Pathogens, toxins, and lipid rafts

The plasma membrane is not a uniform two-dimensional space hut includes var ious types of specialized regions containing specific lipids and proteins. These include clathrin-coated pits and caveolae. The existence of other cho lesterol- and glycosphingolipid-rich microdomains has also been proposed. T he aim of this review is to illustrate that these latter domains, also call ed lipid rafts, may he the preferential interaction sites between a variety of toxins, bacteria, and viruses and the target cell. These pathogens and toxins have hijacked components that are preferentially found in rafts, suc h as glycosylphosphatidylinositol-anchored proteins. sphingomyelin, and cho lesterol. These molecules not only allow binding of the pathogen or toxin t o the proper target cell but also appear to potentiate the toxic action. We briefly review the structure and proposed functions of cholesterol- and gl ycosphingolipid-rich microdomains and then describe the toxins and pathogen s that interact with them. When possible the advantage conferred by the int eraction with microdomains will be discussed.