Name: cell communication through gap junctions
Uploaded: 2023-04-30T11:55:54.000Z
Duration: 1 min 27 s
Channel: JoVE

ギャップ結合は、隣接する動物細胞間の通信チャネルです。
これらのチャネルは、コネキシンと呼ばれる膜貫通タンパク質で構成されています。6つのコネキシン分子がコネクソンと呼ばれる半チャネルを形成します。
ホモマーコネクソンは、同じコネキシンタンパク質の6つのコピーで構成されていますが、ヘテロマーコネクソンは、異なるコネキシンタンパク質によって形成されます。
コネクソンはメンブレンを通じて動的に拡散することができます。細胞膜上の1つのコネクソンが隣接する細胞上の別のコネクソンと出会うと、それらはペアになって完全なチャネルを形成します。
このようなチャネルのクラスターは、細胞間のイオン、二次メッセンジャー、糖、およびその他の小分子の交換を可能にするギャップ結合プラークを形成します。
コネキシンとその組み合わせの多様性は、特定の分子に対するチャネル選択性を付与します。
溶質の輸送は、電圧差、カルシウムイオン濃度、pHなどのさまざまな刺激に応答してチャネルが開閉することでさらに制御されます。
例えば、心筋のギャップ結合は電圧差に反応し、筋肉細胞のグループ間のイオンの流れを同期させることで、心臓にリズミカルな収縮を引き起こします。

<ol>
	<li>レアード、デールW.「健康と病気におけるコネキシンのライフサイクル」 生化学ジャーナル 394.3(2006):527-543。</li>
	<li>「細胞間コミュニケーション:ギャップ結合タンパク質のショウジョウバエイネキシンマルチタンパク質ファミリー」 Chemistry & biology 12.5 (2005): 515-526.</li>
	<li>「Plasmodesmata at a glance」 Journal of cell science 131.11 (2018): jcs209346.</li>
</ol>

ギャップ結合

Gap Junctions

隣接する動物細胞の細胞質は、ギャップ結合を形成するコミュニケーションチャネルを介して、小分子、イオン、二次メッセンジャーを交換できます。 これらの接合部は数百から数千の分子チャネルを構成し、それぞれがコネクソンヘミチャネルと呼ばれる 2 つの半分で構成されています。 コネクソンは、6 回膜貫通コネキシンタンパク質の六量体であり、放射状に集合して中心に孔またはチャネルを形成します。 1 つのコネクソン ヘミチャネルが、隣接するセル上の対応するコネクソンと結合し、チャネルが完成します。

ギャップジャンクションダイナミクス

コネキシンは、粗面小胞体上のリボソームによって翻訳され、翻訳と同時に小胞体膜に挿入されます。 その後、モノマーはゴルジネットワークに輸送され、そこでオリゴマー化されます。 六量体コネクソンは、分泌小胞を介してトランスゴルジネットワークから細胞膜に輸送されます。 コネクソンは、他のコネクソンに遭遇してクラスターを形成するまで、原形質膜に沿って自由に移動できます。 したがって、成長するクラスターの周囲には新しいコネクソンが継続的に追加され、ギャップ結合プラークを形成します。 このプラークの中心では、古いコネクソンがエンドサイトーシスされ、分解のマークが付けられます。 したがって、ギャップ結合は、膜でのコネクソンの絶え間ない代謝回転を伴う動的集合体です。

無脊椎動物のギャップ結合

無脊椎動物のギャップ結合は脊椎動物のギャップ結合と同様の構造を持っています。 ただし、それらはイネキシン（無脊椎動物コネキシン）と呼ばれる異なるタンパク質で構成されています。 イネキシンは同様の膜貫通構造を持っていますが、コネキシンと配列相同性を共有しません。 また、イネクソンヘミチャネルを形成するのに6つのユニットではなく8つのユニットを必要とする点でも、対応する脊椎動物とは異なります。

植物における対応物

隣接する細胞の膜が直接接触している動物組織とは異なり、植物組織の細胞壁は隣接する細胞膜の直接接触を防ぎます。 したがって、細胞間のコミュニケーションと分子の交換は、原形質連絡と呼ばれる特殊な接合部を介して起こります。 1 つの細胞の膜はこれらの接合部で隣接する細胞の膜と連続しており、直径約 20 ～ 40 nm の管状チャネルを形成しています。 したがって、隣接する細胞の細胞質は連続しており、さまざまな小分子の調節された交換が可能です。

隣接する動物細胞の細胞質は、ギャップを形成する通信チャネルを介して、小分子、イオン、および二次メッセンジャーを交換することができます...

