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

Publication date: 8 August 2017
Source:Cell Reports, Volume 20, Issue 6
Author(s): Patrick Ebner, Arif Luqman, Sebastian Reichert, Ksenia Hauf, Peter Popella, Karl Forchhammer, Michael Otto, Friedrich Götz
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 ECP, while PSMβ peptides or δ-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. PSMα 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, PSMα peptides non-specifically boost the translocation of CPs by their membrane-damaging activity.

Graphical abstract

Teaser

Ebner et al. find that in pathogenic Staphylococcus aureus strains, the release of cytoplasmic proteins (CPs) is not caused by co-secretion through known secretion systems but by the expression of the α-type phenol-soluble modulins (PSMα) that make the cytoplasmic membrane leaky for CPs.


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