エンドプラズマ網膜のストレス中のリアルタイムのリドックス測定は,相互に関連したタンパク質の折り畳み機能を明らかにします
Philip I Merksamer1, Ala Trusina, Feroz R Papa
1Department of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA.
Cell
|November 26, 2008
まとめ
研究者は,エンドプラズマ網膜 (ER) のリドックス状態を測定するための新しい方法を開発し,リドックス変化がERストレスとタンパク質折り畳み障害に伴うことを明らかにしました. この研究は,ストレスに対する細胞の反応に関する新しい洞察を明らかにします.
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
- 分子生物学は分子生物学である.
背景:
- エンドプラズマ網膜 (ER) ストレスは,展開されたタンパク質が蓄積すると発生します.
- 展開されたタンパク質応答 (UPR) は,展開されたタンパク質を減らすために活性化されます.
- 展開されたタンパク質の直接的な in vivo 測定は困難であり,一般的な"ER ストレス"の定義につながります.
研究 の 目的:
- 測定可能なリドックス変化が,ERにおける展開されたタンパク質の蓄積に伴っているかどうかを調査する.
- 単細胞におけるERリドックス状態とUPR活動のダイナミックな測定のためのツールを開発する.
- ERリドックスポテンシャル,タンパク質の折りたたみ,UPRの活性化との関係を理解する.
主な方法:
- ERの酸化還元状態をリアルタイムで監視するために,光タンパク質レポーターを使用しました.
- 単細胞におけるUPR活性を測定し,再酸化状態と同時に測定した.
- 様々なストレス要因に対する細胞の反応を研究するために遺伝分析を行いました.
- 同性細胞集団内のリドックス異質性を調査した.
主要な成果:
- 様々な実験的および生理学的ストレス要因は,UPRのホメオスタティックコントロールが失われると,ERタンパク質の酸化を危うくします.
- レドックス変化がERタンパク質の折りたたみ障害と関連していることが確認されました.
- ERタンパク質の折りたたみ,改変,および品質管理システムの間の機能的な相互リンクを明らかにした.
- アイソゲン細胞集団における認識されたリドックス異質性.
結論:
- ERのリドックス状態は,展開されたタンパク質の蓄積の測定可能な指標として機能します.
- この研究は,一般的なUPRの活性化を超えて,ERのストレスを評価するための新しいアプローチを提供します.
- 発見は,ERにおける酸化還元バランスとタンパク質ホメオスタシスの間の複雑な関係を強調しています.
関連する概念動画
01:26Protein Modifications in the RER
Modification of secretory and transmembrane proteins entering the rough ER begins in the ER lumen. These modifications aid in protein folding and stabilize the acquired tertiary structure. Protein modifications in the rough ER co-occur at different stages of protein folding.
Broadly, these modifications can be categorized into four main categories — glycosylation, formation of disulfide bonds, assembly of protein subunits, and specific proteolytic cleavages like removal of signal sequences.
Broadly, these modifications can be categorized into four main categories — glycosylation, formation of disulfide bonds, assembly of protein subunits, and specific proteolytic cleavages like removal of signal sequences.
01:31Regulation of the Unfolded Protein Response
Inositol-requiring kinase one or IRE1 is the most conserved eukaryotic unfolded protein response (UPR) receptor. It is a type I transmembrane protein kinase receptor with a distinctive site-specific RNase activity. As the binding mechanics of the misfolded proteins with the N-terminal domain of IRE-1 are unclear, three binding models — direct, indirect, and allosteric -- are proposed for receptor activation. Nevertheless, it is known that once a misfolded protein associates with IRE1, it...
01:37The Unfolded Protein Response
The ER is the hub of protein synthesis in a cell. It has robust systems to quality control protein folding and also for degradation of terminally misfolded proteins. Under normal conditions, a small proportion of misfolded proteins that cannot be salvaged need to be transported to the cytoplasm by the ER-associated degradation or ERAD pathways. However, if the ERAD cannot handle the misfolded proteins, the cell activates the unfolded protein response or UPR to adjust the protein folding...
01:29Protein Folding Quality Check in the RER
ER is the primary site for the maturation and folding of soluble and transmembrane secretory proteins. The calnexin cycle is a specific chaperone system that folds and assesses the confirmation of N-glycosylated proteins before they can exit the ER lumen. The primary players of this quality check pipeline are the lectins, ER-resident chaperones, and a glucosyl transferase enzyme. In case the calnexin system in the lumen fails to salvage a misfolded protein, it is transported to the cytoplasm...
01:32Export of Misfolded Proteins out of the ER
After folding, the ER assesses the quality of secretory and membrane proteins. The correctly folded proteins are cleared by the calnexin cycle for transport to their final destination, while misfolded proteins are held back in the ER lumen. The ER chaperones attempt to unfold and refold the misfolded proteins but sometimes fail to achieve the correct native conformation. Such terminally misfolded proteins are then exported to the cytosol by ER-associated degradation or ERAD pathway for...
01:19Protein Dynamics in Living Cells
Different fluorescence-based techniques are used to study the protein dynamics in living cells. These techniques include FRAP, FRET, and PET.
Fluorescent recovery after photobleaching (FRAP) is a fluorescent-protein-based detection technique used to quantify protein movement rates within the cell. This method exposes a small portion of the cell to an intense laser beam. The laser beam causes permanent photobleaching of the fluorophore-tagged proteins in the exposed region. As the bleached...
Fluorescent recovery after photobleaching (FRAP) is a fluorescent-protein-based detection technique used to quantify protein movement rates within the cell. This method exposes a small portion of the cell to an intense laser beam. The laser beam causes permanent photobleaching of the fluorophore-tagged proteins in the exposed region. As the bleached...