Tight junction - Revision history

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Structure

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	== Structure ==		== Structure ==

	~~[[File:TJsm.jpg\|thumb\|left\|Electron micrograph showing tight junctions between cells.]]~~

	Tight junctions are composed of a complex network of proteins that form a seal between adjacent cell membranes. The primary components of tight junctions include transmembrane proteins such as [[claudins]], [[occludin]], and junctional adhesion molecules (JAMs). These proteins interact with cytoplasmic proteins like [[ZO-1]], [[ZO-2]], and [[ZO-3]], which link the tight junctions to the actin cytoskeleton.		Tight junctions are composed of a complex network of proteins that form a seal between adjacent cell membranes. The primary components of tight junctions include transmembrane proteins such as [[claudins]], [[occludin]], and junctional adhesion molecules (JAMs). These proteins interact with cytoplasmic proteins like [[ZO-1]], [[ZO-2]], and [[ZO-3]], which link the tight junctions to the actin cytoskeleton.

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	~~{{Short description\|Cellular structures that form barriers in tissues}}~~		= Tight Junction =
	~~{{Use dmy dates\|date~~=~~October 2023}}~~

	~~'''Tight junctions''' are specialized connections between adjacent epithelial or endothelial cells~~. ~~They play~~ a ~~crucial role in maintaining the selective permeability of~~ epithelial ~~and endothelial barriers, regulating the passage of ions, molecules, and water between~~ cells. ~~Tight junctions are essential for the function of various organs and tissues, including the [[intestines]~~]~~, [[blood-brain barrier~~]~~], and [[kidneys]].~~		[[File:Cellular_tight_junction_en.svg\|thumb\|right\|Diagram of a tight junction between epithelial cells.]]

	~~==Structure==~~		Tight junctions, also known as zonula occludens, are specialized connections between adjacent epithelial or endothelial cells. They play a crucial role in maintaining the selective permeability barrier of epithelial and endothelial layers, regulating the passage of ions, molecules, and water between cells.
	Tight junctions are ~~composed of a complex network of proteins that form a seal~~ between adjacent cells. ~~The primary proteins involved~~ in ~~tight junctions include [[claudins]]~~, ~~[[occludin]]~~, ~~and junctional adhesion~~ molecules ~~(JAMs). These proteins interact with the actin cytoskeleton of the cell~~, ~~providing structural support~~ and ~~maintaining the integrity of the junction~~.

	~~[[File:Tight junction structure.png\|thumb\|right\|Diagram of tight junction structure showing claudins and occludin.]]~~		== Structure ==

	~~===Claudins===~~		[[File:TJsm.jpg\|thumb\|left\|Electron micrograph showing tight junctions between cells.]]
	~~Claudins are a family of proteins that are critical for the formation and function of tight junctions. They determine the selectivity and permeability of the junctions by forming ion-selective pores~~. ~~Different tissues express different claudins, which contribute to the tissue-specific properties of~~ tight junctions.

	~~===Occludin===~~		Tight junctions are composed of a complex network of proteins that form a seal between adjacent cell membranes. The primary components of tight junctions include transmembrane proteins such as [[claudins]], [[occludin]], and junctional adhesion molecules (JAMs). These proteins interact with cytoplasmic proteins like [[ZO-1]], [[ZO-2]], and [[ZO-3]], which link the tight junctions to the actin cytoskeleton.
	~~Occludin is another integral membrane protein found in tight~~ junctions~~. It plays~~ a ~~role in the regulation~~ of ~~junctional permeability and is involved in signaling pathways~~ that ~~control~~ cell ~~proliferation~~ and ~~differentiation~~.

	===~~Junctional Adhesion Molecules (JAMs)~~===		=== Transmembrane Proteins ===
	JAMs are members of the immunoglobulin superfamily and contribute to the formation and maintenance of tight junctions. They are involved in cell signaling and the regulation of paracellular permeability.

