7 results on '"Gal Kapach"'
Search Results
2. Antimicrobial Peptides against Multidrug-Resistant
- Author
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Daniel, Ben Hur, Gal, Kapach, Naiem Ahmad, Wani, Edo, Kiper, Moshe, Ashkenazi, Gill, Smollan, Natan, Keller, Ori, Efrati, and Yechiel, Shai
- Subjects
Anti-Infective Agents ,Cystic Fibrosis ,Biofilms ,Pseudomonas aeruginosa ,Humans ,Pseudomonas Infections ,Microbial Sensitivity Tests ,Antimicrobial Peptides ,Anti-Bacterial Agents - Abstract
Lung infection is the leading cause of morbidity and mortality in cystic fibrosis (CF) patients and is mainly dominated by
- Published
- 2022
3. Switching Bond: Generation of New Antimicrobial Peptides via the Incorporation of an Intramolecular Isopeptide Bond
- Author
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Gal Kapach, Daniel Ben Hur, Yechiel Shai, Elad Stolovicki, Naiem Ahmad Wani, and Etai Rotem
- Subjects
0301 basic medicine ,Pore Forming Cytotoxic Proteins ,Circular dichroism ,Gram-negative bacteria ,isopeptide bond ,antimicrobial peptide ,030106 microbiology ,Antimicrobial peptides ,Article ,Flow cytometry ,03 medical and health sciences ,Mice ,Immune system ,medicine ,Peptide bond ,Animals ,Humans ,Mode of action ,pexiganan ,chemistry.chemical_classification ,Isopeptide bond ,biology ,medicine.diagnostic_test ,Bacteria ,Chemistry ,Circular Dichroism ,Gram-positive bacteria ,biology.organism_classification ,030104 developmental biology ,Infectious Diseases ,Biochemistry - Abstract
Antimicrobial peptides (AMPs), which can be modified to kill a broad spectrum of microoganisms or a specific microorganism, are considered as promising alternatives to combat the rapidly widespread, resistant bacterial infections. However, there are still several obstacles to overcome. These include toxicity, stability, and the ability to interfere with the immune response and bacterial resistance. To overcome these challenges, we herein replaced the regular peptide bonds with isopeptide bonds to produce new AMPs based on the well-known synthetic peptides Amp1L and MSI-78 (pexiganan). Two new peptides Amp1EP and MSIEP were generated while retaining properties such as size, sequence, charge, and molecular weight. These new peptides have reduced toxicity toward murine macrophage (RAW 264.7) cells, human monocytic (THP-1) cells, and human red blood cells (hRBCs) and enhanced the stability toward proteolytic degradation. Importantly, the new peptides do not repress the pro-inflammatory cytokine and hence should not modulate the immune response. Structurally, the new peptides, Amp1EP and MSIEP, have a structure of random coils in contrast to the helical structures of the parental peptides as revealed by circular dichroism (CD) analysis. Their mode of action, assessed by flow cytometry, includes permeabilization of the bacterial membrane. Overall, we present here a new approach to modulate AMPs to develop antimicrobial peptides for future therapeutic purposes.
- Published
- 2021
4. Loss of the Periplasmic Chaperone Skp and Mutations in the Efflux Pump AcrAB-TolC Play a Role in Acquired Resistance to Antimicrobial Peptides in
- Author
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Shir Ferrera, Reut Nuri, Roman G. Gerlach, Alon Savidor, Christiane Schmidt, Adi Danin, Gal Kapach, and Yechiel Shai
- Subjects
Microbiology (medical) ,Antimicrobial peptides ,lcsh:QR1-502 ,Microbiology ,lcsh:Microbiology ,03 medical and health sciences ,Antibiotic resistance ,ddc:610 ,030304 developmental biology ,Original Research ,periplasm ,0303 health sciences ,AcrAB-TolC ,biology ,030306 microbiology ,Chemistry ,Periplasmic space ,bacterial resistance ,Skp ,biology.organism_classification ,Salmonella enterica ,Chaperone (protein) ,biology.protein ,efflux pump ,Efflux ,antimicrobial peptide (AMPs) ,ramR ,Bacterial outer membrane ,610 Medizin und Gesundheit ,Bacteria - Abstract
Bacterial resistance to antibiotics is a major concern worldwide, leading to an extensive search for alternative drugs. Promising candidates are antimicrobial peptides (AMPs), innate immunity molecules, shown to be highly efficient against multidrug resistant bacteria. Therefore, it is essential to study bacterial resistance mechanisms against them. For that purpose, we used experimental evolution, and isolated a Salmonella enterica serovar typhimurium-resistant line to the AMP 4DK5L7. This AMP displayed promising features including widespread activity against Gram-negative bacteria and protection from proteolytic degradation. However, the resistance that evolved in the isolated strain was particularly high. Whole genome sequencing revealed that five spontaneous mutations had evolved. Of these, three are novel in the context of acquired AMP resistance. Two mutations are related to the AcrAB-TolC multidrug efflux pump. One occurred in AcrB, the substrate-binding domain of the system, and the second in RamR, a transcriptional regulator of the system. Together, the mutations increased the minimal inhibitory concentration (MIC) by twofold toward this AMP. Moreover, the mutation in AcrB induced hypersusceptibility toward ampicillin and colistin. The last mutation occurred in Skp, a periplasmic chaperone that participates in the biogenesis of outer membrane proteins (OMPs). This mutation increased the MIC by twofold to 4DK5L7 and by fourfold to another AMP, seg5D. Proteomic analysis revealed that the mutation abolished Skp expression, reduced OMP abundance, and increased DegP levels. DegP, a protease that was reported to have an additional chaperone activity, escorts OMPs through the periplasm along with Skp, but is also associated with AMP resistance. In conclusion, our data demonstrate that both loss of Skp and manipulation of the AcrAB-TolC system are alternative strategies of AMP acquired resistance in Salmonella typhimurium and might represent a common mechanism in other Gram-negative bacteria.
