Biology subjects

Guan, Z.

Publications and source records attributed to Guan, Z..

At least 37 records · Page 2Linked to original sources

bioRxiv2024

TamL is a key player of the outer membrane homeostasis in Bacteroidetes.

In Proteobacteria, the outer membrane protein TamA and the inner membrane-anchored protein TamB form the Translocation and Assembly Module (TAM) complex, which facilitates the transport of autotransporters, virulence factors, and likely lipids across the two membranes. In Bacteroidetes TamA is replaced by TamL, a TamA-like lipoprotein with a lipid modification at its N-terminus that likely anchors it to the outer membrane. This structural difference suggests that TamL may have a distinct function compared to TamA. However, the role of TAM in bacterial phyla other than Proteobacteria remains unexplored. Our study aimed to elucidate the functional importance of TamL in Flavobacterium johnsoniae, an environmental Bacteroidetes. Unlike its homologues in Proteobacteria, we found that TamL and TamB are essential in F. johnsoniae. Through genetic, phenotypic, proteomic, and lipidomic analyses, we discovered that TamL depletion severely compromises outer membrane integrity, as evidenced by reduced cell viability, altered cell shape, increased susceptibility to membrane-disrupting agents, and elevated levels of outer membrane lipoproteins. Notably, we did not observe any impact on outer membrane lipid composition. Via pull-down protein assays, we confirmed that TamL interacts with TamB in F. johnsoniae, likely forming the TAM complex. Furthermore, our in silico analysis revealed that the presence of TamL and TamB monocistronic genes is a shared genetic feature among Bacteroidetes members, including the human pathogen Capnocytophaga canimorsus where we also confirmed the essentiality of the TamL and TamB homologs. To our knowledge, this study is the first to provide functional insights into a TAM subunit beyond Proteobacteria. SignificanceIn Proteobacteria, the outer membrane (OM) protein TamA forms with the inner membrane (IM)-anchored protein TamB the Translocation and Assembly Module Complex (TAM). which contributes to efficient biogenesis of the OM. In Bacteroidetes TamA is replaced by TamL, a TamA-like lipoprotein of unknown role. In this work, we studied TamL in the Bacteroidetes Flavobacterium johnsoniae. We found that TamL and TamB are essential for cell viability, and that TamL depletion disrupts outer membrane stability, increases outer membrane vesicle size, and lead to higher sensitivity to OM stressors. These findings highlight TamL critical role in maintaining OM structure in Bacteroidetes. To our surprise, we also identified multiple TamL, TamB and TamA homologs in Bacteroidetes. Altogether, our findings extend the current knowledge on TAM and provide novel insights into a field of research barely investigated outside Proteobacteria.

microbiology↗

bioRxiv2024

Biosynthesis of glucosaminyl phosphatidylglycerol in Pseudomonas aeruginosa

Glucosaminyl phosphatidylglycerol (GlcN-PG) was first identified in bacteria in the 1960s and was recently reported in Pseudomonas aeruginosa. Despite the important implications in altering membrane charge (by the modification of anionic PG with cationic glucosamine), the biosynthesis and functions of GlcN-PG have remained uncharacterized. Using bioinformatic and lipidomic analysis, we identified a 3-gene predicted operon, renamed as gpgSDF, that is responsible for the biosynthesis and potential transport of GlcN-PG in P. aeruginosa: gpgS encodes a novel glycotransferase that is responsible for the modification of phosphatidylglycerol (PG) with N-acetylglucosamine (GlcNAc) to produce GlcNAc-PG, and gpgD encodes a novel deacetylase that removes the acetyl group from GlcNAc-PG to produce GlcN-PG. The third gene, gpgF, is predicted to encode a flippase whose activity remains to be experimentally verified. A P. aeruginosa gpgD transposon mutant accumulates GlcNAc-PG and lacks GlcN-PG, and as expected, the complementation of gpgD restores the production of GlcN-PG. Moreover, the heterologous expression of gpgSDF in Escherichia coli resulted in production of both GlcNAc-PG and GlcN-PG. The identification of the biosynthetic genes of GlcN-PG paves the way for the investigation of its biological and pathological functions, which has significant implications in our understanding of the unique membrane physiology, pathogenesis and antimicrobial resistance of P. aeruginosa. ImportanceThe identification of the biosynthetic genes of GlcN-PG paves the way for the investigation of its biological and pathological functions, which has significant implications in our understanding of the unique membrane physiology, pathogenesis and antimicrobial resistance of P. aeruginosa.

