Defense Date

3-11-2024

Graduation Date

Spring 5-10-2024

Availability

Immediate Access

Submission Type

dissertation

Degree Name

PhD

Department

Biological Sciences

School

School of Science and Engineering

Committee Chair

Jana Patton-Vogt

Committee Member

Michael Jensen-Seaman

Committee Member

John Pollock

Committee Member

Jeffrey Brodsky

Keywords

baker's yeast, lipid, fission yeast, metabolism, glycerophosphocholine, phosphatidylcholine

Abstract

Glycerophosphocholine (GPC) is an abundant metabolite in eukaryotes. In baker’s yeast, Saccharomyces cerevisiae, GPC can be produced via deacylation of the major membrane glycerophospholipid phosphatidylcholine (PC). My lab has identified a novel pathway to re-synthesize PC from GPC by acylating it at the sn-1 and sn-2 positions; this pathway has been termed the PC Deacylation-Reacylation Pathway (PC-DRP). We previously characterized the acyltransferase Gpc1 and its ability to synthesize one-tailed lyso-PC from GPC, as well as that noting that GPC1 is upregulated in inositol-free conditions and results in more saturated PC. Here, I add to this basic characterization by establishing that GPC1 is upregulated in conditions that induce the unfolded protein response (UPR), a transcriptional response to proteotoxic or bilayer stress. A knockout strain lacking GPC1 also has increased sensitivity to UPR-inducing proteotoxic compounds. I repeat our prior findings that Gpc1 activity results in increased monounsaturated PC and decreased diunsaturated PC, and show that loss of GPC1 upregulates the UPR via bilayer stress – concordant with the knowledge that altered saturation can induce the UPR. The second project related to GPC that is presented here involves its transport, toxicity, and metabolic fates in S. cerevisiae and fission yeast, Schizosaccharomyces pombe. This work was done in collaboration with the Schwer lab (Weill Cornell Medical University) and the Shuman lab (Sloan Kettering Institute). Based on the Schwer/Shuman labs’ findings that S. pombe with an upregulated glycerophosphodiester transporter are sensitive to added GPC, I have characterized this transporter (Tgp1) and that it transports GPC but not glycerophosphoinositol. I show that loss of the glycerophosphodiesterase Gde1 confers resistance to GPC, and through growth curves, radiolabeling experiments, and column chromatography, demonstrate that both the active site and inositol pyrophosphate-binding SPX domains are required for Gde1 regulation. I also find that similarly to S. pombe, S. cerevisiae is sensitive to excess GPC when GDE1 is upregulated. On the other hand, loss of Gpc1, providing the alternative metabolic fate for GPC (acylation) from Gde1 (breakdown), does not impact sensitivity in either organism. Furthermore, a high level of necrosis does not occur upon GPC provision in either organism.

Language

English

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