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誤った折りたたまれたポリトピック膜タンパク質のER関連分解を剖析する
Kunio Nakatsukasa1, Gregory Huyer, Susan Michaelis
1Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA.
Cell
|January 15, 2008
まとめ
チャペロンは,エンドプラズマ網膜関連分解 (ERAD) を通して,誤った折りたたまれた膜タンパク質の分解を積極的に支援します. ポリユビキチネーションとCdc48複合体は,これらのタンパク質を破壊するためにERから抽出するために不可欠です.
科学分野:
- 分子生物学は分子生物学である.
- 細胞生物学 細胞生物学
- タンパク質の分解
背景:
- ERADによる誤った折り畳まれた膜タンパク質の分解は完全に理解されていません.
- チャペロンは,集積傾向のあるモチーフを溶解させる可能性があります.
- 膜タンパク質のERADは複雑で,さらなる解明が必要である.
研究 の 目的:
- ポリトピック膜タンパク質 Ste6pのERAD経路を再構成し,定義する.
- 膜タンパク質ERADにおけるチャペロンとユビキチンリガゼの役割を明らかにする.
- 膜タンパク質の抽出と分解のメカニズムを調査する.
主な方法:
- ステップ6pの再構成 in vitro.
- ユビキチネーション前のチャペロン関与の分析.
- レトロトランスロケーションと分解におけるCdc48複合体とUfd2pの役割の調査.
主要な成果:
- 特定のHsp70/40チャペロンは,Ste6pとE3リガゼとの結合を容易にする.
- Cdc48複合体とATPを含むレトロトランスロケーションにはポリユビキチン化が必要です.
- ステップ6の抽出は溶解性であり,Ufd2pとは独立していたが,Ufd2pはユビキチン化と分解を強めた.
結論:
- ポリトピック膜タンパク質は,ERADの間にERから抽出することができます.
- チャペロンは,分解のために誤った折りたたまれた膜タンパク質をターゲットにすることに積極的な役割を果たします.
- Ufd2pは,ユビキチネーションの程度と膜タンパク質の分解速度に影響を与える.
関連する概念動画
Export 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...
ER Retrieval Pathway
In the secretory pathway, vesicles transport proteins from one cellular compartment to another in forward transport to deliver the protein to its correct location. Occasionally, misfolded proteins and incorrect proteins escape their original compartments, and a retrieval pathway is used to return the escaped proteins to their original compartment.
The ER uses many checkpoints to prevent the entry of incorrectly folded or a resident protein as cargo onto a transport vesicle. These mechanisms...
The ER uses many checkpoints to prevent the entry of incorrectly folded or a resident protein as cargo onto a transport vesicle. These mechanisms...
The 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...
Protein 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...
Insertion of Single-pass Transmembrane Proteins in the RER
Integral membrane proteins are proteins adhered to the lipid bilayer of a cell organelle or membrane. They can be of two types: transmembrane integral proteins that span the lipid bilayer and monotopic proteins that are attached to either side of the membrane but do not pass through it.
Integral transmembrane proteins possess transmembrane and extra membrane domains. The transmembrane domains are primarily made of 20-25 hydrophobic amino acids arranged in a helical secondary confirmation. These...
Integral transmembrane proteins possess transmembrane and extra membrane domains. The transmembrane domains are primarily made of 20-25 hydrophobic amino acids arranged in a helical secondary confirmation. These...
Protein 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.

