scholarly journals Cathelicidin and PMB neutralize endotoxins by multifactorial mechanisms including LPS interaction and targeting of host cell membranes

2021 ◽  
Vol 118 (27) ◽  
pp. e2101721118
Author(s):  
Andra B. Schromm ◽  
Laura Paulowski ◽  
Yani Kaconis ◽  
Franziska Kopp ◽  
Max Koistinen ◽  
...  
Keyword(s):  
Host Cell ◽  
Direct Interaction ◽  
Polymyxin B ◽  
Peptide Antibiotic ◽  
Membrane Domains ◽  
Bacterial Sepsis ◽  
Systematic Analysis ◽  
Key Factor ◽  
Host Defense Peptide ◽  
Host Cell Membranes

Antimicrobial peptides (AMPs) contribute to an effective protection against infections. The antibacterial function of AMPs depends on their interactions with microbial membranes and lipids, such as lipopolysaccharide (LPS; endotoxin). Hyperinflammation induced by endotoxin is a key factor in bacterial sepsis and many other human diseases. Here, we provide a comprehensive profile of peptide-mediated LPS neutralization by systematic analysis of the effects of a set of AMPs and the peptide antibiotic polymyxin B (PMB) on the physicochemistry of endotoxin, macrophage activation, and lethality in mice. Mechanistic studies revealed that the host defense peptide LL-32 and PMB each reduce LPS-mediated activation also via a direct interaction of the peptides with the host cell. As a biophysical basis, we demonstrate modifications of the structure of cholesterol-rich membrane domains and the association of glycosylphosphatidylinositol (GPI)-anchored proteins. Our discovery of a host cell–directed mechanism of immune control contributes an important aspect in the development and therapeutic use of AMPs.

Glycerol metabolism promotes biofilm formation byPseudomonas aeruginosa

2016 ◽  
Vol 62 (8) ◽  
pp. 704-710 ◽  
Author(s):  
Jessica Scoffield ◽  
Laura Silo-Suh
Keyword(s):  
Cystic Fibrosis ◽  
Fatty Acids ◽  
Pseudomonas Aeruginosa ◽  
Host Cell ◽  
Biofilm Formation ◽  
Glycerol Metabolism ◽  
Persistent Infections ◽  
Expression Of Genes ◽  
Key Factor ◽  
Host Cell Membranes

Pseudomonas aeruginosa causes persistent infections in the airways of cystic fibrosis (CF) patients. Airway sputum contains various host-derived nutrients that can be utilized by P. aeruginosa, including phosphotidylcholine, a major component of host cell membranes. Phosphotidylcholine can be degraded by P. aeruginosa to glycerol and fatty acids to increase the availability of glycerol in the CF lung. In this study, we explored the role that glycerol metabolism plays in biofilm formation by P. aeruginosa. We report that glycerol metabolism promotes biofilm formation by both a chronic CF isolate (FRD1) and a wound isolate (PAO1) of P. aeruginosa. Moreover, loss of the GlpR regulator, which represses the expression of genes involved in glycerol metabolism, enhances biofilm formation in FRD1 through the upregulation of Pel polysaccharide. Taken together, our results suggest that glycerol metabolism may be a key factor that contributes to P. aeruginosa persistence by promoting biofilm formation.

scholarly journals The V Antigen of Pseudomonas aeruginosa Is Required for Assembly of the Functional PopB/PopD Translocation Pore in Host Cell Membranes

2004 ◽  
Vol 72 (8) ◽  
pp. 4741-4750 ◽  
Author(s):  
Julien Goure ◽  
Alexandrine Pastor ◽  
Eric Faudry ◽  
Jacqueline Chabert ◽  
Andréa Dessen ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Host Cell ◽  
Cell Membranes ◽  
Fluorescent Protein ◽  
Direct Interaction ◽  
Wild Type ◽  
Gene Deletions ◽  
Infected Rbcs ◽  
Green Fluorescent ◽  
Host Cell Membranes

