Name: cell adhesion in tissues and infection
Uploaded: 2023-04-30T11:55:15.000Z
Duration: 1 min 24 s
Channel: JoVE

تقاطع الالتصاق هو تقاطع تثبيت يربط الخلايا معا في أنسجة مثل الظهارة.
تقاطعات الالتصاق عبارة عن مجمعات كبيرة متعددة البروتينات تتكون من ثلاث فئات رئيسية من البروتين - الكاديرين اللاصق ، والهيكل الخلوي للأكتين المثبت ، والكاتينين الرابط.
تبدأ مجموعة تقاطع الملتصقات ببلمرة مونومرات الأكتين بالقرب من غشاء الخلية لتشكيل نتوءات تسمى الصفيحة.
عندما تكون الصفيحة الصفيحية من الخلايا المجاورة قريبة بدرجة كافية ، تتفاعل الكاديرين على سطحها وتؤدي إلى توطين المزيد من الكاديرين ، وتشكيل مجموعات.
يتم تثبيت هذه المجموعات بواسطة بيتا وألفا و p120 catenins ، مما يساعد على تجنيد المزيد من مجمعات الكادرين الكاتينين في موقع النمو.
مع توسع منطقة التلامس بين الخليتين ، تحول ألفا كاتينين بلمرة الأكتين من متفرعة إلى غير متفرعة ، وترتيبها بالتوازي مع غشاء الخلية.
ثم ترتبط خيوط الأكتين هذه بالميوسين لتشكيل حزم مقلصة ، وبالتالي تشكل تقاطعا ناضجا ملتصقا.
يربط الوصلة الهيكل الخلوي لخلية واحدة بأخرى ، متماسكة معا عبر التفاعلات خارج الخلية لجزيئات الكاديرين.

<ol>
	<li>نيسن ، كارين م. ، وكارا جيه جوتاردي. "المكونات الجزيئية لتقاطع الملتصقات". Biochimica et Biophysica Acta (BBA) - الأغشية الحيوية 1778.3 (2008): 562-571.</li>
	<li>بوم ، باز ، وماريوس جورجيو. "ديناميكيات التقاطعات الملتصقة في التأسيس الظهاري وصيانته وإعادة تشكيله". مجلة بيولوجيا الخلية 192.6 (2011): 907-917.</li>
	<li>Mengaud، Jérôme، et al. "E-cadherin هو مستقبل الإنترنالين، وهو بروتين سطحي مطلوب لدخول L. monocytogenes إلى الخلايا الظهارية." الخلية 84.6 (1996): 923-932.</li>
</ol>

تقاطعات الملتصقة

Adherens Junctions

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نقاط الاتصال القوية بين الخلايا المتجاورة تربطها ببعضها البعض، وتشكل الأنسجة. هذه التقاطعات المثبتة هي من نوعين - التقاطعات الملتصقة والديزموسومات. تتواجد التقاطعات الملتصقة بكثرة في الأنسجة مثل الظهارة والبطانة، وتشكل منطقة التصاق مستمرة تسمى حزام الالتصاق. وفي الأنسجة الأخرى، مثل عضلة القلب، تظهر على شكل مجموعات، تربط الخلايا لإنتاج انقباض منسق لعضلة القلب.

التقاطعات الملتصقة ديناميكية

ترتبط الخلايا البطانية المغطية للأوعية الدموية ارتباطًا وثيقًا، وتشكل حاجزًا يمنع هروب الخلايا والجزيئات الأخرى من مجرى الدم إلى الأنسجة المحيطة. ومع ذلك، أثناء الاستجابة المناعية، يجب أن تمر الكريات البيض من مجرى الدم عبر هذا الحاجز وتصل إلى الأنسجة المستهدفة. تؤدي الجزيئات الالتهابية مثل الهيستامين، وبروتينات الإشارة مثل عامل نمو بطانة الأوعية الدموية (VEGF)، إلى تحفيز العمليات النهائية، مثل الفسفرة واستيعاب الكادهيرين الموجودة على سطح الخلية البطانية. يؤدي هذا إلى تفكيك التقاطعات الملتصقة وزيادة نفاذية بطانة الأوعية الدموية عن طريق خلق فجوات تسمح للخلايا المناعية والجزيئات الأخرى بالمرور من خلالها. وبالتالي يتم تنظيم صيانة وانهيار التقاطعات الملتصقة ديناميكيًا استجابةً لمحفزات محددة.

التقاطعات الملتصقة والعدوى

يمكن للعوامل المعدية مثل هيليكوباكتر بيلوري أن تدخل الأنسجة المضيفة عن طريق تعطيل التقاطعات الملتصقة والتحرك عبر الفجوات بين الخلايا. تنتج هذه البكتيريا البروتياز الذي يشق المجال خارج الخلية للكادهيرين، مما يؤدي إلى تفكيك الوصلة. يتم أيضًا اختطاف الكادهيرين سطح الخلية كمستقبلات بواسطة بكتيريا مثل العقدية الرئوية لتلتصق بظهارة الجهاز التنفسي العلوي.

ومع ذلك، ربما يكون الاختطاف الأكثر إثارة للإعجاب هو الليستيريا المستوحدة. تعبر هذه البكتيريا عن بروتينات جدار الخلية التي تربط الكادهيرين الإلكترونية وتؤدي إلى تجنيد الكاتينين ɑ و β و p120 في الموقع. يؤدي هذا التوظيف إلى بدء بلمرة الأكتين الديناميكية، مما يشكل نتوءات غشائية تبتلع البكتيريا في عملية تسمى البلعمة المستحثة. وهكذا تتمكن البكتيريا من الدخول إلى خلية غير بلعمية وتتكاثر داخل المضيف.
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نقاط الاتصال القوية بين الخلايا المجاورة تربطها ببعضها البعض ، وتشكل الأنسجة. تقاطعات التثبيت هذه من نوعين - الالتصاق ...

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 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 endothelial cells form a barrier that normally keeps cells and molecules inside the bloodstream. During an immune response, leukocytes, or white blood cells, must cross this barrier to reach damaged tissue. Inflammatory molecules such as histamines and signaling proteins such as vascular endothelial growth factor, or VEGF, can trigger phosphorylation and internalization of cadherins on the endothelial cell surface. Cadherins are adhesion proteins that help cells stick together. When this happens, adherens junctions break down, permeability increases, and gaps open for immune cells and other molecules to pass through.

Some infections also take advantage of adherens junctions. Helicobacter pylori can disrupt these junctions by producing proteases that cut the extracellular part of cadherins. This breaks the junctions and helps the bacteria move through the spaces between cells. Other bacteria, such as Streptococcus pneumoniae, use cadherins as receptors to attach to the upper respiratory epithelium. Listeria monocytogenes uses a more complex strategy. It binds E-cadherins and recruits alpha-, beta-, and p120-catenins, which starts actin polymerization. This creates membrane protrusions that engulf the bacteria in induced phagocytosis, allowing it to enter a nonphagocytic cell and multiply inside the host.

Cell Adhesion in Tissues and Infection

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

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 adherens junctions hold tissues together, open during immune responses, and can be disrupted by bacteria like H. pylori, S. pneumoniae, and Listeria.

Cell Adhesion in Tissues and Infection | 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 Adhesion in Tissues and Infection

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