	~~==Function==~~		[[File:Tight_Junction_Transmembrane_Proteins.jpg\|thumb\|right\|Illustration of tight junction transmembrane proteins.]]
	~~Tight junctions serve several critical functions in the body~~:

	* '''Barrier Function''': Tight junctions ~~create~~ a ~~barrier~~ that ~~controls~~ the ~~movement~~ of ~~substances between~~ the ~~apical and basolateral surfaces of epithelial cells~~. ~~This barrier~~ is ~~essential for maintaining~~ the ~~distinct environments on either side~~ of ~~the epithelium~~.		The transmembrane proteins of tight junctions are integral to their function. Claudins are a large family of proteins that determine the selectivity and permeability of the tight junctions. Occludin is another important protein that contributes to the barrier and signaling functions of tight junctions. Junctional adhesion molecules (JAMs) are involved in cell adhesion and signaling.

	* '''Selective Permeability''': Tight junctions regulate the passage of ions and small molecules through the paracellular pathway. This selectivity is crucial for processes such as nutrient absorption in the intestines and the maintenance of the blood-brain barrier.		== Function ==

	* '''Cell Polarity''': Tight junctions ~~help establish~~ and ~~maintain cell polarity by demarcating the boundary between the apical and basolateral surfaces of epithelial cells.~~		Tight junctions serve several critical functions in epithelial and endothelial tissues:

	* '''~~Signal Transduction~~''': Tight junctions ~~are involved~~ in signaling pathways that ~~influence~~ cell ~~behavior, including~~ proliferation, differentiation, and ~~apoptosis~~.		* '''Barrier Function''': They create a paracellular barrier that controls the flow of molecules and ions between cells, maintaining the distinct composition of the apical and basolateral environments.
			* '''Fence Function''': Tight junctions prevent the mixing of membrane proteins and lipids between the apical and basolateral surfaces of the cell, preserving cell polarity.
			* '''Signaling''': They participate in intracellular signaling pathways that regulate cell proliferation, differentiation, and survival.

	==Clinical Significance==		== Signaling ==
	Disruption of tight junctions can lead to ~~various pathological conditions. For example,~~ increased permeability ~~of tight junctions in the intestines can result in [[~~inflammatory bowel disease~~]] and [[~~celiac disease]]. In the ~~[[blood-brain barrier]], compromised~~ tight ~~junctions can contribute to neurological disorders such as [[multiple sclerosis]] and [[Alzheimer's disease]]~~.
			[[File:Occludin_signaling.jpg\|thumb\|left\|Occludin signaling pathways in tight junctions.]]

			Tight junctions are not merely passive barriers; they are dynamic structures involved in signaling pathways. Occludin, for example, is involved in signaling pathways that regulate cell proliferation and apoptosis. The interaction of tight junction proteins with signaling molecules can influence various cellular processes, including gene expression and cytoskeletal organization.

			== Clinical Significance ==

			Tight junctions are critical for maintaining tissue homeostasis, and their dysfunction is associated with various diseases. Disruption of tight junctions can lead to increased permeability, contributing to conditions such as inflammatory bowel disease, celiac disease, and certain types of cancer. Understanding the molecular mechanisms of tight junction regulation is important for developing therapeutic strategies for these conditions.

			== Related Pages ==

	~~==Related pages==~~
	* [[Adherens junction]]		* [[Adherens junction]]
	* [[Desmosome]]		* [[Desmosome]]
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	[[Category:Cellular processes]]		[[Category:Cellular processes]]
	[[Category:Cell ~~biology~~]]		[[Category:Cell anatomy]]
	[[Category:~~Histology~~]]		[[Category:Intercellular junctions]]

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	~~'''Tight junctions''' are a type of [[cell junction]]~~ that ~~forms a continuous, watertight seal around cells and serves as a barrier to prevent the leakage of ions and molecules through the space between cells. They are found~~ in ~~[[epithelial cells]] and [[endothelial cells]], which line the surfaces and cavities of the body.~~		{{Short description\|Cellular structures that form barriers in tissues}}
			{{Use dmy dates\|date=October 2023}}

	~~== Structure ==~~		'''Tight junctions''' are specialized connections between adjacent epithelial or endothelial cells. They play a crucial role in maintaining the selective permeability of epithelial and endothelial barriers, regulating the passage of ions, molecules, and water between cells. Tight junctions are essential for the function of various organs and tissues, including the [[intestines]], [[blood-brain barrier]], and [[kidneys]].