ABSTRACT Pseudomonas aeruginosa efficiently intoxicates eukaryotic cells through the activity of the type III secretion-translocation system (TTSS). Gene deletions within the translocation operon pcrGVH-popBD abolish pore-forming activity of P. aeruginosa strains with macrophages and TTSS-dependent hemolysis. Here we investigated the requirements for PcrV, PopB, and PopD in pore formation by analyzing specific mutants using red blood cells (RBCs) and fibroblasts expressing green fluorescent protein fused to actin. Simultaneous secretion of three proteins, PopB, PopD, and PcrV, was required to achieve wild-type hemolysis and effector translocation. Deletion of pcrV in a cytotoxic strain did not affect secretion of PopB and PopD but abolished hemolytic activity and translocation of effectors into fibroblasts. Notably, the PcrV-deficient mutant was not capable of inserting PopD into host cell membranes, whereas PopB and PopD, but not PcrV, were readily found within membranes of wild-type-infected RBCs. Immunoprecipitation experiments performed by using a liposome model of pore assembly revealed a direct interaction between PopD and PopB but not between PopD and PcrV. Consequently, PcrV is necessary for the functional assembly of the PopB/D translocon complex but does not interact directly with pore-forming Pop proteins.

scholarly journals The Extended Intermediate of the SARS-CoV-2 Spike Protein uses Extreme Reach and Flexibility to Capture Host Cell Membranes

2021 ◽  
Vol 120 (3) ◽  
pp. 321a
Author(s):  
Rui Su ◽  
Jin Zeng ◽  
Sathish Thiyagarajan ◽  
Ben O'Shaughnessy
Keyword(s):  
Host Cell ◽  
Cell Membranes ◽  
Spike Protein ◽  
Host Cell Membranes

scholarly journals Bound To Shock: Protection from Lethal Endotoxemic Shock by a Novel, Nontoxic, Alkylpolyamine Lipopolysaccharide Sequestrant

2007 ◽  
Vol 51 (8) ◽  
pp. 2811-2819 ◽  
Author(s):  
Diptesh Sil ◽  
Anurupa Shrestha ◽  
Matthew R. Kimbrell ◽  
Thuan B. Nguyen ◽  
Ashok K. Adisechan ◽  
...  
Keyword(s):  
Polymyxin B ◽  
In Vitro Assays ◽  
Critically Ill Patient ◽  
Peptide Antibiotic ◽  
Outer Membranes ◽  
Wide Range ◽  
Endotoxemic Shock ◽  
Inflammatory Processes ◽  
Shock Protection

ABSTRACT Lipopolysaccharide (LPS), or endotoxin, a structural component of gram-negative bacterial outer membranes, plays a key role in the pathogenesis of septic shock, a syndrome of severe systemic inflammation which leads to multiple-system organ failure. Despite advances in antimicrobial chemotherapy, sepsis continues to be the commonest cause of death in the critically ill patient. This is attributable to the lack of therapeutic options that aim at limiting the exposure to the toxin and the prevention of subsequent downstream inflammatory processes. Polymyxin B (PMB), a peptide antibiotic, is a prototype small molecule that binds and neutralizes LPS toxicity. However, the antibiotic is too toxic for systemic use as an LPS sequestrant. Based on a nuclear magnetic resonance-derived model of polymyxin B-LPS complex, we had earlier identified the pharmacophore necessary for optimal recognition and neutralization of the toxin. Iterative cycles of pharmacophore-based ligand design and evaluation have yielded a synthetically easily accessible N 1,mono-alkyl-mono-homologated spermine derivative, DS-96. We have found that DS-96 binds LPS and neutralizes its toxicity with a potency indistinguishable from that of PMB in a wide range of in vitro assays, affords complete protection in a murine model of LPS-induced lethality, and is apparently nontoxic in vertebrate animal models.

scholarly journals A Cluster of Ring Stage–specific Genes Linked to a Locus Implicated in Cytoadherence inPlasmodium falciparumCodes for PEXEL-negative and PEXEL-positive Proteins Exported into the Host Cell

2006 ◽  
Vol 17 (8) ◽  
pp. 3613-3624 ◽  
Author(s):  
Tobias Spielmann ◽  
Paula L. Hawthorne ◽  
Matthew W.A. Dixon ◽  
Mandy Hannemann ◽  
Kathleen Klotz ◽  
...  
Keyword(s):  
Host Cell ◽  
Major Part ◽  
Asexual Development ◽  
Sequence Motif ◽  
Ring Stage ◽  
Systematic Analysis ◽  
Development Cycle ◽  
Cell Remodeling ◽  
Membrane Compartments ◽  
Exported Protein

