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Biochimica Et Biophysica Acta.... Feb 2022Aquaporins play a crucial role in water homeostasis in the human body, and recently the physiological importance of aquaporins as glycerol channels have been...
Aquaporins play a crucial role in water homeostasis in the human body, and recently the physiological importance of aquaporins as glycerol channels have been demonstrated. The aquaglyceroporins (AQP3, AQP7, AQP9 and AQP10) represent key glycerol channels, enabling glycerol flux across the membranes of cells. Adipocytes are the major source of glycerol and during lipolysis, glycerol is released to be metabolized by other tissues through a well-orchestrated process. Here we show that both AQP3 and AQP7 bind to the lipid droplet protein perilipin 1 (PLIN1), suggesting that PLIN1 is involved in the coordination of the subcellular translocation of aquaglyceroporins in human adipocytes. Moreover, in addition to aquaglyceroporins, we discovered by transcriptome sequencing that AQP1 is expressed in human primary adipocytes. AQP1 is mainly a water channel and thus is thought to be involved in the response to hyper-osmotic stress by efflux of water during hyperglycemia. Thus, this data suggests a contribution of both orthodox aquaporin and aquaglyceroporin in human adipocytes to maintain the homeostasis of glycerol and water during fasting and feeding.
Topics: Adipocytes; Aquaglyceroporins; Aquaporin 1; Aquaporin 3; Aquaporins; Gene Expression Regulation; Glycerol; Homeostasis; Humans; Hyperglycemia; Perilipin-1; Transcriptome; Water
PubMed: 34627746
DOI: 10.1016/j.bbamem.2021.183795 -
Nature Reviews. Microbiology Mar 2020Gram-negative bacteria and their complex cell envelope, which comprises an outer membrane and an inner membrane, are an important and attractive system for studying the... (Review)
Review
Gram-negative bacteria and their complex cell envelope, which comprises an outer membrane and an inner membrane, are an important and attractive system for studying the translocation of small molecules across biological membranes. In the outer membrane of Enterobacteriaceae, trimeric porins control the cellular uptake of small molecules, including nutrients and antibacterial agents. The relatively slow porin-mediated passive uptake across the outer membrane and active efflux via efflux pumps in the inner membrane creates a permeability barrier. The synergistic action of outer membrane permeability, efflux pump activities and enzymatic degradation efficiently reduces the intracellular concentrations of small molecules and contributes to the emergence of antibiotic resistance. In this Review, we discuss recent advances in our understanding of the molecular and functional roles of general porins in small-molecule translocation in Enterobacteriaceae and consider the crucial contribution of porins in antibiotic resistance.
Topics: Anti-Bacterial Agents; Bacterial Outer Membrane Proteins; Biological Transport; Cell Membrane; Drug Resistance, Bacterial; Enterobacteriaceae; Porins
PubMed: 31792365
DOI: 10.1038/s41579-019-0294-2 -
Emerging Microbes & Infections Dec 2024Carbapenem-resistant Enterobacterales (CRE), specifically those resistant to only ertapenem among carbapenems (ETP-mono-resistant), are increasingly reported, while the... (Randomized Controlled Trial)
Randomized Controlled Trial
Carbapenem-resistant Enterobacterales (CRE), specifically those resistant to only ertapenem among carbapenems (ETP-mono-resistant), are increasingly reported, while the optimal therapy options remain uncertain. To investigate the prevalence and characteristics of ETP-mono-resistant CRE, CRE strains were systematically collected from 102 hospitals across China between 2018 and 2021. A 1:1 randomized matching study was conducted with ETP-mono-resistant strains to meropenem- and/or imipenem-resistant (MEM/IPM-resistant) strains. Antimicrobial susceptibility testing, whole-genome sequencing, carbapenem-hydrolysing activity and the expression of carbapenemase genes were determined. In total, 18.8% of CRE strains were ETP-mono-resistant, with relatively low ertapenem MIC values. ETP-mono-resistant strains exhibited enhanced susceptibility to β-lactams, β-lactam/β-lactamase inhibitor combinations, levofloxacin, fosfomycin, amikacin and polymyxin than MEM/IPM-resistant strains ( < 0.05). Phylogenetic analysis revealed high genetic diversity among ETP-mono-resistant strains. Extended-spectrum β-lactamases (ESBLs) and/or AmpC, as well as porin mutations, were identified as potential major mechanisms mediating ETP-mono-resistance, while the presence of carbapenemases was found to be the key factor distinguishing the carbapenem-resistant phenotypes between the two groups ( < 0.001). Compared with the MEM/IPM-resistant group, limited carbapenemase-producing CRE (CP-CRE) strains in the ETP-mono-resistant group showed a significantly lower prevalence of ESBLs and porin mutations, along with reduced expression of carbapenemase. Remarkably, spot assays combined with modified carbapenem inactivation method indicated that ETP-mono-resistant CP-CRE isolates grew at meropenem concentrations eightfold above their corresponding MIC values, accompanied by rapidly enhanced carbapenem-hydrolysing ability. These findings illustrate that ETP-mono-resistant CRE strains are relatively prevalent and that caution should be exercised when using meropenem alone for treatment. The detection of carbapenemase should be prioritized.
