Name: cell junctions in tissues
Uploaded: 2023-04-30T11:54:51.000Z
Duration: 1 min 14 s
Channel: JoVE

تقاطعات الخلايا عبارة عن مجمعات كبيرة متعددة البروتينات يمكنها ربط الخلايا بالمصفوفة خارج الخلية التي تشكل تقاطعات مصفوفة الخلية ، أو تعمل كنقاط اتصال بين الخلايا المجاورة في الأنسجة لتشكيل تقاطعات بين الخلية والخلايا.
تحتوي الخلايا عادة على ثلاثة أنواع رئيسية من تقاطعات الخلية الخلوية - تقاطعات ضيقة ، ومثبتة ، وفجوة ، ولكل منها بنية ووظيفة متميزة.
ضع في اعتبارك الظهارة العمودية. تحافظ الوصلات الضيقة بالقرب من قمم هذه الخلايا على أغشية البلازما المجاورة معا وتعمل كحاجز أمام تدفق الجزيئات عبر المساحات بين الخلايا.
يوجد أسفل هذا الجزء القمي نوعان من تقاطعات التثبيت - تقاطعات الالتصاق والتصريف.
تشكل تقاطعات التثبيت هذه معا شبكة هيكل خلوي مترابطة عبر الخلايا تساعد على مقاومة القوى الميكانيكية.
النوع الثالث ، تقاطعات الفجوة ، مشتت في جميع أنحاء غشاء البلازما ، خاصة باتجاه الطرف القاعدية. تعمل هذه التقاطعات كقنوات اتصال بين الخلايا المجاورة ، مما يسمح للجزيئات والأيونات بالمرور.

<ol>
	<li>كامبل ، هانا ك. ، جيسيكا إل مايرز ، وكريس أ. ديمالي. "التفاعل بين التقاطعات الضيقة والتقاطعات الملتصقة". أبحاث الخلايا التجريبية 358.1 (2017): 39-44.</li>
	<li>جيبمانز ، بن إن جي. "تقاطعات الفجوة والبروتينات المتفاعلة مع الكونيكسين". أبحاث القلب والأوعية الدموية 62.2 (2004): 233-245.</li>
</ol>

نظرة عامة على تقاطعات الخلايا

Overview of Cell-Cell Junctions

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يتم تحديد ترتيب المعقد ثلاثي الأبعاد للخلايا في أي كائن متعدد الخلايا والحفاظ عليه من خلال تفاعلات الخلايا مع بعضها البعض ومع النسيج البيني خارج الخلية. تقاطعات الخلايا الخلوية هي بنيات متخصصة حيث تتفاعل معقدات البروتين المتعددة الموجودة في خلية واحدة مع المعقدات متعددة البروتين الموجودة في خلية أخرى. يتم تصنيف التقاطعات الخلوية هذه إلى ثلاثة أنواع رئيسية بناءً على وظيفتها - التقاطعات المسدودة، والتثبيتية، وتقاطعات الفجوة.

التقاطعات المسدودة أو الضيقة

تعمل التقاطعات الضيقة في المقام الأول على منع حركة الجزيئات مثل الماء والمواد المذابة عبر المساحات بين الخلايا. وهي موجودة كسلسلة من بروتينات الغشاء التي تتفاعل بشكل مباشر مع نفس البروتينات الموجودة على الغشاء المجاور. وبالتالي، فإنهما يحتفظان بغشاء البلازما بالقرب من بعضهما البعض، مما يمنع مرور الجزيئات. يمكن أيضًا أن تكون التقاطعات الضيقة ذات نفاذية بشكل انتقائي، مما يسمح للأيونات الخاصة بالشحن بالتحرك من خلالها، بينما تمنع الأيونات الأخرى.

