Movement of apolipoprotein B into the lumen of microsomes from hepatocytes is disrupted in membranes enriched in phosphatidylmonomethylethanolamine

A E Rusiñol, E Y Chan, J E Vance

Research output: Contribution to journalArticle

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Abstract

When monolayer cultures of rat hepatocytes are incubated with the ethanolamine/choline analogue, monomethylethanolamine, the secretion of apolipoproteins B100 and B48, as well as the lipid constituents, of very low density lipoprotein (VLDL) is inhibited by approximately 50% (Vance, J. E. (1991) J. Lipid Res. 32, 1971-1982). In the present study we have investigated the mechanism by which monomethylethanolamine disrupts VLDL secretion. Hepatocytes were treated with 400 microM monomethylethanolamine overnight, which resulted in an increase in the cellular content of the derived phospholipid, phosphatidylmonomethylethanolamine, from 0.32 +/- 0.15 to 2.92 +/- 0.74 nmol/mg of cell protein. The biosynthesis of apoproteins B100 and B48 was not impaired by treatment of cells with monomethylethanolamine. However, monomethylethanolamine decreased by approximately 50% the amount of apoproteins B, but not of the typical secretory protein, albumin, present in the luminal content subfraction of microsomes. The intracellular degradation of apoproteins B was also increased in phosphatidylmonomethylethanolamine-enriched, compared with control, cells. Moreover, the pool of apoprotein B present in intact microsomes from hepatocytes incubated with monomethylethanolamine was more accessible to exogenously added trypsin, presumably because a larger pool of the apoprotein B was exposed on the cytosolic surface of these microsomes. The data strongly suggest that an increase in the microsomal content of phosphatidylmonomethylethanolamine diminishes the ability of apoprotein B to translocate across the endoplasmic reticulum membrane into the luminal compartment. Consequently, the association of apoprotein B with lipids and/or the normal assembly of mature VLDL particles is impaired.

LanguageEnglish
Pages25168-75
Number of pages8
JournalJournal of Biological Chemistry
Volume268
Issue number33
Publication statusPublished - 25 Nov 1993

Fingerprint

Apolipoproteins B
Microsomes
Hepatocytes
Membranes
VLDL Lipoproteins
Lipids
Apolipoprotein B-48
Ethanolamine
Apoproteins
Biosynthesis
Choline
Endoplasmic Reticulum
Trypsin
Rats
Albumins
Monolayers
Phospholipids
Proteins
Cells
Association reactions

Keywords

  • animals
  • apolipoproteins B
  • biological transport
  • cell membrane
  • cells, Cultured
  • male
  • microsomes, liver
  • phosphatidylethanolamines
  • rats
  • rats, sprague-dawley
  • trypsin

Cite this

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title = "Movement of apolipoprotein B into the lumen of microsomes from hepatocytes is disrupted in membranes enriched in phosphatidylmonomethylethanolamine",
abstract = "When monolayer cultures of rat hepatocytes are incubated with the ethanolamine/choline analogue, monomethylethanolamine, the secretion of apolipoproteins B100 and B48, as well as the lipid constituents, of very low density lipoprotein (VLDL) is inhibited by approximately 50{\%} (Vance, J. E. (1991) J. Lipid Res. 32, 1971-1982). In the present study we have investigated the mechanism by which monomethylethanolamine disrupts VLDL secretion. Hepatocytes were treated with 400 microM monomethylethanolamine overnight, which resulted in an increase in the cellular content of the derived phospholipid, phosphatidylmonomethylethanolamine, from 0.32 +/- 0.15 to 2.92 +/- 0.74 nmol/mg of cell protein. The biosynthesis of apoproteins B100 and B48 was not impaired by treatment of cells with monomethylethanolamine. However, monomethylethanolamine decreased by approximately 50{\%} the amount of apoproteins B, but not of the typical secretory protein, albumin, present in the luminal content subfraction of microsomes. The intracellular degradation of apoproteins B was also increased in phosphatidylmonomethylethanolamine-enriched, compared with control, cells. Moreover, the pool of apoprotein B present in intact microsomes from hepatocytes incubated with monomethylethanolamine was more accessible to exogenously added trypsin, presumably because a larger pool of the apoprotein B was exposed on the cytosolic surface of these microsomes. The data strongly suggest that an increase in the microsomal content of phosphatidylmonomethylethanolamine diminishes the ability of apoprotein B to translocate across the endoplasmic reticulum membrane into the luminal compartment. Consequently, the association of apoprotein B with lipids and/or the normal assembly of mature VLDL particles is impaired.",
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Movement of apolipoprotein B into the lumen of microsomes from hepatocytes is disrupted in membranes enriched in phosphatidylmonomethylethanolamine. / Rusiñol, A E; Chan, E Y; Vance, J E.

