actomyosin contractile ring

Definition

Target type: cellularcomponent

A cytoskeletal structure composed of actin filaments and myosin that forms beneath the plasma membrane of many cells, including animal cells and yeast cells, in a plane perpendicular to the axis of the spindle, i.e. the cell division plane. In animal cells, the contractile ring is located at the cleavage furrow. In budding fungal cells, e.g. mitotic S. cerevisiae cells, the contractile ring forms at the mother-bud neck before mitosis. [GOC:expert_jrp, GOC:sgd_curators, GOC:vw, ISBN:0805319409, ISBN:0815316194, PMID:28914606]

The actomyosin contractile ring is a dynamic structure essential for cytokinesis, the process by which a dividing cell separates into two daughter cells. It is composed primarily of actin filaments, myosin II motor proteins, and various regulatory proteins. The ring assembles at the cell cortex during late anaphase and contracts to constrict the cell membrane, eventually leading to daughter cell separation.

**Actin Filaments:**

* **Organization:** Actin filaments in the contractile ring are organized into a dense, parallel array, with their barbed ends oriented towards the cell interior.
* **Dynamics:** Actin filaments are constantly polymerizing and depolymerizing, ensuring the ring's dynamic nature.
* **Regulation:** Actin polymerization is tightly regulated by various proteins, including formins, profilin, and capping proteins.

**Myosin II:**

* **Function:** Myosin II is a motor protein that generates the force for ring contraction. It binds to and slides along actin filaments, pulling the ring inward.
* **Regulation:** Myosin II activity is regulated by phosphorylation and dephosphorylation, allowing for controlled contraction.

**Regulatory Proteins:**

* **RhoA:** A small GTPase that plays a crucial role in regulating actin polymerization and myosin II activation during ring assembly.
* **Anillin:** A scaffold protein that binds to actin, myosin II, and other regulatory proteins, helping to organize the ring structure.
* **IQGAP:** Another scaffold protein that contributes to ring assembly and stability.

**Cellular Localization:**

The contractile ring is positioned at the cell cortex, the region just beneath the plasma membrane. It is associated with the cleavage furrow, the inward indentation of the cell membrane that eventually divides the cell.

**Overall, the actomyosin contractile ring is a highly dynamic and regulated structure essential for cytokinesis. Its precise composition and organization ensure efficient and accurate cell division.**'
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Proteins (1)

Compounds (1)