Name: tight junction proteins and cell barriers
Uploaded: 2023-04-30T11:55:38.000Z
Duration: 1 min 29 s
Channel: JoVE

Böbrekler ve bağırsaklar gibi organlarda, epitel hücreleri, makromoleküllerin, iyonların ve küçük çözünen maddelerin paraselüler boşluktan akışını önlemek için sıkı bağlantılarla birlikte kapatılır.
Sıkı bağlantılar esas olarak, her biri dört zarı kapsayan alfa sarmalına sahip claudin ve oklüdin transmembran proteinlerini içerir.
Kladinler ve oklüdinler sıraları zar üzerinde polimerize olur ve bir sızdırmazlık iplikçikleri ağı oluşturur.
Bu iplikler, hücre dışı döngüleri ile bitişik hücre üzerindeki benzer protein ipliklerine bağlanır ve böylece iki zarı bir arada tutar.
Sitoplazmik tarafta, bu proteinlerin C-terminal kuyrukları, zonula okcludens veya ZO adı verilen büyük iskele proteinlerinin PDZ alanları ile ilişkilidir.
ZO proteinleri birden fazla protein bağlama alanına sahiptir ve bu nedenle kladudinler, oklüdinler, aktin ve diğer ZO proteinlerini bağlayarak bu sızdırmazlık ipliklerini organize eden ve stabilize eden bir ağ oluşturabilir.
Paraselüler boşluğu kapatmaya ek olarak, sıkı bağlantılar, glikoz taşıyıcıları gibi proteinlerin zar boyunca yanal hareketini de önler. Bu, bu proteinlerin glikoz emilimi için bağırsak epitelinin apikal yüzeyine lokalize edilmesine yardımcı olur.

<ol>
	<li>Sawada, Norimasa. "Sıkı kavşak ile ilgili insan hastalıkları." Patoloji uluslararası 63.1 (2013): 1-12. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7168075/">Link</a></li>
	<li>Anderson, James M. ve Christina M. Van Itallie. "Sıkı bağlantının fizyolojisi ve işlevi." Biyolojide Cold Spring Harbor perspektifleri 1.2 (2009): a002584. <a href="https://cshperspectives.cshlp.org/content/1/2/a002584.full">Link</a></li>
	<li>Mariano, Cibelle, et al. "Trisellüline ve sıkı bağlantı oluşumu ve bakımındaki rolüne bir bakış." Avrupa hücre biyolojisi dergisi 90.10 (2011): 787-796. <a href=" https://d1wqtxts1xzle7.cloudfront.net/52322075/A_look_at_tricellulin_and_its_role_in_ti20170327-17112-1qhpwe8-libre.pdf?1490608194=&response-content-disposition=inline%3B+filename%3DA_look_at_tricellulin_and_its_role_in_ti.pdf&Expires=1654205963&Signature=IelR0FUZCC6ZcqAcJvs1JTGe6liRDBX6aqaYzcw4sMZ2yqyhu5BuZ9DDbujaDRUN9SwX20yuCRLRyzxl6MWAa4QfY2cZ1wtZb4qfoi5otW~z0rhB3ba231uB1~pdP0rZpdHB4~snYhLr-~nZRsoaUqTFJmJaJXpxtHnoBGC4HFP29Q8D3q0rNHNDJGq9Qx9SfcLWmDISH7n8IfsUozT6rdpn421eOVufn5lNVunpqMX6iiRAT4D7p8bJEPpfd2~3cygJP7Ltc32RiIm2RHGvp9CRUoXs015y2aR4A7--dka7UzL97Aa~DDZ8ES90wX9D58qA~jX24DnmzNeNwlAayg__&Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA">Bağlantı</a></li>
</ol>