Topics: Anti-Bacterial Agents; Bacterial Proteins; beta-Lactamases; Carbapenems; Ertapenem; Meropenem; Microbial Sensitivity Tests; Phylogeny; Porins; Prevalence; China
PubMed: 38517707
DOI: 10.1080/22221751.2024.2332658 -
Trends in Microbiology Apr 2024Neisseria gonorrhoeae is a human-specific pathogen responsible for the sexually transmitted infection, gonorrhoea. N. gonorrhoeae promotes its survival by manipulating... (Review)
Review
Neisseria gonorrhoeae is a human-specific pathogen responsible for the sexually transmitted infection, gonorrhoea. N. gonorrhoeae promotes its survival by manipulating both innate and adaptive immune responses. The most abundant gonococcal outer-membrane protein is PorB, an essential porin that facilitates ion exchange. Importantly, gonococcal PorB has several immunomodulatory properties. To subvert the innate immune response, PorB suppresses killing mechanisms of macrophages and neutrophils, and recruits negative regulators of complement to the gonococcal cell surface. For manipulation of adaptive immune responses, gonococcal PorB suppresses the capability of dendritic cells to stimulate proliferation of T cells. As gonococcal PorB is highly abundant in outer-membrane vesicles, consideration of the immunomodulatory properties of this porin is critical when designing gonococcal vaccines.
Topics: Humans; Gonorrhea; Neisseria gonorrhoeae; Porins; Cell Membrane; Immunity
PubMed: 37891023
DOI: 10.1016/j.tim.2023.10.002 -
Methods in Enzymology 2021Pore forming proteins are released as water-soluble monomers that form-mostly oligomeric-pores in target membranes. Our understanding of such pore formation relies in...
Pore forming proteins are released as water-soluble monomers that form-mostly oligomeric-pores in target membranes. Our understanding of such pore formation relies in part on the direct visualization of their assemblies on and in the membrane. Here, we discuss the application of atomic force microscopy (AFM) to visualize and understand membrane pore formation, illustrated specifically by studies of proteins of the MACPF/CDC superfamily on supported lipid bilayers. Besides detailed protocols, we also point out common imaging artefacts and strategies to avoid them, and briefly outline how AFM can be effectively used in conjunction with other methods.
Topics: Lipid Bilayers; Microscopy, Atomic Force; Porins
PubMed: 33712186
DOI: 10.1016/bs.mie.2021.01.002 -
American Journal of Physiology. Cell... Jul 2023Cell migration is an essential process that underlies many physiological processes, including the immune response, organogenesis in the embryo, and angiogenesis, as well... (Review)
Review
Cell migration is an essential process that underlies many physiological processes, including the immune response, organogenesis in the embryo, and angiogenesis, as well as pathological processes such as cancer metastasis. Cells have at their disposal a variety of migratory behaviors and mechanisms that seem to be specific to cell type and the microenvironment. Research over the past two decades has elucidated the water channel protein family of aquaporins (AQPs) as a regulator of many cell migration-related processes, from physical phenomena to biological signaling pathways. The roles that AQPs play in cell migration are both cell type- and isoform-specific; thus, a large swath of information has accumulated as researchers seek to identify the responses across these distinct variables. There does not seem to be a universal role that AQPs play in cell migration; the complex interplay between AQPs and cell volume management, signaling pathway activation, and in a few identified circumstances, gene expression regulation, has shown the intricate, and perhaps paradoxical, role of AQPs in cell migration. The objective of this review is to provide an organized and integrated collection of recent work that has elucidated the many mechanisms by which AQPs regulate cell migration. Research has elucidated the water channel protein family of aquaporins (AQPs) as a regulator of many cell migration-related processes, from physical phenomena to biological signaling pathways. The roles that AQPs play in cell migration are both cell type- and isoform-specific; thus, a large swath of information has accumulated as researchers seek to identify the responses across these distinct variables. This review compiles insights into the recent findings linking AQPs to physiological cell migration.
