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21 Jun 15:19

Principles of peptide selection by the transporter associated with antigen processing

by James LeeMichael L. OldhamVictor ManonJue ChenaLaboratory of Membrane Biophysics and Biology, The Rockefeller University, New York, NY 10065bHHMI, Chevy Chase, MD 20815
Proceedings of the National Academy of Sciences, Volume 121, Issue 23, June 2024.
07 Jun 17:02

Glycoengineering-based anti-PD-1-iRGD peptide conjugate boosts antitumor efficacy through T cell engagement

by Yunfeng Pan

Cell Rep Med. 2024 May 29:101590. doi: 10.1016/j.xcrm.2024.101590. Online ahead of print.

ABSTRACT

Despite the important breakthroughs of immune checkpoint inhibitors in recent years, the objective response rates remain limited. Here, we synthesize programmed cell death protein-1 (PD-1) antibody-iRGD cyclic peptide conjugate (αPD-1-(iRGD)2) through glycoengineering methods. In addition to enhancing tissue penetration, αPD-1-(iRGD)2 simultaneously engages tumor cells and PD-1+ T cells via dual targeting, thus mediating tumor-specific T cell activation and proliferation with mild effects on non-specific T cells. In multiple syngeneic mouse models, αPD-1-(iRGD)2 effectively reduces tumor growth with satisfactory biosafety. Moreover, results of flow cytometry and single-cell RNA-seq reveal that αPD-1-(iRGD)2 remodels the tumor microenvironment and expands a population of "better effector" CD8+ tumor infiltrating T cells expressing stem- and memory-associated genes, including Tcf7, Il7r, Lef1, and Bach2. Conclusively, αPD-1-(iRGD)2 is a promising antibody conjugate therapeutic beyond antibody-drug conjugate for cancer immunotherapy.

PMID:38843844 | DOI:10.1016/j.xcrm.2024.101590

04 Jun 20:19

[ASAP] Mitochondrial Thermogenesis Can Trigger Heat Shock Response in the Nucleus

by Myeong-Gyun Kang, Hwa-Ryeon Kim, Hee Yong Lee, Chulhwan Kwak, Hyewon Koh, Byoung Heon Kang, Jae-Seok Roe, and Hyun-Woo Rhee

TOC Graphic

ACS Central Science
DOI: 10.1021/acscentsci.3c01589
03 Jun 20:31

A Glycolipid-Peptide-Hapten Tricomponent Conjugate Vaccine Generates Durable Antihapten Antibody Responses in Mice

by Theresa E Pankhurst

ACS Chem Biol. 2024 Jun 21;19(6):1366-1375. doi: 10.1021/acschembio.4c00214. Epub 2024 Jun 3.

ABSTRACT

Eliciting an antihapten antibody response to vaccination typically requires the use of constructs where multiple copies of the hapten are covalently attached to a larger carrier molecule. The carrier is required to elicit T cell help via presentation of peptide epitopes on major histocompatibility complex (MHC) class II molecules; as such, attachment to full-sized proteins, alone or in a complex, is generally used to account for the significant MHC diversity in humans. While such carrier-based vaccines have proven extremely successful, particularly in protecting against bacterial diseases, they can be challenging to manufacture, and repeated use can be compromised by pre-existing immunity against the carrier. One approach to reducing these complications is to recruit help from type I natural killer T (NKT) cells, which exhibit limited diversity in their antigen receptors and respond to glycolipid antigens presented by the highly conserved presenting molecule CD1d. Synthetic vaccines for universal use can, therefore, be prepared by conjugating haptens to an NKT cell agonist such as α-galactosylceramide (αGalCer, KRN7000). An additional advantage is that the quality of NKT cell help is sufficient to overcome the need for an extra immune adjuvant. However, while initial studies with αGalCer-hapten conjugate vaccines report strong and rapid antihapten antibody responses, they can fail to generate lasting memory. Here, we show that antibody responses to the hapten 4-hydoxy-3-nitrophenyl acetyl (NP) can be improved through additional attachment of a fusion peptide containing a promiscuous helper T cell epitope (Pan DR epitope, PADRE) that binds diverse MHC class II molecules. Such αGalCer-hapten-peptide tricomponent vaccines generate strong and sustained anti-NP antibody titers with increased hapten affinity compared to vaccines without the helper epitope. The tricomponent vaccine platform is therefore suitable for further exploration in the pursuit of efficacious antihapten immunotherapies.

