{"id":{"repo_id":"columbia-diss","oai_identifier":"oai:academiccommons.columbia.edu:10.7916/D86D60ZV"},"canonical_url":"https://search.dev.ndltd.org/etd/columbia-diss/oai:academiccommons.columbia.edu:10.7916/D86D60ZV","repository":{"repo_id":"columbia-diss","name":"Columbia University","base_url":"https://academiccommons.columbia.edu/oai"},"display":{"title":"Characterization of ARV1-Mediated Sterol Transport in Yeast and Mammalian Systems","abstract":"Saccharomyces cerevisiae Arv1p (𝘈𝘙𝘌2 required for viability 1) is an endoplasmic reticulum (ER)-localized, functionally conserved protein that was initially observed to mediate subcellular sterol distribution, and has since been implicated in the movement of multiple lipid species. In this thesis, we examined the role of ARV1 in S. cerevisiae and mammalian systems by two approaches. In yeast, we used gene deletion to access loss of Arv1p function. In mammalian cells we utilized antisense oligonucleotides (ASOs) to decrease 𝘈𝘙𝘝1 expression 𝘪𝘯 𝘷𝘪𝘵𝘳𝘰 and 𝘪𝘯 𝘷𝘪𝘷𝘰. In the yeast model, loss of Arv1p function results in sensitivity to modulators of sphingolipid homeostasis and aberrant accumulation of exogenous sterols. Transcription microarrays demonstrated that ARV1 deletion impacts ER homeostasis and activates the transcription factor HAC1, a component of the unfolded protein response (UPR) signaling cascade in yeast. Moreover, 𝘢𝘳𝘷1𝛥 strains exhibited constitutive UPR induction, mediated by the unfolded protein sensor Ire1p. Genetic interaction studies revealed that the 𝘢𝘳𝘷1𝛥 𝘪𝘳𝘦1𝛥 homozygous haploid strain is inviable, suggesting the UPR protects the cell from 𝘢𝘳𝘷1𝛥-mediated stress. In order to assess the stimulus for 𝘢𝘳𝘷1𝛥-mediated UPR induction, 𝘢𝘳𝘷1𝛥 𝘪𝘳𝘦1𝛥 heterozygous diploids were transformed with mutated Ire1p core luminal domains (cLDs) that are sufficient to transmit the signal for UPR induction but are defective in sensing unfolded proteins in the ER lumen. The mutant cLDs were able to rescue the lethality of the 𝘢𝘳𝘷1𝛥 𝘪𝘳𝘦1𝛥 haploid. These strains exhibited increased UPR induction that was independent and additive with protein misfolding. Furthermore, ARV1 deficiency in murine macrophages activated PERK-mediated UPR induction, particularly an upregulation of the cell death effector, CHOP. ARV1 deficiency also caused apoptosis, likely due to prolonged UPR induction, a phenomenon that was exacerbated by inhibiting cholesterol esterification at the ER. In murine and human models, ARV1 is implicated in intracellular cholesterol homeostasis and bile acid metabolism. 𝘈𝘙𝘝1-mediated decreases in 𝘈𝘙𝘝1 expression 𝘪𝘯 𝘷𝘪𝘷𝘰 occurred primarily in the liver and adipose. ARV1 ASO-treated animals did not exhibit UPR activation but were hypercholesterolemic and had increased levels of hepatic and plasma bile acids. Consequently, accumulating bile acids transiently activated FXR-regulatory pathways, including target genes 𝘚𝘏𝘗, 𝘊𝘠𝘗7𝛼1, 𝘕𝘛𝘊𝘗 and 𝘈𝘉𝘊𝘉11. Furthermore, knockdown of 𝘈𝘙𝘝1 expression in hepatocytes established a role for human ARV1 in intracellular cholesterol distribution. 𝘈𝘙𝘝1 ASO-treated HepG2 cells exhibited accumulation of ER cholesterol, decreased SREBP processing and decreased expression of SREBP targets, suggesting that human ARV1 may mediate cholesterol export from the ER. In summation, loss of ARV1 has a profound impact on lipid homeostasis in yeast and metazoans. Various sterol detoxification pathways are activated in order to offset the loss of ARV1. In a hepatocyte, cholesterol biosynthesis is decreased and bile acid secretion is increased, in response to 𝘈𝘙𝘝1 deficiency. In yeast and macrophage models, where conversion of excess sterols into bile acids is not possible, the UPR is activated in order to compensate for loss of ARV1 function. Taken as a whole, these studies reflect the role of ARV1 in ER sterol distribution and trafficking, and the profound impact of decreased 𝘈𝘙𝘝1 expression on intracellular sterol homeostasis.","abstract_html":"Saccharomyces cerevisiae Arv1p (𝘈𝘙𝘌2 required for viability 1) is an endoplasmic reticulum (ER)-localized, functionally conserved protein that was initially observed to mediate subcellular sterol distribution, and has since been implicated in the movement of multiple lipid species. In this thesis, we examined the role of ARV1 in S. cerevisiae and mammalian systems by two approaches. In yeast, we used gene deletion to access loss of Arv1p function. In mammalian cells we utilized antisense oligonucleotides (ASOs) to decrease 𝘈𝘙𝘝1 expression 𝘪𝘯 𝘷𝘪𝘵𝘳𝘰 and 𝘪𝘯 𝘷𝘪𝘷𝘰. In the yeast model, loss of Arv1p function results in sensitivity to modulators of sphingolipid homeostasis and aberrant accumulation of exogenous sterols. Transcription microarrays demonstrated that ARV1 deletion impacts ER homeostasis and activates the transcription factor HAC1, a component of the unfolded protein response (UPR) signaling cascade in yeast. Moreover, 𝘢𝘳𝘷1𝛥 strains exhibited constitutive UPR induction, mediated by the unfolded protein sensor Ire1p. Genetic interaction studies revealed that the 𝘢𝘳𝘷1𝛥 𝘪𝘳𝘦1𝛥 homozygous haploid strain is inviable, suggesting the UPR protects the cell from 𝘢𝘳𝘷1𝛥-mediated stress. In order to assess the stimulus for 𝘢𝘳𝘷1𝛥-mediated UPR induction, 𝘢𝘳𝘷1𝛥 𝘪𝘳𝘦1𝛥 heterozygous diploids were transformed with mutated Ire1p core luminal domains (cLDs) that are sufficient to transmit the signal for UPR induction but are defective in sensing unfolded proteins in the ER lumen. The mutant cLDs were able to rescue the lethality of the 𝘢𝘳𝘷1𝛥 𝘪𝘳𝘦1𝛥 haploid. These strains exhibited increased UPR induction that was independent and additive with protein misfolding. Furthermore, ARV1 deficiency in murine macrophages activated PERK-mediated UPR induction, particularly an upregulation of the cell death effector, CHOP. ARV1 deficiency also caused apoptosis, likely due to prolonged UPR induction, a phenomenon that was exacerbated by inhibiting cholesterol esterification at the ER. In murine and human models, ARV1 is implicated in intracellular cholesterol homeostasis and bile acid metabolism. 𝘈𝘙𝘝1-mediated decreases in 𝘈𝘙𝘝1 expression 𝘪𝘯 𝘷𝘪𝘷𝘰 occurred primarily in the liver and adipose. ARV1 ASO-treated animals did not exhibit UPR activation but were hypercholesterolemic and had increased levels of hepatic and plasma bile acids. Consequently, accumulating bile acids transiently activated FXR-regulatory pathways, including target genes 𝘚𝘏𝘗, 𝘊𝘠𝘗7𝛼1, 𝘕𝘛𝘊𝘗 and 𝘈𝘉𝘊𝘉11. Furthermore, knockdown of 𝘈𝘙𝘝1 expression in hepatocytes established a role for human ARV1 in intracellular cholesterol distribution. 𝘈𝘙𝘝1 ASO-treated HepG2 cells exhibited accumulation of ER cholesterol, decreased SREBP processing and decreased expression of SREBP targets, suggesting that human ARV1 may mediate cholesterol export from the ER. In summation, loss of ARV1 has a profound impact on lipid homeostasis in yeast and metazoans. Various sterol detoxification pathways are activated in order to offset the loss of ARV1. In a hepatocyte, cholesterol biosynthesis is decreased and bile acid secretion is increased, in response to 𝘈𝘙𝘝1 deficiency. In yeast and macrophage models, where conversion of excess sterols into bile acids is not possible, the UPR is activated in order to compensate for loss of ARV1 function. Taken as a whole, these studies reflect the role of ARV1 in ER sterol distribution and trafficking, and the profound impact of decreased 𝘈𝘙𝘝1 expression on intracellular sterol homeostasis.","abstract_has_math":false,"creators":["Shechtman, Caryn"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2011,"date_issued":"2011","date_published":"2011","updated_at":"2026-07-24T01:44:13Z","subjects":["Nutrition","Saccharomyces cerevisiae--Genetic aspects","Yeast--Genetics","Mammals--Genetics","Sterols"],"languages":["English"],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://doi.org/10.7916/D86D60ZV","outbound_label":"DOI","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Shechtman, Caryn"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2011"]},{"key":"dc:type","label":"Dc