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Non-classical Protein Excretion Is Boosted by PSM?-Induced Cell Leakage.

ABSTRACT: Release of cytoplasmic proteins into the supernatant occurs both in bacteria and eukaryotes. Because the underlying mechanism remains unclear, the excretion of cytoplasmic proteins (ECP) has been referred to as "non-classical protein secretion." We show that none of the known specific protein transport systems of Gram-positive bacteria are involved in ECP. However, the expression of the cationic and amphipathic ?-type phenol-soluble modulins (PSMs), particularly of PSM?2, significantly increase ECP, while PSM? peptides or ?-toxin have no effect on ECP. Because psm expression is strictly controlled by the accessory gene regulator (agr), ECP is also reduced in agr-negative mutants. PSM? peptides damage the cytoplasmic membrane, as indicated by the release of not only CPs but also lipids, nucleic acids, and ATP. Thus, our results show that in Staphylococcus aureus, PSM? peptides non-specifically boost the translocation of CPs by their membrane-damaging activity.

SUBMITTER: Ebner P

PROVIDER: S-EPMC6129975 | biostudies-literature | 2017 Aug

REPOSITORIES: biostudies-literature

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Non-classical Protein Excretion Is Boosted by PSMα-Induced Cell Leakage.

Ebner Patrick P Luqman Arif A Reichert Sebastian S Hauf Ksenia K Popella Peter P Forchhammer Karl K Otto Michael M Götz Friedrich F

Cell reports 20170801 6

Release of cytoplasmic proteins into the supernatant occurs both in bacteria and eukaryotes. Because the underlying mechanism remains unclear, the excretion of cytoplasmic proteins (ECP) has been referred to as "non-classical protein secretion." We show that none of the known specific protein transport systems of Gram-positive bacteria are involved in ECP. However, the expression of the cationic and amphipathic α-type phenol-soluble modulins (PSMs), particularly of PSMα2, significantly increase ...[more]

PMID: 28793253

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Project description:BackgroundAlcohol intoxication can increase inflammation and worsen injury, yet the mechanisms involved are not clear. We investigated whether acute alcohol intoxication increases microvascular permeability and investigated potential signaling mechanisms in endothelial cells that may be involved.MethodsConscious rats received a 2.5 g/kg alcohol bolus via gastric catheters to produce acute intoxication. Microvascular leakage of intravenously administered fluorescein isothiocyanate (FITC)-conjugated albumin (FITC-albumin) from the mesenteric microcirculation was assessed by intravital microscopy. Endothelial-specific mechanisms were studied using cultured endothelial cell monolayers. Transendothelial electrical resistance (TER) served as an index of barrier function, before and after treatment with alcohol or its metabolite acetaldehyde. Pharmacologic agents were used to test the roles of alcohol metabolism, oxidative stress, p38 mitogen-activated protein kinase (MAPK), myosin light-chain kinase (MLCK), rho kinase (ROCK), and exchange protein activated by cAMP (Epac). VE-cadherin localization was investigated to assess junctional integrity. Rac1 and RhoA activation was assessed by ELISA assays.ResultsAlcohol significantly increased FITC-albumin extravasation from the mesenteric microcirculation. Alcohol also significantly decreased TER and disrupted VE-cadherin organization at junctions. Acetaldehyde significantly decreased TER, but inhibition of alcohol dehydrogenase or application of a superoxide dismutase mimetic failed to prevent alcohol-induced decreases in TER. Inhibition of p38 MAPK, but not MLCK or ROCK, significantly attenuated the alcohol-induced barrier dysfunction. Alcohol rapidly decreased GTP-bound Rac1 but not RhoA during the drop in TER. Activation of Epac increased TER, but did not prevent alcohol from decreasing TER. However, activation of Epac after initiation of alcohol-induced barrier dysfunction quickly resolved TER to baseline levels.ConclusionsOur results suggest that alcohol intoxication increases microvascular permeability to plasma proteins. The data also suggest the endothelial-specific mechanism involves the p38 MAPK, Rac1, and reorganization of VE-cadherin at junctions. Last, activation of Epac can quickly resolve alcohol-induced endothelial barrier dysfunction.

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Non-classical Protein Excretion Is Boosted by PSM?-Induced Cell Leakage.

Publications

Non-classical Protein Excretion Is Boosted by PSMα-Induced Cell Leakage.

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