生体膜リン脂質脂肪酸鎖の膜タンパク質機能における役割

抄録

Biological membranes such as plasma membrane are formed by a phospholipid bilayer. Phospholipids have two fatty acyl chains attached to them, and these fatty acyl chains vary from saturated fatty acids to highly unsaturated fatty acids. The hydrophobic environment formed by these fatty acyl chains not only functions as a barrier between the inside and outside of the membrane, but also interacts with hydrophobic regions of membrane-bound proteins, which may affect the localization, stability, and function of membrane-bound proteins. For example, lipid rafts composed of sphingomyelin and cholesterol in the plasma membrane accumulate certain membrane proteins such as GPI-anchored proteins. We have found that dipalmitoylphosphatidylcholine (DPPC), whose phase transition temperature (42°C) is higher than body temperature, varies greatly in content from cell to cell, and that the function of a certain membrane receptor is greatly modified by the amount of DPPC. On the other hand, for example, phospholipids with highly unsaturated fatty acyl chains are abundant in the retina and play an important role in retinal function. We have generated a cell culture system deficient in highly unsaturated fatty acids and suggested the existence of a membrane-bound protein population requiring phospholipids with highly unsaturated fatty acid chains. As a result of advances in lipidome analysis and the elucidation of many lipid-metabolizing enzymes, we have reached a point where biomembrane fatty acid chains can be artificially regulated. Under these circumstances, it has become possible to comprehensively analyze the role of biomembrane fatty acid chains with respect to membrane-bound proteins.