Cytoplasmic confinement of breast cancer resistance protein (BCRP/ABCG2) as a novel mechanism of adaptation to short-term folate deprivation

Ilan Ifergan, Gerrit Jansen, Yehuda G Assaraf

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

The unique capability of breast cancer resistance protein (BCRP/ABCG2) to export mono-, di-, and triglutamates of folates should limit cellular proliferation under conditions of folate deprivation, particularly upon BCRP overexpression. Here, we explored the mode of adaptation of BCRP-overexpressing cells to short-term folate deprivation. MCF-7/MR cells grown in high folate medium (2.3 muM folic acid) containing mitoxantrone had 62% of their overexpressed BCRP in the plasma membrane and only 38% in the cytoplasm. In contrast, cells grown for 2 weeks in folic acid-free medium followed by an adaptation week in low folate medium (1 nM folic acid) had 86% of BCRP in the cytoplasm and only 14% in the plasma membrane. Unlike BCRP, various transmembrane proteins retained their normal plasma membrane localization in folate-deprived cells. Folate deprivation was also associated with a 3-fold decrease in BCRP and multidrug resistance protein 1 (MRP1/ABCC1) levels. Confocal microscopy with folate-deprived cells revealed that cytoplasmic BCRP colocalized with calnexin, an established endoplasmic reticulum resident. The loss of BCRP from the plasma membrane in folate-deprived cells consistently resulted in a 4.5-fold increase in [(3)H]folic acid accumulation relative to MCF-7/MR cells. Hence, cellular adaptation to shortterm folate deprivation results in a selective confinement of BCRP to the cytoplasm along with a moderate decrease in BCRP and MRP1 levels aimed at preserving the poor intracellular folate pools. These results constitute a novel mechanism of cellular adaptation to short-term folate deprivation and provide further support to the possible role of BCRP in the maintenance of cellular folate homeostasis.

Original languageEnglish
Pages (from-to)1349-59
Number of pages11
JournalMolecular Pharmacology
Volume67
Issue number4
DOIs
Publication statusPublished - Apr 2005

Cite this

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title = "Cytoplasmic confinement of breast cancer resistance protein (BCRP/ABCG2) as a novel mechanism of adaptation to short-term folate deprivation",
abstract = "The unique capability of breast cancer resistance protein (BCRP/ABCG2) to export mono-, di-, and triglutamates of folates should limit cellular proliferation under conditions of folate deprivation, particularly upon BCRP overexpression. Here, we explored the mode of adaptation of BCRP-overexpressing cells to short-term folate deprivation. MCF-7/MR cells grown in high folate medium (2.3 muM folic acid) containing mitoxantrone had 62{\%} of their overexpressed BCRP in the plasma membrane and only 38{\%} in the cytoplasm. In contrast, cells grown for 2 weeks in folic acid-free medium followed by an adaptation week in low folate medium (1 nM folic acid) had 86{\%} of BCRP in the cytoplasm and only 14{\%} in the plasma membrane. Unlike BCRP, various transmembrane proteins retained their normal plasma membrane localization in folate-deprived cells. Folate deprivation was also associated with a 3-fold decrease in BCRP and multidrug resistance protein 1 (MRP1/ABCC1) levels. Confocal microscopy with folate-deprived cells revealed that cytoplasmic BCRP colocalized with calnexin, an established endoplasmic reticulum resident. The loss of BCRP from the plasma membrane in folate-deprived cells consistently resulted in a 4.5-fold increase in [(3)H]folic acid accumulation relative to MCF-7/MR cells. Hence, cellular adaptation to shortterm folate deprivation results in a selective confinement of BCRP to the cytoplasm along with a moderate decrease in BCRP and MRP1 levels aimed at preserving the poor intracellular folate pools. These results constitute a novel mechanism of cellular adaptation to short-term folate deprivation and provide further support to the possible role of BCRP in the maintenance of cellular folate homeostasis.",
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Cytoplasmic confinement of breast cancer resistance protein (BCRP/ABCG2) as a novel mechanism of adaptation to short-term folate deprivation. / Ifergan, Ilan; Jansen, Gerrit; Assaraf, Yehuda G.

