まとめ
細胞皮質のアクチンフィラメントネットワークは,逆説的な硬さと流動性を表しています. アルファ-アクティニンによって形成されるようなクロスリンクの急速な再編成が,この行動を説明し,細胞は侮辱に耐えながらも,必要に応じて変形することを可能にします.
科学分野:
- 細胞生物学 細胞生物学
- バイオフィジックス 生物物理学
- 細胞骨格のダイナミクス
背景:
- 細胞運動に不可欠な細胞皮質は,広範な変形を起こすことができる硬いアクチンフィラメントネットワークで構成されています.
- 従来のモデルは,アクチンデポリメリゼーション/再ポリメリゼーションまたはフィラメント断片化/アンニングを通じて皮質のメカニズムを説明します.
- 皮質の固体のような硬さと流体のような変形性の同時発生は,まだ完全に理解されていません.
研究 の 目的:
- 細胞皮質におけるアクチン・フィラメント・ネットワークのパラドックスな機械的特性の基礎にある分子機構を調査する.
- アクチン繊維とクロスリンクするタンパク質が,硬さと流動性の両方にどのように貢献するかを調査する.
- アクチンネットワークの機械的振る舞いを調節するアカンタモエバアルファアクチニンの役割を明らかにする.
主な方法:
- アクチン繊維とアカンタモエバアルファ-アクチニンからなるモデルシステムの機械的特徴.
- アクチン-アルファ-アクチニン混合物の機械的性質の比較分析と,異なる変形速度のアクチン繊維のみの比較分析.
- 速くて遅い変形に対する時間依存の機械的反応の評価.
主要な成果:
- アクチン-アルファ-アクチニン混合物は,急激に変形すると,アクチン繊維のみより40倍も硬さを示した.
- 遅い変形下では,アクチン-アルファ-アクチニン混合物の機械的性質は,アクチン線維のみと区別がつかない.
- これらの時間に依存する性質は,複数の,急速に再編成されるクロスリンクを含むメカニズムを示唆する.
結論:
- アルファ-アクティニンによって例示される,急速に再配置されるクロスリンクは,皮質の二重の機械的性質のための分子機構を提供します.
- このクロスリンクメカニズムは,皮質が急速なストレスから弾性的に後退し,持続的で低い力の下で変形する能力を説明します.
- この発見は,Frey-Wysslingが提唱した,アクチンとアルファ-アクチニンの発見より前の,細胞プラズマの行動モデルを支持する.
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関連する概念動画
Introduction to Actin
Actin is a highly conserved cytoskeletal protein found abundantly in eukaryotic cells. It constitutes 10% weight of the total cellular protein in muscle cells, while in non-muscle cells, it is lower and makes up around 1–5 percent of the total cell protein. Actin found in the unicellular amoebae and complex multicellular animals is around 80% similar, demonstrating their conservation over a billion years of evolution. Actin coding genes are conserved within species and across different species.
Actin Polymerization
Actin polymerization occurs through the head-to-tail association of binding sites on monomeric actin or G-actin to form filamentous or F-actin. The polymerization can be divided into three phases ̶ nucleation, elongation, and steady-state phase.
The nucleation phase involves forming a stable nucleus consisting of three actin monomers to form a new actin filament. Actin-binding proteins such as formins and Arp2/3 complex help filament growth post-nucleation. The Formins form straight actin...
The nucleation phase involves forming a stable nucleus consisting of three actin monomers to form a new actin filament. Actin-binding proteins such as formins and Arp2/3 complex help filament growth post-nucleation. The Formins form straight actin...
Generation of Straight or Branched Actin Filaments
The straight or branched structure formation of actin filaments is controlled by nucleating proteins such as the formins and Arp2/3 complex. Formin-mediated assembly results in straight filaments, whereas Arp2/3 protein complex-mediated assembly results in branched actin filaments.
Arp2/3 Complex
Arp2/3 complex is a seven-subunit complex consisting of two proteins similar to actin- Arp2 and Arp3, and five other subunits that help keep Arp2 and Arp3 inactive. When required, the complex is...
Arp2/3 Complex
Arp2/3 complex is a seven-subunit complex consisting of two proteins similar to actin- Arp2 and Arp3, and five other subunits that help keep Arp2 and Arp3 inactive. When required, the complex is...
Actin Filament Depolymerization
Actin filaments (F-actin) are composed of actin subunits. The dissociation of actin monomers can occur from either end of F-actin. The rate of dissociation is faster from the minus-end or the pointed end, where the actin subunits exist with a bound ADP, together known as ADP-actin. The depolymerization of F-actin is aided by proteins, including the actin-depolymerizing factor (ADF) and cofilin family of proteins, gelsolin, and glia maturation factor (GMF).
In F-actin, the ADF/cofilin proteins...
In F-actin, the ADF/cofilin proteins...
Actin Polymerization and Cell Motility
Actin is a family of globular proteins that are highly abundant in eukaryotic cells. It makes up approximately 1-5% of total cell protein concentration. Actin monomers polymerize to form a complex network of polarized filaments, the actin cytoskeleton, that plays a crucial role in many cellular processes, including cell motility, division, endocytosis, and metastasis of cancer cells.
Actin cytoskeleton dynamics can produce pushing, pulling, and resistance forces that help the cell to migrate.
Actin cytoskeleton dynamics can produce pushing, pulling, and resistance forces that help the cell to migrate.
Actin Treadmilling
Actin filaments undergo polymerization and depolymerization from either end. The polymerization and depolymerization rates depend on the cytosolic concentration of free G-actins. The polymerization rate is generally higher at the plus or barbed end, while the depolymerization rate is higher at the minus or pointed end. At a steady state, critical concentration describes the concentration of free G-actin monomers at which the polymerization rate at the plus end is equal to that of the...