PMID:38829263 | DOI:10.1021/acschembio.4c00214

03 Jun 13:52

Highly biased agonism for GPCR ligands via nanobody tethering

by Shivani Sachdev

Nature Communications, Published online: 01 June 2024; doi:10.1038/s41467-024-49068-5

Activated GPCRs signal through multiple pathways. Ligands that signal through a single pathway are highly valued. The authors demonstrate that tethering ligands to receptors via conjugation with binding nanobodies enables pathway-specific signaling.
31 May 20:49

In Situ Synthesis of an Immune-Checkpoint Blocker from Engineered Bacteria Elicits a Potent Antitumor Response

by Yuting Wei

ACS Synth Biol. 2024 Jun 21;13(6):1679-1693. doi: 10.1021/acssynbio.3c00569. Epub 2024 May 31.

ABSTRACT

Immune-checkpoint blockade (ICB) reinvigorates T cells from exhaustion and potentiates T-cell responses to tumors. However, most patients do not respond to ICB therapy, and only a limited response can be achieved in a "cold" tumor with few infiltrated lymphocytes. Synthetic biology can be used to engineer bacteria as controllable bioreactors to synthesize biotherapeutics in situ. We engineered attenuated Salmonella VNP20009 with synthetic gene circuits to produce PD-1 and Tim-3 scFv to block immunosuppressive receptors on exhausted T cells to reinvigorate their antitumor response. Secreted PD-1 and Tim-3 scFv bound PD-1+ Tim-3+ T cells through their targeting receptors in vitro and potentiated the T-cell secretion of IFN-γ. Engineered bacteria colonized the hypoxic core of the tumor and synthesized PD-1 and Tim-3 scFv in situ, reviving CD4+ T cells and CD8+ T cells to execute an antitumor response. The bacteria also triggered a strong innate immune response, which stimulated the expansion of IFN-γ+ CD4+ T cells within the tumors to induce direct and indirect antitumor immunity.

PMID:38819389 | DOI:10.1021/acssynbio.3c00569

31 May 18:27

Imaging the Granzyme Mediated Host Immune Response to Viral and Bacterial Pathogens In Vivo Using Positron Emission Tomography

by Apurva Pandey

ACS Infect Dis. 2024 May 31. doi: 10.1021/acsinfecdis.4c00114. Online ahead of print.

ABSTRACT

Understanding how the host immune system engages complex pathogens is essential to developing therapeutic strategies to overcome their virulence. While granzymes are well understood to trigger apoptosis in infected host cells or bacteria, less is known about how the immune system mobilizes individual granzyme species in vivo to combat diverse pathogens. Toward the goal of studying individual granzyme function directly in vivo, we previously developed a new class of radiopharmaceuticals termed "restricted interaction peptides (RIPs)" that detect biochemically active endoproteases using positron emission tomography (PET). In this study, we showed that secreted granzyme B proteolysis in response to diverse viral and bacterial pathogens could be imaged with [64Cu]Cu-GRIP B, a RIP that specifically targets granzyme B. Wild-type or germline granzyme B knockout mice were instilled intranasally with the A/PR/8/34 H1N1 influenza A strain to generate pneumonia, and granzyme B production within the lungs was measured using [64Cu]Cu-GRIP B PET/CT. Murine myositis models of acute bacterial (E. coli, P. aeruginosa, K. pneumoniae, and L. monocytogenes) infection were also developed and imaged using [64Cu]Cu-GRIP B. In all cases, the mice were studied in vivo using mPET/CT and ex vivo via tissue-harvesting, gamma counting, and immunohistochemistry. [64Cu]Cu-GRIP B uptake was significantly higher in the lungs of wild-type mice that received A/PR/8/34 H1N1 influenza A strain compared to mice that received sham or granzyme B knockout mice that received either treatment. In wild-type mice, [64Cu]Cu-GRIP B uptake was significantly higher in the infected triceps muscle versus normal muscle and the contralateral triceps inoculated with heat killed bacteria. In granzyme B knockout mice, [64Cu]Cu-GRIP B uptake above the background was not observed in the infected triceps muscle. Interestingly, live L. monocytogenes did not induce detectable granzyme B on PET, despite prior in vitro data, suggesting a role for granzyme B in suppressing their pathogenicity. In summary, these data show that the granzyme response elicited by diverse human pathogens can be imaged using PET. These results and data generated via additional RIPs specific for other granzyme proteases will allow for a deeper mechanistic study analysis of their complex in vivo biology.

