Nutrient acquisition systems are often crucial for pathogen growth and survival during infection, and represent attractive therapeutic targets. Here, we study the protein machinery required for heme ...uptake in the opportunistic pathogen Acinetobacter baumannii. We show that the hemO locus, which includes a gene encoding the heme-degrading enzyme, is required for high-affinity heme acquisition from hemoglobin and serum albumin. The hemO locus includes a gene coding for a heme scavenger (HphA), which is secreted by a Slam protein. Furthermore, heme uptake is dependent on a TonB-dependent receptor (HphR), which is important for survival and/or dissemination into the vasculature in a mouse model of pulmonary infection. Our results indicate that A. baumannii uses a two-component receptor system for the acquisition of heme from host heme reservoirs.
Iron acquisition systems are crucial for pathogen growth and survival in iron-limiting host environments. To overcome nutritional immunity, bacterial pathogens evolved to use diverse mechanisms to ...acquire iron. Here, we examine a heme acquisition system that utilizes hemophores called hemophilins which are also referred to as HphAs in several Gram-negative bacteria. In this study, we report three new HphA structures from
,
, and
. Structural determination of HphAs revealed an N-terminal clamp-like domain that binds heme and a C-terminal eight-stranded β-barrel domain that shares the same architecture as the Slam-dependent Neisserial surface lipoproteins. The genetic organization of HphAs consists of genes encoding a Slam homolog and a TonB-dependent receptor (TBDR). We investigated the Slam-HphA system in the native organism or the reconstituted system in
cells and found that the efficient secretion of HphA depends on Slam. The TBDR also played an important role in heme uptake and conferred specificity for its cognate HphA. Furthermore, bioinformatic analysis of HphA homologs revealed that HphAs are conserved in the alpha, beta, and gammaproteobacteria. Together, these results show that the Slam-dependent HphA-type hemophores are prevalent in Gram-negative bacteria and further expand the role of Slams in transporting soluble proteins.
This paper describes the structure and function of a family of Slam (Type IX secretion System) secreted hemophores that bacteria use to uptake heme (iron) while establishing an infection. Using structure-based bioinformatics analysis to define the diversity and prevalence of this heme acquisition pathway, we discovered that a large portion of gammaproteobacterial harbors this system. As organisms, including
, utilize this system to facilitate survival during host invasion, the identification of this heme acquisition system in bacteria species is valuable information and may represent a target for antimicrobials.
Lipoproteins decorate the surface of many Gram-negative bacterial pathogens, playing essential roles in immune evasion and nutrient acquisition. In Neisseria spp., the causative agents of gonorrhoea ...and meningococcal meningitis, surface lipoproteins (SLPs) are required for virulence and have been extensively studied as prime candidates for vaccine development. However, the machinery and mechanism that allow for the surface display of SLPs are not known. Here, we describe a transposon (Tn5)-based search for the proteins required to deliver SLPs to the surface of Neisseria meningitidis, revealing a family of proteins that we have named the surface lipoprotein assembly modulator (Slam). N. meningitidis contains two Slam proteins, each exhibiting distinct substrate preferences. The Slam proteins are sufficient to reconstitute SLP transport in laboratory strains of Escherichia coli, which are otherwise unable to efficiently display these lipoproteins on their cell surface. Immunoprecipitation and domain probing experiments suggest that the SLP, TbpB, interacts with Slam during the transit process; furthermore, the membrane domain of Slam is sufficient for selectivity and proper surface display of SLPs. Rather than being a Neisseria-specific factor, our bioinformatic analysis shows that Slam can be found throughout proteobacterial genomes, indicating a conserved but until now unrecognized virulence mechanism.
Netrin-G ligand-3 (NGL-3) is a postsynaptic adhesion molecule known to directly interact with the excitatory postsynaptic scaffolding protein postsynaptic density-95 (PSD-95) and trans-synaptically ...with leukocyte common antigen-related (LAR) family receptor tyrosine phosphatases to regulate presynaptic differentiation. Although NGL-3 has been implicated in the regulation of excitatory synapse development by in vitro studies, whether it regulates synapse development or function, or any other features of brain development and function, is not known. Here, we report that mice lacking NGL-3 (Ngl3-/- mice) show markedly suppressed normal brain development and postnatal survival and growth. A change of the genetic background of mice from pure to hybrid minimized these developmental effects but modestly suppressed N-methyl-D-aspartate (NMDA) receptor (NMDAR)-mediated synaptic transmission in the hippocampus without affecting synapse development, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor (AMPAR)-mediated basal transmission, and presynaptic release. Intriguingly, long-term depression (LTD) was near-completely abolished in Ngl3-/- mice, and the Akt/glycogen synthase kinase 3β (GSK3β) signaling pathway, known to suppress LTD, was abnormally enhanced. In addition, pharmacological inhibition of Akt, but not activation of NMDARs, normalized the suppressed LTD in Ngl3-/- mice, suggesting that Akt hyperactivity suppresses LTD. Ngl3-/- mice displayed several behavioral abnormalities, including hyperactivity, anxiolytic-like behavior, impaired spatial memory, and enhanced seizure susceptibility. Among them, the hyperactivity was rapidly improved by pharmacological NMDAR activation. These results suggest that NGL-3 regulates brain development, Akt/GSK3β signaling, LTD, and locomotive and cognitive behaviors.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Objective
As a component of Endosomal Sorting Complex Required for Transport (ESCRT) complex I, the tumor susceptibility gene 101 (Tsg101) carries out multiple functions. In this work, we report that ...oocyte‐specific deletion of tumor susceptibility gene 101 (Tsg101) leads to age‐dependent oocyte demise in mice.
Materials and Method
Tsg101 floxed mice (Tsg101f/f) were bred with Zp3cre transgenic mice to examine oocyte‐specific roles of Tsg101. Multiple cellular and molecular biological approaches were taken to examine what leads to oocyte demise in the absence of Tsg101.
Results
The death of oocytes from Zp3cre/Tsg101f/f (Tsg101d/d thereafter) mice showed a strong correlation with sexual maturation, as gonadotropin‐releasing hormone antagonist injections improved the survival rate of oocytes from 5‐week‐old Tsg101d/d mice. Maturation of oocytes from prepubertal Tsg101d/d mice proceeded normally, but was largely abnormal in oocytes from peripubertal Tsg101d/d mice, showing shrinkage or rupture. Endolysosomal structures in oocytes from peripubertal Tsg101d/d mice showed abnormalities, with aberrant patterns of early and late endosomal markers and a high accumulation of lysosomes. Dying oocytes showed plasma membrane blebs and leakage. Blockage of endocytosis in oocytes at 4°C prevented cytoplasmic shrinkage of oocytes from Tsg101d/d mice until 9 h. The depletion of tsg‐101 in Caenorhabditis elegans increased the permeability of oocytes and embryos, suggesting a conserved role of Tsg101 in maintaining membrane integrity.
Conclusions
Collectively, Tsg101 plays a dual role in maintaining the integrity of membranous structures, which is influenced by age in mouse oocytes.
Tsg101 deficiency in mouse oocytes leads to a complex phenotype involving the plasma membrane (PM). These oocytes are normal until mice reach five weeks of age when oocytes begin to show PM rupture, PM blebbing, and cytoplasmic shrinkage. PM blebbing and cytoplasmic shrinkage can be postponed with a general endocytosis block, but death ensues. In both mouse and in Caenorhabditis elegans, Tsg101 plays a crucial role in maintaining the integrity of PM.
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