microvillus organization

Definition

Target type: biologicalprocess

A process that is carried out at the cellular level which results in the assembly, arrangement of constituent parts, or disassembly of a microvillus, a thin cylindrical membrane-covered projection on the surface of a cell. [GOC:mah]

Microvilli are finger-like projections of the plasma membrane that extend from the apical surface of epithelial cells. They are particularly abundant in cells involved in absorption, such as those lining the small intestine and kidney tubules. The organization of microvilli is a complex process that involves the coordinated action of a number of different proteins. These proteins are responsible for:

1. **Nucleation and Elongation:** The core of a microvillus is made up of a bundle of actin filaments. These filaments are nucleated and elongated by a protein complex called the **formin family**.

2. **Bundling and Stabilization:** Once the actin filaments are assembled, they are bundled and stabilized by **villin and fimbrin**, two proteins that cross-link the actin filaments into a tight parallel array.

3. **Anchoring and Attachment:** The microvillar core is anchored to the apical cytoskeleton by a protein called **ezrin**. Ezrin binds to the actin filaments in the core and to transmembrane proteins in the plasma membrane, thereby linking the microvillus to the cell.

4. **Regulation of Length and Structure:** The length and structure of microvilli are dynamically regulated by a variety of signaling pathways. For example, the **small GTPase Rho** has been shown to promote microvillus formation, while the **protein kinase A** (PKA) can inhibit microvillus formation.

5. **Transport of Proteins:** The microvillus cytoskeleton is also involved in the transport of proteins and other molecules to the apical surface. Motor proteins, such as **myosin I** , are thought to move cargo along the actin filaments in the microvillus core.

6. **Membrane Remodeling:** Microvilli are also involved in membrane remodeling. The process of **endocytosis** can occur at the tip of microvilli, allowing cells to internalize extracellular material.

7. **Interactions with Other Cells:** In some tissues, microvilli can interact with neighboring cells to form junctions. For example, the tight junctions that seal the epithelial barrier are often found at the base of microvilli.

The precise mechanisms involved in microvillus organization vary depending on the cell type and its function. However, the proteins described above play key roles in the assembly, maintenance, and dynamic regulation of these important cellular structures.'
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Proteins (1)

Compounds (24)