Topics: Aquaporins; Gene Expression Regulation; Signal Transduction; Cell Movement
PubMed: 37246634
DOI: 10.1152/ajpcell.00502.2022 -
Small (Weinheim An Der Bergstrasse,... Apr 2022The outer membrane (OM) of gram-negative bacteria is highly asymmetric. The outer leaflet comprises lipopolysaccharides (LPS) and the inner leaflet phospholipids. Here,...
The outer membrane (OM) of gram-negative bacteria is highly asymmetric. The outer leaflet comprises lipopolysaccharides (LPS) and the inner leaflet phospholipids. Here, it is shown that the outer membrane lipid bilayer (OMLB) of Escherichia coli can be reconstructed as a droplet interface bilayer (DIB), which separates two aqueous droplets in oil. The trimeric porin OmpF is inserted into the model OMLB and the translocation of the bacteriocin colicin E9 (colE9) through it is monitored. By contrast with LPS-free bilayers, it is found that colE9 made multiple failed attempts to engage with OmpF in an OMLB before successful translocation occurred. In addition, the observed rate for the second step of colE9 translocation is 3-times smaller than that in LPS-free bilayers, and further, the colE9 dissociates when the membrane potential is reversed. The findings demonstrate the utility of the DIB approach for constructing model OMLBs from physiologically realistic lipids and that the properties of the model OMLBs differ from those of a simple lipid bilayer. The model OMLB offers a credible platform for screening the properties of antibiotics.
Topics: Bacterial Outer Membrane Proteins; Colicins; Escherichia coli; Escherichia coli Proteins; Lipid Bilayers; Lipopolysaccharides; Porins
PubMed: 35289495
DOI: 10.1002/smll.202200007 -
Microbiology Spectrum Dec 2022OmpA, the most abundant porin in Stenotrophomonas maltophilia KJ, exists as a two-domain structure with an N-terminal domain of β-barrel structure embedded in the outer...
OmpA, the most abundant porin in Stenotrophomonas maltophilia KJ, exists as a two-domain structure with an N-terminal domain of β-barrel structure embedded in the outer membrane and a C-terminal domain collocated in the periplasm. KJΔOmpA, an mutant of S. maltophilia KJ with a truncated OmpA devoid of 299 to 356 amino acids (aa), was able to stably embed in the outer membrane. KJΔOmpA was more susceptible to β-lactams than wild-type KJ. We aimed to elucidate the mechanism underlying the Δ-mediated increase in β-lactam susceptibility (abbreviated as "ΔOmpA phenotype"). KJΔOmpA displayed a lower ceftazidime (CAZ)-induced β-lactamase activity than KJ. Furthermore, KJ2, a L1/L2 β-lactamases-null mutant, and KJ2ΔOmpA, a KJ2 mutant with truncated OmpA devoid of299 to 356 aa, had comparable β-lactam susceptibility. Both lines of evidence indicate that decreased β-lactamase activity contributes to the ΔOmpA phenotype. We analyzed the transcriptome results of KJ and KJΔOmpA, focusing on PG homeostasis-associated genes. Among the 36 genes analyzed, the gene was upregulated 4.65-fold in KJΔOmpA. Deletion of the gene from the chromosome of KJΔOmpA restored β-lactam susceptibility and CAZ-induced β-lactamase activity to wild-type levels, verifying that -upregulation in KJΔOmpA contributes to the ΔOmpA phenotype. Furthermore, transcriptome analysis revealed that (Smlt3555) and (Smlt3514) were significantly upregulated in KJΔOmpA. The deletion mutant construction, β-lactam susceptibility, and β-lactamase activity analysis demonstrated that σ, but not σ, was involved in the ΔOmpA phenotype. A real-time quantitative (qRT-PCR) assay confirmed that is a member of the σ regulon. The involvement of the σ-NagA-L1/L2 regulatory circuit in the ΔOmpA phenotype was manifested. Porins of Gram-negative bacteria generally act as channels that allow the entry or extrusion of molecules. Moreover, the structural role of porins in stabilizing the outer membrane by interacting with peptidoglycan (PG) and the outer membrane has been proposed. The linkage between porin deficiency and antibiotic resistance increase has been reported widely, with a rationale for blocking antibiotic influx. In this study, a link between porin defects and β-lactam susceptibility increase was demonstrated. The underlying mechanism revealed that a novel σ-NagA-L1/L2 regulatory circuit is triggered due to the loss of the OmpA-PG interaction. This study extends the understanding on the porin defect and antibiotic susceptibility. Porin defects may cause opposite impacts on antibiotic susceptibility, which is dependent on the involvement of the defect. Blocking the porin channel role can increase antibiotic resistance; in contrast, the loss of porin structure role may increase antibiotic susceptibility.
