Role of diacylglycerol in the cellular response to lysophosphatidylcholine analogues
Date
2019-09-19
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Abstract
Diacylglycerol (DAG) is a key signaling lipid and intermediate in lipid metabolism. Our knowledge of DAG distribution in cell membranes is limited. Using the C1 domain from mammalian PKCĪ“ and PKD, we monitored the localization of yeast cytosolic-facing pools of DAG for the very first time and investigated alteration in distribution in response to conditions where DAG levels were known to be altered. Two main pools were monitored over time using DAG sensors. One stable pool was associated with vacuolar membranes and a second temporal pool was localized to sites of polarized growth. Dynamic changes in DAG distribution were observed during resumption of growth from stationary phase, when DAG is used to support phospholipid synthesis for membrane proliferation. Vacuolar membranes experienced constant morphological changes displaying DAG enriched microdomains co-existing with liquid-disordered areas demarcated by Vph1. Formation of these domains was dependent on TAG lipolysis. DAG domains and puncta were closely connected to lipid droplets and our findings suggest that DAG could link lipid droplets and tubular ER upon growth resumption from stationary phase. DAG polarization was regulated by DAG to PA conversion upon TAG mobilization, phosphatidylserine synthesis/traffic and sphingolipid synthesis in the Golgi. We also investigated another condition where DAG accumulates, which is in cells treated with the lysophosphatidylcholine analogue edelfosine. We hypothesized that by manipulating levels of PA and DAG, cells confer resistance to edelfosine, possibly due to mislocalized PA and DAG which prevent cellular response to edelfosine. Experiment where PA and DAG levels were manipulated clearly support a protective role of PA in the response to edelfosine. Interestingly, edelfosine induced drastic change in the localization of DAG. A synthetic genetic array analysis pointed to endocytic and retrograde trafficking proteins as key players in modulating DAG distribution. Many of these trafficking mutants were also resistant to edelfosine, suggesting mislocalization of DAG is advantageous in the presence of edelfosine. In addition, a putative lipase Ydr444w and the PI4P phosphatase Sac1 were also identified as novel regulators of DAG homeostasis. An up-to-date map of the spatiotemporal distribution of the cytosolic pools of DAG in yeast emerged from this body of work.
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Keywords
lysophosphatidylcholine , antitumor lipids, diacylglycerol, lipid metabolism
Citation
Ganesan, S. (2019). Role of diacylglycerol in the cellular response to lysophosphatidylcholine analogues (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.