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J Cell Sci. 2016 Jan 1;129(1):51-64. doi: 10.1242/jcs.176701. Epub 2015 Nov 24.

LPS impairs oxygen utilization in epithelia by triggering degradation of the mitochondrial enzyme Alcat1.

Author information

1
Department of Medicine, Acute Lung Injury Center of Excellence, University of Pittsburgh, Pittsburgh, PA 15213, USA.
2
Institute of Biomedicine & National Engineering Research Center of Genetic Medicine, College of Life Science and Technology, Jinan University, Guangzhou 510630, China.
3
Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA 15213, USA.
4
Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, PA 15213, USA.
5
Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA 15213, USA Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, PA 15213, USA.
6
Department of Medicine, Acute Lung Injury Center of Excellence, University of Pittsburgh, Pittsburgh, PA 15213, USA Department of Cell Biology and Physiology and Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA Medical Specialty Service Line, Veterans Affairs Pittsburgh Healthcare System, Pittsburgh, PA 15240, USA mallampallirk@upmc.edu.

Abstract

Cardiolipin (also known as PDL6) is an indispensable lipid required for mitochondrial respiration that is generated through de novo synthesis and remodeling. Here, the cardiolipin remodeling enzyme, acyl-CoA:lysocardiolipin-acyltransferase-1 (Alcat1; SwissProt ID, Q6UWP7) is destabilized in epithelia by lipopolysaccharide (LPS) impairing mitochondrial function. Exposure to LPS selectively decreased levels of carbon 20 (C20)-containing cardiolipin molecular species, whereas the content of C18 or C16 species was not significantly altered, consistent with decreased levels of Alcat1. Alcat1 is a labile protein that is lysosomally degraded by the ubiquitin E3 ligase Skp-Cullin-F-box containing the Fbxo28 subunit (SCF-Fbxo28) that targets Alcat1 for monoubiquitylation at residue K183. Interestingly, K183 is also an acetylation-acceptor site, and acetylation conferred stability to the enzyme. Histone deacetylase 2 (HDAC2) interacted with Alcat1, and expression of a plasmid encoding HDAC2 or treatment of cells with LPS deacetylated and destabilized Alcat1, whereas treatment of cells with a pan-HDAC inhibitor increased Alcat1 levels. Alcat1 degradation was partially abrogated in LPS-treated cells that had been silenced for HDAC2 or treated with MLN4924, an inhibitor of Cullin-RING E3 ubiquitin ligases. Thus, LPS increases HDAC2-mediated Alcat1 deacetylation and facilitates SCF-Fbxo28-mediated disposal of Alcat1, thus impairing mitochondrial integrity.

KEYWORDS:

Degradation; Mitochondria; Ubiquitin

PMID:
26604221
PMCID:
PMC4732295
DOI:
10.1242/jcs.176701
[Indexed for MEDLINE]
Free PMC Article

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