microbiology↗

bioRxiv2024

Structure and inhibition mechanisms of Mycobacterium tuberculosis essential transporterefflux protein A

A broad chemical genetics screen in Mycobacterium tuberculosis (Mtb) to identify inhibitors of established or previously untapped targets for therapeutic development yielded compounds (BRD-8000.3 and BRD-9327) that inhibit the essential efflux pump EfpA. To understand the mechanisms of inhibition by these compounds, we determined the structures of EfpA with inhibitors bound at 2.7 -3.4 [A] resolution. Our structures reveal different mechanisms of inhibition for the two inhibitors. BRD-8000.3 binds in a tunnel making contact with the lipid bilayer and extending toward the central cavity to displace the fatty acid chain of a lipid molecule bound in the apo structure, suggesting its blocking of an access route for a natural lipidic substrate, in contrast to its uncompetitive mechanism for the small molecule substrate ethidium bromide which likely enters through an alternative tunnel. Meanwhile, BRD-9327 binds in the outer vestibule without complete blockade of the substrate path to the outside, suggesting its possible inhibition of the dynamical motion necessary for "alternate access" to the two different sides of the membrane, as is characteristic of major facilitator superfamily (MFS) transporters. Both inhibitors may have a role in inhibiting the "alternate access" mechanism that could account for the uncompetitive nature of their efflux of some substrates. Our results explain the basis of the synergy of these inhibitors and their potential for combination in a multi drug strategy for anti-tuberculosis therapy. They also potentially point to a possible function for this essential efflux pump as a lipid transporter. The structures provide a foundation for rational modification of these inhibitors to increase potency.

biochemistry↗

bioRxiv2024

Dynamin 1-mediated endocytic recycling of glycosylated N-cadherin sustains the plastic mesenchymal state to promote ovarian cancer metastasis

Epithelial-to-mesenchymal transition (EMT) is a key process that confers metastatic plasticity to ovarian cancer cells, enabling them to disseminate aggressively throughout the peritoneal cavity and contributing to poor clinical outcomes for patients. However, a pharmacologically exploitable driver of EMT in ovarian cancer has yet to be identified. To address this, we utilized a master regulators algorithm to prioritize EMT regulators from a dataset of over 8,000 patient samples, including multidimensional omics data from more than 20 cancer types in TCGA. Further analysis identified dynamin-1 (DNM1), an endocytic regulator, as a novel master regulator of EMT in ovarian cancer. Clinically, DNM1 overexpression was found to be associated with the mesenchymal subtype and advanced/metastatic stages of ovarian carcinomas. Molecular assays revealed that DNM1 upregulates N-cadherin, a hallmark mesenchymal marker, by promoting its endocytosis and recycling, thereby inducing cell polarization and motility. In addition, integration of ATAC-seq and RNA-seq analyses uncovered the repression of beta-1,3-galactosyltransferase (B3GALT1), a glycosyltransferase, in metastatic cells. B3GALT1-mediated glycosylation hindered the recycling of N-cadherin. Functional studies demonstrated that depletion of DNM1 or pharmacological inhibition of endocytic recycling significantly impaired cell polarity, migration, and also cancer stemness. Importantly, in vivo experiments showed that the loss of DNM1 significantly suppressed peritoneal metastatic colonization. Interestingly, metastatic cells with elevated DNM1-mediated endocytosis showed increased susceptibility to nanoparticle delivery. Collectively, these results establish the DNM1-N-cadherin axis as an important regulator of EMT-associated ovarian cancer metastasis and suggest its potential as a biomarker for targeted nanodrug therapy.

cancer biology↗

bioRxiv2024

Apoptotic caspases cleave DRP1 to promote mitochondrial fusion and anti-viral immune responses

