Fas ligand

Fas ligand (also known as FasL, CD95L, or CD178) is a type-1 transmembrane protein that belongs to the tumor necrosis factor (TNF) family. It binds with the Fas receptor (CD95) to induce apoptosis, a process of programmed cell death. Fas ligand plays a crucial role in the regulation of the immune system and the progression of cancer.

Structure

Fas ligand is a type-II transmembrane protein, which means it has an extracellular C-terminal domain and a cytoplasmic N-terminal domain. The extracellular domain of Fas ligand is what interacts with the Fas receptor. The cytoplasmic domain is not required for apoptosis induction.

Function

The primary function of Fas ligand is to bind to the Fas receptor and initiate a series of events that lead to apoptosis. This process is critical for the regulation of the immune system. It helps to maintain immune homeostasis and prevent autoimmune diseases by killing off excess or harmful cells.

Fas ligand is also involved in immune privilege, a state in which certain body sites are able to tolerate the introduction of antigens without eliciting an inflammatory immune response. This is achieved by Fas ligand-mediated apoptosis of invading immune cells.

Role in Disease

Alterations in the Fas ligand/Fas receptor system can lead to various diseases. For example, mutations in the Fas ligand or Fas receptor can cause autoimmune lymphoproliferative syndrome (ALPS), a rare disorder characterized by non-malignant lymphoproliferation, autoimmunity, and increased risk of lymphoma.

In cancer, Fas ligand expression can be a double-edged sword. On one hand, cancer cells can use Fas ligand to kill attacking immune cells and evade the immune response. On the other hand, therapies that enhance Fas ligand expression can be used to kill cancer cells.

See Also

• Apoptosis
• Fas receptor
• Tumor necrosis factor (TNF) family
• Autoimmune lymphoproliferative syndrome (ALPS)
• Immune privilege