trans-Golgi network

Definition

Target type: cellularcomponent

The network of interconnected tubular and cisternal structures located within the Golgi apparatus on the side distal to the endoplasmic reticulum, from which secretory vesicles emerge. The trans-Golgi network is important in the later stages of protein secretion where it is thought to play a key role in the sorting and targeting of secreted proteins to the correct destination. [GOC:vw, ISBN:0815316194]

The trans-Golgi network (TGN) is a complex cellular compartment located at the "trans" face of the Golgi apparatus. It acts as a central sorting station, receiving newly synthesized proteins and lipids from the Golgi cisternae and directing them to their final destinations. The TGN is characterized by its unique protein composition, distinct morphology, and dynamic nature.

**Protein Composition:**

The TGN harbors a diverse array of resident proteins, including:

* **Sorting receptors:** These proteins bind to specific cargo molecules, such as lysosomal hydrolases, proteins destined for the plasma membrane, and secretory proteins, facilitating their sorting into different transport vesicles. Examples include mannose 6-phosphate receptor (MPR), clathrin adaptor proteins (APs), and sorting nexin (SNX) proteins.
* **Transport factors:** These proteins mediate the movement of cargo vesicles between the TGN and other compartments. Examples include small GTPases like Rab proteins, which regulate vesicle docking and fusion.
* **Enzymes:** The TGN houses various enzymes, including glycosidases, sulfatases, and kinases, which modify the cargo molecules before their final delivery.

**Morphology:**

The TGN is often depicted as a network of interconnected tubules and cisternae, forming a complex and dynamic structure. This network allows for efficient sorting and transport of cargo. It can also be characterized by its distinctive morphology, featuring:

* **Tubular domains:** These are elongated, thin structures that facilitate the transport of cargo to different destinations.
* **Cisternal domains:** These are more flattened, disk-like structures that act as holding areas for cargo prior to sorting.
* **Golgi matrix:** A network of protein filaments that provides structural support to the TGN and maintains its organization.

**Dynamic Nature:**

The TGN is a highly dynamic compartment, constantly undergoing changes in its structure and protein composition. These changes are regulated by various factors, including:

* **Cargo influx:** The arrival of new cargo from the Golgi cisternae triggers the formation of new tubules and cisternae, expanding the TGN.
* **Vesicle budding:** The formation of transport vesicles from the TGN is a continuous process, allowing for the efficient delivery of cargo to various destinations.
* **Protein trafficking:** The movement of proteins between the TGN and other compartments is dynamic and regulated by signaling pathways.

**Functions:**

The TGN performs several critical functions in the cell, including:

* **Sorting and packaging:** The TGN acts as a central sorting station, directing proteins and lipids to their appropriate destinations, such as lysosomes, endosomes, plasma membrane, or secretory vesicles.
* **Post-translational modifications:** The TGN is a site for final post-translational modifications of proteins, including glycosylation, sulfation, and phosphorylation.
* **Quality control:** The TGN acts as a checkpoint for proteins destined for secretion, ensuring their proper folding and assembly.
* **Secretion:** The TGN is responsible for the packaging and release of secretory proteins, which are exported from the cell.

**Clinical Relevance:**

Disruptions in TGN function can lead to various diseases, including:

* **Lysosomal storage disorders:** Mutations in proteins involved in lysosomal enzyme sorting can lead to the accumulation of undigested materials in lysosomes.
* **Neurodegenerative diseases:** Defects in TGN trafficking can contribute to the misfolding and aggregation of proteins, leading to neuronal dysfunction.
* **Cancer:** The TGN plays a role in the secretion of growth factors and other molecules involved in tumor growth and metastasis.

In conclusion, the trans-Golgi network is a complex and vital cellular compartment that plays a critical role in protein sorting, trafficking, and secretion. Its dynamic nature and diverse protein composition enable it to perform these functions efficiently, ensuring proper cellular function and homeostasis.'
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Proteins (27)

Compounds (1,657)