Apoptosis has been recognized as a suicidal host-defense programmed cell death pathway against invading pathogens. However, recent evidences showed that viruses can employ caspases to cleave and inactivate immune signaling molecules to facilitate infection. Whether caspases can instead promote anti-viral immune responses is currently unknown. Here, we demonstrated that the NSs protein of RVFV triggers activation of apoptotic caspases, which cleave the mitochondrial fission factor DRP1 resulting in mitochondrial elongation. Elongated mitochondria promote MAVS aggregation leading to enhanced anti-viral immunity. Apoptotic caspases, including caspase-3, -6, -7 and -8, cleave DRP1 at the motifs of D500FAD503 and/or AEAD556, suggesting that this cleavage event may occur during infection of different viruses. Indeed, infection of H1N1, SeV and HSV-1 all triggered apoptotic caspases activation to cleave DRP1 promoting anti-viral immune responses. Compared with wild-type DRP1, introduction of caspase-resistant DRP1 strongly attenuated immune responses triggered by virus infection. These results revealed a mechanism through which apoptotic caspases promote anti-viral immunity by regulating mitochondrial morphodynamics.

microbiology↗

bioRxiv2024

Monocyte-derived fibrocytes contribute to nucleus pulposus fibrosis and intervertebral disc degeneration

Fibrotic remodeling of nucleus pulposus (NP) leads to structural and mechanical anomalies of intervertebral discs that prone to degeneration, leading to low back pain incidence and disability. Emergence of fibroblastic cells in disc degeneration has been reported, yet their nature and origin remain elusive. In this study, we performed an integrative analysis of multiple single-cell RNA sequencing datasets to interrogate the cellular heterogeneity and fibroblast-like entities in degenerative human NP specimens. We found that disc degeneration severity is associated with an enrichment of fibrocyte-like phenotype, characterized by CD45 and collagen I dual positivity, and expression of myofibroblast marker -smooth muscle actin. Refined clustering and classification distinguished the fibrocyte-like populations as subtypes in the NP cells - and immunocytes-clusters, expressing disc degeneration markers HTRA1 and ANGPTL4 and genes related to response to TGF-{beta}. In injury-induced mouse disc degeneration model, fibrocyte-like cells were found recruited into the NP undergoing fibrosis and adopted a myofibroblast phenotype. Depleting the fibrocyte-like cells in CD11b-DTR mice in which monocytic lineages were ablated by diphtheria toxin could markedly attenuate fibrous modeling and myofibroblast formation in the NP of the degenerative discs, and prevent disc height loss and histomorphological abnormalities. Marker analysis supports that disc degeneration progression is dependent on a function of CD45+COL1A1+ and SMA+ cells. Our findings reveal that fibrocyte-like cells play a pivotal role in NP fibrosis and may therefore be a target for modifying disc degeneration and promoting its repair.

physiology↗

bioRxiv2023

Lipid discovery enabled by sequence statistics and machine learning

Bacterial membranes are complex and dynamic, arising from an array of evolutionary pressures. One enzyme that alters membrane compositions through covalent lipid modification is MprF. We recently identified that Streptococcus agalactiae MprF synthesizes lysyl-phosphatidylglycerol (Lys-PG) from anionic PG, and a novel cationic lipid, lysyl-glucosyl-diacylglycerol (Lys-Glc-DAG), from neutral glycolipid Glc-DAG. This unexpected result prompted us to investigate whether Lys-Glc-DAG occurs in other MprF-containing bacteria, and whether other novel MprF products exist. Here, we studied protein sequence features determining MprF substrate specificity. First, pairwise analyses identified several streptococ-cal MprFs synthesizing Lys-Glc-DAG. Second, a restricted Boltzmann machine-guided approach led us to discover an entirely new substrate for MprF in Enterococcus, diglucosyl-diacylglycerol (Glc2-DAG), and an expanded set of organisms that modify glycolipid substrates using MprF. Overall, we combined the wealth of available sequence data with machine learning to model evolutionary constraints on MprF sequences across the bacterial domain, thereby identifying a novel cationic lipid.