	Tight junctions are composed of a complex network of ~~[[protein]]s~~ that ~~link the [[cytoskeleton]] of~~ adjacent cells. The primary proteins involved in ~~the formation of~~ tight junctions ~~are~~ [[claudins]], [[occludin]], and [[junctional adhesion ~~molecule]]~~ (~~JAM~~). These proteins interact with ~~each other~~ and ~~with other cellular proteins to form~~ the ~~tight~~ junction ~~[[strand]], a continuous, belt-like structure that encircles the cell~~.		==Structure==
			Tight junctions are composed of a complex network of proteins that form a seal between adjacent cells. The primary proteins involved in tight junctions include [[claudins]], [[occludin]], and junctional adhesion molecules (JAMs). These proteins interact with the actin cytoskeleton of the cell, providing structural support and maintaining the integrity of the junction.

	~~== Function ==~~		[[File:Tight junction structure.png\|thumb\|right\|Diagram of tight junction structure showing claudins and occludin.]]

	~~The primary~~ function of tight junctions ~~is to prevent the passage of molecules and ions through the intercellular space~~. They ~~act as a barrier to~~ the ~~free diffusion of water~~ and ~~solutes between the [[apical]] and [[basolateral]] sides~~ of the ~~cell~~. ~~This allows cells to maintain distinct internal environments and~~ to ~~regulate~~ the ~~movement~~ of ~~substances across the [[epithelial barrier]]~~.		===Claudins===
			Claudins are a family of proteins that are critical for the formation and function of tight junctions. They determine the selectivity and permeability of the junctions by forming ion-selective pores. Different tissues express different claudins, which contribute to the tissue-specific properties of tight junctions.

	~~Tight~~ junctions ~~also play~~ a role in ~~maintaining cell polarity by preventing~~ the ~~lateral diffusion~~ of ~~proteins~~ and ~~lipids between the apical and basolateral domains of the~~ cell ~~membrane. This is important for the proper functioning of epithelial and endothelial cells, which have distinct apical~~ and ~~basolateral functions~~.		===Occludin===
			Occludin is another integral membrane protein found in tight junctions. It plays a role in the regulation of junctional permeability and is involved in signaling pathways that control cell proliferation and differentiation.

	== ~~Clinical significance~~ ==		===Junctional Adhesion Molecules (JAMs)===
			JAMs are members of the immunoglobulin superfamily and contribute to the formation and maintenance of tight junctions. They are involved in cell signaling and the regulation of paracellular permeability.

	~~Alterations in the structure or function of tight~~ junctions ~~can lead to a variety of diseases. For example, mutations~~ in the genes encoding tight junction proteins can cause [[hereditary deafness]], [[renal disease]], and [[skin disorders]]. In addition, the breakdown of tight junctions is a key feature of many inflammatory diseases, including [[inflammatory bowel disease]] and [[asthma]].		==Function==
			Tight junctions serve several critical functions in the body:

	Tight junctions ~~are also~~ a ~~target for many pathogens. Some viruses~~ and ~~bacteria can disrupt tight junctions to gain entry into~~ cells ~~or to spread from cell to cell~~. This ~~makes tight junctions a potential target~~ for the ~~development~~ of ~~new [[therapeutic]] strategies~~.		* '''Barrier Function''': Tight junctions create a barrier that controls the movement of substances between the apical and basolateral surfaces of epithelial cells. This barrier is essential for maintaining the distinct environments on either side of the epithelium.

	~~== See also ==~~		* '''Selective Permeability''': Tight junctions regulate the passage of ions and small molecules through the paracellular pathway. This selectivity is crucial for processes such as nutrient absorption in the intestines and the maintenance of the blood-brain barrier.

			* '''Cell Polarity''': Tight junctions help establish and maintain cell polarity by demarcating the boundary between the apical and basolateral surfaces of epithelial cells.

			* '''Signal Transduction''': Tight junctions are involved in signaling pathways that influence cell behavior, including proliferation, differentiation, and apoptosis.

