Evidence favoring a positive feedback loop for physiologic auto upregulation of hnRNP-E1 during prolonged folate deficiency in human placental cells

Ying Sheng Tang, Rehana A. Khan, Suhong Xiao, Deborah K. Hansen, Sally P. Stabler, Praveen Kusumanchi, Hiremagalur N. Jayaram, Asok Antony

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

Background: Previously, we determined that heterogeneous nuclear ribonucleoprotein E1 (hnRNP-E1) functions as an intracellular physiologic sensor of folate deficiency. In this model, L-homocysteine, which accumulates intracellularly in proportion to the extent of folate deficiency, covalently binds to and thereby activates homocysteinylated hnRNP-E1 to interact with folate receptor-α mRNA; this high-affinity interaction triggers the translational upregulation of cell surface folate receptors, which enables cells to optimize folate uptake from the external milieu. However, integral to this model is the need for ongoing generation of hnRNP-E1 to replenish homocysteinylated hnRNP-E1 that is degraded. Objective: We searched for an interrelated physiologic mechanism that could also maintain the steady-state concentration of hnRNP-E1 during prolonged folate deficiency. Methods: A novel RNA-protein interaction was functionally characterized by using molecular and biochemical approaches in vitro and in vivo. Results: L-homocysteine triggered a dose-dependent high-affinity interaction between hnRNP-E1 and a 25-nucleotide cis element within the 5'-untranslated region of hnRNP-E1 mRNA; this led to a proportionate increase in these RNA-protein complexes, and translation of hnRNP-E1 both in vitro and within placental cells. Targeted perturbation of this RNA-protein interaction either by specific 25-nucleotide antisense oligonucleotides or mutation within this cis element or by small interfering RNA to hnRNP-E1 mRNA significantly reduced cellular biosynthesis of hnRNP-E1. Conversely, transfection of hnRNP-E1 mutant proteins that mimicked homocysteinylated hnRNP-E1 stimulated both cellular hnRNP-E1 and folate receptor biosynthesis. In addition, ferrous sulfate heptahydrate [iron(II)], which also binds hnRNP-E1, significantly perturbed this L-homocysteine-triggered RNA-protein interaction in a dose-dependent manner. Finally, folate deficiency induced dual upregulation of hnRNP-E1 and folate receptors in cultured human cells and tumor xenografts, and more selectively in various fetal tissues of folate-deficient dams. Conclusions: This novel positive feedback loop amplifies hnRNP-E1 during prolonged folate deficiency and thereby maximizes upregulation of folate receptors in order to restore folate homeostasis toward normalcy in placental cells. It will also functionally impact several other mRNAs of the nutrition-sensitive, folate-responsive posttranscriptional RNA operon that is orchestrated by homocysteinylated hnRNP-E1.

Original languageEnglish (US)
Pages (from-to)482-498
Number of pages17
JournalJournal of Nutrition
Volume147
Issue number4
DOIs
StatePublished - 2017

Fingerprint

Heterogeneous-Nuclear Ribonucleoproteins
Folic Acid
Up-Regulation
ferrous sulfate
RNA
Homocysteine
Messenger RNA
Nucleotides
Cultured Tumor Cells
Proteins

Keywords

  • ACP1
  • Folate deficiency
  • Folate receptors
  • Glutathione
  • Iron chaperone
  • L-homocysteine
  • MRNA-binding protein
  • Nutrition-sensitive
  • Poly(C)- binding proteins
  • Posttranscriptional RNA operon

ASJC Scopus subject areas

  • Medicine (miscellaneous)
  • Nutrition and Dietetics

Cite this

Evidence favoring a positive feedback loop for physiologic auto upregulation of hnRNP-E1 during prolonged folate deficiency in human placental cells. / Tang, Ying Sheng; Khan, Rehana A.; Xiao, Suhong; Hansen, Deborah K.; Stabler, Sally P.; Kusumanchi, Praveen; Jayaram, Hiremagalur N.; Antony, Asok.

In: Journal of Nutrition, Vol. 147, No. 4, 2017, p. 482-498.

