Overexpression of OSBP-related protein 2 (ORP2) induces changes in cellular cholesterol metabolism and enhances endocytosis

R Hynynen, S Laitinen, Reijo Käkelä, Kimmo Tanhuanpää, S Lusa, C Ehnholm, P Somerharju, Elina Ikonen, V M Olkkonen

Research output: Contribution to journalArticleScientificpeer-review

Abstract

ORP2 [OSBP (oxysterol-binding protein)-related protein 2] belongs to the 12-member mammalian ORP gene/protein family. We characterize in the present study the effects of inducible ORP2 overexpression on cellular cholesterol metabolism in HeLa cells and compare the results with those obtained for CHO cells (Chinese-hamster ovary cells) that express ORP2 constitutively. In both cell systems, the prominent phenotype is enhancement of [C-14]cholesterol efflux to all extracellular acceptors, which results in a reduction of cellular free cholesterol. No change was observed in the plasma membrane cholesterol content or distribution between raft and non-raft domains upon ORP2 expression. However, elevated HMG-CoA (3-hydroxy-3-methyl-glutaryl-CoA) reductase activity and LDL (low-density lipoprotein) receptor expression, as well as enhanced transport of newly synthesized cholesterol to a cyclodextrin-accessible pool, suggest that the ORP2 expression stimulates transport of cholesterol out of the endoplasmic reticulum. In contrast with ORP2/CHO cells, the inducible ORP2/HeLa cells do not show down-regulation of cholesterol esterification, suggesting that this effect represents an adaptive response to long-term cholesterol depletion in the CHO cell model. Finally, we provide evidence that ORP2 binds PtdIns(3,4,5)P-3 and enhances endocytosis, phenomena that are probably interconnected. Our results suggest a function of ORP2 in both cholesterol trafficking and control of endocytic membrane transport.
Original languageEnglish
JournalBiochemical Journal
Volume390
Pages (from-to)273-283
Number of pages11
ISSN0264-6021
DOIs
Publication statusPublished - 2005
MoE publication typeA1 Journal article-refereed

Fields of Science

  • cholesterol efflux
  • cholesterol homoeostasis
  • cholesterol metabolism
  • endocytosis
  • oxysterol-binding protein (OSBP)
  • transferrin
  • OXYSTEROL-BINDING-PROTEIN
  • PLECKSTRIN HOMOLOGY DOMAIN
  • ENDOPLASMIC-RETICULUM
  • VESICLE TRANSPORT
  • GOLGI-COMPLEX
  • CELLS
  • 25-HYDROXYCHOLESTEROL
  • PATHWAY
  • EFFLUX
  • FAMILY
  • 118 Biological sciences
  • 411 Agriculture and forestry

Cite this

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title = "Overexpression of OSBP-related protein 2 (ORP2) induces changes in cellular cholesterol metabolism and enhances endocytosis",
abstract = "ORP2 [OSBP (oxysterol-binding protein)-related protein 2] belongs to the 12-member mammalian ORP gene/protein family. We characterize in the present study the effects of inducible ORP2 overexpression on cellular cholesterol metabolism in HeLa cells and compare the results with those obtained for CHO cells (Chinese-hamster ovary cells) that express ORP2 constitutively. In both cell systems, the prominent phenotype is enhancement of [C-14]cholesterol efflux to all extracellular acceptors, which results in a reduction of cellular free cholesterol. No change was observed in the plasma membrane cholesterol content or distribution between raft and non-raft domains upon ORP2 expression. However, elevated HMG-CoA (3-hydroxy-3-methyl-glutaryl-CoA) reductase activity and LDL (low-density lipoprotein) receptor expression, as well as enhanced transport of newly synthesized cholesterol to a cyclodextrin-accessible pool, suggest that the ORP2 expression stimulates transport of cholesterol out of the endoplasmic reticulum. In contrast with ORP2/CHO cells, the inducible ORP2/HeLa cells do not show down-regulation of cholesterol esterification, suggesting that this effect represents an adaptive response to long-term cholesterol depletion in the CHO cell model. Finally, we provide evidence that ORP2 binds PtdIns(3,4,5)P-3 and enhances endocytosis, phenomena that are probably interconnected. Our results suggest a function of ORP2 in both cholesterol trafficking and control of endocytic membrane transport.",
keywords = "cholesterol efflux, cholesterol homoeostasis, cholesterol metabolism, endocytosis, oxysterol-binding protein (OSBP), transferrin, OXYSTEROL-BINDING-PROTEIN, PLECKSTRIN HOMOLOGY DOMAIN, ENDOPLASMIC-RETICULUM, VESICLE TRANSPORT, GOLGI-COMPLEX, CELLS, 25-HYDROXYCHOLESTEROL, PATHWAY, EFFLUX, FAMILY, 118 Biological sciences, 411 Agriculture and forestry",
author = "R Hynynen and S Laitinen and Reijo K{\"a}kel{\"a} and Kimmo Tanhuanp{\"a}{\"a} and S Lusa and C Ehnholm and P Somerharju and Elina Ikonen and Olkkonen, {V M}",
year = "2005",
doi = "10.1042/BJ20042082",
language = "English",
volume = "390",
pages = "273--283",
journal = "Biochemical Journal",
issn = "0264-6021",
publisher = "Portland Press Ltd.",

}

Overexpression of OSBP-related protein 2 (ORP2) induces changes in cellular cholesterol metabolism and enhances endocytosis. / Hynynen, R ; Laitinen, S ; Käkelä, Reijo; Tanhuanpää, Kimmo; Lusa, S ; Ehnholm, C ; Somerharju, P ; Ikonen, Elina; Olkkonen, V M .