Type","values":["Theses"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Nutrition","Saccharomyces cerevisiae--Genetic aspects","Yeast--Genetics","Mammals--Genetics","Sterols"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["English"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://doi.org/10.7916/D86D60ZV"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Saccharomyces cerevisiae Arv1p (𝘈𝘙𝘌2 required for viability 1) is an endoplasmic reticulum (ER)-localized, functionally conserved protein that was initially observed to mediate subcellular sterol distribution, and has since been implicated in the movement of multiple lipid species. In this thesis, we examined the role of ARV1 in S. cerevisiae and mammalian systems by two approaches. In yeast, we used gene deletion to access loss of Arv1p function. In mammalian cells we utilized antisense oligonucleotides (ASOs) to decrease 𝘈𝘙𝘝1 expression 𝘪𝘯 𝘷𝘪𝘵𝘳𝘰 and 𝘪𝘯 𝘷𝘪𝘷𝘰. In the yeast model, loss of Arv1p function results in sensitivity to modulators of sphingolipid homeostasis and aberrant accumulation of exogenous sterols. Transcription microarrays demonstrated that ARV1 deletion impacts ER homeostasis and activates the transcription factor HAC1, a component of the unfolded protein response (UPR) signaling cascade in yeast. Moreover, 𝘢𝘳𝘷1𝛥 strains exhibited constitutive UPR induction, mediated by the unfolded protein sensor Ire1p. Genetic interaction studies revealed that the 𝘢𝘳𝘷1𝛥 𝘪𝘳𝘦1𝛥 homozygous haploid strain is inviable, suggesting the UPR protects the cell from 𝘢𝘳𝘷1𝛥-mediated stress. In order to assess the stimulus for 𝘢𝘳𝘷1𝛥-mediated UPR induction, 𝘢𝘳𝘷1𝛥 𝘪𝘳𝘦1𝛥 heterozygous diploids were transformed with mutated Ire1p core luminal domains (cLDs) that are sufficient to transmit the signal for UPR induction but are defective in sensing unfolded proteins in the ER lumen. The mutant cLDs were able to rescue the lethality of the 𝘢𝘳𝘷1𝛥 𝘪𝘳𝘦1𝛥 haploid. These strains exhibited increased UPR induction that was independent and additive with protein misfolding. Furthermore, ARV1 deficiency in murine macrophages activated PERK-mediated UPR induction, particularly an upregulation of the cell death effector, CHOP. ARV1 deficiency also caused apoptosis, likely due to prolonged UPR induction, a phenomenon that was exacerbated by inhibiting cholesterol esterification at the ER. In murine and human models, ARV1 is implicated in intracellular cholesterol homeostasis and bile acid metabolism. 𝘈𝘙𝘝1-mediated decreases in 𝘈𝘙𝘝1 expression 𝘪𝘯 𝘷𝘪𝘷𝘰 occurred primarily in the liver and adipose. ARV1 ASO-treated animals did not exhibit UPR activation but were hypercholesterolemic and had increased levels of hepatic and plasma bile acids. Consequently, accumulating bile acids transiently activated FXR-regulatory pathways, including target genes 𝘚𝘏𝘗, 𝘊𝘠𝘗7𝛼1, 𝘕𝘛𝘊𝘗 and 𝘈𝘉𝘊𝘉11. Furthermore, knockdown of 𝘈𝘙𝘝1 expression in hepatocytes established a role for human ARV1 in intracellular cholesterol distribution. 𝘈𝘙𝘝1 ASO-treated HepG2 cells exhibited accumulation of ER cholesterol, decreased SREBP processing and decreased expression of SREBP targets, suggesting that human ARV1 may mediate cholesterol export from the ER. In summation, loss of ARV1 has a profound impact on lipid homeostasis in yeast and metazoans. Various sterol detoxification pathways are activated in order to offset the loss of ARV1. In a hepatocyte, cholesterol biosynthesis is decreased and bile acid secretion is increased, in response to 𝘈𝘙𝘝1 deficiency. In yeast and macrophage models, where conversion of excess sterols into bile acids is not possible, the UPR is activated in order to compensate for loss of ARV1 function. Taken as a whole, these studies reflect the role of ARV1 in ER sterol distribution and trafficking, and the profound impact of decreased 𝘈𝘙𝘝1 expression on intracellular sterol homeostasis."]