Disruption of lipid homeostasis in the Gram-negative cell envelope activates a novel cell death pathway.

TitleDisruption of lipid homeostasis in the Gram-negative cell envelope activates a novel cell death pathway.
Publication TypeJournal Article
Year of Publication2016
AuthorsSutterlin, HA, Shi, H, May, KL, Miguel, A, Khare, S, Huang, KCasey, Silhavy, TJ
JournalProc Natl Acad Sci U S A
Volume113
Issue11
PaginationE1565-74
Date Published2016 Mar 15
ISSN1091-6490
KeywordsBacterial Outer Membrane Proteins, Cell Membrane, Cell Wall, Escherichia coli, Escherichia coli Proteins, Fatty Acids, Lipid Metabolism, Lipopolysaccharides, Magnesium, Mutation, Permeability, Phospholipases A1, Phospholipids
Abstract

<p>Gram-negative bacteria balance synthesis of the outer membrane (OM), cell wall, and cytoplasmic contents during growth via unknown mechanisms. Here, we show that a dominant mutation (designated mlaA*, maintenance of lipid asymmetry) that alters MlaA, a lipoprotein that removes phospholipids from the outer leaflet of the OM of Escherichia coli, increases OM permeability, lipopolysaccharide levels, drug sensitivity, and cell death in stationary phase. Surprisingly, single-cell imaging revealed that death occurs after protracted loss of OM material through vesiculation and blebbing at cell-division sites and compensatory shrinkage of the inner membrane, eventually resulting in rupture and slow leakage of cytoplasmic contents. The death of mlaA* cells was linked to fatty acid depletion and was not affected by membrane depolarization, suggesting that lipids flow from the inner membrane to the OM in an energy-independent manner. Suppressor analysis suggested that the dominant mlaA* mutation activates phospholipase A, resulting in increased levels of lipopolysaccharide and OM vesiculation that ultimately undermine the integrity of the cell envelope by depleting the inner membrane of phospholipids. This novel cell-death pathway suggests that balanced synthesis across both membranes is key to the mechanical integrity of the Gram-negative cell envelope. </p>

DOI10.1073/pnas.1601375113
Alternate JournalProc. Natl. Acad. Sci. U.S.A.
PubMed ID26929379
PubMed Central IDPMC4801249
Grant ListR01 GM034821 / GM / NIGMS NIH HHS / United States
GM34821 / GM / NIGMS NIH HHS / United States
P50 GM107615 / GM / NIGMS NIH HHS / United States
DP2OD006466 / OD / NIH HHS / United States
R37 GM034821 / GM / NIGMS NIH HHS / United States
DP2 OD006466 / OD / NIH HHS / United States