PMID:38819300 | DOI:10.1021/acsinfecdis.4c00114

31 May 18:27

Capsule-deficient group A Streptococcus evades autophagy-mediated killing in macrophages

by Yong-An Shi

mBio. 2024 May 31:e0077124. doi: 10.1128/mbio.00771-24. Online ahead of print.

ABSTRACT

The hyaluronic acid capsule is crucial in protecting group A Streptococcus (GAS) against phagocytic killing. However, there have been reported outbreaks caused by capsule-deficient GAS strains, and the mechanisms underlying their evasion of immune clearance remain unclear. This study demonstrated that the capsule-deficient mutant [Cap(-)] of the emm1 strain increased survival within phagocytic cells compared to the wild-type strain [Cap(+)]. Although both Cap(+) and Cap(-) strains exhibited similar abilities to disrupt the phagosome, only the Cap(+) strain was colocalized with lysosomes and acidified compartments in phagocytic cells, indicating its susceptibility to autophagosome elimination. In contrast, the Cap(-) mutant evaded the recognition of galectin-8 and ubiquitin, impairing selective autophagy-mediated elimination. These findings suggest that a deficiency in the capsule could impair the intracellular elimination of GAS in macrophages, revealing previously unknown aspects of the host's recognition of the GAS capsule in macrophages.

IMPORTANCE: Group A Streptococcus (GAS) is a Gram-positive bacterium that causes diseases ranging from mild pharyngitis to severe necrotizing fasciitis. Phagocytic cells serve as the primary defense against bacterial infections, exhibiting remarkable efficiency in eliminating intracellular pathogens. The hyaluronic acid capsule is a critical virulence factor that contributes to the resistance of phagocytosis in GAS. Nevertheless, the outbreaks caused by GAS strains that lack the hyaluronic acid capsule have been reported, and the selective advantage of capsule-deficient strains during infection is not fully understood. This study showed that the autophagic adaptor proteins recognize the capsulated GAS strain but not the capsule-deficient mutant, indicating that the hyaluronic acid capsule could be the autophagic target in macrophages. These findings imply that the hyaluronic acid capsule of GAS actually enhances its elimination within phagocytic cells, subverting the understanding of the capsule in GAS pathogenesis.

PMID:38819157 | DOI:10.1128/mbio.00771-24

31 May 18:12

A Gram-negative-selective antibiotic that spares the gut microbiome

by Kristen A. Muñoz

Nature, Published online: 29 May 2024; doi:10.1038/s41586-024-07502-0

Lolamicin, a novel antibiotic developed from a pyridinepyrazole precursor, exhibits potent activity against a broad range of Gram-negative multidrug-resistant clinical isolates, and good efficacy in mouse models of infection without inducing gut dysbiosis.
31 May 14:25

Targeted complement inhibition using bispecific antibodies that bind local antigens and endogenous complement regulators

by Haiyu Wang

Front Immunol. 2024 May 16;15:1288597. doi: 10.3389/fimmu.2024.1288597. eCollection 2024.

ABSTRACT

Complement activation protects against infection but also contributes to pathological mechanisms in a range of clinical conditions such as autoimmune diseases and transplant rejection. Complement-inhibitory drugs, either approved or in development, usually act systemically, thereby increasing the risk for infections. We therefore envisioned a novel class of bispecific antibodies (bsAbs) which are capable of site-directed complement inhibition by bringing endogenous complement regulators in the vicinity of defined cell surface antigens. Here, we analyzed a comprehensive set of obligate bsAbs designed to crosslink a specific target with either complement regulator factor H (FH) or C4b-binding protein (C4BP). The bsAbs were assessed for their capacity to inhibit complement activation and cell lysis in an antigen-targeted manner. We observed that the bsAbs inhibited classical, lectin, and alternative pathway complement activation in which sufficient endogenous serum FH and C4BP could be recruited to achieve local inhibition. Importantly, the bsAbs effectively protected antigen-positive liposomes, erythrocytes, and human leukocytes from complement-mediated lysis. In conclusion, localized complement inhibition by bsAbs capable of recruiting endogenous human complement regulators (such as FH or C4BP) to cell surfaces potentially provides a novel therapeutic approach for the targeted treatment of complement-mediated diseases.

