まとめ
ミトコンドリアのタンパク質の誤折れは,ヒトの細胞における解き放たれたタンパク質反応 (UPRmt) を引き起こす. この反応はチャペロンを増やし,ミトコンドリアの翻訳を減らし,タンパク質の恒常性を維持します.
科学分野:
- 細胞生物学
- 分子生物学
- 遺伝学
背景:
- ミトコンドリアマトリックスは核とミトコンドリアゲノムからタンパク質を統合し,正確な折り畳みと組み立てを必要とします.
- mitochondrial unfolded protein response (UPRmt) はC. elegansのマトリックスタンパク質の誤折り合いを感知し,それに反応する.
- 哺乳類のUPRmtの理解は,急性活性化トリガーの欠如のために制限されています.
研究 の 目的:
- ヒト細胞のミトコンドリアマトリックスタンパク質の誤折りに対する急性細胞反応を調査する.
- ミトコンドリアトランスレーションとタンパク質の折り畳み負荷に対するUPRmt活性化の影響を分析する.
- 哺乳類のUPRmtを解剖するための枠組みを確立する.
主な方法:
- ミトコンドリアマトリックスHSP90/TRAP1またはLONプロテアゼの薬理学的抑制により,UPRmtが誘発される.
- ヒト細胞の全般的な転写とタンパク質解析
- ミトコンドリア翻訳と RNA前処理を評価する機能的研究.
主要な成果:
- 人間の細胞における急性UPRmt活性化は,折り畳み,前RNA処理,および翻訳のためのマトリックスタンパク質を含む広範な核遺伝子発現を誘発する.
- ミトコンドリア翻訳は,UPRmtの間に迅速かつ可逆的に抑制されます.
- 前RNA処理の欠陥は,トランスクリプション抑制とLON依存のMRPP3の周回による.
結論:
- 急性ミトコンドリアタンパク質折り畳みストレスは,チャペロンの可用性の増加と,トランスレーション阻害によるタンパク質合成の減少の両方を活性化します.
- UPRmtは,ストレス下でのミトコンドリアのプロテオスタシスの維持に重要な役割を果たします.
- この研究は,哺乳類のUPRmtメカニズムに関するさらなる研究のための基礎を提供します.
関連する概念動画
The Unfolded Protein Response
6.7K
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...
6.7K
Regulation of the Unfolded Protein Response
3.2K
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...
3.2K
Mitochondrial Precursor Proteins
3.9K
Mitochondrial precursors are partially unfolded or loosely folded polypeptide chains. Newly synthesized precursors are inhibited from spontaneously folding into their native conformation by the cytosolic chaperones, heat shock proteins 70 (Hsp70), and mitochondrial import stimulation factors (MSFs). Precursors bound to MSFs are guided to the TOM70-TOM37 receptors, while precursors bound to Hsp70 chaperones are targetted to TOM20-TOM22 receptor complexes.
Most of the mitochondrial...
Most of the mitochondrial...
3.9K
Mitochondrial Protein Sorting
5.9K
Mitochondria are double-membrane organelles of the eukaryotes involved in cellular metabolism, signaling, ATP synthesis, and programmed cell death. Each of these processes requires specific proteins and enzymes that must be correctly sorted to the right mitochondrial subcompartment for the proper functioning of the organelle.
Most of these mitochondrial proteins are encoded by the nucleus and imported to the mitochondria as unfolded or loosely folded precursors. Mitochondrial precursors...
Most of these mitochondrial proteins are encoded by the nucleus and imported to the mitochondria as unfolded or loosely folded precursors. Mitochondrial precursors...
5.9K
Translocation of Proteins into the Mitochondria
13.6K
Mitochondrial precursors are translocated to the internal subcompartments via independent mechanisms involving distinct protein machineries called translocases.
Sorting of outer membrane proteins:
Mitochondrial outer membrane proteins are of two types: the transmembrane, beta-barrel porins, and the membrane-anchored, alpha-helical proteins. Beta-barrel porin precursors are translocated by the TOM complex and inserted into the outer mitochondrial membrane by the SAM complex. In contrast,...
Sorting of outer membrane proteins:
Mitochondrial outer membrane proteins are of two types: the transmembrane, beta-barrel porins, and the membrane-anchored, alpha-helical proteins. Beta-barrel porin precursors are translocated by the TOM complex and inserted into the outer mitochondrial membrane by the SAM complex. In contrast,...
13.6K
Regulation of Expression at Multiple Steps
1.5K
The gene expression in cells is regulated at different stages: (i) transcription, (ii) RNA processing, (iii) RNA localization, and (iv) translation. Transcriptional regulation is mediated by regulatory proteins such as transcription factors, activators, or repressors—these control gene expression by initiating or inhibiting the transcription of genes. Once a precursor or pre-mRNA is produced, it undergoes post-transcriptional modification, including 5' capping, splicing, and the...
1.5K


