title: CLA-1 and its splicing variant CLA-2 mediate bacterial adhesion and cytosolic bacterial invasion in mammalian cells.
abstract: CD36 and LIMPII analog 1, CLA-1, and its splicing variant, CLA-2 (SR-BI and SR-BII in rodents), are human high density lipoprotein receptors with an identical extracellular domain which binds a spectrum of ligands including bacterial cell wall components. In this study, CLA-1- and CLA-2-stably transfected HeLa and HEK293 cells demonstrated several-fold increases in the uptake of various bacteria over mock-transfected cells. All bacteria tested, including both Gram-negatives (Escherichia coli K12, K1 and Salmonella typhimurium) and Gram-positives (Staphylococcus aureus and Listeria monocytogenes), demonstrated various degrees of lower uptake in control cells. This result is consistent with the presence of high-density lipoprotein-receptor-independent bacterial uptake that is enhanced by CLA-1/CLA-2 overexpression. Bacterial lipopolysaccharides, lipoteichoic acid, and synthetic amphipathic helical peptides (L-37pA and D-37pA) competed with E. coli K12 for CLA-1 and CLA-2 binding. Transmission electron microscopy and confocal microscopy revealed cytosolic accumulation of bacteria in CLA-1/CLA-2-overexpressing HeLa cells. The antibiotic protection assay confirmed that E. coli K12 was able to survive and replicate intracellularly in CLA-1- and CLA-2-overexpressing HeLa, but both L-37pA and D-37pA prevented E. coli K12 invasion. Peritoneal macrophages isolated from SR-BI/BII-knockout mice demonstrated a 30% decrease in bacterial uptake when compared with macrophages from normal mice. Knockout macrophages were also characterized by decreased bacterial cytosolic invasion, ubiquitination, and proteasome mobilization while retaining bacterial lysosomal accumulation. These results indicate that, by facilitating bacterial adhesion and cytosolic invasion, CLA-1 and CLA-2 may play an important role in infection and sepsis.
authors.affiliation: Light Microscopy Core Facility, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Tatyana G
authors.initials: TG
authors.lastname: Vishnyakova
authors.forename: Roger
authors.initials: R
authors.lastname: Kurlander
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Bocharov
authors.forename: Irina N
authors.initials: IN
authors.lastname: Baranova
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Chen
authors.forename: Mones S
authors.initials: MS
authors.lastname: Abu-Asab
authors.forename: Maria
authors.initials: M
authors.lastname: Tsokos
authors.forename: Daniela
authors.initials: D
authors.lastname: Malide
authors.forename: Federica
authors.initials: F
authors.lastname: Basso
authors.forename: Alan
authors.initials: A
authors.lastname: Remaley
authors.forename: Gyorgy
authors.initials: G
authors.lastname: Csako
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Eggerman
authors.forename: Amy P
authors.initials: AP
authors.lastname: Patterson
mesh_terms: D017398:Alternative Splicing; D000818:Animals; D001422:Bacterial Adhesion / Q000502:physiology*; D018955:CD36 Antigens / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D003600:Cytosol / Q000382:microbiology / Q000648:ultrastructure; D048168:Escherichia coli K12 / Q000472:pathogenicity / Q000502:physiology / Q000648:ultrastructure; D006367:HeLa Cells; D006801:Humans; D066298:In Vitro Techniques; D051907:Lysosomal Membrane Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D017737:Macrophages, Peritoneal / Q000382:microbiology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008854:Microscopy, Electron; D051122:Scavenger Receptors, Class B / Q000172:deficiency / Q000235:genetics / Q000502:physiology*
chemical_list: D018955:CD36 Antigens; D051907:Lysosomal Membrane Proteins; C495124:SCARB1 protein, human; C489452:Scarb2 protein, mouse; D051122:Scavenger Receptors, Class B