Blood stages of Plasmodium falciparum export proteins into their erythrocyte host, thereby inducing extensive host cell modifications that become apparent after the first half of the asexual development cycle (ring stage). This is responsible for a major part of parasite virulence. Export of many parasite proteins depends on a sequence motif termed Plasmodium export element (PEXEL) or vacuolar transport signal (VTS). This motif has allowed the prediction of the Plasmodium exportome. Using published genome sequence, we redetermined the boundaries of a previously studied region linked to P. falciparum virulence, reducing the number of candidate genes in this region to 13. Among these, we identified a cluster of four ring stage-specific genes, one of which is known to encode an exported protein. We demonstrate that all four genes code for proteins exported into the host cell, although only two genes contain an obvious PEXEL/VTS motif. We propose that the systematic analysis of ring stage-specific genes will reveal a cohort of exported proteins not present in the currently predicted exportome. Moreover, this provides further evidence that host cell remodeling is a major task of this developmental stage. Biochemical and photobleaching studies using these proteins reveal new properties of the parasite-induced membrane compartments in the host cell. This has important implications for the biogenesis and connectivity of these structures.

scholarly journals Polymyxin B Resistance in El Tor Vibrio cholerae Requires Lipid Acylation Catalyzed by MsbB

2010 ◽  
Vol 192 (8) ◽  
pp. 2044-2052 ◽  
Author(s):  
Jyl S. Matson ◽  
Hyun Ju Yoo ◽  
Kristina Hakansson ◽  
Victor J. DiRita
Keyword(s):  
Antimicrobial Peptides ◽  
Vibrio Cholerae ◽  
Lipid A ◽  
Polymyxin B ◽  
Mass Spectrometry Analysis ◽  
Peptide Antibiotic ◽  
Wild Type ◽  
Spectrometry Analysis ◽  
Antimicrobial Peptide Resistance ◽  
El Tor

ABSTRACTAntimicrobial peptides are critical for innate antibacterial defense. Both Gram-negative and Gram-positive microbes have mechanisms to alter their surfaces and resist killing by antimicrobial peptides. InVibrio cholerae, two natural epidemic biotypes, classical and El Tor, exhibit distinct phenotypes with respect to sensitivity to the peptide antibiotic polymyxin B: classical strains are sensitive and El Tor strains are relatively resistant. We carried out mutant screens of both biotypes, aiming to identify classicalV. choleraemutants resistant to polymyxin B and El TorV. choleraemutants sensitive to polymyxin B. Insertions in a gene annotatedmsbB(encoding a predicted lipid A secondary acyltransferase) answered both screens, implicating its activity in antimicrobial peptide resistance ofV. cholerae. Analysis of a defined mutation in the El Tor biotype demonstrated thatmsbBis required for resistance to all antimicrobial peptides tested. Mutation ofmsbBin a classical strain resulted in reduced resistance to several antimicrobial peptides but in no significant change in resistance to polymyxin B.msbBmutants of both biotypes showed decreased colonization of infant mice, with a more pronounced defect observed for the El Tor mutant. Mass spectrometry analysis showed that lipid A of themsbBmutant for both biotypes was underacylated compared to lipid A of the wild-type isolates, confirming that MsbB is a functional acyltransferase inV. cholerae.

scholarly journals Invasive Ability of an Escherichia coliStrain Isolated from the Ileal Mucosa of a Patient with Crohn’s Disease

1999 ◽  
Vol 67 (9) ◽  
pp. 4499-4509 ◽  
Author(s):  
Jerome Boudeau ◽  
Anne-Lise Glasser ◽  
Estelle Masseret ◽  
Bernard Joly ◽  
Arlette Darfeuille-Michaud
Keyword(s):  
Crohn’S Disease ◽  
Crohn's Disease ◽  
Host Cell ◽  
Bacterial Invasion ◽  
Intestinal Epithelial ◽  
Invasive Ability ◽  
Ileal Mucosa ◽  
Gastrointestinal Infections ◽  
E Coli ◽  
Host Cell Membranes

