Arv1 Regulates PM and ER Membrane Structure and Homeostasis But is Dispensable for Intracellular Sterol Transport

Abstract

The pan-eukaryotic endoplasmic reticulum (ER) membrane protein Arv1 has been suggested to play a role in intracellular sterol transport. We tested this proposal by comparing sterol traffic in wild-type and Arv1-deficient Saccharomyces cerevisiae. We used fluorescence microscopy to track the retrograde movement of exogenously supplied dehydroergosterol (DHE) from the plasma membrane (PM) to the ER and lipid droplets and high performance liquid chromatography to quantify, in parallel, the transport-coupled formation of DHE esters. Metabolic labeling and subcellular fractionation were used to assay anterograde transport of ergosterol from the ER to the PM. We report that sterol transport between the ER and PM is unaffected by Arv1 deficiency. Instead, our results indicate differences in ER morphology and the organization of the PM lipid bilayer between wild-type and arv1Δ cells suggesting a distinct role for Arv1 in membrane homeostasis. In arv1Δ cells, specific defects affecting single C-terminal transmembrane domain proteins suggest that Arv1 might regulate membrane insertion of tail-anchored proteins involved in membrane homoeostasis.

A Functional, Genome-wide Evaluation of Liposensitive Yeast Identifies the “RE2 Required for Viability” (ARV1) Gene Product as a Major Component of Eukaryotic Fatty Acid Resistance

“…1D). The defects in TG homeostasis resulting from altered ARV1 expression may thus be secondary to its role as a possible sterol transporter (although this role has recently been questioned (80)). Alternatively, the global changes in lipid composition and architecture of multiple cellular membranes that arise in ARV1-deficient states may disturb their function to the extent that the additional stress of FA overload or impaired esterification is lethal.…”

Mice lacking have reduced signs of metabolic syndrome and non-alcoholic fatty liver disease

“…Our results strongly suggest that complete loss of Arv1 protects mice from acquiring MetS and NAFLD in response to a HFD challenge. While it is still up for debate as to what is the function of ARV1 (13)(14)(15)18,19,41), evidence is accumulating that suggests it's involvement in maintaining proper sterol distribution (16,20,42,43).…”

“…S. cerevisiae cells lacking ARV1 have defects in PL (phospholipid), SL (sphingolipid), GPI (glycosylphosphatidylinositol) and sterol syntheses, and lack the ability to localize sterol and mobilize PIP 2 (phosphatidylinositol 4,5 bisphosphate) (13)(14)(15)(16). arv1 deficient cells are hypersensitive to the PS (phosphatidylserine) binding agent, papuamide-B, suggesting a mislocalization of PS to the plasma membrane (17). They contain fragmented vacuoles and a disrupted organelle phenotype (17), which most likely activates the unfolded protein response (18).…”

“…arv1 deficient cells are hypersensitive to the PS (phosphatidylserine) binding agent, papuamide-B, suggesting a mislocalization of PS to the plasma membrane (17). They contain fragmented vacuoles and a disrupted organelle phenotype (17), which most likely activates the unfolded protein response (18). Null cells are hypersensitive to fatty acid supplementation (19), suggesting that Arv1 also regulates fatty acid metabolism.…”

Proper Sterol Distribution Is Required for Candida albicans Hyphal Formation and Virulence

“…The topology of the S. cerevisiae Arv1 has been solved. It has three endoplasmic reticular transmembrane-spanning regions, a cytoplasmic-facing AHD, and a single large luminal loop region (Georgiev et al 2013; Villasmil and Nickels 2011). arv1 cells are hypersusceptible to the ergosterol-binding agent nystatin, suggesting a mislocalization of sterol to the plasma membrane (Tinkelenberg et al 2000).…”