Lipidiraftien

Lipidiraftien, commonly referred to as lipid rafts in the context of the cell membrane, are small, dynamic microdomains enriched in cholesterol and sphingolipids. These regions are thought to organize and concentrate specific lipids and proteins, facilitating interactions and signaling at the membrane surface. The domains are typically nanoscale, with estimated sizes ranging from about 10 to 200 nanometers, and they can form and dissolve in response to cellular conditions.

Lipidiraftien are enriched in saturated phospholipids and sphingolipids, particularly cholesterol, which together promote a more ordered, tightly packed membrane environment. They often contain GPI-anchored proteins and certain transmembrane proteins, as well as scaffolding components such as caveolins and flotillins. Because of their lipid composition, these domains show altered detergent solubility and can be isolated as detergent-resistant membranes, though this biochemical approach is controversial as it may not faithfully reflect native rafts.

In signaling, lipidiraftien serve as platforms where receptors, kinases (such as Src family kinases), adaptor proteins, and second-messenger systems can cluster to enhance or regulate signaling cascades. They participate in immune receptor signaling (e.g., T cell and B cell receptors) and in various trafficking pathways, including raft-dependent endocytosis and sorting of membrane proteins.

Direct visualization of discrete rafts in living cells remains challenging, leading to debate about their size, lifetime, and even existence as stable entities. Detergent-based methods can yield artifacts, and some researchers emphasize a model of dynamic, transient nanodomains rather than fixed platforms.

Researchers study lipidiraftien using cholesterol manipulation (e.g., depletion with cyclodextrins), labeling of raft-associated lipids such as GM1 with cholera toxin subunit B, and advanced imaging techniques including super-resolution microscopy and single-molecule tracking.