In: Molecular Pharmacology, Vol. 67, No. 4, 04.2005, p. 1349-59.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - Cytoplasmic confinement of breast cancer resistance protein (BCRP/ABCG2) as a novel mechanism of adaptation to short-term folate deprivation

AU - Ifergan, Ilan

AU - Jansen, Gerrit

AU - Assaraf, Yehuda G

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N2 - The unique capability of breast cancer resistance protein (BCRP/ABCG2) to export mono-, di-, and triglutamates of folates should limit cellular proliferation under conditions of folate deprivation, particularly upon BCRP overexpression. Here, we explored the mode of adaptation of BCRP-overexpressing cells to short-term folate deprivation. MCF-7/MR cells grown in high folate medium (2.3 muM folic acid) containing mitoxantrone had 62% of their overexpressed BCRP in the plasma membrane and only 38% in the cytoplasm. In contrast, cells grown for 2 weeks in folic acid-free medium followed by an adaptation week in low folate medium (1 nM folic acid) had 86% of BCRP in the cytoplasm and only 14% in the plasma membrane. Unlike BCRP, various transmembrane proteins retained their normal plasma membrane localization in folate-deprived cells. Folate deprivation was also associated with a 3-fold decrease in BCRP and multidrug resistance protein 1 (MRP1/ABCC1) levels. Confocal microscopy with folate-deprived cells revealed that cytoplasmic BCRP colocalized with calnexin, an established endoplasmic reticulum resident. The loss of BCRP from the plasma membrane in folate-deprived cells consistently resulted in a 4.5-fold increase in [(3)H]folic acid accumulation relative to MCF-7/MR cells. Hence, cellular adaptation to shortterm folate deprivation results in a selective confinement of BCRP to the cytoplasm along with a moderate decrease in BCRP and MRP1 levels aimed at preserving the poor intracellular folate pools. These results constitute a novel mechanism of cellular adaptation to short-term folate deprivation and provide further support to the possible role of BCRP in the maintenance of cellular folate homeostasis.

AB - The unique capability of breast cancer resistance protein (BCRP/ABCG2) to export mono-, di-, and triglutamates of folates should limit cellular proliferation under conditions of folate deprivation, particularly upon BCRP overexpression. Here, we explored the mode of adaptation of BCRP-overexpressing cells to short-term folate deprivation. MCF-7/MR cells grown in high folate medium (2.3 muM folic acid) containing mitoxantrone had 62% of their overexpressed BCRP in the plasma membrane and only 38% in the cytoplasm. In contrast, cells grown for 2 weeks in folic acid-free medium followed by an adaptation week in low folate medium (1 nM folic acid) had 86% of BCRP in the cytoplasm and only 14% in the plasma membrane. Unlike BCRP, various transmembrane proteins retained their normal plasma membrane localization in folate-deprived cells. Folate deprivation was also associated with a 3-fold decrease in BCRP and multidrug resistance protein 1 (MRP1/ABCC1) levels. Confocal microscopy with folate-deprived cells revealed that cytoplasmic BCRP colocalized with calnexin, an established endoplasmic reticulum resident. The loss of BCRP from the plasma membrane in folate-deprived cells consistently resulted in a 4.5-fold increase in [(3)H]folic acid accumulation relative to MCF-7/MR cells. Hence, cellular adaptation to shortterm folate deprivation results in a selective confinement of BCRP to the cytoplasm along with a moderate decrease in BCRP and MRP1 levels aimed at preserving the poor intracellular folate pools. These results constitute a novel mechanism of cellular adaptation to short-term folate deprivation and provide further support to the possible role of BCRP in the maintenance of cellular folate homeostasis.

KW - ATP Binding Cassette Transporter, Subfamily G, Member 2

KW - ATP-Binding Cassette Transporters/metabolism

KW - Adaptation, Physiological

KW - Breast Neoplasms/metabolism

KW - Cell Line, Tumor

KW - Cell Membrane/metabolism

KW - Cytoplasm/metabolism

KW - Endoplasmic Reticulum/metabolism

KW - Female

KW - Folic Acid/metabolism

KW - Folic Acid Deficiency/metabolism

KW - Glycosylation

KW - Humans

KW - Membrane Proteins/metabolism

KW - Neoplasm Proteins/metabolism

U2 - 10.1124/mol.104.008250

DO - 10.1124/mol.104.008250

M3 - Article

VL - 67

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EP - 1359

JO - Molecular Pharmacology

JF - Molecular Pharmacology

SN - 0026-895X

IS - 4

ER -