PMID:38817607 | PMC:PMC11137741 | DOI:10.3389/fimmu.2024.1288597

31 May 14:24

Structure and activity of the septal peptidoglycan hydrolysis machinery crucial for bacterial cell division

by Yatian Chen

PLoS Biol. 2024 May 30;22(5):e3002628. doi: 10.1371/journal.pbio.3002628. eCollection 2024 May.

ABSTRACT

The peptidoglycan (PG) layer is a critical component of the bacterial cell wall and serves as an important target for antibiotics in both gram-negative and gram-positive bacteria. The hydrolysis of septal PG (sPG) is a crucial step of bacterial cell division, facilitated by FtsEX through an amidase activation system. In this study, we present the cryo-EM structures of Escherichia coli FtsEX and FtsEX-EnvC in the ATP-bound state at resolutions of 3.05 Å and 3.11 Å, respectively. Our PG degradation assays in E. coli reveal that the ATP-bound conformation of FtsEX activates sPG hydrolysis of EnvC-AmiB, whereas EnvC-AmiB alone exhibits autoinhibition. Structural analyses indicate that ATP binding induces conformational changes in FtsEX-EnvC, leading to significant differences from the apo state. Furthermore, PG degradation assays of AmiB mutants confirm that the regulation of AmiB by FtsEX-EnvC is achieved through the interaction between EnvC-AmiB. These findings not only provide structural insight into the mechanism of sPG hydrolysis and bacterial cell division, but also have implications for the development of novel therapeutics targeting drug-resistant bacteria.

PMID:38814940 | PMC:PMC11139282 | DOI:10.1371/journal.pbio.3002628

31 May 13:52

Mitochondrial UCP1: Potential thermogenic mechanistic switch for the treatment of obesity and neurodegenerative diseases using natural and epigenetic drug candidates

by Md Reyad-Ul-Ferdous

Phytomedicine. 2024 Jul 25;130:155672. doi: 10.1016/j.phymed.2024.155672. Epub 2024 May 4.

ABSTRACT

BACKGROUND: Brown fat is known to provide non-shivering thermogenesis through mitochondrial uncoupling mediated by uncoupling protein 1 (UCP1). Non-shivering is not dependent on UCP2, UCP4, and BMCP1/UCP5 genes, which are distinct from UCP1 in a way that they are not constitutive uncouplers. Although they are susceptible to free fatty acid and free radical activation, their functioning has a significant impact on the performance of neurons.

METHODOLOGY: Using subject-specific keywords (Adipose tissue; Adipocytes; Mitochondria; Obesity; Thermogenesis; UCP's in Neurodegeneration; Alzheimer's disease; Parkinson's disease), research articles and reviews were retrieved from Web of Science, ScienceDirect, Google Scholar, and PubMed. This article includespublications published between 2018 and 2023. The drugs that upregulate UCP1 are included in the study while the drugs that do not impact UCP1 are were not included.

RESULTS: Neuronal UCPs have a direct impact on synaptic plasticity, neurodegenerative processes, and neurotransmission, by modulating calcium flux, mitochondrial biogenesis, local temperature, and free radical generation. Numerous significant advances in the study of neuronal UCPs and neuroprotection are still to be made. Identification of the tissue-dependent effects of UCPs is essential first. Pharmacologically targeting neuronal UCPs is a key strategy for preventing both neurodegenerative diseases and physiological aging. Given that UCP2 has activities that are tissue-specific, it will be essential to develop treatments without harmful side effects. The triggering of UCPs by CoQ, an essential cofactor, produces nigral mitochondrial uncoupling, reduces MPTP-induced toxicity, and may even decrease the course of Parkinson's disease, according to early indications.

CONCLUSION: Herein, we explore the potential of UCP1 as a therapeutic target for treating obesity, neurodegenerative diseases as well as a potential activator of both synthetic and natural drugs. A deeper knowledge of synaptic signaling and neurodegeneration may pave the way to new discoveries regarding the functioning and controlling of these genes.

PMID:38810549 | DOI:10.1016/j.phymed.2024.155672

31 May 13:47

ANT2 functions as a translocon for mitochondrial cross-membrane translocation of RNAs

by Pengcheng Wang

Cell Res. 2024 Jul;34(7):504-521. doi: 10.1038/s41422-024-00978-5. Epub 2024 May 29.

