Mol. Cells 2017; 40(12): 935~944  https://doi.org/10.14348/molcells.2017.0201
Inhibition of Autolysis by Lipase LipA in Streptococcus pneumoniae Sepsis
Gyu-Lee Kim1,4, Truc Thanh Luong1,4, Sang-Sang Park3, Seungyeop Lee1, Jung Ah Ha1,
Cuong Thach Nguyen1, Ji Hye Ahn1, Ki-Tae Park1, Man-Jeong Paik2, Suhkneung Pyo1,
David E. Briles3, and Dong-Kwon Rhee1,*
1School of Pharmacy, Sungkyunkwan University, Suwon 16419, Korea, 2College of Pharmacy, Sunchon National University,
Suncheon 57922, Korea, 3Department of Microbiology, University of Alabama at Birmingham, AL 35294-2170, USA, 4These
authors contributed equally to this work.
*Correspondence: dkrhee@skku.edu
Received September 9, 2017; Revised November 19, 2017; Accepted November 21, 2017.; Published online December 26, 2017.
© Korean Society for Molecular and Cellular Biology. All rights reserved.

This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. To view a copy of this license, visit (http://creativecommons.org/licenses/by-nc-sa/3.0/).
ABSTRACT
More than 50% of sepsis cases are associated with pneumonia. Sepsis is caused by infiltration of bacteria into the blood via inflammation, which is triggered by the release of cell wall components following lysis. However, the regulatory mechanism of lysis during infection is not well defined. Mice were infected with Streptococcus pneumoniae D39 wild-type (WT) and lipase mutant (ΔlipA) intranasally (pneumonia model) or intraperitoneally (sepsis model), and survival rate and pneumococcal colonization were determined. LipA and autolysin (LytA) levels were determined by qPCR and western blotting. S. pneumoniae Spd_1447 in the D39 (type 2) strain was identified as a lipase (LipA). In the sepsis model, but not in the pneumonia model, mice infected with the ΔlipA displayed higher mortality rates than did the D39 WT-infected mice. Treatment of pneumococci with serum induced LipA expression at both the mRNA and protein levels. In the presence of serum, the ΔlipA displayed faster lysis rates and higher LytA expression than the WT, both in vitro and in vivo. These results indicate that a pneumococcal lipase (LipA) represses autolysis via inhibition of LytA in a sepsis model.
Keywords: infection, LipA, LytA, sepsis, S. pneumoniae


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