},{"key":"dc:title","label":"Title","values":["Characterization of ARV1-Mediated Sterol Transport in Yeast and Mammalian Systems"]}]}],"canonical_facts":{"dc:creator":["Shechtman, Caryn"],"dc:date":["2011"],"dc:description":["Saccharomyces cerevisiae Arv1p (𝘈𝘙𝘌2 required for viability 1) is an endoplasmic reticulum (ER)-localized, functionally conserved protein that was initially observed to mediate subcellular sterol distribution, and has since been implicated in the movement of multiple lipid species. In this thesis, we examined the role of ARV1 in S. cerevisiae and mammalian systems by two approaches. In yeast, we used gene deletion to access loss of Arv1p function. In mammalian cells we utilized antisense oligonucleotides (ASOs) to decrease 𝘈𝘙𝘝1 expression 𝘪𝘯 𝘷𝘪𝘵𝘳𝘰 and 𝘪𝘯 𝘷𝘪𝘷𝘰. In the yeast model, loss of Arv1p function results in sensitivity to modulators of sphingolipid homeostasis and aberrant accumulation of exogenous sterols. Transcription microarrays demonstrated that ARV1 deletion impacts ER homeostasis and activates the transcription factor HAC1, a component of the unfolded protein response (UPR) signaling cascade in yeast. Moreover, 𝘢𝘳𝘷1𝛥 strains exhibited constitutive UPR induction, mediated by the unfolded protein sensor Ire1p. Genetic interaction studies revealed that the 𝘢𝘳𝘷1𝛥 𝘪𝘳𝘦1𝛥 homozygous haploid strain is inviable, suggesting the UPR protects the cell from 𝘢𝘳𝘷1𝛥-mediated stress. In order to assess the stimulus for 𝘢𝘳𝘷1𝛥-mediated UPR induction, 𝘢𝘳𝘷1𝛥 𝘪𝘳𝘦1𝛥 heterozygous diploids were transformed with mutated Ire1p core luminal domains (cLDs) that are sufficient to transmit the signal for UPR induction but are defective in sensing unfolded proteins in the ER lumen. The mutant cLDs were able to rescue the lethality of the 𝘢𝘳𝘷1𝛥 𝘪𝘳𝘦1𝛥 haploid. These strains exhibited increased UPR induction that was independent and additive with protein misfolding. Furthermore, ARV1 deficiency in murine macrophages activated PERK-mediated UPR induction, particularly an upregulation of the cell death effector, CHOP. ARV1 deficiency also caused apoptosis, likely due to prolonged UPR induction, a phenomenon that was exacerbated by inhibiting cholesterol esterification at the ER. In murine and human models, ARV1 is implicated in intracellular cholesterol homeostasis and bile acid metabolism. 𝘈𝘙𝘝1-mediated decreases in 𝘈𝘙𝘝1 expression 𝘪𝘯 𝘷𝘪𝘷𝘰 occurred primarily in the liver and adipose. ARV1 ASO-treated animals did not exhibit UPR activation but were hypercholesterolemic and had increased levels of hepatic and plasma bile acids. Consequently, accumulating bile acids transiently activated FXR-regulatory pathways, including target genes 𝘚𝘏𝘗, 𝘊𝘠𝘗7𝛼1, 𝘕𝘛𝘊𝘗 and 𝘈𝘉𝘊𝘉11. Furthermore, knockdown of 𝘈𝘙𝘝1 expression in hepatocytes established a role for human ARV1 in intracellular cholesterol distribution. 𝘈𝘙𝘝1 ASO-treated HepG2 cells exhibited accumulation of ER cholesterol, decreased SREBP processing and decreased expression of SREBP targets, suggesting that human ARV1 may mediate cholesterol export from the ER. In summation, loss of ARV1 has a profound impact on lipid homeostasis in yeast and metazoans. Various sterol detoxification pathways are activated in order to offset the loss of ARV1. In a hepatocyte, cholesterol biosynthesis is decreased and bile acid secretion is increased, in response to 𝘈𝘙𝘝1 deficiency. In yeast and macrophage models, where conversion of excess sterols into bile acids is not possible, the UPR is activated in order to compensate for loss of ARV1 function. Taken as a whole, these studies reflect the role of ARV1 in ER sterol distribution and trafficking, and the profound impact of decreased 𝘈𝘙𝘝1 expression on intracellular sterol homeostasis."],"dc:identifier":["https://doi.org/10.7916/D86D60ZV"],"dc:language":["English"],"dc:subject":["Nutrition","Saccharomyces cerevisiae--Genetic aspects","Yeast--Genetics","Mammals--Genetics","Sterols"],"dc:title":["Characterization of ARV1-Mediated Sterol Transport in Yeast and Mammalian Systems"],"dc:type":["Theses"]},"updated_at":"2026-07-24T01:44:13Z"}