ABSTRACT

Bidirectional transcription of mammalian mitochondrial DNA generates overlapping transcripts that are capable of forming double-stranded RNA (dsRNA) structures. Release of mitochondrial dsRNA into the cytosol activates the dsRNA-sensing immune signaling, which is a defense mechanism against microbial and viral attack and possibly cancer, but could cause autoimmune diseases when unchecked. A better understanding of the process is vital in therapeutic application of this defense mechanism and treatment of cognate human diseases. In addition to exporting dsRNAs, mitochondria also export and import a variety of non-coding RNAs. However, little is known about how these RNAs are transported across mitochondrial membranes. Here we provide direct evidence showing that adenine nucleotide translocase-2 (ANT2) functions as a mammalian RNA translocon in the mitochondrial inner membrane, independent of its ADP/ATP translocase activity. We also show that mitochondrial dsRNA efflux through ANT2 triggers innate immunity. Inhibiting this process alleviates inflammation in vivo, providing a potential therapeutic approach for treating autoimmune diseases.

PMID:38811766 | PMC:PMC11217343 | DOI:10.1038/s41422-024-00978-5

29 May 15:01

Mitochondria at the crossroads of health and disease

Publication date: 23 May 2024

Source: Cell, Volume 187, Issue 11

Author(s): Anu Suomalainen, Jodi Nunnari

29 May 14:59

Novel therapeutic strategy for obesity through the gut microbiota-brain axis: A review article

by Romina Kardan

Caspian J Intern Med. 2024 Spring;15(2):215-227. doi: 10.22088/cjim.15.2.215.

ABSTRACT

Background: The interaction between commensal bacteria and the host is essential for health and the gut microbiota-brain axis plays a vital role in this regard. Obesity as a medical problem not only affect the health of the individuals, but also the economic and social aspects of communities. The presence of any dysbiosis in the composition of the gut microbiota disrupts in the gut microbiota-brain axis, which in turn leads to an increase in appetite and then obesity. Because common treatments for obesity have several drawbacks, the use of microbiota-based therapy in addition to treatment and prevention of obesity can have other numerous benefits for the individual. In this review, we intend to investigate the relationship between obesity and the gut microbiota-brain axis as well as novel treatment strategies based on this axis with an emphasis on gut microbiota.

PMID:38807723 | PMC:PMC11129059 | DOI:10.22088/cjim.15.2.215

29 May 14:55

Host defence peptide plectasin targets bacterial cell wall precursor lipid II by a calcium-sensitive supramolecular mechanism

by Shehrazade Jekhmane

Nat Microbiol. 2024 May 23. doi: 10.1038/s41564-024-01696-9. Online ahead of print.

ABSTRACT

Antimicrobial resistance is a leading cause of mortality, calling for the development of new antibiotics. The fungal antibiotic plectasin is a eukaryotic host defence peptide that blocks bacterial cell wall synthesis. Here, using a combination of solid-state nuclear magnetic resonance, atomic force microscopy and activity assays, we show that plectasin uses a calcium-sensitive supramolecular killing mechanism. Efficient and selective binding of the target lipid II, a cell wall precursor with an irreplaceable pyrophosphate, is achieved by the oligomerization of plectasin into dense supra-structures that only form on bacterial membranes that comprise lipid II. Oligomerization and target binding of plectasin are interdependent and are enhanced by the coordination of calcium ions to plectasin's prominent anionic patch, causing allosteric changes that markedly improve the activity of the antibiotic. Structural knowledge of how host defence peptides impair cell wall synthesis will likely enable the development of superior drug candidates.

PMID:38783023 | DOI:10.1038/s41564-024-01696-9

29 May 14:51

Molecular basis for antibody recognition of multiple drug–peptide/MHC complexes

by Lorenzo MasoEpsa RajakInjin BangAkiko KoideTakamitsu HattoriBenjamin G. NeelShohei KoideaLaura and Isaac Perlmutter Cancer Center, New York University Langone Health, New York, NY 10016bDepartment of Medicine, New York University School of Medicine, New York, NY 10016cDepartment of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY 10016
Proceedings of the National Academy of Sciences, Volume 121, Issue 22, May 2024.
29 May 14:50

