Microtubulus

Microtubulus is a term sometimes used to refer to microtubules, the hollow cylindrical polymers that form a major part of the eukaryotic cytoskeleton. The more common English usage is microtubule. Microtubuli (the plural form in some Latinized usages) are found in nearly all eukaryotic cells and play essential roles in structure, transport, and division.

Structure and composition: Microtubules are built from tubulin dimers, consisting of alpha- and beta-tubulin. These dimers polymerize end-to-end to form protofilaments that align to create a hollow tube about 25 nanometers in diameter. The length of microtubules is highly dynamic, varying from short to several micrometers or longer, depending on cellular needs and regulatory factors.

Functions: They provide mechanical support that helps determine cell shape and polarity. As intracellular tracks, microtubules guide the movement of organelles and vesicles via motor proteins such as kinesin and dynein. During mitosis and meiosis, they organize into the mitotic spindle to separate chromosomes. In cilia and flagella, highly organized microtubule arrays power movement.

Dynamics and regulation: Microtubules exhibit dynamic instability, growing and shrinking through GTP-tubulin hydrolysis at their plus ends. Their behavior is controlled by microtubule-associated proteins (MAPs), plus-end tracking proteins, and other regulators. Nucleation commonly occurs at microtubule organizing centers, such as the centrosome in animal cells, though some organisms use alternative nucleation sites.

Clinical and research interest: Because of their central role in cell division and intracellular transport, microtubules are frequent targets in cancer therapy, with drugs that stabilize or destabilize microtubules affecting mitosis. Defects in microtubule function can contribute to neurodevelopmental and ciliopathy-related disorders.