ABSTRACT Crohn’s disease (CD) is an inflammatory bowel disease in whichEscherichia coli strains have been suspected of being involved. We demonstrated previously that ileal lesions of CD are colonized by E. coli strains able to adhere to intestinal Caco-2 cells but devoid of the virulence genes so far described in the pathogenic E. coli strains involved in gastrointestinal infections. In the present study we compared the invasive ability of one of these strains isolated from an ileal biopsy of a patient with CD, strain LF82, with that of reference enteroinvasive (EIEC), enteropathogenic (EPEC), enterotoxigenic (ETEC), enteraggregative (EAggEC), enterohemorrhagic (EHEC), and diffusely adhering (DAEC)E. coli strains. Gentamicin protection assays showed thatE. coli LF82 was able to efficiently invade HEp-2 cells. Its invasive level was not significantly different from that of EIEC and EPEC strains (P > 0.5) but significantly higher than that of ETEC (P < 0.03), EHEC (P < 0.005), EAggEC (P < 0.004) and DAEC (P < 0.02) strains. Strain LF82 also demonstrated efficient ability to invade intestinal epithelial cultured Caco-2, Intestine-407, and HCT-8 cells. Electron microscopy examination of infected HEp-2 cells revealed the presence of numerous intracellular bacteria located in vacuoles or free in the host cell cytoplasm. In addition, the interaction of strain LF82 with epithelial cells was associated with the elongation of microvillar extensions that extruded from the host cell membranes and engulfed the bacteria. This internalization mechanism strongly resembles Salmonella- orShigella-induced macropinocytosis. The use of cytochalasin D and colchicine showed that the uptake of strain LF82 by HEp-2 cells was mediated by both an actin microfilament-dependent mechanism and microtubule involvement. In addition, strain LF82 survived for at least 24 h in HEp-2 and Intestine-407 cells and efficiently replicated intracellularly in HEp-2 cells. PCR and hybridization experiments did not reveal the presence of any of the genetic determinants encoding EIEC, EPEC, or ETEC proteins involved in bacterial invasion. Thus, these findings show that LF82, which colonized the ileal mucosa of a patient with CD, is a true invasive E. coli strain and suggest the existence of a new potentially pathogenic group of E. coli, which we propose be designated adherent-invasive E. coli.

Salmonella type III effectors PipB and PipB2 are targeted to detergent-resistant microdomains on internal host cell membranes

2004 ◽  
Vol 49 (3) ◽  
pp. 685-704 ◽  
Author(s):  
Leigh A. Knodler ◽  
Bruce A. Vallance ◽  
Michael Hensel ◽  
Daniela Jäckel ◽  
B. Brett Finlay ◽  
...  
Keyword(s):  
Host Cell ◽  
Cell Membranes ◽  
Type Iii Effectors ◽  
Type Iii ◽  
Host Cell Membranes

scholarly journals Targeting and Stability of Na/Ca Exchanger 1 in Cardiomyocytes Requires Direct Interaction with the Membrane Adaptor Ankyrin-B

2006 ◽  
Vol 282 (7) ◽  
pp. 4875-4883 ◽  
Author(s):  
Shane R. Cunha ◽  
Naina Bhasin ◽  
Peter J. Mohler
Keyword(s):  
Molecular Mechanisms ◽  
Cardiac Tissue ◽  
Direct Interaction ◽  
Binding Activity ◽  
Membrane Domains ◽  
Excitable Cells ◽  
Expression Activity ◽  
Cellular Pathways ◽  
Ankyrin B ◽  
Calcium Extrusion

Na/Ca exchanger activity is important for calcium extrusion from the cardiomyocyte cytosol during repolarization. Animal models exhibiting altered Na/Ca exchanger expression display abnormal cardiac phenotypes. In humans, elevated Na/Ca exchanger expression/activity is linked with pathophysiological conditions including arrhythmia and heart failure. Whereas the molecular mechanisms underlying Na/Ca exchanger biophysical properties are widely studied and generally well characterized, the cellular pathways and molecular partners underlying the specialized membrane localization of Na/Ca exchanger in cardiac tissue are essentially unknown. In this report, we present the first direct evidence for a protein pathway required for Na/Ca exchanger localization and stability in primary cardiomyocytes. We define the minimal structural requirements on ankyrin-B for direct Na/Ca exchanger interactions. Moreover, using ankyrin-B mutants that lack Na/Ca exchanger binding activity, and primary cardiomyocytes with reduced ankyrin-B expression, we demonstrate that direct interaction with the membrane adaptor ankyrin-B is required for the localization and post-translational stability of Na/Ca exchanger 1 in neonatal mouse cardiomyocytes. These results raise exciting new questions regarding potentially dynamic roles for ankyrin proteins in the biogenesis and maintenance of specialized membrane domains in excitable cells.

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