Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.23.5 (cathepsin D)
 4,130 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Pathogenic strains of Helicobacter pylori cause progressive vacuolation and death of epithelial cells. To identify the nature of vacuoles, the distribution of markers of various membrane traffic compartments was studied. Vacuoles derive from the endocytic pathway since they include the fluid-phase marker Lucifer yellow. Early endosome markers such as rab5, transferrin, and transferrin receptor, as well as the lysosomal hydrolase cathepsin D, are excluded from these structures. In contrast, the vacuolar membrane is specifically stained by affinity-purified antibodies against rab7, a small GTPase, localized to late endosomal compartments. The labeling of rab7 on vacuolar membranes increases as vacuolation progresses, without a concomitant increase of cellular rab7. Cell vacuolation is inhibited by the microtubule-depolymerizing agents nocodazole and colchicine. Taken together, these findings indicate that the vacuoles specifically originate from late endosomal compartments.
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PMID:Cellular vacuoles induced by Helicobacter pylori originate from late endosomal compartments. 793 79

The porin (PorB) of Neisseria gonorrhoeae has been implicated in the pathogenesis of this species. Porin is believed to translocate from the bacterial outer membrane into target cell membranes affecting various cell functions. Here we investigated the effect of porin on phagosome maturation. Phagocytosis of latex beads by human macrophages was allowed in the presence or absence of purified porin. Isolation of latex bead-containing phagosomes and subsequent two-dimensional gel electrophoresis revealed substantial differences in the phagosomal protein composition. Immunoblotting detected higher amounts of annexin II and the early endocytic markers Rab5 and transferrin receptor and decreased levels of the late endocytic markers Rab7 and cathepsin D in phagosomes obtained in the presence of porin compared with those obtained in its absence. Furthermore, association of Rab4 with the latex bead-containing phagosomes was revealed by flow cytometry. The amount of this small GTPase was markedly higher in the phagosomes isolated in the presence of porin. The data thus indicate that neisserial porin is itself able to arrest phagosome maturation within macrophages.
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PMID:Neisseria gonorrhoeae porin modulates phagosome maturation. 985 75

Following entry into non-phagocytic HeLa cells, the facultative pathogen Salmonella typhimurium survives and replicates within a membrane-bound vacuole. Preceding the initiation of intracellular replication there is a lag phase, during which the bacteria modulate their environment. This phase is characterized by the rapid recycling of early endosomal proteins present on the nascent vacuole followed by the acquisition of a subset of lysosomal proteins. To gain a better understanding of the mechanism of intracellular survival, we have followed the biogenesis of the S. typhimurium-containing vacuole (SCV) in HeLa cells expressing different mutant forms of the small GTPase rab7. We demonstrate that the SCV recruits pre-existing lysosomal glycoproteins (Lgps) in a rab7-dependent manner, without directly interacting with lysosomes. We also show the transient accumulation, in the vicinity of the SCV, of novel rab7- and Lgp-containing vesicles containing very low amounts of cathepsin D. The size of these vesicles is dependent on rab7 activity, suggesting a role for rab7 in their homotypic fusion. Taken together, these results indicate that rab7 regulates SCV biogenesis during the phase characterized by the rapid acquisition of lysosomal proteins. We propose that SCV maturation involves its interaction with rab7/Lgp-containing vesicles which are possible intermediate cargo components of the late endocytic pathway.
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PMID:The rab7 GTPase controls the maturation of Salmonella typhimurium-containing vacuoles in HeLa cells. 1044 5

