Anionic lipids and the cytoskeletal proteins MreB and RodZ define the spatio-temporal distribution and function of membrane stress controller PspA in Escherichia coli

Abstract

All cell types must maintain the integrity of their membranes. The conserved bacterial membraneassociated protein PspA is a major effector acting upon extracytoplasmic stress and is implicated in protection of the inner membrane of pathogens, formation of biofilms and multi-drug-resistant persister cells. PspA and its homologues in Gram-positive bacteria and archaea protect the cell envelope whilst also supporting thylakoid biogenesis in cyanobacteria and higher plants. In enterobacteria, PspA is a dual function protein negatively regulating the Psp system in the absence of stress and acting as an effector of membrane integrity upon stress. We show that in Escherichia coli the low-order oligomeric PspA regulatory complex associates with cardiolipinrich, curved polar inner membrane regions. There, cardiolipin and the flotillin 1 homologue YqiK support the PspBC sensors in transducing a membrane stress signal to the PspA-PspF inhibitory complex. After stress perception, PspA high-order oligomeric effector complexes initially assemble in polar membrane regions. Subsequently, the discrete spatial distribution and dynamics of PspA effector(s) in lateral membrane regions depend on the actin homologue MreB and the peptidoglycan machinery protein RodZ. The consequences of loss of cytoplasmic membrane anionic lipids, MreB, RodZ and/or YqiK suggest that the mode of action of the PspA effector is closely associated with cell envelope organization.

Evaluating the role of phage-shock protein A in Burkholderia pseudomallei

“…Previous studies have observed the formation of 36-mers by E. coli PspA in vitro (Hankamer et al , 2004), supported by further data showing that PspA forms up to 36-mers in vivo (Jovanovic et al , 2014b). Similarly, in B. subtilis the Lia system contains a PspA homologue, LiaH, which has been shown to form large oligomeric rings (Wolf et al , 2010).…”

“…This behaviour may aid in the stabilization of the B. pseudomallei cytoplasmic membrane during induction of the Psp-like response as a result of stressful conditions. Recently, it has been proposed that in E. coli PspA is potentially targeted to areas of the inner membrane associated with peptidoglycan biosynthesis machinery (Jovanovic et al , 2014b). In light of this, the presence of a gene encoding a penicillin-binding protein, mrcA , directly upstream of BPSL2105 may be significant.…”

The Phage Shock Protein Response

“…Observation of fluorescent PspA indicated that the movement of oligomers is important for PMF preservation and depends on the cytoskeletal proteins MreB and RodZ (25,45). Therefore, it was suggested that PspA function relates to cell envelope organization, with links to peptidoglycan and phospholipid biogenesis (25,48). The molecular details of how this mechanism might work are unclear, and caution should probably be taken when interpreting the effects of mreB-or rodZ-null mutations because of the possibility of pleotropic effects on the cell envelope.…”

Is the cellular and molecular machinery docile in the stationary phase of Escherichia coli?

“…The repressive PspF-PspA complex bound to psp promoter(s) on the DNA dynamically and transiently communicates with the IM under non-stress conditions. Under IM stress conditions, PspA dissociates from the PspF-PspA inhibitory complex and binds the stressed membrane as a higher order oligomer [7][8][9]. Under all experimental conditions, the PspF assembled and localized on the DNA as a single hexameric species, binding and activating a single psp promoter (pspA or pspG) at a time [7].…”