Research output: Contribution to journalArticle

Tang, Ying Sheng ; Khan, Rehana A. ; Xiao, Suhong ; Hansen, Deborah K. ; Stabler, Sally P. ; Kusumanchi, Praveen ; Jayaram, Hiremagalur N. ; Antony, Asok. / Evidence favoring a positive feedback loop for physiologic auto upregulation of hnRNP-E1 during prolonged folate deficiency in human placental cells. In: Journal of Nutrition. 2017 ; Vol. 147, No. 4. pp. 482-498.
@article{793e84e2a71842a89cad4ebbd77c0e3d,
title = "Evidence favoring a positive feedback loop for physiologic auto upregulation of hnRNP-E1 during prolonged folate deficiency in human placental cells",
abstract = "Background: Previously, we determined that heterogeneous nuclear ribonucleoprotein E1 (hnRNP-E1) functions as an intracellular physiologic sensor of folate deficiency. In this model, L-homocysteine, which accumulates intracellularly in proportion to the extent of folate deficiency, covalently binds to and thereby activates homocysteinylated hnRNP-E1 to interact with folate receptor-α mRNA; this high-affinity interaction triggers the translational upregulation of cell surface folate receptors, which enables cells to optimize folate uptake from the external milieu. However, integral to this model is the need for ongoing generation of hnRNP-E1 to replenish homocysteinylated hnRNP-E1 that is degraded. Objective: We searched for an interrelated physiologic mechanism that could also maintain the steady-state concentration of hnRNP-E1 during prolonged folate deficiency. Methods: A novel RNA-protein interaction was functionally characterized by using molecular and biochemical approaches in vitro and in vivo. Results: L-homocysteine triggered a dose-dependent high-affinity interaction between hnRNP-E1 and a 25-nucleotide cis element within the 5'-untranslated region of hnRNP-E1 mRNA; this led to a proportionate increase in these RNA-protein complexes, and translation of hnRNP-E1 both in vitro and within placental cells. Targeted perturbation of this RNA-protein interaction either by specific 25-nucleotide antisense oligonucleotides or mutation within this cis element or by small interfering RNA to hnRNP-E1 mRNA significantly reduced cellular biosynthesis of hnRNP-E1. Conversely, transfection of hnRNP-E1 mutant proteins that mimicked homocysteinylated hnRNP-E1 stimulated both cellular hnRNP-E1 and folate receptor biosynthesis. In addition, ferrous sulfate heptahydrate [iron(II)], which also binds hnRNP-E1, significantly perturbed this L-homocysteine-triggered RNA-protein interaction in a dose-dependent manner. Finally, folate deficiency induced dual upregulation of hnRNP-E1 and folate receptors in cultured human cells and tumor xenografts, and more selectively in various fetal tissues of folate-deficient dams. Conclusions: This novel positive feedback loop amplifies hnRNP-E1 during prolonged folate deficiency and thereby maximizes upregulation of folate receptors in order to restore folate homeostasis toward normalcy in placental cells. It will also functionally impact several other mRNAs of the nutrition-sensitive, folate-responsive posttranscriptional RNA operon that is orchestrated by homocysteinylated hnRNP-E1.",
keywords = "ACP1, Folate deficiency, Folate receptors, Glutathione, Iron chaperone, L-homocysteine, MRNA-binding protein, Nutrition-sensitive, Poly(C)- binding proteins, Posttranscriptional RNA operon",
author = "Tang, {Ying Sheng} and Khan, {Rehana A.} and Suhong Xiao and Hansen, {Deborah K.} and Stabler, {Sally P.} and Praveen Kusumanchi and Jayaram, {Hiremagalur N.} and Asok Antony",
year = "2017",
doi = "10.3945/jn.116.241364",
language = "English (US)",
volume = "147",
pages = "482--498",
journal = "Journal of Nutrition",
issn = "0022-3166",
publisher = "American Society for Nutrition",
number = "4",

}

TY - JOUR

T1 - Evidence favoring a positive feedback loop for physiologic auto upregulation of hnRNP-E1 during prolonged folate deficiency in human placental cells

AU - Tang, Ying Sheng

AU - Khan, Rehana A.

AU - Xiao, Suhong

AU - Hansen, Deborah K.

AU - Stabler, Sally P.

AU - Kusumanchi, Praveen

AU - Jayaram, Hiremagalur N.