microbiology↗

bioRxiv2023

Pneumonic plague protection induced by a monophosphoryl lipid A decorated Yersinia outer-membrane-vesicle vaccine

A newly constructed Yersinia pseudotuberculosis mutant (YptbS46) carrying the lpxE insertion and pmrF-J deletion exclusively synthesized an adjuvant form of lipid A, monophosphoryl lipid A (MPLA). Outer membrane vesicles (OMVs) isolated from YptbS46 harboring an lcrV expression plasmid, pSMV13, were designated OMV46-LcrV, which contained MPLA and high amounts of LcrV and displayed low activation of Toll-like receptor 4 (TLR4). Similar to the previous OMV44-LcrV, intramuscular prime-boost immunization with 30 {micro}g of OMV46-LcrV exhibited substantially reduced reactogenicity and conferred complete protection to mice against a high-dose of respiratory Y. pestis challenge. OMV46-LcrV immunization induced robust adaptive responses in both lung mucosal and systemic compartments and orchestrated innate immunity in the lung, which were correlated with rapid bacterial clearance and unremarkable lung damage during Y. pestis challenge. Additionally, OMV46-LcrV immunization conferred long-term protection. Moreover, immunization with reduced doses of OMV46-LcrV exhibited further lower reactogenicity and still provided great protection against pneumonic plague. Our studies strongly demonstrate the feasibility of OMV46-LcrV as a new type of plague vaccine candidate.

immunology↗

bioRxiv2023

Defense mechanism of a bacterial retron supramolecular assembly

Retrons are a class of multigene antiphage defense system typically consisting of a retron reverse transcriptase, a non-coding RNA, and a cognate effector. Although the triggers for several retron systems have been discovered recently, the full picture of how retron systems sense invading phages and mediate defense remains to be elucidated. Here, we focus on the retron Ec86 defense system and report its modes of activation and action. We identified a phage-encoded DNA cytosine methyltransferase (Dcm) as the trigger of the Ec86 system and show that Ec86 senses msDNA methylation and becomes activated. We further determined the structure of a tripartite retron Ec86 supramolecular assembly, which is primed for activation by Dcm, and demonstrated that the activated system confers defense through depletion of nucleoside derivatives. These findings emphasize the role of retrons being a second line of defense and highlight an emerging theme of anti-phage defense through supramolecular complex assemblies.

microbiology↗

bioRxiv2023

Stochastic RNA editing of the Complexin C-terminus within single neurons regulates neurotransmitter release

Neurotransmitter release requires assembly of the SNARE complex fusion machinery, with multiple SNARE-binding proteins regulating this process to control when and where synaptic vesicle fusion occurs. Complexin (Cpx) controls spontaneous and evoked neurotransmitter release by modulating SNARE complex zippering. Although the central SNARE-binding helix is essential, post-translational modifications to Cpxs C-terminal membrane-binding amphipathic helix modulate its activity. Here we demonstrate that RNA editing of the Cpx C-terminus regulates its ability to clamp SNARE-mediated fusion and alters presynaptic output. RNA editing of Cpx within single neurons is stochastic, generating up to eight edit variants that fine-tune neurotransmitter release by changing the subcellular localization and clamping properties of the protein. Similar editing rules for other synaptic genes were observed, indicating stochastic editing at single adenosines and across multiple mRNAs can generate unique synaptic proteomes within the same population of neurons to fine-tune presynaptic output.

neuroscience↗

bioRxiv2023

Characterization of an evolutionarily distinct bacterial ceramide kinase from Caulobacter crescentus