التقاطعات التثبيتية

تعمل التقاطعات التثبيتية على تثبيت الخلايا معًا وتوفر القوة الميكانيكية لبنية الأنسجة. إنها تشكل نقاط اتصال حيث يرتكز الهيكل الخلوي لخلية واحدة على الخلايا المجاورة لها عبر جزيئات التصاق عبر الغشاء تسمى الكادهيرين. هناك نوعان من تقاطعات التثبيت:

<ol style="list-style-type: disc;">
	<li>تلتصق بالتقاطعات التي تربط الهيكل الخلوي للأكتين و</li>
	<li>الديسموسومات التي تربط الخيوط الوسيطة.</li>
</ol>

وبالتالي، فإنها تشكل شبكة هيكلية خلوية واسعة النطاق تعمل بشكل تعاوني للحفاظ على بنية الأنسجة ووظيفتها.

تقاطعات الفجوة

تقاطعات الفجوة هي قنوات بروتينية تسهل التواصل بين الخلايا. تشكل بروتينات الغشاء المكونة قناة تربط سيتوبلازم الخلايا المجاورة وتسمح بتبادل الجزيئات والنبضات الكهربائية. يتم تنظيم حركة الجزيئات عن طريق فتح وإغلاق بروتينات القناة. على سبيل المثال، يتم تمرير إشارة الانقباضات الإيقاعية للقلب من خلية إلى أخرى عبر تقاطعات الفجوة في أنسجة عضلة القلب. ومع ذلك، لا تستطيع الخلايا النباتية تبادل الجزيئات عبر تقاطعات الفجوة بسبب جدار الخلية. وبدلاً من ذلك، فإنها تشكل قنوات اتصال تسمى بالبلازموديسماتا. وهي عبارة عن مساماًاً مبطنة بغشاء تربط الخلايا عبر جدران الخلايا بحيث يكون سيتوبلازم خلية واحدة متجاورًا مع سيتوبلازم خلية أخرى. وبالتالي، هناك حركة حرة للمواد المذابة والأيونات عبر الخلايا النباتية المرتبطة بالبلازموديسماتا.


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يتم تحديد الترتيب المعقد ثلاثي الأبعاد للخلايا في أي كائن متعدد الخلايا والحفاظ عليه من خلال تفاعلات الخلايا مع بعضها البعض و ...

Education

JoVE Core

Cell Biology

بيولوجيا الخلية

Unit 1

الوحدة الأولى

Cell-Cell Interactions

التفاعلات بين الخلايا

KEY TERMS AND CONCEPTS

المصطلحات والمفاهيم الأساسية

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 occluding junctions, stop water and solutes from moving through the spaces between cells. They do this with transmembrane proteins that match and bind to the same proteins on the adjacent cell membrane, keeping the two membranes close together. Tight junctions can also be selectively permeable, so some charge-specific ions can pass while others are blocked.

Anchoring junctions give tissues mechanical strength by holding cells together. They create contact points where the cytoskeleton of one cell attaches to the cytoskeleton of a neighboring cell through transmembrane adhesion molecules called cadherins. Two main forms are adherens junctions, which link actin filaments, and desmosomes, which link intermediate filaments. Together, these connections build a strong cytoskeletal network that supports tissue structure and function.

Gap junctions are channels that let cells communicate with each other. Their transmembrane proteins form a passage between the cytoplasms of adjacent cells, allowing molecules and electrical impulses to move across. The channels can open and close to control movement. In cardiac muscle, gap junctions help pass the signal for rhythmic heart contractions from cell to cell.

Plant cells do not use gap junctions because of the cell wall. Instead, they connect through plasmodesmata, which are membrane-lined pores that pass through the cell walls. These channels link the cytoplasm of one plant cell to another, allowing solutes and ions to move freely between them.

Cell Junctions in Tissues

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 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

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...

key terms and concepts

Learn how tight junctions, anchoring junctions, and gap junctions help cells stay connected, strengthen tissues, and pass signals in animals and plants.

Cell Junctions in Tissues | JoVE K12

cell biology

JoVE Core Cell Biology illustrates complex cellular processes in easy-to-understand yet comprehensive animated video lessons. This collection focuses on the essential components and functions of cells, including organelles and membranes, cellular transport, and cell energetics. It is complemented by scientist-in-action videos that demonstrate the application of cell biology in real-world research experiments.

Cell Junctions in Tissues

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