AU - Antony, Asok

PY - 2017

Y1 - 2017

N2 - Background: Previously, we determined that heterogeneous nuclear ribonucleoprotein E1 (hnRNP-E1) functions as an intracellular physiologic sensor of folate deficiency. In this model, L-homocysteine, which accumulates intracellularly in proportion to the extent of folate deficiency, covalently binds to and thereby activates homocysteinylated hnRNP-E1 to interact with folate receptor-α mRNA; this high-affinity interaction triggers the translational upregulation of cell surface folate receptors, which enables cells to optimize folate uptake from the external milieu. However, integral to this model is the need for ongoing generation of hnRNP-E1 to replenish homocysteinylated hnRNP-E1 that is degraded. Objective: We searched for an interrelated physiologic mechanism that could also maintain the steady-state concentration of hnRNP-E1 during prolonged folate deficiency. Methods: A novel RNA-protein interaction was functionally characterized by using molecular and biochemical approaches in vitro and in vivo. Results: L-homocysteine triggered a dose-dependent high-affinity interaction between hnRNP-E1 and a 25-nucleotide cis element within the 5'-untranslated region of hnRNP-E1 mRNA; this led to a proportionate increase in these RNA-protein complexes, and translation of hnRNP-E1 both in vitro and within placental cells. Targeted perturbation of this RNA-protein interaction either by specific 25-nucleotide antisense oligonucleotides or mutation within this cis element or by small interfering RNA to hnRNP-E1 mRNA significantly reduced cellular biosynthesis of hnRNP-E1. Conversely, transfection of hnRNP-E1 mutant proteins that mimicked homocysteinylated hnRNP-E1 stimulated both cellular hnRNP-E1 and folate receptor biosynthesis. In addition, ferrous sulfate heptahydrate [iron(II)], which also binds hnRNP-E1, significantly perturbed this L-homocysteine-triggered RNA-protein interaction in a dose-dependent manner. Finally, folate deficiency induced dual upregulation of hnRNP-E1 and folate receptors in cultured human cells and tumor xenografts, and more selectively in various fetal tissues of folate-deficient dams. Conclusions: This novel positive feedback loop amplifies hnRNP-E1 during prolonged folate deficiency and thereby maximizes upregulation of folate receptors in order to restore folate homeostasis toward normalcy in placental cells. It will also functionally impact several other mRNAs of the nutrition-sensitive, folate-responsive posttranscriptional RNA operon that is orchestrated by homocysteinylated hnRNP-E1.

AB - Background: Previously, we determined that heterogeneous nuclear ribonucleoprotein E1 (hnRNP-E1) functions as an intracellular physiologic sensor of folate deficiency. In this model, L-homocysteine, which accumulates intracellularly in proportion to the extent of folate deficiency, covalently binds to and thereby activates homocysteinylated hnRNP-E1 to interact with folate receptor-α mRNA; this high-affinity interaction triggers the translational upregulation of cell surface folate receptors, which enables cells to optimize folate uptake from the external milieu. However, integral to this model is the need for ongoing generation of hnRNP-E1 to replenish homocysteinylated hnRNP-E1 that is degraded. Objective: We searched for an interrelated physiologic mechanism that could also maintain the steady-state concentration of hnRNP-E1 during prolonged folate deficiency. Methods: A novel RNA-protein interaction was functionally characterized by using molecular and biochemical approaches in vitro and in vivo. Results: L-homocysteine triggered a dose-dependent high-affinity interaction between hnRNP-E1 and a 25-nucleotide cis element within the 5'-untranslated region of hnRNP-E1 mRNA; this led to a proportionate increase in these RNA-protein complexes, and translation of hnRNP-E1 both in vitro and within placental cells. Targeted perturbation of this RNA-protein interaction either by specific 25-nucleotide antisense oligonucleotides or mutation within this cis element or by small interfering RNA to hnRNP-E1 mRNA significantly reduced cellular biosynthesis of hnRNP-E1. Conversely, transfection of hnRNP-E1 mutant proteins that mimicked homocysteinylated hnRNP-E1 stimulated both cellular hnRNP-E1 and folate receptor biosynthesis. In addition, ferrous sulfate heptahydrate [iron(II)], which also binds hnRNP-E1, significantly perturbed this L-homocysteine-triggered RNA-protein interaction in a dose-dependent manner. Finally, folate deficiency induced dual upregulation of hnRNP-E1 and folate receptors in cultured human cells and tumor xenografts, and more selectively in various fetal tissues of folate-deficient dams. Conclusions: This novel positive feedback loop amplifies hnRNP-E1 during prolonged folate deficiency and thereby maximizes upregulation of folate receptors in order to restore folate homeostasis toward normalcy in placental cells. It will also functionally impact several other mRNAs of the nutrition-sensitive, folate-responsive posttranscriptional RNA operon that is orchestrated by homocysteinylated hnRNP-E1.

KW - ACP1

KW - Folate deficiency

KW - Folate receptors

KW - Glutathione

KW - Iron chaperone

KW - L-homocysteine

KW - MRNA-binding protein

KW - Nutrition-sensitive

KW - Poly(C)- binding proteins

KW - Posttranscriptional RNA operon

UR - http://www.scopus.com/inward/record.url?scp=85020200420&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85020200420&partnerID=8YFLogxK

U2 - 10.3945/jn.116.241364

DO - 10.3945/jn.116.241364

M3 - Article

VL - 147

SP - 482

EP - 498

JO - Journal of Nutrition

JF - Journal of Nutrition

SN - 0022-3166

IS - 4

ER -