にとって極めて重要であることが判明しました. アポプトーシス中のフリッパース活性を非活性化すると,フォスファディチルセリンの暴露を防止し,マクロファージの吸収を阻害します.
科学分野:
- 細胞生物学 細胞生物学
- バイオケミストリー バイオケミストリー
- アポトーシスの研究
背景:
- フォスフォリピドは,細胞機能に不可欠なプラズマ膜で非対称な分布を示します.
- この非対称性は,アポプトーシス中に破壊され,細胞表面にフォスファディチルセリン (PtdSer) 曝露につながります.
- PtdSerの曝露は,細胞クリアランスの信号として機能する.
研究 の 目的:
- アミノフォスフォリピドの転位を維持する分子機構を特定する.
- アポプトティックPtdSer被曝におけるフリッパース活性 (flippase activity) の役割を調査する.
- PtdSerが"私を食べる"信号として作用するメカニズムを解明する.
主な方法:
- ヒト細胞でハプロイド遺伝子スクリーンを実施し,フォスフォリピド転位に関与する遺伝子を特定しました.
- サイト・ディレクテッド・ミュータゲネシスを利用して,カスパースに耐性のあるATP11Cの変種を作り出した.
- 操作されたATP11CおよびCDC50A機能を有する細胞におけるPtdSer曝露とマクロファージの包囲を評価した.
主要な成果:
- アミノフォスフォリピド転位に不可欠なATP11CとCDC50Aを特定し,フリッパース活性を示した.
- アポトーシス中のPtdSer曝露には,ATP11Cのフリッパース活性に対するカスパース媒介の不活性化が必要であることが示された.
- カスパースに抵抗するATP11Cが,PtdSerの暴露とそれに続くマクロファージの吸収を防ぐことが示された.
- CDC50A欠乏がPtdSerの表面曝露とマクロファージの認識につながることが確認されました.
結論:
- ATP11CとCDC50Aはフリッパース複合体として機能し,血のリンパ脂質非対称性を維持する.
- アポプトーシス中のこのフリッパース活動の無活性化は,PtdSerを暴露するための重要なステップです.
- フォスファディチルセリンは,他のアポプトシスマーカーとは独立して,マクロファージファゴサイトーシスのための十分な"私を食べなさい"信号です.
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