A common feature among nearly all Gram-negative bacteria is the requirement for lipopolysaccharide (LPS) in the outer leaflet of the outer membrane. LPS provides structural integrity to the bacterial membrane which aids bacteria in maintaining their shape and acts as a barrier from environmental stress and harmful substances such as detergents and antibiotics. Recent work has demonstrated that Caulobacter crescentus can survive without LPS due to the presence of the anionic sphingolipid ceramide-phosphoglycerate. Based on genetic evidence, we predicted that protein CpgB functions as a ceramide kinase and performs the first step in generating the phosphoglycerate head group. Here, we characterized the kinase activity of recombinantly expressed CpgB and demonstrated that it can phosphorylate ceramide to form ceramide 1-phosphate. The pH optimum for CpgB was 7.5, and the enzyme required Mg2+ as a cofactor. Mn2+, but not other divalent cations, could substitute for Mg2+. Under these conditions, the enzyme exhibited typical Michaelis-Menten kinetics with respect to NBD-C6-ceramide (Km,app=19.2 {+/-} 5.5 M; Vmax,app=2586.29 {+/-} 231.99 pmol/min/mg enzyme) and ATP (Km,app=0.29 {+/-} 0.07 mM; Vmax,app=10067.57 {+/-} 996.85 pmol/min/mg enzyme). Phylogenetic analysis of CpgB revealed that CpgB belongs to a new class of ceramide kinases which is distinct from its eukaryotic counterpart; furthermore, the pharmacological inhibitor of human ceramide kinase (NVP-231) had no effect on CpgB. The characterization of a new bacterial ceramide kinase opens avenues for understanding the structure and function of the various microbial phosphorylated sphingolipids.

biochemistry↗

bioRxiv2023

Structure and dynamics of the essential endogenous mycobacterial polyketide synthasePks13

Mycobacterium tuberculosis is currently the leading cause of death by any bacterial infection1. The mycolic acid layer of the cell wall is essential for viability and virulence, and the enzymes responsible for its synthesis are therefore front line targets for antimycobacterial drug development2,3. Polyketide synthase 13 (Pks13) is a module comprised of a closely symmetric parallel dimer of chains, each encoding several enzymatic and transport functions, that carries out the condensation of two different very long chain fatty acids to produce mycolic acids that are essential components of the mycobacterial cell wall. Consequently individual enzymatic domains of Pks13 are targets for antimycobacterial drug development4. To understand this machinery, we sought to determine the structure and domain trajectories of the dimeric multi-enzyme Pks13, a 2x198,426 Dalton complex, from protein purified endogenously from mycobacteria under normal growth conditions, to capture it with normal substrates bound trapped in action. Structures of the multi-domain assembly revealed by cryogenic electron microscopy (cryoEM) define the ketosynthase (KS), linker, and acyltransferase (AT) domains, each at atomic resolution (1.8[A]), with bound substrates defined at 2.4[A] and 2.9[A] resolution. Image classification reveals two distinct structures with alternate locations of the N-terminal acyl carrier protein (termed ACP1a, ACP1b) seen at 3.6[A] and 4.6[A] resolution respectively. These two structures suggest plausible intermediate states, related by a ~60[A] movement of ACP1, on the pathway for substrate delivery from the fatty acyl-ACP ligase (FadD32) to the ketosynthase domain. The linking sequence between ACP1 and the KS includes an 11 amino acid sequence with 6 negatively charged side chains that lies in different positively charged grooves on the KS in ACP1a versus ACP1b structures. This charge complementarity between the extended chain and the grooves suggests some stabilization of these two distinct orientations. Other domains are visible at lower resolution and indicate flexibility relative to the KS-AT core. The chemical structures of three bound endogenous long chain fatty acid substrates with their proximal regions defined in the structures were determined by electrospray ionization mass spectrometry. The domain proximities were probed by chemical cross-linking and identified by mass spectrometry. These were incorporated into integrative structure modeling to define multiple domain configurations that transport the very long fatty acid chains throughout the multistep Pks13 mediated synthetic pathway.

biochemistry↗

bioRxiv2022

HexSDF are Required for Synthesis of a Novel Glycolipid that Mediates Daptomycin and Bacitracin Resistance in C. difficile

