nuclear export

Definition

Target type: biologicalprocess

The directed movement of substances out of the nucleus. [GOC:ai]

Nuclear export is a fundamental cellular process that governs the movement of proteins, RNAs, and other molecules from the nucleus to the cytoplasm. This process is essential for maintaining cellular homeostasis, regulating gene expression, and facilitating various cellular functions.

The nuclear envelope, a double membrane that surrounds the nucleus, acts as a barrier between the nucleus and the cytoplasm. This barrier is selectively permeable, allowing only specific molecules to pass through.

Nuclear export relies on a complex machinery involving several key players:

1. **Nuclear Export Signals (NESs):** These are short amino acid sequences within proteins that act as "zip codes" for export. NESs are recognized by nuclear export receptors.

2. **Nuclear Export Receptors (NERs):** These are proteins that bind to NESs and facilitate the transport of cargo molecules through the nuclear pore complex (NPC), a large protein channel embedded in the nuclear envelope. One of the most well-studied NERs is **CRM1**, also known as exportin 1.

3. **The Nuclear Pore Complex (NPC):** This intricate structure is embedded within the nuclear envelope and acts as a gateway for the passage of molecules between the nucleus and the cytoplasm. The NPC is composed of multiple proteins organized into a ring-like structure with channels that regulate the movement of molecules.

4. **Ran GTPase:** This small GTP-binding protein plays a crucial role in regulating the directionality of nuclear transport. Ran exists in two forms: RanGTP and RanGDP. The active form, RanGTP, is primarily found in the nucleus, while RanGDP is mainly present in the cytoplasm.

**The process of nuclear export can be summarized in these steps:**

1. **Cargo loading:** A protein with an NES binds to an NER, forming a cargo-receptor complex.
2. **Translocation through the NPC:** The cargo-receptor complex interacts with the NPC and translocates through the channel.
3. **RanGTP-mediated release:** In the cytoplasm, RanGTP binds to the NER, triggering the release of the cargo molecule.
4. **Recycling of the NER:** The NER, now bound to RanGTP, returns to the nucleus.
5. **RanGTP hydrolysis:** In the nucleus, RanGTP is hydrolyzed to RanGDP, releasing the NER and completing the cycle.

Nuclear export is a tightly regulated process, ensuring the proper distribution of molecules within the cell. Dysregulation of nuclear export can lead to various diseases, including cancer and neurodevelopmental disorders.'
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Proteins (2)

Compounds (5)