Dual role of the peptide-loading complex as proofreader and limiter of MHC-I presentation

by Jamina BrunnbergMartina BarendsStefan FrühschulzChristian WinterClaire BattinBen de WetDavid K. ColePeter SteinbergerRobert TampéaInstitute of Biochemistry, Biocenter, Goethe University Frankfurt, Frankfurt am Main 60438, GermanybInstitute of Immunology, Center for Pathophysiology, Infectiology and Immunology, Medical University of Vienna, Vienna 1090, AustriacImmunocore Ltd., Abingdon OX14 4RY, United Kingdom
Proceedings of the National Academy of Sciences, Volume 121, Issue 22, May 2024.
29 May 14:50

Type VII secretion system extracellular protein B targets STING to evade host anti–Staphylococcus aureus immunity

by Lin GaoTian TianTingrong XiongXiaomei ZhangNing WangLuxuan LiuYun ShiQiang LiuDongshui LuPing LuoWeijun ZhangPing ChengQiang GouYu WangHao ZengXiaokai ZhangQuanming ZouaNational Engineering Research Center of Immunological Products, Department of Microbiology and Biochemical Pharmacy, College of Pharmacy, Third Military Medical University, Chongqing 400038, ChinabDepartment of Medical Engineering, Xinqiao Hospital, Third Military Medical University, Chongqing 400038, ChinacInstitute of Biopharmaceutical Research, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, ChinadDepartment of Basic Courses, Non-Commissioned Officer School, Third Military Medical University, Shijiazhuang 050081, ChinaeState Key Laboratory of Trauma, Burn and Combined Injury, Third Military Medical University, Chongqing 400038, China
Proceedings of the National Academy of Sciences, Volume 121, Issue 22, May 2024.
29 May 13:51

New molecule found to suppress bacterial antibiotic resistance evolution

Researchers from the University of Oxford have developed a new small molecule that can suppress the evolution of antibiotic resistance in bacteria and make resistant bacteria more susceptible to antibiotics. The paper, "Development of an inhibitor of the mutagenic SOS response that suppresses the evolution of quinolone antibiotic resistance," has been published in the journal Chemical Science.
22 May 16:31

[ASAP] Naked-Eye LAMP Assay of M. tuberculosis in Sputum by In Situ Au Nanoprobe Identification: For the In Vitro Diagnostics of Tuberculosis

by Xiaochang Zhang, Yongshuai Tian, Yali Shi, Jianan Liu, Chenlin Zhao, Chia-Chen Chang, Tohru Takarada, Mizuo Maeda, and Guoqing Wang

TOC Graphic

ACS Infectious Diseases
DOI: 10.1021/acsinfecdis.4c00013
21 May 13:58

Merging Flow Synthesis and Enzymatic Maturation to Expand the Chemical Space of Lasso Peptides

by Kevin Schiefelbein

J Am Chem Soc. 2024 Jun 26;146(25):17261-17269. doi: 10.1021/jacs.4c03898. Epub 2024 May 17.

ABSTRACT

Many peptidic natural products, such as lasso peptides, cyclic peptides, and cyclotides, are conformationally constrained and show biological stability, making them attractive scaffolds for drug development. Although many peptides can be synthesized and modified through chemical methods, knot-like lasso peptides such as microcin J25 (MccJ25) and their analogues remain elusive. As the chemical space of MccJ25 analogues accessible through purely biological methods is also limited, we proposed a hybrid approach: flow-based chemical synthesis of non-natural precursor peptides, followed by in vitro transformation with recombinant maturation enzymes, to yield a more diverse array of lasso peptides. Herein, we established the rapid, flow-based synthesis of chemically modified MccJ25 precursor peptides (57 amino acids). Heterologous expression of enzymes McjB and McjC was extensively optimized to improve yields and facilitate the synthesis of multiple analogues of MccJ25, including the incorporation of non-canonical tyrosine and histidine derivatives into the lasso scaffold. Finally, using our chemoenzymatic strategy, we produced a biologically active analogue containing three d-amino acids in the loop region and incorporated backbone N-methylations. Our method provides rapid access to chemically modified lasso peptides that could be used to investigate structure-activity relationships, epitope grafting, and the improvement of therapeutic properties.

