Replication of Coxiella burnetii in a Lysosome-Like Vacuole Does Not Require Lysosomal Hydrolases

• Published in: Infection and immunity Vol. 87; no. 11
• Main Authors: Miller, Heather E, Hoyt, Forrest H, Heinzen, Robert A
• Format: Journal Article
• Language: English
• Published: United States American Society for Microbiology 01.11.2019
• Subjects: Amino Acids - administration & dosage; Amino Acids - pharmacology; Cathepsin D; Cell Proliferation; Cellular Microbiology: Pathogen-Host Cell Molecular Interactions; Cholesterol - metabolism; Coxiella burnetii; Culture Media; HeLa Cells; Humans; Hydrogen-Ion Concentration; Hydrolases - metabolism; Lysosomes; Macrolides - pharmacology; Microbial Viability; autophagy; Q fever; Coxiella; hydrolases; Coxiella-containing vacuole; vesicular trafficking; GNPTAB knockout cells; LC3; lysosome; mannose-6-phosphate receptor
• ISSN: 0019-9567; 1098-5522
• DOI: 10.1128/IAI.00493-19

is an intracellular bacterium that causes query, or Q fever, a disease that typically manifests as a severe flu-like illness. The initial target of is the alveolar macrophage. Here, it regulates vesicle trafficking pathways and fusion events to establish a large replication vacuole called the -containing vacuole (CCV). Similar to a phagolysosome, the CCV has an acidic pH and contains lysosomal hydrolases obtained via fusion with late endocytic vesicles. Lysosomal hydrolases break down various lipids, carbohydrates, and proteins; thus, it is assumed derives nutrients for growth from these degradation products. To investigate this possibility, we utilized a GNPTAB HeLa cell line that lacks lysosomal hydrolases in endocytic compartments. Unexpectedly, examination of growth in GNPTAB HeLa cells revealed replication and viability are not impaired, indicating does not require by-products of hydrolase degradation to survive and grow in the CCV. However, although bacterial growth was normal, CCVs were abnormal, appearing dark and condensed rather than clear and spacious. Lack of degradation within CCVs allowed waste products to accumulate, including intraluminal vesicles, autophagy protein LC3, and cholesterol. The build-up of waste products coincided with an altered CCV membrane, where LAMP1 was decreased and CD63 and LAMP1 redistributed from a punctate to uniform localization. This disruption of CCV membrane organization may account for the decreased CCV size due to impaired fusion with late endocytic vesicles. Collectively, these results demonstrate lysosomal hydrolases are not required for survival and growth but are needed for normal CCV development. These data provide insight into mechanisms of CCV biogenesis while raising the important question of how obtains essential nutrients from its host.