Regulation of lipid droplet dynamics in Saccharomyces cerevisiae depends on the Rab7-like Ypt7p, HOPS complex and V1-ATPase

Abstract

It has now been clearly shown that lipid droplets (LDs) play a dynamic role in the cell. This was reinforced by LD proteomics which suggest that a significant number of trafficking proteins are associated with this organelle. Using microscopy, we showed that LDs partly co-localize with the vacuole in S. cerevisiae. Immunoblot experiments confirmed the association of the vacuolar Rab GTPase Rab7-like Ypt7p with LDs. We observed an increase in fatty acid content and LD number in ypt7Δ mutant and also changes in LD morphology and intra LD fusions, revealing a direct role for Ypt7p in LD dynamics. Using co-immunoprecipitation, we isolated potential Ypt7p partners including, Vma13p, the H subunit of the V1 part of the vacuolar (H+) ATPase (V-ATPase). Deletion of the VMA13 gene, as well as deletion of three other subunits of the V1 part of the V-ATPase, also increased the cell fatty acid content and LD number. Mutants of the Homotypic fusion and vacuole protein sorting (HOPS) complex showed similar phenotypes. Here, we demonstrated that LD dynamics and membrane trafficking between the vacuole and LDs are regulated by the Rab7-like Ypt7p and are impaired when the HOPS complex and the V1 domain of the V-ATPase are defective.

Regulation and Functions of Autophagic Lipolysis

“…Microscopic and proteomic analysis demonstrated that Ypt7p is associated with LDs in yeast grown in poor medium. Defective Ypt7p strains have increased FFA content and numbers of LDs in low nutrient conditions [26]. Together with the previous mammalian findings, these studies indicate that Rab7 may be a conserved regulator of lipophagy.…”

“…Consistent with a conserved regulatory role of Rab7 in lipophagy is that the yeast Rab7-like protein Ypt7p regulates LD dynamics and membrane trafficking in S. Cerevisiae [26]. Microscopic and proteomic analysis demonstrated that Ypt7p is associated with LDs in yeast grown in poor medium.…”

“…In yeast, Ypt7p partners have been identified by co-immunoprecipitation studies, among which the H subunit of the V-ATPase proton pump, Vma13p, is involved in LD dynamics. Selective mutagenesis studies showed that another component of the V-ATPase is required for lipophagy, the homotypic fusion and protein sorting (HOPS)-tethering complex [26], which mediates autophagosome-lysosome fusion [27]. In mammals, Rab-interacting lysosomal protein (RILP) protein has been reported to be essential for Rab7 function in starvation-induced LD breakdown in hepatocytes [24].…”

A squalene synthase protein degradation method for improved sesquiterpene production in Saccharomyces cerevisiae

“…These regions have been reported as lipid droplets (LDs) (Bouchez et al, 2015;Wolinski et al, 2011).…”

Molecular Mechanisms and Physiological Significance of Organelle Interactions and Cooperation

“…Endosomes have also been observed to enwrap LDs, potentially promoting the delivery of LDs to lysosomes allowing for the transfer of cholesterol (Martin and Parton, 2005;Ouimet et al, 2011). Even though the interaction of LDs and other organelles (e.g., endosomes, ER, and vacuole) appears to be regulated by several Rab GTPases (Liu et al, 2007;Murphy et al, 2009;Bouchez et al, 2015), and the fusion events between LDs themselves, or LDs and mitochondria likely involves SNARE-mediated homotypic fusion Jägerström et al, 2009;Olofsson et al, 2009), the underlying molecular mechanisms remain largely unknown. In this respect, the LD-associated protein perilipin 5 is regarded as a candidate for the physical and metabolic linkage of mitochondria to LDs (Wang et al, 2011), whereas the molecular basis for a peroxisome-LD interaction remains elusive.…”