title: Rickettsia parkeri invasion of diverse host cells involves an Arp2/3 complex, WAVE complex and Rho-family GTPase-dependent pathway.
abstract: Rickettsiae are obligate intracellular pathogens that are transmitted to humans by arthropod vectors and cause diseases such as spotted fever and typhus. Although rickettsiae require the host cell actin cytoskeleton for invasion, the cytoskeletal proteins that mediate this process have not been completely described. To identify the host factors important during cell invasion by Rickettsia parkeri, a member of the spotted fever group (SFG), we performed an RNAi screen targeting 105 proteins in Drosophila melanogaster S2R+ cells. The screen identified 21 core proteins important for invasion, including the GTPases Rac1 and Rac2, the WAVE nucleation-promoting factor complex and the Arp2/3 complex. In mammalian cells, including endothelial cells, the natural targets of R. parkeri, the Arp2/3 complex was also crucial for invasion, while requirements for WAVE2 as well as Rho GTPases depended on the particular cell type. We propose that R. parkeri invades S2R+ arthropod cells through a primary pathway leading to actin nucleation, whereas invasion of mammalian endothelial cells occurs via redundant pathways that converge on the host Arp2/3 complex. Our results reveal a key role for the WAVE and Arp2/3 complexes, as well as a higher degree of variation than previously appreciated in actin nucleation pathways activated during Rickettsia invasion.
authors.affiliation: Microbiology Graduate Group, University of California, Berkeley, CA 94720, USA.
authors.forename: Shawna C O
authors.initials: SC
authors.lastname: Reed
authors.forename: Alisa W
authors.initials: AW
authors.lastname: Serio
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Welch
mesh_terms: D008841:Actin Cytoskeleton / Q000235:genetics / Q000378:metabolism; D051376:Actin-Related Protein 2-3 Complex / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D019556:COS Cells; D002460:Cell Line; D002522:Chlorocebus aethiops; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000166:cytology / Q000378:metabolism / Q000382:microbiology*; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism / Q000382:microbiology; D005455:Fluorescent Antibody Technique; D054884:Host-Pathogen Interactions; D006801:Humans; D051379:Mice; D050296:Microbial Viability; D010957:Plasmids / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D012281:Rickettsia / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D012282:Rickettsia Infections / Q000382:microbiology; D015398:Signal Transduction; D014162:Transfection; D014709:Vero Cells; D051300:Wiskott-Aldrich Syndrome Protein Family / Q000235:genetics / Q000378:metabolism*; D020744:rac GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D051376:Actin-Related Protein 2-3 Complex; D001426:Bacterial Proteins; D029721:Drosophila Proteins; C090146:Rac1 protein, Drosophila; D051300:Wiskott-Aldrich Syndrome Protein Family; D020744:rac GTP-Binding Proteins