Clostridioides difficile is a Gram-positive opportunistic pathogen that results in 250,000 infections, 12,000 deaths, and $1 billion in medical costs in the US each year. There has been recent interest in using a daptomycin analog, Surotomycin, to treat C. difficile infections. Daptomycin interacts with both phosphatidylglycerol and Lipid II to disrupt the membrane and halt peptidoglycan synthesis. C. difficile has an unusual lipid membrane composition as it has no phosphatidylserine or phosphatidylethanolamine, and [~]50% of its membrane is composed of glycolipids, including the unique C. difficile lipid aminohexosyl-hexosyldiradylglycerol (HNHDRG). We identified a two-component system (TCS) HexRK that is required for C. difficile resistance to daptomycin. Using RNAseq we found that HexRK regulates a three gene operon of unknown function hexSDF. Based on bioinformatic predictions, hexS encodes a monogalactosyldiacylglycerol synthase, hexD encodes a polysaccharide deacetylase, and hexF encodes an MprF-like flippase. We find that deletion of hexRK leads to a 4-fold decrease in daptomycin MIC, and that deletion of hexSDF leads to an 8-16-fold decrease in daptomycin MIC. The {Delta}hexSDF mutant is also 4-fold less resistant to bacitracin but no other cell wall active antibiotics. Our data indicate that in the absence of HexSDF the phospholipid membrane composition is altered. In WT C. difficile the unique glycolipid, HNHDRG makes up [~]17% of the lipids in the membrane. However, in a {Delta}hexSDF mutant, HNHDRG is completely absent. While it is unclear how HNHDRG contributes daptomycin resistance, the requirement for bacitracin resistance suggests it has a general role in cell membrane biogenesis. ImportanceClostridioides difficile is a major cause of hospital acquired diarrhea and represents an urgent concern due to the prevalence of antibiotic resistance and the rate of recurrent infections. Little is understood about C. difficile membrane lipids, but a unique glycolipid, HNHDRG, has been previously identified in C. difficile and, currently, has not been identified in other organisms. Here we show that HexSDF and HexRK are required for synthesis of HNHDRG, and that production of HNHDRG impacts resistance to daptomycin and bacitracin.

microbiology↗

bioRxiv2022

Caulobacter requires anionic sphingolipids and deactivation of fur to lose lipid A

Lipid A, the membrane-anchored portion of lipopolysaccharide, is an essential component of the outer membrane (OM) of nearly all Gram-negative bacteria. Here, we identify regulatory and structural factors that together permit Caulobacter crescentus to eliminate lipid A from its OM. Mutations in the ferric uptake regulator fur allow Caulobacter to survive in the absence of either LpxC, which catalyzes an early step of lipid A synthesis, or CtpA, a tyrosine phosphatase homolog which we find is needed for wild-type lipid A structure and abundance. Alterations in Fur-regulated processes, rather than iron status per se, underlie the ability to eliminate lipid A. Fitness of lipid A-deficient Caulobacter requires a previously uncharacterized anionic sphingolipid, ceramide phosphoglycerate (CPG), which also mediates sensitivity to the antibiotic colistin. Our results demonstrate that, in an altered regulatory landscape, anionic sphingolipids can support the integrity of a lipid A-deficient OM.

microbiology↗

bioRxiv2021

The Flowering Repressor SVP recruits the TOPLESS co-repressor to control flowering in chrysanthemum and Arabidopsis

Plant flowering time is a consequence of the perception of environmental and endogenous signals. The MCM1-AGAMOUSDEFICIENS-SRF-box (MADS-box) gene SHORT VEGETATIVE PHASE (SVP) is a pivotal repressor that negatively regulates the floral transition during the vegetative phase. The transcriptional corepressor TOPLESS (TPL) plays critical roles in many aspects of plant life. An interaction first identified between the second LXLXLX motif (LRLGLP) of CmSVP with CmTPL1-2, which can repress the expression of a key flowering factor CmFTL3 by binding its promotor CArG element in chrysanthemum. Genetic analysis suggested that the CmSVP-CmTPL1-2 transcriptional complex is a prerequisite for SVP to act as a floral repressor, which reduces CmFTL3 transcriptional activity. CmSVP rescued the phenotype of the svp-31 mutant in Arabidopsis, and overexpression of AtSVP or CmSVP in the Arabidopsis dominant negative mutation tpl-1 led to a loss-of-function in late flowering, which confirmed the highly conserved function of SVP in the two completely different species. Thus, we have validated a conserved machinery wherein SVP relies on TPL to inhibit flowering through the direct regulation of FT, which is more meaningful for the evolution of species and could be translated to high-quality cultivation and breeding of crops.

