Targeting of Salmonella typhimurium to vesicles containing lysosomal membrane glycoproteins bypasses compartments with mannose 6-phosphate receptors.

作者：Francisco Garcı́a-del Portillo, B. Brett Finlay · 发表于：The Journal of Cell Biology · 年份：1995 · DOI：10.1083/jcb.129.1.81 · 被引用次数：258 · 研究领域：Legionella and Acanthamoeba research、Bacterial biofilms and quorum sensing、Vibrio bacteria research studies

Salmonella typhimurium is an intracellular bacterial pathogen that remains enclosed in vacuoles (SCV) upon entry into the host cell. In this study we have examined the intracellular trafficking route of S. typhimurium within epithelial cells. Indirect immunofluorescence analysis showed that bacteria initiated fusion with lysosomal membrane glycoprotein (lgp)-containing compartments approximately 15 min after bacterial internalization. This process was completed approximately 75 min later and did not require microtubules. Cation-independent (CI)- or cation-dependent (CD)-mannose 6-phosphate receptors (M6PRs) were not observed at detectable levels in SCV. Lysosomal enzymes showed a different distribution in SCV: lysosomal-acid phosphatase (LAP) was incorporated into these vacuoles with the same kinetics as lgps, while cathepsin D was present in a low proportion (approximately 30%) of SCV. Uptake experiments with fluid endocytic tracers such as fluorescein-dextran sulphate (F-DX) or horseradish-peroxidase (HRP) showed that after 2 h of uptake, F-DX was present in approximately 75% of lgp-containing vesicles in uninfected cells, while only approximately 15% of SCV contained small amounts of the tracer during the same uptake period. SCV also showed only partial fusion with HRP-preloaded secondary lysosomes, with approximately 30% of SCV having detectable amounts of HRP at 6 h after infection. These results indicate that SCV show limited accessibility to fluid endocytic tracers and...