Metabolic control of cytosolic‐facing pools of diacylglycerol in budding yeast.

Diacylglycerol (DAG) is a key signaling lipid and intermediate in lipid metabolism. Our knowledge of DAG distribution and dynamics in cell membranes is limited. Using live‐cell fluorescence microscopy we investigated the localization of yeast cytosolic‐facing pools of DAG in response to conditions where lipid homeostasis and DAG levels were known to be altered. Two main pools were monitored over time using DAG sensors. One pool was associated with vacuolar membranes and the other 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 coexisting with liquid‐disordered areas demarcated by Vph1. Formation of these domains was dependent on triacylglycerol (TAG) lipolysis. DAG domains and puncta were closely connected to lipid droplets. Lack of conversion of DAG to phosphatidate in growth conditions dependent on TAG mobilization, led to the accumulation of DAG in a vacuolar‐associated compartment, impacting the polarized distribution of DAG at budding sites. DAG polarization was also regulated by phosphatidylserine synthesis/traffic and sphingolipid synthesis in the Golgi. Cytosolic‐facing pools of diacylglycerol (DAG) are monitored in live yeast during growth resumption from stationary phase. Two dynamic pools are revealed at vacuoles and sites of polarized growth. Vacuolar DAG forms liquid ordered microdomains and puncta interacting with lipid droplets. Lack of conversion of DAG to phosphatidate when triacylglycerol (TAG) lipolysis is enhanced induces DAG accumulation in an intermediate compartment. Phosphatidylserine synthesis and traffic through the Golgi in conjunction with sphingolipid synthesis promotes polarized DAG localization. [ABSTRACT FROM AUTHOR]