Aktiiniverkon

Aktiiniverkon, known in English as actin network or actin cytoskeleton, is a dynamic structure within eukaryotic cells. It is a complex of filamentous actin proteins that plays a crucial role in maintaining cell shape, enabling cell movement, and facilitating intracellular transport. Actin filaments, also called microfilaments, are thin, flexible rods that polymerize and depolymerize rapidly, allowing the network to constantly remodel.

This network is organized into various structures, including filopodia, lamellipodia, and stress fibers. Filopodia are finger-like projections involved in sensing the environment and cell adhesion. Lamellipodia are broad, sheet-like extensions that drive cell migration. Stress fibers are bundles of actin filaments that provide mechanical strength and help anchor the cell to its surroundings.

The formation and organization of the actin network are tightly regulated by a multitude of actin-binding proteins. These proteins can promote or inhibit actin polymerization, cross-link filaments into bundles or networks, and anchor the network to the cell membrane or other organelles. Proteins like profilin, cofilin, and gelsolin are essential for dynamic remodeling, while tropomyosin and alpha-actinin help stabilize and organize filaments.

The actin network is fundamental to numerous cellular processes. It is involved in muscle contraction, where interactions with myosin motor proteins generate force. It is also critical for cytokinesis, the division of the cytoplasm during cell division, and for endocytosis and exocytosis, the processes of internalizing and secreting substances from the cell. Furthermore, it plays a significant role in cell signaling pathways and the response to external stimuli. Disruptions to the actin network can lead to various cellular defects and diseases.