title: Autophagosomes induced by a bacterial Beclin 1 binding protein facilitate obligatory intracellular infection.
abstract: Autophagy, a cytoplasmic catabolic process, plays a critical role in defense against intracellular infection. In turn, evasion or inhibition of autophagy has emerged as an important virulence factor for intracellular pathogens. However, Anaplasma phagocytophilum, the obligatory intracellular bacterium that causes human granulocytic anaplasmosis, replicates in the membrane-bound compartment resembling early autophagosome. Here, we found that Anaplasma translocated substrate 1 (Ats-1), a type IV secretion effector, binds Beclin 1, a subunit of the class III PI3K and Atg14L, and it nucleates autophagosomes with markers of omegasomes, double FYVE-containing protein 1, Atg14L, and LC3. Ats-1 autophagy induction did not activate the starvation signaling pathway of mammalian target of rapamycin. These autophagy proteins were also localized to the Anaplasma inclusion. Ectopically expressed Ats-1 targeted the Anaplasma inclusions and enhanced infection, whereas host cytoplasmic delivery of anti-Ats-1 or Beclin 1 depletion by siRNA suppressed the infection; beclin 1 heterozygous-deficient mice were resistant to Anaplasma infection. Furthermore, Anaplasma growth arrest by the class III PI3K inhibitor 3-methyladenine was alleviated by essential amino acid supplementation. Thus, Anaplasma actively induces autophagy by secreting Ats-1 that hijacks the Beclin 1-Atg14L autophagy initiation pathway likely to acquire host nutrients for its growth.
authors.affiliation: Department of Veterinary Biosciences, Ohio State University, Columbus, OH 43210, USA.
authors.forename: Hua
authors.initials: H
authors.lastname: Niu
authors.forename: Qingming
authors.initials: Q
authors.lastname: Xiong
authors.forename: Akitsugu
authors.initials: A
authors.lastname: Yamamoto
authors.forename: Mitsuko
authors.initials: M
authors.lastname: Hayashi-Nishino
authors.forename: Yasuko
authors.initials: Y
authors.lastname: Rikihisa
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000737:chemistry* / Q000378:metabolism; D041081:Anaplasma phagocytophilum / Q000378:metabolism; D051017:Apoptosis Regulatory Proteins / Q000737:chemistry* / Q000378:metabolism; D001343:Autophagy; D000071183:Autophagy-Related Proteins; D000071186:Beclin-1; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D057809:HEK293 Cells; D018922:HL-60 Cells; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism; D008856:Microscopy, Fluorescence / Q000379:methods; D008928:Mitochondria / Q000378:metabolism; D008954:Models, Biological; D011485:Protein Binding; D034741:RNA, Small Interfering / Q000378:metabolism; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism
chemical_list: C539000:ATG14 protein, human; D033942:Adaptor Proteins, Vesicular Transport; D051017:Apoptosis Regulatory Proteins; D000071183:Autophagy-Related Proteins; C491997:BECN1 protein, human; D000071186:Beclin-1; D008565:Membrane Proteins; D034741:RNA, Small Interfering; D049452:Green Fluorescent Proteins; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases