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How organisms lacking oxidizable lipids utilize lipid peroxidation for signaling: lipidomics approach

Ting, Hsiu-Chi (2019) How organisms lacking oxidizable lipids utilize lipid peroxidation for signaling: lipidomics approach. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Polyunsaturated lipids are lipids which contain two or more carbon-carbon double bonds in their constituent hydrocarbon chains. They also serve as excellent substrates for lipid peroxidation. However, the roles of lipid peroxidation and its associated enzymes in organisms lacking polyunsaturated fatty acids (PUFA) synthesis remain unclear. In this thesis, we studied 1) the function of the cardiolipin (CL) remodeling enzyme CL deacylase 1 (Cld1) in CL peroxidation in Saccharomyces cerevisiae (S. cerevisiae) and 2) the significance of pLoxA, a lipoxygenase (LOX) in Pseudomonas aeruginosa (P. aeruginosa), in triggering ferroptosis in host bronchial epithelial (HBE) cells.

In the first study, we detected oxidized CL (CLox) and other oxidized PLs (PLox) in both Δ12-desaturase-expressing WT and cld1Δ yeast. The higher molar ratio of CLox than other PL and the absence of phosphatidylserine oxidation suggested the oxidation events occurred in the mitochondria. The loss of cld1 elevated the levels of mono-hydroperoxy-CLs and decreased the chronological lifespan, mitochondrial membrane potential, and respiratory capacity of the yeast. We also found that CLox is a preferred substrate for Cld1 in vitro compared to non-oxidized CLs. These data suggest CL remodeling is required to mitigate CL peroxidation. In the second study, we demonstrated pLoxA is required for P. aeruginosa to induce ferroptosis in HBE cells. We found that clinical P. aeruginosa isolate-induced ferroptosis correlated significantly with the amount of pLoxA and its 15LOX activity.We found that pro-ferroptotic lipid signals 15-hydroperoxy-arachidonoyl phosphatidylethanolamines were elevated in both HBE cells treated with P. aeruginosa supernatants and in airway tissues from cystic fibrosis (CF) patients with P. aeruginosa. Computational studies showed that the catalytic site of LOX is highly conserved among species. The α-helical-lid interaction of pLoxA facilitates AA-PE binding, resembling the function of the PE-binding protein (PEBP) in the PEBP-15LOX complex in mammalian cells. These data showed that P. aeruginosa hijacks host polyunsaturated PEs to induce ferroptosis in the bronchial epithelium.

For public health significance, the function of CL remodeling in mitigating CL peroxidation could contribute to the study of CL remodeling defects in Barth syndrome. The pLoxA-driven ferroptosis could be a potential therapeutic target against P. aeruginosa–associated diseases.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Ting, Hsiu-Chihst9@pitt.eduhst9
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairKagan,
Committee MemberPitt,
Committee MemberBayır, Hü
Committee MemberGreenberger,
Date: 27 June 2019
Date Type: Publication
Defense Date: 13 December 2018
Approval Date: 27 June 2019
Submission Date: 31 January 2019
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 168
Institution: University of Pittsburgh
Schools and Programs: School of Public Health > Environmental and Occupational Health
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: Cld1; cardiolipin; lipid peroxidation; mass spectrometry (MS); polyunsaturated fatty acid (PUFA); remodeling; yeast; Bacterial infections; Cell Biology; Infectious disease
Date Deposited: 27 Jun 2019 19:46
Last Modified: 27 Jun 2019 19:46


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