plant biology↗

bioRxiv2021

Oxalic acid binds to gustatory receptor Gr23a and inhibits feeding in the brown planthopper

Plants produce diverse secondary compounds as natural protection against microbial and insect attack. Most of these compounds, including bitters and acids, are sensed by insect gustatory receptors (Grs). Acids are potentially toxic to insects, but there are few reports on sour compounds as ligands of insect Grs. Here, using two different heterologous expression systems, the insect Sf9 cell line and the mammalian HEK293T cell line, we started from crude extracts of rice (Oryza sativa) and successfully identified oxalic acid (OA) as a ligand of NlGr23a, a Gr in the brown planthopper Nilaparvata lugens. The antifeedant effect of OA on the brown planthopper was dose dependent, and NlGr23a is essential for OAs antifeedant activity in both artificial diets and rice plants. NlGr23a is also indispensable for tarsal OA sensing. To our knowledge, OA is the first identified ligand starting from plant crude extracts and the first known strong acid for insect Grs. These findings on rice-planthopper interactions will be of broad interest for pest control in agriculture and also for better understanding of how insects select host plants. Research organismNilaparvata lugens

ecology↗

bioRxiv2021

Disruption of the surfactant protein A receptor SP-R210L (CD245α/MYO18Aα) alters respiratory function and iron sequestration in alveolar macrophages of aged mice

Previous studies demonstrated that the host defense collectins, surfactant protein A and complement component 1q, modulate tissue-dependent macrophage activation, pathogen clearance, and regulatory macrophage functions through the receptor SP-R210, which consists of two isoforms SP-R210L and SP-R210S. These isoforms are encoded by alternatively spliced mRNAs of the Myo18a MYO18A gene in mice and humans. The present study in conditional transgenic mice revealed novel age-related functions of the SP-R210L isoform in modulating pulmonary mechanics, iron sequestration in alveolar macrophages (AMs), and life-long maintenance of the alveolar macrophage population. Our findings support the novel idea that SP-R210L-deficient AMs undergo bi-directional epigenetic adaptation that results in chronic dysregulation of broncho-alveolar function, immune homeostasis, and maintenance of oncotic balance at the airway-capillary interface. Disruption of SP-R210L increases the risk for development of severe interstitial lung disease during development and aging.

physiology↗

bioRxiv2021

Streptococcus pneumoniae, S. pyogenes, and S. agalactiae membrane phospholipid remodeling in response to human serum

Streptococcus pneumoniae, S. pyogenes (Group A Streptococcus; GAS), and S. agalactiae (Group B Streptococcus; GBS) are major etiological agents of diseases in humans. The cellular membrane, a crucial site in host-pathogen interactions, is poorly characterized in streptococci. Moreover, little is known about whether or how environmental conditions influence their lipid compositions. Using normal phase liquid chromatography coupled with electrospray ionization mass spectrometry, we characterized the phospholipids and glycolipids of S. pneumoniae, GAS, and GBS in routine undefined laboratory medium, streptococcal defined medium, and, in order to mimic the host environment, defined medium supplemented with human serum. In human serum-supplemented medium, all three streptococcal species synthesize phosphatidylcholine (PC), a zwitterionic phospholipid commonly found in eukaryotes but relatively rare in bacteria. We previously reported that S. pneumoniae utilizes the glycerophosphocholine (GPC) biosynthetic pathway to synthesize PC. Through substrate tracing experiments, we confirm that GAS and GBS scavenge lysoPC, a major metabolite in human serum, thereby using an abbreviated GPC pathway for PC biosynthesis. Furthermore, we found that plasmanyl-PC is uniquely present in the GBS membrane during growth with human serum, suggesting GBS possesses unusual membrane biochemical or biophysical properties. In summary, we report cellular lipid remodeling by the major pathogenic streptococci in response to metabolites present in human serum.

microbiology↗