microtubule nucleation by microtubule organizing center

Definition

Target type: biologicalprocess

The 'de novo' formation of a microtubule, mediated by the microtubule organizing center. [GOC:ai]

Microtubule nucleation, the initiation of new microtubule assembly, is a critical process in eukaryotic cells that is primarily orchestrated by microtubule organizing centers (MTOCs). MTOCs are specialized cellular structures that serve as the starting points for microtubule growth. The most prominent MTOC in animal cells is the centrosome, a pair of centrioles surrounded by pericentriolar material (PCM).

Microtubule nucleation at MTOCs involves a multi-step process:

1. **γ-Tubulin ring complex (γTuRC) assembly:** The γTuRC is a protein complex that acts as a template for microtubule nucleation. It consists of multiple γ-tubulin subunits arranged in a ring-like structure, along with other associated proteins.

2. **γTuRC recruitment to the MTOC:** The γTuRC is recruited to the MTOC through interactions with various proteins, including pericentrin and ninein, which are components of the PCM.

3. **Microtubule initiation:** Once assembled at the MTOC, the γTuRC provides a binding site for α- and β-tubulin dimers, the building blocks of microtubules. The γTuRC acts as a seed for the initial assembly of a short microtubule protofilament.

4. **Microtubule elongation:** The initial microtubule protofilament, stabilized by the γTuRC, serves as a platform for further tubulin dimer addition, leading to the elongation of the microtubule. This elongation process occurs at the plus end of the microtubule, which is the rapidly growing end.

5. **Dynamic instability:** Microtubules are highly dynamic structures that undergo cycles of growth and shrinkage. This phenomenon, known as dynamic instability, is essential for various cellular functions, including cell division, migration, and transport.

6. **Regulation of microtubule dynamics:** The nucleation and dynamics of microtubules are tightly regulated by various factors, including the concentration of tubulin dimers, the availability of γTuRCs, and the activity of microtubule-associated proteins (MAPs) that bind to and modify microtubules.

In summary, microtubule nucleation at MTOCs is a complex process that involves the assembly and recruitment of γTuRCs, providing a template for microtubule initiation and elongation. The dynamic instability of microtubules, regulated by various cellular factors, is critical for their diverse functions in eukaryotic cells.'
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Proteins (2)

Compounds (3)