Fas ligand: Difference between revisions
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'''Fas ligand''' ( | = Fas Ligand = | ||
[[File:Fas_signaling.jpg|thumb|right|Diagram of Fas signaling pathway]] | |||
'''Fas ligand''' ('''FasL''') is a type-II transmembrane protein that belongs to the [[tumor necrosis factor]] (TNF) family. It plays a crucial role in the regulation of the [[immune system]] and the induction of [[apoptosis]]. Fas ligand is primarily expressed on the surface of activated [[T cells]] and [[natural killer cells]]. | |||
== Structure == | == Structure == | ||
Fas ligand is a | Fas ligand is a homotrimeric protein, meaning it forms a complex of three identical subunits. Each subunit consists of an extracellular domain, a transmembrane domain, and a short cytoplasmic tail. The extracellular domain is responsible for binding to its receptor, [[Fas receptor]] (also known as CD95), which is a member of the TNF receptor superfamily. | ||
== Function == | == Function == | ||
Fas ligand is involved in the induction of apoptosis, a form of programmed cell death. When Fas ligand binds to the Fas receptor on the surface of a target cell, it triggers a cascade of intracellular signaling events that lead to cell death. This process is essential for maintaining immune system homeostasis and preventing autoimmune diseases. | |||
=== Apoptosis Induction === | |||
Upon binding of Fas ligand to Fas receptor, the receptor trimerizes and recruits the adaptor protein [[FADD]] (Fas-associated death domain). FADD then recruits [[procaspase-8]], forming the death-inducing signaling complex (DISC). Activation of procaspase-8 leads to the activation of downstream effector caspases, such as caspase-3, ultimately resulting in apoptosis. | |||
[[File:Signal_transduction_pathways.svg|thumb|left|Overview of signal transduction pathways, including Fas signaling]] | |||
== Role in | == Role in the Immune System == | ||
Fas ligand is critical for the regulation of the immune response. It is involved in the elimination of activated [[lymphocytes]] and the maintenance of [[immune privilege]] in certain tissues, such as the [[eye]] and [[testis]]. Fas ligand-mediated apoptosis is also important for the deletion of autoreactive T cells in the [[thymus]], preventing the development of autoimmune diseases. | |||
== Clinical Significance == | |||
Dysregulation of Fas ligand expression or function can lead to various pathological conditions. Overexpression of Fas ligand can contribute to tissue damage in [[autoimmune diseases]], while insufficient Fas ligand activity can result in the accumulation of autoreactive lymphocytes. Mutations in the Fas or Fas ligand genes are associated with autoimmune lymphoproliferative syndrome (ALPS), a disorder characterized by lymphadenopathy, splenomegaly, and autoimmune cytopenias. | |||
== | == Related Pages == | ||
* [[Apoptosis]] | * [[Apoptosis]] | ||
* [[Fas receptor]] | * [[Fas receptor]] | ||
* [[Tumor necrosis factor | * [[Tumor necrosis factor]] | ||
* [[ | * [[Immune system]] | ||
* [[ | * [[Autoimmune disease]] | ||
{{Tumor necrosis factor ligand family}} | |||
[[Category:Apoptosis]] | [[Category:Apoptosis]] | ||
[[Category:Immune system]] | |||
[[Category:Signal transduction]] | |||
Latest revision as of 14:23, 21 February 2025
Fas Ligand[edit]
Fas ligand (FasL) is a type-II transmembrane protein that belongs to the tumor necrosis factor (TNF) family. It plays a crucial role in the regulation of the immune system and the induction of apoptosis. Fas ligand is primarily expressed on the surface of activated T cells and natural killer cells.
Structure[edit]
Fas ligand is a homotrimeric protein, meaning it forms a complex of three identical subunits. Each subunit consists of an extracellular domain, a transmembrane domain, and a short cytoplasmic tail. The extracellular domain is responsible for binding to its receptor, Fas receptor (also known as CD95), which is a member of the TNF receptor superfamily.
Function[edit]
Fas ligand is involved in the induction of apoptosis, a form of programmed cell death. When Fas ligand binds to the Fas receptor on the surface of a target cell, it triggers a cascade of intracellular signaling events that lead to cell death. This process is essential for maintaining immune system homeostasis and preventing autoimmune diseases.
Apoptosis Induction[edit]
Upon binding of Fas ligand to Fas receptor, the receptor trimerizes and recruits the adaptor protein FADD (Fas-associated death domain). FADD then recruits procaspase-8, forming the death-inducing signaling complex (DISC). Activation of procaspase-8 leads to the activation of downstream effector caspases, such as caspase-3, ultimately resulting in apoptosis.
Role in the Immune System[edit]
Fas ligand is critical for the regulation of the immune response. It is involved in the elimination of activated lymphocytes and the maintenance of immune privilege in certain tissues, such as the eye and testis. Fas ligand-mediated apoptosis is also important for the deletion of autoreactive T cells in the thymus, preventing the development of autoimmune diseases.
Clinical Significance[edit]
Dysregulation of Fas ligand expression or function can lead to various pathological conditions. Overexpression of Fas ligand can contribute to tissue damage in autoimmune diseases, while insufficient Fas ligand activity can result in the accumulation of autoreactive lymphocytes. Mutations in the Fas or Fas ligand genes are associated with autoimmune lymphoproliferative syndrome (ALPS), a disorder characterized by lymphadenopathy, splenomegaly, and autoimmune cytopenias.
