Hebert Kathryn S, Seidman David, Oki Aminat T, Izac Jerilyn, Emani Sarvani, Oliver Lee D, Miller Daniel P, Tegels Brittney K, Kannagi Reiji, Marconi Richard T, Carlyon Jason A
Department of Microbiology and Immunology, Virginia Commonwealth University Medical Center, School of Medicine, Richmond, Virginia, USA.
Research Complex for Medical Frontiers, Aichi Medical University, Yazako, Nagakute, Japan.
Infect Immun. 2017 Feb 23;85(3). doi: 10.1128/IAI.00968-16. Print 2017 Mar.
causes bovine anaplasmosis, a debilitating and potentially fatal tick-borne infection of cattle. Because is an obligate intracellular organism, its adhesins that mediate entry into host cells are essential for survival. Here, we demonstrate that outer membrane protein A (AmOmpA; AM854) contributes to the invasion of mammalian and tick host cells. AmOmpA exhibits predicted structural homology to OmpA of (ApOmpA), an adhesin that uses key lysine and glycine residues to interact with α2,3-sialylated and α1,3-fucosylated glycan receptors, including 6-sulfo-sialyl Lewis x (6-sulfo-sLe). Antisera against AmOmpA or its predicted binding domain inhibits infection of host cells. Residues G55 and K58 are contributory, and K59 is essential for recombinant AmOmpA to bind to host cells. Enzymatic removal of α2,3-sialic acid and α1,3-fucose residues from host cell surfaces makes them less supportive of AmOmpA binding. AmOmpA is both an adhesin and an invasin, as coating inert beads with it confers adhesiveness and invasiveness. Recombinant forms of AmOmpA and ApOmpA competitively antagonize infection of host cells, but a monoclonal antibody against 6-sulfo-sLe fails to inhibit AmOmpA adhesion and infection. Thus, the two OmpA proteins bind related but structurally distinct receptors. This study provides a detailed understanding of AmOmpA function, identifies its essential residues that can be targeted by blocking antibody to reduce infection, and determines that it binds to one or more α2,3-sialylated and α1,3-fucosylated glycan receptors that are unique from those targeted by ApOmpA.
引起牛无浆体病，这是一种使牛衰弱并可能致命的蜱传播感染。由于 是一种专性细胞内生物，其介导进入宿主细胞的黏附素对其生存至关重要。在此，我们证明 外膜蛋白A（AmOmpA；AM854）有助于入侵哺乳动物和蜱宿主细胞。AmOmpA与 的OmpA（ApOmpA）表现出预测的结构同源性，ApOmpA是一种黏附素，利用关键的赖氨酸和甘氨酸残基与α2,3 - 唾液酸化和α1,3 - 岩藻糖基化聚糖受体相互作用，包括6 - 磺基 - 唾液酸化路易斯x（6 - 磺基 - sLe）。针对AmOmpA或其预测的结合域的抗血清抑制宿主细胞的 感染。残基G55和K58有作用，而K59对于重组AmOmpA结合宿主细胞至关重要。从宿主细胞表面酶促去除α2,3 - 唾液酸和α1,3 - 岩藻糖残基会使其对AmOmpA结合的支持性降低。AmOmpA既是黏附素又是侵袭素，因为用它包被惰性珠子会赋予其黏附性和侵袭性。重组形式的AmOmpA和ApOmpA竞争性拮抗宿主细胞的 感染，但针对6 - 磺基 - sLe的单克隆抗体未能抑制AmOmpA黏附及 感染。因此，这两种OmpA蛋白结合相关但结构不同的受体。本研究详细了解了AmOmpA的功能，确定了其可被阻断抗体靶向以减少感染的关键残基，并确定它与一种或多种α2,3 - 唾液酸化和α1,3 - 岩藻糖基化聚糖受体结合，这些受体与ApOmpA靶向的受体不同。