PMID:38759637 | PMC:PMC11212047 | DOI:10.1021/jacs.4c03898

21 May 13:33

Elevated Na is a dynamic and reversible modulator of mitochondrial metabolism in the heart

by Yu Jin Chung

Nat Commun. 2024 May 20;15(1):4277. doi: 10.1038/s41467-024-48474-z.

ABSTRACT

Elevated intracellular sodium Nai adversely affects mitochondrial metabolism and is a common feature of heart failure. The reversibility of acute Na induced metabolic changes is evaluated in Langendorff perfused rat hearts using the Na/K ATPase inhibitor ouabain and the myosin-uncoupler para-aminoblebbistatin to maintain constant energetic demand. Elevated Nai decreases Gibb's free energy of ATP hydrolysis, increases the TCA cycle intermediates succinate and fumarate, decreases ETC activity at Complexes I, II and III, and causes a redox shift of CoQ to CoQH2, which are all reversed on lowering Nai to baseline levels. Pseudo hypoxia and stabilization of HIF-1α is observed despite normal tissue oxygenation. Inhibition of mitochondrial Na/Ca-exchange with CGP-37517 or treatment with the mitochondrial ROS scavenger MitoQ prevents the metabolic alterations during Nai elevation. Elevated Nai plays a reversible role in the metabolic and functional changes and is a novel therapeutic target to correct metabolic dysfunction in heart failure.

PMID:38769288 | PMC:PMC11106256 | DOI:10.1038/s41467-024-48474-z

20 May 16:06

Lipid A in outer membrane vesicles shields bacteria from polymyxins

by Marie Burt

J Extracell Vesicles. 2024 May;13(5):e12447. doi: 10.1002/jev2.12447.

ABSTRACT

The continuous emergence of multidrug-resistant bacterial pathogens poses a major global healthcare challenge, with Klebsiella pneumoniae being a prominent threat. We conducted a comprehensive study on K. pneumoniae's antibiotic resistance mechanisms, focusing on outer membrane vesicles (OMVs) and polymyxin, a last-resort antibiotic. Our research demonstrates that OMVs protect bacteria from polymyxins. OMVs derived from Polymyxin B (PB)-stressed K. pneumoniae exhibited heightened protective efficacy due to increased vesiculation, compared to OMVs from unstressed Klebsiella. OMVs also shield bacteria from different bacterial families. This was validated ex vivo and in vivo using precision cut lung slices (PCLS) and Galleria mellonella. In all models, OMVs protected K. pneumoniae from PB and reduced the associated stress response on protein level. We observed significant changes in the lipid composition of OMVs upon PB treatment, affecting their binding capacity to PB. The altered binding capacity of single OMVs from PB stressed K. pneumoniae could be linked to a reduction in the lipid A amount of their released vesicles. Although the amount of lipid A per vesicle is reduced, the overall increase in the number of vesicles results in an increased protection because the sum of lipid A and therefore PB binding sites have increased. This unravels the mechanism of the altered PB protective efficacy of OMVs from PB stressed K. pneumoniae compared to control OMVs. The lipid A-dependent protective effect against PB was confirmed in vitro using artificial vesicles. Moreover, artificial vesicles successfully protected Klebsiella from PB ex vivo and in vivo. The findings indicate that OMVs act as protective shields for bacteria by binding to polymyxins, effectively serving as decoys and preventing antibiotic interaction with the cell surface. Our findings provide valuable insights into the mechanisms underlying antibiotic cross-protection and offer potential avenues for the development of novel therapeutic interventions to address the escalating threat of multidrug-resistant bacterial infections.

PMID:38766978 | PMC:PMC11103557 | DOI:10.1002/jev2.12447

20 May 16:04

Structure and mechanism of biosynthesis of Streptococcus mutans cell wall polysaccharide

by Jeffrey S Rush

bioRxiv [Preprint]. 2024 May 9:2024.05.09.593426. doi: 10.1101/2024.05.09.593426.

ABSTRACT

Streptococcus mutans, the causative agent of human dental caries, expresses a cell wall attached Serotype c- specific Carbohydrate (SCC) that is critical for cell viability. SCC consists of a repeating →3)α-Rha(1→2)α-Rha(1→ polyrhamnose backbone, with glucose (Glc) side-chains and glycerol phosphate (GroP) decorations. This study reveals that SCC has one major and two minor Glc modifications. The major Glc modification, α-Glc, attached to position 2 of 3-rhamnose, is installed by SccN and SccM glycosyltransferases and is the site of the GroP addition. The minor Glc modifications are β-Glc linked to position 4 of 3-rhamnose installed by SccP and SccQ glycosyltransferases, and α-Glc attached to position 4 of 2-rhamnose installed by SccN working in tandem with an unknown enzyme. Both the major and the minor β-Glc modifications control bacterial morphology, but only the GroP and major Glc modifications are critical for biofilm formation.

