filopódíum

Filopodia are thin, actin-rich protrusions that extend from the cell membrane of various cell types, including fibroblasts, neurons, and immune cells. They are dynamic structures that constantly grow, retract, and explore the cellular environment. These finger-like projections are typically several micrometers long and only a few hundred nanometers in diameter.

The primary function of filopodia is cell sensing and exploration. They act as sensory organelles, detecting physical and chemical cues in the extracellular space. This detection can include gradients of signaling molecules, the presence of other cells, or the physical properties of the substrate. By extending and probing the environment, filopodia play crucial roles in processes such as cell migration, tissue development, and neuronal guidance.

The formation and behavior of filopodia are tightly regulated by the actin cytoskeleton. Actin filaments polymerize at the tip of the filopodium, driving its extension. Various motor proteins and regulatory proteins are involved in their assembly and disassembly, allowing for rapid responses to cellular signals. They can also serve as contact points for cell-cell adhesion or for establishing connections with the extracellular matrix. In some cases, filopodia are precursors to lamellipodia, broader sheet-like extensions involved in cell movement.