Education

JoVE Core

Cell Biology

細胞生物学

Unit 1

ユニット1

Cell-Cell Interactions

細胞間相互作用

KEY TERMS AND CONCEPTS

主要用語と概念

cell communication through gap junctions

Gap junctions let adjacent animal cells share small molecules, ions, and secondary messengers. These communication channels connect the cytoplasm of neighboring cells. They are built from many molecular channels, often from a few hundred to thousands in one junction.

Each channel is made of two halves called connexon hemichannels. A connexon is a hexamer, meaning it is formed by six transmembrane connexin proteins. The six proteins arrange in a ring and create a pore in the center. One connexon from one cell docks with a matching connexon from the neighboring cell to complete the channel.

Connexins are made on ribosomes attached to the rough endoplasmic reticulum. They are inserted into the ER membrane as they are made. The monomers then move to the Golgi network, where they oligomerize, or assemble into larger units. The hexameric connexons travel from the trans-Golgi network to the plasma membrane in secretory vesicles.

Once at the membrane, connexons can move freely until they meet other connexons. They cluster together and form a gap junction plaque. New connexons keep joining at the outer edge of the plaque. At the center, older connexons are endocytosed and marked for degradation, so gap junctions keep turning over over time.

Invertebrate gap junctions are similar in shape to vertebrate ones, but they use different proteins called innexins. Innexins are not sequence homologs of connexins, even though they have a similar transmembrane structure. They also form hemichannels with eight units instead of six.

Plants use plasmodesmata instead of gap junctions because their cell walls keep adjacent plasma membranes from touching directly. These junctions allow intercellular communication and the exchange of molecules between plant cells. The membrane of one cell continues into the next, forming a tubular channel about 20 to 40 nm wide. This makes the cytoplasm of neighboring cells continuous and allows the regulated movement of small molecules.

Cell Communication Through Gap Junctions

cell adhesion molecules - types and functions

cell-adhesion-molecules-types-and-functions

Cell Adhesion Molecules in Tissues

Cell adhesion molecules help cells stick together and work as part of a tissue. They give multicellular organisms physical strength and also help cells send signals across the plasma membrane. These proteins are important for coordinated activity in tissues and organ systems. CAMs are grouped into four main families: integrins, cadherins, selectins, and immunoglobulin-like CAMs, or IgCAMs. Each family supports cell interactions in a different way. Some CAMs help cells attach firmly, while...

structure of cadherins

Cadherins in Cell Junctions and Disease

Cadherins are cell adhesion proteins that help cells stick together and build tissues. Their name comes from their calcium-dependent binding. Early examples were named E-cadherin, P-cadherin, and N-cadherin after the epithelial, placental, and neuronal cells where they were first found. Classical cadherins share similar sequences and structures. Other cadherins, including those involved in cell signaling, are grouped as non-classical cadherins. This diversity comes from multiple cadherin genes...

cadherins in tissue organization

Cadherins Guide Cell Sorting in Tissues

Cadherins help cells sort into the right tissues during development. They are a large superfamily of cell adhesion molecules, with more than 180 variants. Different tissues express specific cadherin combinations, which helps cells recognize and stick to the right neighbors. Cadherins usually bind to the same or a closely related cadherin on another cell. This is called homophilic binding. Because of this matching behavior, cells of the same type tend to group together and form clusters that...

catenins

Catenins in Cell Junctions and Signaling

Catenins help cells stay connected and also support signaling inside the body. These proteins act as linker proteins in cell junction complexes because they have multiple binding domains and flexible structures. Most catenins contain a protein sequence called the armadillo repeat, so they are also known as armadillo proteins. Alpha-catenin is the main exception. Catenins bind to cell adhesion molecules such as cadherins. They then connect cadherins to cytoskeletal proteins, and the exact link...

