Interaction of a Wolbachia WSP-like protein with a nuclear-encoded protein of Brugia malayi

Abstract

The Brugia malayi endosymbiont Wolbachia has recently been shown to be essential for its host’s survival and development. However, relatively little is known about Wolbachia proteins that interact with the filarial host and which might be important in maintaining the obligate symbiotic relationship. The Wolbachia surface proteins (WSPs) are members of the outer membrane protein family and we hypothesize that they might be involved in the Wolbachia-Brugia symbiotic relationship. Notably, immunolocalization studies of two WSP members, WSP-0432 and WSP-0284 in B. malayi female adult worms showed that the corresponding proteins are not only present on the surface of Wolbachia but also in the host tissues, with WSP-0284 more abundant in the cuticle, hypodermis and the nuclei within the embryos. These results confirmed that WSPs might be secreted by Wolbachia into the worm’s tissue. Our present studies focus on the potential involvement of WSP-0284 in the symbiotic relationship of Wolbachia with its filarial host. We show that WSP-0284 binds specifically to B. malayi crude protein extracts. Furthermore, a fragment of the hypothetical B. malayi protein (Bm1_46455) was found to bind WSP-0284 by panning of a B. malayi cDNA library. The interaction of WSP-0284 and this protein was further confirmed by ELISA and pull-down assays. Localization by immunoelectron microscopy within Wolbachia cells as well as in the worm’s tissues, cuticle and nuclei within embryos established that both proteins are present in similar locations within the parasite and the bacteria. Identifying such specific interactions between B. malayi and Wolbachia proteins should lead to a better understanding of the molecular basis of the filarial nematode and Wolbachia symbiosis.

Comparative Analysis of the Secretome from a Model Filarial Nematode (Litomosoides sigmodontis) Reveals Maximal Diversity in Gravid Female Parasites

“…GroEL, as a chaperonin, would be expected to be confined to the cytosol, although GroEL homologs have been reported to "moonlight" on the surface of some bacterial species (103). We also detected Wolbachia surface protein by surface labeling of adult L. sigmodontis, as has been reported in B. malayi (102). This protein is a putative ligand of Toll-like receptors 2 and 4 (100), and our finding supports the hypothesis that Wolbachia modifies and perhaps misdirects the immune response to filariae (104).…”

“…It has been proposed that Wolbachia may be present in uterine fluid (99), inside degenerating embryos (100), or may exit via the secretory pore (101). Additionally, they apparently secrete proteins into structures that lack bacterial cells, such as the cuticle (102). Wolbachia-derived proteins were present in very low amounts in B. malayi secreted products (17).…”

Wolbachia endosymbionts and human disease control

“…About 2/3 of both the predicted B. malayi and Wolbachia proteomes appear to be made, including about half of those genes annotated as hypothetical [6]. Using data compiled from several filarial nematodes, the free living nematode C. elegans and the Wolbachia proteome, predictions can be made for potential protein-protein interactors which might be involved in the symbiotic relationship [5,49]. For example, Wolbachia wsp (Wolbachia surface protein) is one of the highly expressed transcripts and proteins.…”

“…For example, Wolbachia wsp (Wolbachia surface protein) is one of the highly expressed transcripts and proteins. With the hypothesis that outer membrane might interact with nematode, it was used as a bait in pull down, ELISA and panning experiments against B. malayi protein extracts [5]. One hypothetical Brugia protein was identified as the first example of a Brugia-Wolbachia interacting protein pair.…”

Nematode-Bacterium Symbioses—Cooperation and Conflict Revealed in the “Omics” Age

“…This study did not include the Wolbachia proteome with the Brugia dataset but prediction of the Wolbachia - Brugia interactome is highly warranted given their likely physiological integration. Based on the hypothesis that outer membrane proteins such as Wolbachia surface protein (WSP) might interact with nematode proteins, WSP was used to bind B. malayi protein extracts, for panning a Brugia cDNA library and for ELISA and pull-down assays (Melnikow et al , 2011). One Brugia protein annotated as hypothetical was identified by all approaches and provides the first example of a Brugia - Wolbachia interacting protein pair.…”