Lipidraften

Lipidraften are nanoscale, dynamic membrane microdomains that organize lipids and proteins within cellular membranes. The term describes specialized regions in the plasma membrane, and in some contexts internal membranes, that have a distinct lipid composition and physical state compared with the surrounding bilayer.

Composition and properties

Lipidraften are typically enriched in cholesterol and sphingolipids, such as sphingomyelin, and proteins with specific lipid anchors or transmembrane domains that favor ordered lipid packing. This composition promotes a liquid-ordered phase that is more tightly packed than the surrounding liquid-disordered membrane, leading to distinct physical and chemical properties. Size estimates commonly place these domains in the tens of nanometers to a few hundred nanometers range, and they are highly dynamic, forming, dissolving, and rearranging in response to cellular conditions.

Biological roles

Lipidraften are thought to concentrate and organize signaling molecules, receptors, and trafficking machinery to regulate signal transduction, endocytosis, and membrane sorting. In immune cells, raft clustering can influence receptor activation and downstream pathways. They also participate in the entry and trafficking of certain pathogens and in the organization of protein complexes at the cell surface.

Detection and interpretation

Researchers study lipidraften using methods such as detergent-resistant membrane isolation, fluorescence labeling, and super-resolution imaging. Each technique has limitations, and detergent-based approaches can introduce artifacts. As a result, lipidraften are described as dynamic, context-dependent, and sometimes controversial in their exact composition and physical definition.

Occurrence and significance

Lipidraften are reported in many eukaryotic cell types, most prominently in animal cells, with evidence suggesting raft-like domains in plants and fungi. The concept remains a useful heuristic for understanding membrane organization and signaling, though exact details are still actively investigated.