selectins

Selectins in Immune Cell Capture

Selectins help cells make short, temporary contacts during immune responses. They are cell adhesion molecules that bind carbohydrate ligands on other cells. These rod-like proteins have a long outside region and end in a lectin domain, which binds carbohydrates only when calcium ions are present. Three main selectins are known: L-selectin, P-selectin, and E-selectin. Their names reflect where they are found and how long they are. This tissue specificity helps explain why selectins act in...

immunoglobulin-like cell adhesion molecules

immunoglobulin-like-cell-adhesion-molecules

Ig-CAMs in Neural Growth and Disease

Ig-CAMs, or immunoglobulin-like cell adhesion molecules, are cell surface glycoproteins in the immunoglobulin superfamily. They contain immunoglobulin domains, and some also have fibronectin type III domains. Their Ig domains can be glycosylated to different degrees. These molecules can bind to the same kind of Ig-CAM or to other ligands, such as integrins. Most Ig-CAMs help cells stick together only for a short time. The nectin class is different because it helps form stable junctions,...

overview of cell-cell junctions

Cell Junctions in Tissues

Cell junctions help hold tissues together and let neighboring cells communicate. In multicellular organisms, the three-dimensional shape of tissues depends on interactions between cells and the extracellular matrix. Cell-cell junctions are specialized structures made of multi-protein complexes on one cell that connect with similar complexes on another cell. These junctions are grouped into three main types based on function: occluding, anchoring, and gap junctions. Tight junctions, also called...

adherens junctions

Cell Adhesion in Tissues and Infection

Adherens junctions are strong cell-to-cell anchors that help tissues stay connected. These anchoring junctions work with desmosomes, another type of junction that holds adjacent cells together. In many epithelial and endothelial tissues, adherens junctions form a continuous adhesion belt. In heart muscle, they often appear as clusters that help cells work together for coordinated contraction. Adherens junctions are also dynamic, especially in the cells that line blood vessels. These...

tension response at adherens junctions

How Adherens Junctions Sense Force

Adherens junctions help cells stay attached while they respond to mechanical force. These multi-protein complexes can adapt to tensile force and shear stress. When the force changes, mechanosensory proteins in the junction can change shape. This process is called mechanotransduction. Alpha-catenin is one of the main force-sensing proteins in adherens junctions. It is an allosteric protein, which means its shape affects how it works. Alpha-catenin has three VH, or vinculin homology, domains...

desmosomes

Desmosomes and Cell Anchoring

Desmosomes are cell junctions that anchor cells together. They are button-like structures that create an interlinked network of intermediate filaments across cells. This strong link helps tissues resist mechanical stress and maintain tissue integrity. Desmosomes are built from multiple proteins. Their core includes desmosomal cadherins, which are adhesion proteins that bind to cadherins on neighboring cells. The two desmosomal cadherins are desmogleins and desmocollins. These transmembrane...

tight junctions

Tight Junction Proteins and Cell Barriers

Tight junction proteins form seals between neighboring cells. These molecular barriers help stop fluids, ions, and other small solutes from leaking across body cavities and tissue compartments in multicellular organisms. They are an important part of cell barriers in places where controlled movement matters. The main tight junction proteins are claudin and occludin. Other proteins include tricellulin and JAM, which stands for junctional adhesion molecule. Most of these proteins are 4-pass...

gap junctions

Gap junctions let adjacent animal cells share small molecules, ions, and secondary messengers. These communication channels connect the cytoplasm of neighboring cells. They are built from many molecular channels, often from a few hundred to thousands in one junction. Each channel is made of two halves called connexon hemichannels. A connexon is a hexamer, meaning it is formed by six transmembrane connexin proteins. The six proteins arrange in a ring and create a pore in the center. One...

key terms and concepts

Learn how gap junctions connect animal cells, how connexins build connexon channels, and how innexins and plasmodesmata support cell communication.

Cell Communication Through Gap Junctions | JoVE K12

cell biology

JoVE Core 細胞生物学は、複雑な細胞プロセスを、わかりやすく包括的なアニメーション ビデオ レッスンで説明します。このコレクションは、細胞小器官や膜、細胞輸送、細胞のエネルギー学など、細胞の必須コンポーネントと機能に焦点を当てています。これは、実際の研究実験における細胞生物学の応用を実証する科学者による実際のビデオによって補足されています。

Cell Communication Through Gap Junctions

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