The molecular machinery behind lysosome biogenesis and the maintenance of the perinuclear aggregate of late endocytic structures is not well understood. A likely candidate for being part of this machinery is the small GTPase Rab7, but it is unclear whether this protein is associated with lysosomes or plays any role in the regulation of the perinuclear lysosome compartment. Previously, Rab7 has mainly been implicated in transport from early to late endosomes. We have now used a new approach to analyze the role of Rab7: transient expression of Enhanced Green Fluorescent Protein (EGFP)-tagged Rab7 wt and mutant proteins in HeLa cells. EGFP-Rab7 wt was associated with late endocytic structures, mainly lysosomes, which aggregated and fused in the perinuclear region. The size of the individual lysosomes as well as the degree of perinuclear aggregation increased with the expression levels of EGFP-Rab7 wt and, more dramatically, the active EGFP-Rab7Q67L mutant. In contrast, upon expression of the dominant-negative mutants EGFP-Rab7T22N and EGFP-Rab7N125I, which localized mainly to the cytosol, the perinuclear lysosome aggregate disappeared and lysosomes, identified by colocalization of cathepsin D and lysosome-associated membrane protein-1, became dispersed throughout the cytoplasm, they were inaccessible to endocytosed molecules such as low-density lipoprotein, and their acidity was strongly reduced, as determined by decreased accumulation of the acidotropic probe LysoTracker Red. In contrast, early endosomes associated with Rab5 and the transferrin receptor, late endosomes enriched in the cation-independent mannose 6-phosphate receptor, and the trans-Golgi network, identified by its enrichment in TGN-38, were unchanged. These data demonstrate for the first time that Rab7, controlling aggregation and fusion of late endocytic structures/lysosomes, is essential for maintenance of the perinuclear lysosome compartment.
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PMID:Rab7: a key to lysosome biogenesis. 1067 7

Acquisition of microbicidal properties by phagosomes requires the action of molecules which regulate the interactions between phagosomes and endocytic organelles. Members of the protein kinase C (PKC) superfamily of serine/threonine kinases are recruited to phagosomes with various kinetics during phagolysosome biogenesis. To study the role of PKC-alpha in this process, we compared the composition of latex bead-containing phagosomes isolated from control and dominant-negative (DN) PKC-alpha-overexpressing RAW 264.7 macrophages. Western blot analysis indicated that the levels of both lysosomal-associated membrane protein-1 and flotillin-1, which are acquired through interactions with late endosomes and lysosomes, are reduced in phagosomes from DN PKC-alpha-overexpressing macrophages. Proteomic characterization of latex bead-containing phagosomes revealed that recruitment of the small GTPase Rab7, cathepsin D, and cathepsin S is inhibited by DN PKC-alpha. Collectively, these data provide evidence that PKC-alpha plays a role in phagolysosome biogenesis, a critical process of the innate immune response against infections.
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PMID:Proteomic analysis reveals a role for protein kinase C-alpha in phagosome maturation. 1518 55

Helicobacter pylori colonizes the gastric epithelium of at least 50% of the world's human population, playing a causative role in the development of chronic gastritis, peptic ulcers, and gastric adenocarcinoma. Current evidence indicates that H. pylori can invade epithelial cells in the gastric mucosa. However, relatively little is known about the biology of H. pylori invasion and survival in host cells. Here, we analyze both the nature of and the mechanisms responsible for the formation of H. pylori's intracellular niche. We show that in AGS cells infected with H. pylori, bacterium-containing vacuoles originate through the fusion of late endocytic organelles. This process is mediated by the VacA-dependent retention of the small GTPase Rab7. In addition, functional interactions between Rab7 and its downstream effector, Rab-interacting lysosomal protein (RILP), are necessary for the formation of the bacterial compartment since expression of mutant forms of RILP or Rab7 that fail to bind each other impaired the formation of this unique bacterial niche. Moreover, the VacA-mediated sequestration of active Rab7 disrupts the full maturation of vacuoles as assessed by the lack of both colocalization with cathepsin D and degradation of internalized cargo in the H. pylori-containing vacuole. Based on these findings, we propose that the VacA-dependent isolation of the H. pylori-containing vacuole from bactericidal components of the lysosomal pathway promotes bacterial survival and contributes to the persistence of infection.
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PMID:Helicobacter pylori VacA toxin promotes bacterial intracellular survival in gastric epithelial cells. 1700 Jul 20