sıkı bağlantılar

Tight Junctions

Sıkı bağlantılar, çok hücreli organizmalardaki boşluklar ve bölmeler boyunca sıvıların, iyonların ve diğer küçük çözünen maddelerin sızmasını önleyen, hücreler arasındaki moleküler contalardır. Bunlar esas olarak klaudin ve okludin transmembran proteinlerinden ve tricellulin ve JAM (bağlantısal yapışma molekülü) gibi diğer proteinlerden oluşur. İmmünoglobulin süper ailesine ait tek geçişli bir transmembran proteini olan JAM dışında tüm bu proteinler 4 geçişli transmembran proteinleridir. Bu sıkı bağlantı proteinlerinin hücre dışı alanları, bitişik hücre zarındakilerle etkileşime girer, böylece iki bitişik hücreyi bir araya getirir ve kapatır. Sıkı Bağlantıların Seçici Geçirgenliği Transmembran claudin'in insanlarda ifade edilen 24'e kadar farklı tipte birden fazla izoformu vardır. Claudin proteininin çeşitliliği, farklı sıkı bağlantılara seçici geçirgenlik kazandırır. Örneğin böbrek epitelinde ifade edilen claudin-16, magnezyum iyonlarına geçirgenliği arttırır, böylece filtrasyon sırasında bunların kandan geri alınmasına izin verir. Buna karşılık, beyin kılcal damarlarının endotel hücrelerinde ifade edilen claudin-5, kan-beyin bariyeri boyunca iyon geçirgenliğini seçici olarak azaltır. Üç Hücreli Bağlantılar Sıkı bağlantılar, iki hücre arasındaki boşlukları kapatmanın yanı sıra, üç hücrenin (üç hücreli bağlantı) birleştiği yerde oluşan boşlukları da kapatır. Üç hücreli bağlantıların yapısı ilk olarak 1970'lerde donma-kırılma elektron mikroskobu kullanılarak gözlemlendi. Bu bağlantı noktalarında sızdırmazlık şeritleri, iki hücreli sıkı bağlantı şeritlerine dik olarak yönlendirilir. Böylece üç hücreli temas noktası, moleküllerin hücre içi hareketini kontrol eden yaklaşık 10 nm çapında dar bir dikey tüp oluşturur. Tricellulin, bu üç hücreli bağlantılarda konsantre olduğu tanımlanan ilk proteindi. Okludin proteinleri ile sekans homolojisini paylaşır ve insanlarda dört izoform sergiler. İlginç bir şekilde, triselülin genindeki (TRIC) mutasyonların işitme bozukluğuna neden olduğu gösterildi; bu da, iç kulaktaki bir yapı olan Corti organında gerekli olan sıkı contaların korunmasındaki önemini ortaya koyuyor.

Sıkı Bağlantılar

Sıkı bağlantılar, sıvıların, iyonların ve diğer küçük çözünen maddelerin boşluklar ve bölmeler boyunca sızmasını önleyen hücreler arasındaki moleküler contalardır.

Education

JoVE Core

Cell Biology

Hücre Biyolojisi

Unit 1

Ünite 1

Cell-Cell Interactions

Hücre-Hücre Etkileşimleri

KEY TERMS AND CONCEPTS

TEMEL TERİMLER VE KAVRAMLAR

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 transmembrane proteins, meaning they cross the cell membrane four times. JAM is different because it is a single-pass transmembrane protein in the immunoglobulin superfamily. The extracellular parts of these proteins interact with matching parts on the nearby cell membrane. This brings two adjacent cells together and helps seal them.

Claudin proteins are especially important because there are many isoforms, or forms, of claudin. Humans express up to 24 different types. This diversity gives tight junctions selective permeability, which means some substances pass more easily than others. For example, claudin-16 in kidney epithelium increases permeability to magnesium ions. This helps magnesium move back into the body during filtration. In contrast, claudin-5 in endothelial cells of brain capillaries lowers ion permeability across the blood-brain barrier.

Tight junctions also seal tricellular junctions, which are the gaps where three cells meet. These junctions were first seen in the 1970s with freeze-fracture electron microscopy. At these contact points, the sealing strands run perpendicular to the strands in bicellular tight junctions. The center of the tricellular contact forms a narrow vertical tube about 10 nm wide. This structure helps control paracellular movement, which is movement between cells.

Tricellulin is the first protein known to concentrate at tricellular junctions. It is related in sequence to occludin and has four isoforms in humans. Mutations in the tricellulin gene, TRIC, can cause hearing impairment. This shows how important tight seals are in the organ of Corti, a structure in the inner ear.

Tight Junction Proteins and Cell Barriers

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cell adhesion molecules - types and functions

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immunoglobulin-like cell adhesion molecules

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tight junctions

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

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key terms and concepts

Learn how claudin, occludin, tricellulin, and JAM seal cells, control selective permeability, and support barriers like the blood-brain barrier.

Tight Junction Proteins and Cell Barriers | JoVE K12

cell biology

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Tight Junction Proteins and Cell Barriers

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