Tight junction: Difference between revisions

Revision as of 17:42, 18 February 2025

Cellular structures that form barriers in tissues

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.

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.

File:Tight junction structure.png

Diagram of tight junction structure showing claudins and occludin.

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.

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.

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.

Function

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.

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

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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]]
-* [[Desmosome]]
+* [[Epithelial tissue]]
-* [[Hemidesmosome]]
+* [[Endothelial cell]]
-* [[Adherens junction]]
+[[Category:Cellular processes]]
 [[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>