Topics: Stenotrophomonas maltophilia; Microbial Sensitivity Tests; beta-Lactamases; Anti-Bacterial Agents; Ceftazidime; Porins; Bacterial Proteins
PubMed: 36350132
DOI: 10.1128/spectrum.02797-22 -
Journal of Hazardous Materials Oct 2023Mycotoxin contamination can cause severe health issues for both humans and animals. This study examined the potential of enzymes derived from Acinetobacter nosocomialis...
Mycotoxin contamination can cause severe health issues for both humans and animals. This study examined the potential of enzymes derived from Acinetobacter nosocomialis Y1 to simultaneously degrade aflatoxin B (AFB) and zearalenone (ZEN), which could have significant implications in reducing mycotoxin contamination. Two enzymes, Porin and Peroxiredoxin, were identified with molecular weights of 27.8 and 20.8 kDa, respectively. Porin could completely degrade 2 µg/mL of AFB and ZEN within 24 h at 80 °C and 60 °C, respectively. Peroxiredoxin could completely degrade 2 µg/mL of AFB and reduce ZEN by 91.12% within 24 h. The addition of Na, Cu, and K ions enhanced the degradation activities of both enzymes. LC-MS/MS analysis revealed that the molar masses of the degradation products of AFB and ZEN were 286 g/mol and 322.06 g/mol, and the products were identified as AFD and α or β-ZAL, respectively. Vibrio fischeri bioluminescence assays further confirmed that the cytotoxicity of the two degradation products was significantly lower than that of AFB and ZEN. Based on these results, it can be inferred that the degradation product of ZEN is β-ZAL. These findings suggest that both enzymes have the potential to be utilized as detoxification enzymes in food and feed.
Topics: Humans; Animals; Zearalenone; Aflatoxin B1; Peroxiredoxins; Chromatography, Liquid; Porins; Tandem Mass Spectrometry; Mycotoxins; Food Contamination
PubMed: 37494799
DOI: 10.1016/j.jhazmat.2023.132105 -
International Journal of Molecular... Jul 2023The outer membrane of Gram-negative bacteria contains a variety of pore-forming structures collectively referred to as porins. Some of these are voltage dependent, but...
The outer membrane of Gram-negative bacteria contains a variety of pore-forming structures collectively referred to as porins. Some of these are voltage dependent, but weakly so, closing at high voltages. Triplin, a novel bacterial pore-former, is a three-pore structure, highly voltage dependent, with a complex gating process. The three pores close sequentially: pore 1 at positive potentials, 2 at negative and 3 at positive. A positive domain containing 14 positive charges (the voltage sensor) translocates through the membrane during the closing process, and the translocation is proposed to take place by the domain entering the pore and thus blocking it, resulting in the closed conformation. This mechanism of pore closure is supported by kinetic measurements that show that in the closing process the voltage sensor travels through most of the transmembrane voltage before reaching the energy barrier. Voltage-dependent blockage of the pores by polyarginine, but not by a 500-fold higher concentrations of polylysine, is consistent with the model of pore closure, with the sensor consisting mainly of arginine residues, and with the presence, in each pore, of a complementary surface that serves as a binding site for the sensor.
Topics: Humans; Ion Channel Gating; Porins; Thiourea; Translocation, Genetic
PubMed: 37511231
DOI: 10.3390/ijms241411473