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Membrane phospholipid remodeling modulates nonalcoholic steatohepatitis progression by regulating mitochondrial homeostasis [Lpcat3_OE]

ABSTRACT: Nonalcoholic steatohepatitis (NASH), characterized by inflammation and fibrosis, is emerging as a leading etiology of hepatocellular carcinoma (HCC). However, the mechanisms underlying the pathogenesis of NASH are not well understood. Here, we show that membrane phospholipid (PL) composition determined by a remodeling process modulates the progression of NASH. The expression of lysophosphatidylcholine acyltransferase 3 (LPCAT3), a PL remodeling enzyme that produces polyunsaturated PLs, is dramatically suppressed in human NASH livers compared to controls. LPCAT3 expression is inversely correlated with NAFLD activity score and fibrosis stage. Loss of Lpcat3 in mouse liver promotes the development of both spontaneous and diet-induced NASH/HCC. Mechanistically, Lpcat3 deficiency increases reactive oxygen species production, likely due to impaired mitochondrial homeostasis as demonstrated by reduced mitochondrial DNA content and fragmented mitochondrial morphology. Overexpressing Lpcat3 in the liver ameliorates inflammation and fibrosis of NASH. These results suggest that manipulating LPCAT3 expression may be an effective therapeutic strategy for NASH.

ORGANISM(S): Mus musculus

PROVIDER: GSE218074 | GEO | 2024/06/05

REPOSITORIES: GEO

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Project description:Membrane protein and phospholipid (PL) compositions change in response to environmental cues and during infections. Covalent modification (e.g., unsaturation and cyclopropanation) and remodeling the acyl chain length of PLs is an important bacterial adaptation mechanism. However, little is known about which bacterial pathways are regulated in response to the alteration of PL composition. Here, we show that P. aeruginosa PlaF, which modulates membrane PL composition, is important for biofilm biogenesis, and we performed whole-cell quantitative proteomics of P. aeruginosa wild-type and ∆plaF biofilms to identify pathways regulated by PlaF. The results revealed profound alterations in the abundance of 14 two-component systems (TCS), including the PprA-PprB, which controls the transition to biofilm. Activation of PprA-the PprB system observed by proteomics was confirmed by mRNA quantification. Furthermore, we have observed a unique phosphorylation pattern of transcriptional regulators, transporters and metabolic enzymes, and differential production of nine proteases in ∆plaF, indicating that PlaF-mediated virulence adaptation involves complex transcriptional and post-transcriptional regulation. Moreover, proteomics revealed that the pyoverdin-mediated iron uptake pathway proteins were depleted in ∆plaF, which agrees with decreased concentrations of extracellular pyoverdine and intracellular iron in ∆plaF and is likely responsible for its prolonged lag phase due to reduced iron uptake. Conversely, the accumulation of proteins from alternative iron-uptake systems in ∆plaF suggests that PlaF may function as a switch between different iron-acquisition pathways. The observation that ∆plaF accumulates PL-acyl chain modifying enzymes and PlsX, an initiator of de novo PL synthesis, reveals novel insights into the relationship between degradation, covalent modification and biosynthesis of PLs for membrane homeostasis. Although the precise mechanism by which PlaF simultaneously affects multiple pathways remains to be elucidated, we suggest that PlaF-catalyzed degradation of PLs is a signal which is amplified by proteins of TCS, phosphorylation and proteolytic degradation systems to elicit the global adaptive response in P. aeruginosa.

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Membrane phospholipid remodeling modulates nonalcoholic steatohepatitis progression by regulating mitochondrial homeostasis [Lpcat3_OE]

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