In: Biochemical Journal, Vol. 390, 2005, p. 273-283.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Overexpression of OSBP-related protein 2 (ORP2) induces changes in cellular cholesterol metabolism and enhances endocytosis

AU - Hynynen, R

AU - Laitinen, S

AU - Käkelä, Reijo

AU - Tanhuanpää, Kimmo

AU - Lusa, S

AU - Ehnholm, C

AU - Somerharju, P

AU - Ikonen, Elina

AU - Olkkonen, V M

PY - 2005

Y1 - 2005

N2 - ORP2 [OSBP (oxysterol-binding protein)-related protein 2] belongs to the 12-member mammalian ORP gene/protein family. We characterize in the present study the effects of inducible ORP2 overexpression on cellular cholesterol metabolism in HeLa cells and compare the results with those obtained for CHO cells (Chinese-hamster ovary cells) that express ORP2 constitutively. In both cell systems, the prominent phenotype is enhancement of [C-14]cholesterol efflux to all extracellular acceptors, which results in a reduction of cellular free cholesterol. No change was observed in the plasma membrane cholesterol content or distribution between raft and non-raft domains upon ORP2 expression. However, elevated HMG-CoA (3-hydroxy-3-methyl-glutaryl-CoA) reductase activity and LDL (low-density lipoprotein) receptor expression, as well as enhanced transport of newly synthesized cholesterol to a cyclodextrin-accessible pool, suggest that the ORP2 expression stimulates transport of cholesterol out of the endoplasmic reticulum. In contrast with ORP2/CHO cells, the inducible ORP2/HeLa cells do not show down-regulation of cholesterol esterification, suggesting that this effect represents an adaptive response to long-term cholesterol depletion in the CHO cell model. Finally, we provide evidence that ORP2 binds PtdIns(3,4,5)P-3 and enhances endocytosis, phenomena that are probably interconnected. Our results suggest a function of ORP2 in both cholesterol trafficking and control of endocytic membrane transport.

AB - ORP2 [OSBP (oxysterol-binding protein)-related protein 2] belongs to the 12-member mammalian ORP gene/protein family. We characterize in the present study the effects of inducible ORP2 overexpression on cellular cholesterol metabolism in HeLa cells and compare the results with those obtained for CHO cells (Chinese-hamster ovary cells) that express ORP2 constitutively. In both cell systems, the prominent phenotype is enhancement of [C-14]cholesterol efflux to all extracellular acceptors, which results in a reduction of cellular free cholesterol. No change was observed in the plasma membrane cholesterol content or distribution between raft and non-raft domains upon ORP2 expression. However, elevated HMG-CoA (3-hydroxy-3-methyl-glutaryl-CoA) reductase activity and LDL (low-density lipoprotein) receptor expression, as well as enhanced transport of newly synthesized cholesterol to a cyclodextrin-accessible pool, suggest that the ORP2 expression stimulates transport of cholesterol out of the endoplasmic reticulum. In contrast with ORP2/CHO cells, the inducible ORP2/HeLa cells do not show down-regulation of cholesterol esterification, suggesting that this effect represents an adaptive response to long-term cholesterol depletion in the CHO cell model. Finally, we provide evidence that ORP2 binds PtdIns(3,4,5)P-3 and enhances endocytosis, phenomena that are probably interconnected. Our results suggest a function of ORP2 in both cholesterol trafficking and control of endocytic membrane transport.

KW - cholesterol efflux

KW - cholesterol homoeostasis

KW - cholesterol metabolism

KW - endocytosis

KW - oxysterol-binding protein (OSBP)

KW - transferrin

KW - OXYSTEROL-BINDING-PROTEIN

KW - PLECKSTRIN HOMOLOGY DOMAIN

KW - ENDOPLASMIC-RETICULUM

KW - VESICLE TRANSPORT

KW - GOLGI-COMPLEX

KW - CELLS

KW - 25-HYDROXYCHOLESTEROL

KW - PATHWAY

KW - EFFLUX

KW - FAMILY

KW - 118 Biological sciences

KW - 411 Agriculture and forestry

U2 - 10.1042/BJ20042082

DO - 10.1042/BJ20042082

M3 - Article

VL - 390

SP - 273

EP - 283

JO - Biochemical Journal

JF - Biochemical Journal

SN - 0264-6021

ER -