Biology subjects

Starai, V. J.

Publications and source records attributed to Starai, V. J..

5 recordsLinked to original sources

bioRxiv2025

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

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.

microbiology↗

bioRxiv2022

Helicobacter pylori FlgV forms a flagellar motor ring structure required for optimal motility

The bacterium Helicobacter pylori has a large flagellar motor that generates significantly higher torque than the archetypical Escherichia coli motor. To understand how H. pylori navigates the viscous environment of the stomach, it is essential to establish how specific motor components contribute to efficient motility. We show here that the protein FlgV, required for motility in Campylobacter jejuni, forms a novel ring associated with the MS and C rings in H. pylori. Deletion of flgV from H. pylori B128 or a highly motile variant of H. pylori G27 (G27M) resulted in reduced motility in soft agar medium. Based on comparative analyses of in-situ flagellar motor structures of H. pylori wild-type and {Delta}flgV mutants, the reduced motility of the {Delta}flgV mutants and the location of the FlgV ring suggest it stabilizes interactions between the MS and C rings and/or plays a role in switching the direction of flagellar rotation. Overall, these results identify a novel motor accessory likely adapted to promote flagellar function for bacterial colonization of high-load environments such as the gastric mucosa.

microbiology↗

bioRxiv2022

Wbm0076, a candidate effector protein of the Wolbachia endosymbiont of Brugia malayi, disrupts eukaryotic actin dynamics

Brugia malayi, a parasitic roundworm of humans, is colonized by the obligate intracellular bacterium, Wolbachia pipientis. The symbiosis between this nematode and bacterium is essential for nematode reproduction and long-term survival in a human host. Therefore, identifying molecular mechanisms required by Wolbachia to persist in and colonize B. malayi tissues will provide new essential information regarding the basic biology of this endosymbiosis. Wolbachia utilize a Type IV secretion system to translocate so-called "effector" proteins into the cytosol of B. malayi cells to promote colonization of the eukaryotic host. However, the characterization of these Wolbachia secreted proteins (wSPs) has remained elusive due to the genetic intractability of both organisms. Strikingly, expression of the wSP, Wbm0076, in the surrogate eukaryotic cell model, Saccharomyces cerevisiae, resulted in the disruption of the yeast actin cytoskeleton and inhibition of endocytosis. Genetic analyses show that Wbm0076 is a member of the family of Wiskott-Aldrich syndrome proteins (WAS[p]), a well-conserved eukaryotic protein family required for the organization of actin skeletal structures. Thus, Wbm0076 likely plays a central role in the active cell-to-cell movement of Wolbachia throughout B. malayi tissues during nematode development. As most Wolbachia isolates sequenced to date encode at least partial orthologs of Wbm0076, we find it likely that the ability of Wolbachia to directly manipulate host actin dynamics is an essential requirement of all Wolbachia endosymbioses, independent of host cell species. AUTHOR SUMMARYFilarial nematodes of the family Onchocercidae cause several debilitating human diseases such as lymphatic filariasis and onchocerciasis; more than 50 million people are infected by these arthropod-borne roundworms in mostly tropical and sub-tropical regions. Many of these nematodes, including Brugia malayi, are obligately colonized by an intracellular bacterium of the genus Wolbachia, which is absolutely required for the proper development and reproduction of these worms in a mammalian host. Clearance of Wolbachia from these nematodes leads to a loss of both worm viability and its ability to cause disease in humans. Efforts to understand the molecular interactions required to maintain this important bacterium:nematode endosymbiosis, however, have been hampered due to the genetic intractability of these organisms. In this work, we utilize yeast as a surrogate eukaryotic cell to show that a candidate secreted effector protein from Wolbachia, Wbm0076, disrupts actin dynamics and endocytosis. We also observe interactions of Wbm0076 with a highly-conserved eukaryotic actin regulatory protein. As some intracellular bacteria manipulate host actin dynamics to promote mobility within or into host cells, our study provides evidence of an important Wolbachia protein activity that may be essential for its proper localization during the development of B. malayi.

microbiology↗

bioRxiv2020

Legionella pneumophila LegC7 effector protein drives aberrant ER:endosome fusion in yeast

Legionella pneumophila is a facultative intracellular bacterial pathogen, causing the severe form of pneumonia known as Legionnaires disease. Legionella actively alters host organelle trafficking through the activities of effector proteins secreted via a TypeIVB secretion system, in order to construct the bacteria-laden Legionella-containing vacuole (LCV) and prevent lysosomal degradation. The LCV is derived from membrane derived from host ER, secretory vesicles, and phagosomes, although the precise molecular mechanisms that drive its synthesis remain poorly understood. In an effort to characterize the in vivo activity of the LegC7/YlfA SNARE-like effector protein from Legionella in the context of eukaryotic membrane trafficking in yeast, we find that LegC7 interacts with the Emp46p/Emp47p ER-to-Golgi glycoprotein cargo adapter complex, alters ER morphology, and induces aberrant ER:endosome fusion, as measured by visualization of ER cargo degradation, reconstitution of split-GFP proteins, and enhanced oxidation of the ER lumen. LegC7-dependent toxicity, disruption of ER morphology, and ER:endosome fusion events were dependent upon endosomal VPS class C tethering complexes and the endosomal t-SNARE, Pep12p. This work establishes a model in which LegC7 functions to recruit host ER material to the bacterial phagosome during infection by inducing membrane fusion, potentially through interaction with host membrane tethering complexes and/or cargo adapters.

microbiology↗

bioRxiv2019

The Toxoplasma Vacuolar H+-ATPase regulates intracellular pH, and impacts the maturation of essential secretory proteins

Vacuolar-proton ATPases (V-H+-ATPases) are conserved complexes that couple the hydrolysis of ATP to the pumping of protons across membranes. V-H+-ATPases are known to play diverse roles in cellular physiology. We studied the Toxoplasma gondii V-H+-ATPase complex and discovered a novel dual role of the pump in protecting parasites against ionic stress and in the maturation of secretory proteins in endosomal-like compartments. Toxoplasma V-H+-ATPase subunits localize to the plasma membrane and to acidic vesicles and characterization of conditional mutants of the a1 subunit highlighted the functionality of the complex at both locations. Microneme and rhoptry proteins are required for invasion and modulation of host cells and they traffic via endosome-like compartments in which proteolytic maturation occurs. We show that the V-H+-ATPase supports the maturation of rhoptry and microneme proteins, and their maturases, during their traffic to their corresponding organelles. This work underscores a novel role for V-H+-ATPases in regulating virulence pathways.

microbiology↗