Wbm0152, an outer membrane lipoprotein of the Wolbachia endosymbiont of Brugia malayi, inhibits yeast ESCRT complex activity

Abstract

Human pathogenic filarial nematodes of the family Onchocercidae, including Brugia malayi and Onchocerca volvulus, cause debilitating filarial diseases such as lymphatic filariasis and river blindness. These mosquito-borne pathogens are obligately colonized by the gram-negative intracellular alphaproteobacterium, Wolbachia pipientis, which is essential for nematode sexual reproduction, long-term survival, and pathogenicity in the mammalian host. Like many intracellular bacteria, Wolbachia likely uses numerous surface-exposed and secreted effector proteins to regulate its ability to persist and replicate within nematode host cells. However, due to the inability to cultivate Wolbachia in the laboratory and the genetic intractability of both filarial nematodes and the bacterium, the molecular underpinnings that define the bacterium:nematode relationship are almost completely unknown. In this work, we show that the expression of a Wolbachia outer membrane lipoprotein, wBm0152, in Saccharomyces cerevisiae inhibits the activity of the conserved Endosomal Sorting Complex Required for Transport (ESCRT) complex and strongly disrupts endosomal maturation, leading to defects in ubiquitylated protein turnover. Using in vivo bimolecular fluorescence complementation, we find that Wbm0152 interacts with the Vps2p subunit of the ESCRT-III subcomplex as well as the Vps2p ortholog (BmVps2, Bm6583b) from a Wolbachia host nematode, Brugia malayi. These data suggest a novel role of ESCRT in Wolbachia persistence providing insight into the elusive relationship between these two organisms. AUTHOR SUMMARYFilarial diseases of mammals, including lymphatic filariasis and canine heartworm, are caused by vector-borne filarial nematodes of the family Onchocercidae. Many of the nematodes in this family are obligately colonized by an intracellular bacterium, Wolbachia pipientis, which is essential for the nematodes long-term survival, reproduction, and pathogenicity. Therefore, understanding the mechanisms used by Wolbachia to persist and replicate within host cells could provide new molecular targets for treating filarial infections. Due to the genetic intractability of both nematode and bacterium, however, significant progress on characterizing these interactions have proven difficult. In this work, we show that a predicted outer membrane lipoprotein, Wbm0152, of the Wolbachia endosymbiont of Brugia malayi inhibits yeast Endosomal Sorting Complex Required for Transport (ESCRT) complex activity in vivo. Wbm0152 interacts with a core subunit of the yeast ESCRT-III complex, as well as with the orthologous ESCRT-III protein from Brugia. ESCRTs are conserved across eukaryotes and are important for diverse cellular processes such as endosomal maturation, autophagy, and cellular division. As Wolbachia persists within a membrane-bound compartment within Brugia and must avoid host autophagic pathways, this study presents a potential mechanism by which Wolbachia may regulate Brugia membrane trafficking pathways to ensure its intracellular survival.