The toxicity of sterols to cells is a significant component of several disease syndromes ranging from Alzheimer's disease to Atherosclerosis. We hypothesize that a pivotal component of obviating this threat is the removal of the offending metabolite to non-toxic environments, for neutralization by esterification or efflux to extracellular acceptors. The endoplasmic reticulum is a critical organelle with regard to sterol homeostasis. Sterol levels in this organelle are maintained at very low levels, relative to the plasma membrane, in part by anteriograde transport. We have identified an evolutionary conserved component of this transport, Arvlp that directs the egress of sterol from the endoplasmic reticulum to the plasma membrane. Furthermore, one consequence of loss of Arvlp is induction of the unfolded protein response. The association of this pathway with membrane related changes is unprecedented and will likely impact pathologies that arise from protein misfolding (e.g. prion disorders). Our studies will utilize genetic approaches to understand the mechanisms and consequences of ARVl-mediated sterol transport. In this revised proposal, we will continue to exploit genetic and cell biology approaches in yeast, and expand these approaches to understanding the role of Arvl in higher cells and multicellular organisms.
Our specific aims and hypotheses are: 1. To define the mechanisms by which Arvlp mediates sterol transport in yeast. We hypothesize that the structure of ARV1 (Zn-binding motif and transmembrane nature) is required for sterol transport and that these domains mediate ligand (lipid and protein) binding. 2. To identify and characterize new components of sterol homeostasis. We hypothesize that ARV1 represents a decision point in terms of responses to sterol overloading of a cell. Factors that interact with ARV1 will be critical to sterol homeostasis and cell survival. One example of such a pathway is the Unfolded Protein response (UPR) which is induced by loss of ARVl. We will identify and analyze these pathways using genetic and biochemical approaches. 3. To define the role of Arvlp in mammalian cells. We hypothesize that the role of ARVl in human cells is also to transport sterol to the plasma membrane. We will test the ramifications of overexpression or knockdown of human ARVl in various tissue culture cell models. Lipid efflux to extracellular acceptors will be studied in detail.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK054320-08
Application #
7113220
Study Section
Integrative Nutrition and Metabolic Processes Study Section (INMP)
Program Officer
Haft, Carol R
Project Start
1999-05-01
Project End
2009-07-31
Budget Start
2006-08-01
Budget End
2007-07-31
Support Year
8
Fiscal Year
2006
Total Cost
$287,675
Indirect Cost
Name
Columbia University (N.Y.)
Department
Miscellaneous
Type
Schools of Medicine
DUNS #
621889815
City
New York
State
NY
Country
United States
Zip Code
10032
Munkacsi, Andrew B; Hammond, Natalie; Schneider, Remy T et al. (2017) Normalization of Hepatic Homeostasis in the Npc1nmf164 Mouse Model of Niemann-Pick Type C Disease Treated with the Histone Deacetylase Inhibitor Vorinostat. J Biol Chem 292:4395-4410
Gulati, Sonia; Balderes, Dina; Kim, Christine et al. (2015) ATP-binding cassette transporters and sterol O-acyltransferases interact at membrane microdomains to modulate sterol uptake and esterification. FASEB J 29:4682-94
Ruggles, Kelly V; Garbarino, Jeanne; Liu, Ying et al. (2014) A functional, genome-wide evaluation of liposensitive yeast identifies the ""ARE2 required for viability"" (ARV1) gene product as a major component of eukaryotic fatty acid resistance. J Biol Chem 289:4417-31
Ruggles, Kelly V; Turkish, Aaron; Sturley, Stephen L (2013) Making, baking, and breaking: the synthesis, storage, and hydrolysis of neutral lipids. Annu Rev Nutr 33:413-51
Sturley, Stephen L; Hussain, M Mahmood (2012) Lipid droplet formation on opposing sides of the endoplasmic reticulum. J Lipid Res 53:1800-10
Munkacsi, Andrew B; Chen, Fannie W; Brinkman, Matthew A et al. (2011) An ""exacerbate-reverse"" strategy in yeast identifies histone deacetylase inhibition as a correction for cholesterol and sphingolipid transport defects in human Niemann-Pick type C disease. J Biol Chem 286:23842-51
Shechtman, Caryn F; Henneberry, Annette L; Seimon, Tracie A et al. (2011) Loss of subcellular lipid transport due to ARV1 deficiency disrupts organelle homeostasis and activates the unfolded protein response. J Biol Chem 286:11951-9
Fakas, Stylianos; Qiu, Yixuan; Dixon, Joseph L et al. (2011) Phosphatidate phosphatase activity plays key role in protection against fatty acid-induced toxicity in yeast. J Biol Chem 286:29074-85
Gulati, Sonia; Liu, Ying; Munkacsi, Andrew B et al. (2010) Sterols and sphingolipids: dynamic duo or partners in crime? Prog Lipid Res 49:353-65
Madra, Moneek; Sturley, Stephen L (2010) Niemann-Pick type C pathogenesis and treatment: from statins to sugars. Clin Lipidol 5:387-395

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