PMID:38766245 | PMC:PMC11100793 | DOI:10.1101/2024.05.09.593426

20 May 16:02

The roles of B cells in cardiovascular diseases

by Jian Ma

Mol Immunol. 2024 May 18;171:36-46. doi: 10.1016/j.molimm.2024.05.002. Online ahead of print.

ABSTRACT

Damage to the heart can start the repair process and cause cardiac remodeling. B cells play an important role in this process. B cells are recruited to the injured place and activate cardiac remodeling through secreting antibodies and cytokines. Different types of B cells showed specific functions in the heart. Among all types of B cells, heart-associated B cells play a vital role in the heart by secreting TGFβ1. B cells participate in the activation of fibroblasts and promote cardiac fibrosis. Four subtypes of B cells in the heart revealed the relationship between the B cells' heterogeneity and cardiac remodeling. Many cardiovascular diseases like atherosclerosis, heart failure (HF), hypertension, myocardial infarction (MI), and dilated cardiomyopathy (DCM) are related to B cells. The primary mechanisms of these B cell-related activities will be discussed in this review, which may also suggest potential novel therapeutic targets.

PMID:38763105 | DOI:10.1016/j.molimm.2024.05.002

20 May 16:02

Poly-β-(1→6)-N-acetyl-D-glucosamine mediates surface attachment, biofilm formation, and biocide resistance in Cutibacterium acnes

by Jeffrey B Kaplan

Front Microbiol. 2024 May 1;15:1386017. doi: 10.3389/fmicb.2024.1386017. eCollection 2024.

ABSTRACT

BACKGROUND: The commensal skin bacterium Cutibacterium acnes plays a role in the pathogenesis of acne vulgaris and also causes opportunistic infections of implanted medical devices due to its ability to form biofilms on biomaterial surfaces. Poly-β-(1→6)-N-acetyl-D-glucosamine (PNAG) is an extracellular polysaccharide that mediates biofilm formation and biocide resistance in a wide range of bacterial pathogens. The objective of this study was to determine whether C. acnes produces PNAG, and whether PNAG contributes to C. acnes biofilm formation and biocide resistance in vitro.

METHODS: PNAG was detected on the surface of C. acnes cells by fluorescence confocal microscopy using the antigen-specific human IgG1 monoclonal antibody F598. PNAG was detected in C. acnes biofilms by measuring the ability of the PNAG-specific glycosidase dispersin B to inhibit biofilm formation and sensitize biofilms to biocide killing.

RESULTS: Monoclonal antibody F598 bound to the surface of C. acnes cells. Dispersin B inhibited attachment of C. acnes cells to polystyrene rods, inhibited biofilm formation by C. acnes in glass and polypropylene tubes, and sensitized C. acnes biofilms to killing by benzoyl peroxide and tetracycline.

CONCLUSION: C. acnes produces PNAG, and PNAG contributes to C. acnes biofilm formation and biocide resistance in vitro. PNAG may play a role in C. acnes skin colonization, biocide resistance, and virulence in vivo.

PMID:38751716 | PMC:PMC11094747 | DOI:10.3389/fmicb.2024.1386017

20 May 16:00

Gut microbes may influence cardiovascular health

by Iris Marchal

Nature Biotechnology, Published online: 17 May 2024; doi:10.1038/s41587-024-02259-3

Gut microbes may influence cardiovascular health
20 May 16:00

Gut microbes linked to fatty diet drive tumour growth

by Gillian Dohrn

Nature, Published online: 16 May 2024; doi:10.1038/d41586-024-01443-4

Scientists know there is a link between obesity and some cancers. A study in mice and people suggests why that might be.
17 May 16:57

[ASAP] Development and Application of Cationic Nile Blue Probes in Live-Cell Super-Resolution Imaging and Specific Targeting to Mitochondria

by Yunsheng Li, Xiaoyu Bai, and Dan Yang

TOC Graphic

ACS Central Science
DOI: 10.1021/acscentsci.4c00073