TY - JOUR

T1 - The role of full-length apoE in clearance of Gram-negative bacteria and their endotoxins

AU - Petruk, Ganna

AU - Elven, Malin

AU - Hartman, Erik

AU - Davoudi, Mina

AU - Schmidtchen, Artur

AU - Puthia, Manoj

AU - Petrlova, Jitka

PY - 2021

Y1 - 2021

N2 - ApoE is a well-known lipid-binding protein that plays a main role in the metabolism and transport of lipids. More recently, apoE-derived peptides have been shown to exert antimicrobial effects. Here, we investigated the antibacterial activity of apoE using in vitro assays, advanced imaging techniques, and in vivo mouse models. The formation of macromolecular complexes of apoE and endotoxins from Gram-negative bacteria was explored using gel shift assays, transmission electron microscopy, and CD spectroscopy followed by calculation of the a-helical content. The binding affinity of apoE to endotoxins was also confirmed by fluorescent spectroscopy detecting the quenching and shifting of tryptophan intrinsic fluorescence. We showed that apoE exhibits antibacterial activity particularly against Gram-negative bacteria such as Pseuclomonas aeruginosa and Escherichia coli. ApoE protein folding was affected by binding of bacterial endotoxin components such as lipopolysaccharide (LPS) and lipid A, yielding similar increases in the apoE a-helical content. Moreover, high-molecular-weight complexes of apoE were formed in the presence of LPS, but not to the same extent as with lipid A. Together, our results demonstrate the ability of apoE to kill Gramnegative bacteria, interact with their endotoxins, which leads to the structural changes in apoE and the formation of aggregate-like complexes.

AB - ApoE is a well-known lipid-binding protein that plays a main role in the metabolism and transport of lipids. More recently, apoE-derived peptides have been shown to exert antimicrobial effects. Here, we investigated the antibacterial activity of apoE using in vitro assays, advanced imaging techniques, and in vivo mouse models. The formation of macromolecular complexes of apoE and endotoxins from Gram-negative bacteria was explored using gel shift assays, transmission electron microscopy, and CD spectroscopy followed by calculation of the a-helical content. The binding affinity of apoE to endotoxins was also confirmed by fluorescent spectroscopy detecting the quenching and shifting of tryptophan intrinsic fluorescence. We showed that apoE exhibits antibacterial activity particularly against Gram-negative bacteria such as Pseuclomonas aeruginosa and Escherichia coli. ApoE protein folding was affected by binding of bacterial endotoxin components such as lipopolysaccharide (LPS) and lipid A, yielding similar increases in the apoE a-helical content. Moreover, high-molecular-weight complexes of apoE were formed in the presence of LPS, but not to the same extent as with lipid A. Together, our results demonstrate the ability of apoE to kill Gramnegative bacteria, interact with their endotoxins, which leads to the structural changes in apoE and the formation of aggregate-like complexes.

KW - antimicrobial peptides

KW - bacteria

KW - host defense

KW - innate immunity

KW - infection

KW - aggregation

KW - lipopolysaccharide

KW - lipid A

KW - CD

KW - HUMAN APOLIPOPROTEIN-E

KW - C-TERMINAL FRAGMENTS

KW - E-DEFICIENT MICE

KW - ANTIMICROBIAL PEPTIDE

KW - BINDING

KW - LIPOPOLYSACCHARIDE

KW - SUSCEPTIBILITY

KW - LIPOPROTEINS

KW - APOPROTEIN

KW - PROTEGRIN

U2 - 10.1016/j.jlr.2021.100086

DO - 10.1016/j.jlr.2021.100086

M3 - Journal article

C2 - 34019903

VL - 62

JO - Journal of Lipid Research

JF - Journal of Lipid Research

SN - 0022-2275

M1 - 100086

ER -