Lipid Raft - Lipid Raft and Signal Transduction

Lipid Raft and Signal Transduction

Signal transduction at the cellular level refers to any process by which a cell converts one kind of signal or stimulus into another. The movement of signal or stimulus can be simple, like that associated with receptor molecules. More complex signal transduction involves the coupling of ligand-receptor interactions to many intracellular events. These events include phosphorylations by tyrosine kinases and/or serine/threonine kinases. The specificity and fidelity of signal transduction are essential for cells to respond efficiently to changes in their environment. This is achieved in part by the differential localization of proteins that participate in signalling pathways. In the plasma membrane, one approach of compartmentalization utilizes lipid rafts. One reasonable way to consider lipid rafts is that small rafts can form concentrating platforms after ligand binding activation for individual receptors. If receptor activation takes place in a lipid raft, the signalling complex is protected from non-raft enzymes such as membrane phosphatases. Overall, raft binding recruits proteins to a new micro-environment so that the phosphorylation state can be modified by local kinases and phosphatases to give downstream signalling. Lipid rafts have been found by researchers to be involved in many signal transduction processes, such as Immunoglobulin E signalling, T cell antigen receptor signalling, B cell antigen receptor signalling, EGF receptor signalling, insulin receptor signalling and so on. In order to illustrate these principles, detailed examples of signalling pathways that involve lipid rafts are described below.