Hexanes, isopropyl alcohol, chloroform, methanol, citric acid, and sodium chloride were purchased from Fisher. previous studies on other proteins, which had a more permissive sterol dependence. This study suggests that agents could be designed to interfere with internalization of without disturbing endocytosis. is an enteropathogenic bacteria that in humans can cause mild diarrhea, enterocolitis, mesenteric lymphadenitis, reactive arthritis, and occasionally sepsis (1). Infection typically occurs via ingestion of contaminated food. When the bacterium arrives at the terminal ileum, it enters into and translocates across M cells, thus breaching the intestinal epithelial barrier and leading Ranirestat to colonization of the subepithelial Peyer’s patches and lamina propria (2, 3). Human infection occurs sporadically in all continents of the world, including in North America, Ranirestat Europe, Russia, and Japan (4). In Europe, the infection typically causes a self-limiting gastroenteritis, whereas in Russia and Japan, infection can also manifest itself in severe systemic inflammatory symptoms called Far East Ranirestat scarlet-like fever, making it a health problem (4). In addition, is considered a direct ancestor of and strains have indicated that is a clone of that evolved as recently as 2,000C10,000 years ago (5). The invasion mechanism of has been studied by several groups, but the role of cholesterol in the host cell plasma membrane for the infection has not been defined. Infections of diverse pathogens, such as adhesins, invasin and YadA (encoded by and genes, respectively), are largely responsible for the adhesion to and internalization into epithelial cells (19). Invasin promotes internalization of into intestinal cells immediately after oral infection (20,C22). In host cell plasma membranes, invasin binds to 1 1 integrin complexed with any of several integrins (23). High densities both of invasin in outer membrane and of 1 1 integrin in host cell plasma membrane are needed for efficient bacterial internalization into host cells. At lower densities, there is adhesion without internalization (24, 25). YadA can enhance adhesion and internalization of under circumstances in which invasin expression is suppressed (26, 27). YadA also interacts with 1 integrin. However, unlike the direct interaction between invasin and 1 integrin, the interaction between YadA and integrin occurs indirectly though extracellular matrix (24, 26, 28, 29). Invasin and YadA compete for binding to 1 1 integrin, so interaction of host cells with can depend on the expression level of each adhesin (30). The interaction of invasin and YadA with 1 integrin is likely to play a key role in uptake into host cells. Their binding to 1 1 integrin induces its clustering within the host cell plasma membrane (24, 30, 31). This clustered integrin interacts with extracellular matrix and cytoskeleton, and adhesion complexes involved in cell movements along a substrate control this process by transmitting signals between the outside and inside of cells (32, 33). Disassembly of the adhesion complexes, which is important for regulation of cell movements, might be controlled by rapid endocytosis of 1 1 integrin (34,C36). An analogous set of events may occur during bacterial uptake. Clustered 1 integrin induces cytoskeletal rearrangements and a phagocytosis-related signaling pathway, promoting internalization of (20, 26). Little is known about the role of cholesterol in this process, although it has been reported that cholesterol enhances intracellular growth of the bacterium (37). In addition, cholesterol may impact infection via its effect on 1 integrin. There have been reports that endocytosis of 1 1 integrin is lipid raftCmediated (38), and that 1 integrin expression increases the amount of raft domainCforming lipids in cell plasma membranes (39). This suggests the possibility that host cell lipids, including cholesterol, could affect phagocytosis of adherence to host MDA-MB-231 cells. In contrast, internalization of into host cells was only observed when host membranes contained cholesterol, 7-dehydrocholesterol, or desmosterol. The effect of sterol type Ranirestat upon the antibody-clustered 1 integrin endocytosis was different from its effect upon uptake of into cells, even though uptake of the latter is mediated by 1 integrin-binding adhesins YadA and invasin. 1 integrin endocytosis had a more permissive sterol structure dependence, with a sterol dependence pattern very similar to that for endocytosis of other proteins in this cell line (40). This suggests that 1 integrin-mediated internalization of into host epithelial cells requires more specific sterol properties than does STMN1 membrane protein endocytosis. Results Effect of sterol substitution in host cell plasma membrane upon internalization.