- Published
- 2019
5. Deficient Lipid A Remodeling by the arnB Gene Promotes Biofilm Formation in Antimicrobial Peptide Susceptible Pseudomonas aeruginosa
- Author
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Yoel A. Klug, Hans-Georg Sahl, Yechiel Shai, Michaele Josten, Gal Kapach, and Li-av Segev-Zarko
- Subjects
0301 basic medicine ,Lipopolysaccharide ,030106 microbiology ,Mutant ,Antimicrobial peptides ,medicine.disease_cause ,Biochemistry ,Lipid A ,03 medical and health sciences ,chemistry.chemical_compound ,Bacterial Proteins ,medicine ,biology ,Pseudomonas aeruginosa ,Polysaccharides, Bacterial ,Wild type ,Biofilm ,biochemical phenomena, metabolism, and nutrition ,biology.organism_classification ,Cell biology ,030104 developmental biology ,chemistry ,Biofilms ,Bacteria ,Antimicrobial Cationic Peptides - Abstract
Multidrug resistant bacteria possess various mechanisms that can sense environmental stresses such as antibiotics and antimicrobial peptides and rapidly respond to defend themselves. Two known defense strategies are biofilm formation and lipopolysaccharide (LPS) modification. Though LPS modifications are observed in biofilm-embedded bacteria, their effect on biofilm formation is unknown. Using biochemical and biophysical methods coupled with confocal microscopy, atomic force microscopy, and transmission electron microscopy, we show that biofilm formation is promoted in a Pseudomonas aeruginosa PAO1 strain with a loss of function mutation in the arnB gene. This loss of function prevents the addition of the positively charged sugar 4-amino-4-deoxy-l-arabinose to lipid A of LPS under restrictive magnesium conditions. The data reveal that the arnB mutant, which is susceptible to antimicrobial peptides, forms a biofilm that is more robust than that of the wild type. This is in line with the observations that the arnB mutant exhibits outer surface properties such as hydrophobicity and net negative charge that promote the formation of biofilms. Moreover, when grown under Mg2+ limitation, both the wild type and the arnB mutant exhibited a reduction in the level of membrane-bound polysaccharides. The data suggest that the loss of polysaccharides exposes the membrane and alters its biophysical properties, which in turn leads to more biofilm formation. In summary, we show for the first time that blocking a specific lipid A modification promotes biofilm formation, suggesting a trade-off between LPS remodeling and resistance mechanisms of biofilm formation.
- Published
- 2018
6. The HIV gp41 pocket binding domain enables C-terminal heptad repeat transition from mediating membrane fusion to immune modulation
- Author
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Yoel A. Klug, Etai Rotem, Gal Kapach, Benjamin Dubreuil, and Yechiel Shai
- Subjects
0301 basic medicine ,Repetitive Sequences, Amino Acid ,viruses ,Protein subunit ,Receptors, Antigen, T-Cell ,Biology ,Gp41 ,Biochemistry ,03 medical and health sciences ,Mice ,HIV Fusion Inhibitors ,Animals ,Humans ,Molecular Biology ,Helix bundle ,Lipid bilayer fusion ,Cell Biology ,Virus Internalization ,HIV Envelope Protein gp41 ,Cell biology ,Protein Structure, Tertiary ,Heptad repeat ,030104 developmental biology ,Membrane protein ,HIV-1 ,Peptides ,Function (biology) ,Binding domain ,HeLa Cells - Abstract
For successful infection and propagation viruses must overcome many obstacles such as the immune system and entry into their host cells. The human immunodeficiency virus (HIV), utilizes its trimeric envelope protein gp160, specifically the gp41 subunit, to enter its host cell. During this process, a gp41-central coiled-coil is formed from three N and three C terminal heptad repeats, termed the six helix bundle, which drives membrane fusion. Recently, T-cell suppression has been reported as an additional function for several regions of gp41 by interfering with the T-cell receptor signaling cascade. One of these regions encompasses the conserved pocket binding domain that is situated in the C terminal heptad repeat and stabilizes six-helix bundle formation. This could indicate that the pocket binding domain plays a role in T-cell suppression in addition to its role in membrane fusion. To investigate this dual function, we used two independent cell cultures coupled with biophysical techniques. The data reveal that the pocket binding domain mediates T-cell suppression by stabilizing a T-cell receptor binding conformation in the membrane. Moreover, we show that the clinically used HIV fusion inhibitor T-20 did not show suppressive abilities, in contrast to the potent fusion inhibitor C34. In addition, by focusing on six helix bundle conformation post its assembly, we shed light on a mechanism by which gp41’s function alternates from membrane fusion facilitation to suppression of T-cell receptor activation.
- Published
- 2015
7. The HIV gp41 Conserved Pocket Binding Domain is Bifunctional, Alternatively Mediating both Immunosuppression and Membrane Fusion
- Author
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Gal Kapach, Etai Rotem, Yechiel Shai, Benjamin Dubreuil, and Yoel A. Klug
- Subjects
medicine.medical_treatment ,Biophysics ,Human immunodeficiency virus (HIV) ,Lipid bilayer fusion ,Immunosuppression ,Biology ,medicine.disease_cause ,Gp41 ,chemistry.chemical_compound ,Biochemistry ,chemistry ,medicine ,Bifunctional ,Binding domain - Published
- 2017
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