pseudocilia

Pseudocilia are transient, actin-based cellular protrusions that resemble cilia but lack the stable 9+2 microtubule axoneme structure characteristic of true cilia. These structures are dynamically assembled and disassembled from the cell surface, playing a role in various cellular processes. They are primarily composed of actin filaments, which are organized by proteins like Arp2/3 complex and formin, and are often capped by proteins such as tropomodulin. Their formation is typically triggered by specific signaling pathways, often involving upstream regulators like Rho GTPases. Pseudocilia have been observed in a range of cell types, including epithelial cells, fibroblasts, and immune cells.

The functions of pseudocilia are diverse and context-dependent. They are implicated in mechanosensation, where their extension and retraction can sense mechanical forces and transmit signals within the cell. In some instances, pseudocilia are involved in cell migration, potentially by probing the extracellular environment or facilitating cell-cell interactions. They have also been linked to intracellular trafficking and signaling platform formation. Unlike true cilia, which are involved in motility and fluid transport, pseudocilia are not typically motile and their primary roles are more related to sensing and cellular dynamics. The transient nature of pseudocilia suggests they are a flexible cellular response mechanism rather than a permanent organelle.