			==Clinical Significance==
			Disruption of tight junctions can lead to various pathological conditions. For example, increased permeability of tight junctions in the intestines can result in [[inflammatory bowel disease]] and [[celiac disease]]. In the [[blood-brain barrier]], compromised tight junctions can contribute to neurological disorders such as [[multiple sclerosis]] and [[Alzheimer's disease]].

			==Related pages==
			* [[Adherens junction]]
			* [[Desmosome]]
	* [[Gap junction]]		* [[Gap junction]]
	* [[~~Desmosome~~]]		* [[Epithelial tissue]]
	* [[~~Hemidesmosome]]~~		* [[Endothelial cell]]
	* [[Adherens junction]]

			[[Category:Cellular processes]]
	[[Category:Cell biology]]		[[Category:Cell biology]]
	[[Category:~~Membrane biology~~]]		[[Category:Histology]]
	~~{{Cell-biology-stub}}~~
	~~<gallery>~~
	~~File:Cellular_tight_junction_en.svg\|Diagram of a cellular tight junction~~
	~~File:TJsm.jpg\|Tight junctions in epithelial cells~~
	~~File:Tight_Junction_Transmembrane_Proteins.jpg\|Transmembrane proteins in tight junctions~~
	~~File:Tight_junction_blowup.jpg\|Close-up of a tight junction~~
	~~File:Occludin_signaling.jpg\|Occludin signaling in tight junctions~~
	~~</gallery>~~

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	[[Category:Membrane biology]]		[[Category:Membrane biology]]
	{{Cell-biology-stub}}		{{Cell-biology-stub}}
			<gallery>
			File:Cellular_tight_junction_en.svg\|Diagram of a cellular tight junction
			File:TJsm.jpg\|Tight junctions in epithelial cells
			File:Tight_Junction_Transmembrane_Proteins.jpg\|Transmembrane proteins in tight junctions
			File:Tight_junction_blowup.jpg\|Close-up of a tight junction
			File:Occludin_signaling.jpg\|Occludin signaling in tight junctions
			</gallery>

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New page

'''Tight junctions''' are a type of [[cell junction]] that forms a continuous, watertight seal around cells and serves as a barrier to prevent the leakage of ions and molecules through the space between cells. They are found in [[epithelial cells]] and [[endothelial cells]], which line the surfaces and cavities of the body.

== Structure ==

Tight junctions are composed of a complex network of [[protein]]s that link the [[cytoskeleton]] of adjacent cells. The primary proteins involved in the formation of tight junctions are [[claudins]], [[occludin]], and [[junctional adhesion molecule]] (JAM). These proteins interact with each other and with other cellular proteins to form the tight junction [[strand]], a continuous, belt-like structure that encircles the cell.

== Function ==

The primary function of tight junctions is to prevent the passage of molecules and ions through the intercellular space. They act as a barrier to the free diffusion of water and solutes between the [[apical]] and [[basolateral]] sides of the cell. This allows cells to maintain distinct internal environments and to regulate the movement of substances across the [[epithelial barrier]].

Tight junctions also play a role in maintaining cell polarity by preventing the lateral diffusion of proteins and lipids between the apical and basolateral domains of the cell membrane. This is important for the proper functioning of epithelial and endothelial cells, which have distinct apical and basolateral functions.

== Clinical significance ==

Alterations in the structure or function of tight junctions can lead to a variety of diseases. For example, mutations in the genes encoding tight junction proteins can cause [[hereditary deafness]], [[renal disease]], and [[skin disorders]]. In addition, the breakdown of tight junctions is a key feature of many inflammatory diseases, including [[inflammatory bowel disease]] and [[asthma]].

Tight junctions are also a target for many pathogens. Some viruses and bacteria can disrupt tight junctions to gain entry into cells or to spread from cell to cell. This makes tight junctions a potential target for the development of new [[therapeutic]] strategies.

== See also ==

* [[Gap junction]]
* [[Desmosome]]
* [[Hemidesmosome]]
* [[Adherens junction]]

[[Category:Cell biology]]
[[Category:Membrane biology]]
{{Cell-biology-stub}}