In: Journal of Biological Chemistry, Vol. 268, No. 33, 25.11.1993, p. 25168-75.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Movement of apolipoprotein B into the lumen of microsomes from hepatocytes is disrupted in membranes enriched in phosphatidylmonomethylethanolamine

AU - Rusiñol, A E

AU - Chan, E Y

AU - Vance, J E

PY - 1993/11/25

Y1 - 1993/11/25

N2 - When monolayer cultures of rat hepatocytes are incubated with the ethanolamine/choline analogue, monomethylethanolamine, the secretion of apolipoproteins B100 and B48, as well as the lipid constituents, of very low density lipoprotein (VLDL) is inhibited by approximately 50% (Vance, J. E. (1991) J. Lipid Res. 32, 1971-1982). In the present study we have investigated the mechanism by which monomethylethanolamine disrupts VLDL secretion. Hepatocytes were treated with 400 microM monomethylethanolamine overnight, which resulted in an increase in the cellular content of the derived phospholipid, phosphatidylmonomethylethanolamine, from 0.32 +/- 0.15 to 2.92 +/- 0.74 nmol/mg of cell protein. The biosynthesis of apoproteins B100 and B48 was not impaired by treatment of cells with monomethylethanolamine. However, monomethylethanolamine decreased by approximately 50% the amount of apoproteins B, but not of the typical secretory protein, albumin, present in the luminal content subfraction of microsomes. The intracellular degradation of apoproteins B was also increased in phosphatidylmonomethylethanolamine-enriched, compared with control, cells. Moreover, the pool of apoprotein B present in intact microsomes from hepatocytes incubated with monomethylethanolamine was more accessible to exogenously added trypsin, presumably because a larger pool of the apoprotein B was exposed on the cytosolic surface of these microsomes. The data strongly suggest that an increase in the microsomal content of phosphatidylmonomethylethanolamine diminishes the ability of apoprotein B to translocate across the endoplasmic reticulum membrane into the luminal compartment. Consequently, the association of apoprotein B with lipids and/or the normal assembly of mature VLDL particles is impaired.

AB - When monolayer cultures of rat hepatocytes are incubated with the ethanolamine/choline analogue, monomethylethanolamine, the secretion of apolipoproteins B100 and B48, as well as the lipid constituents, of very low density lipoprotein (VLDL) is inhibited by approximately 50% (Vance, J. E. (1991) J. Lipid Res. 32, 1971-1982). In the present study we have investigated the mechanism by which monomethylethanolamine disrupts VLDL secretion. Hepatocytes were treated with 400 microM monomethylethanolamine overnight, which resulted in an increase in the cellular content of the derived phospholipid, phosphatidylmonomethylethanolamine, from 0.32 +/- 0.15 to 2.92 +/- 0.74 nmol/mg of cell protein. The biosynthesis of apoproteins B100 and B48 was not impaired by treatment of cells with monomethylethanolamine. However, monomethylethanolamine decreased by approximately 50% the amount of apoproteins B, but not of the typical secretory protein, albumin, present in the luminal content subfraction of microsomes. The intracellular degradation of apoproteins B was also increased in phosphatidylmonomethylethanolamine-enriched, compared with control, cells. Moreover, the pool of apoprotein B present in intact microsomes from hepatocytes incubated with monomethylethanolamine was more accessible to exogenously added trypsin, presumably because a larger pool of the apoprotein B was exposed on the cytosolic surface of these microsomes. The data strongly suggest that an increase in the microsomal content of phosphatidylmonomethylethanolamine diminishes the ability of apoprotein B to translocate across the endoplasmic reticulum membrane into the luminal compartment. Consequently, the association of apoprotein B with lipids and/or the normal assembly of mature VLDL particles is impaired.

KW - animals

KW - apolipoproteins B

KW - biological transport

KW - cell membrane

KW - cells, Cultured

KW - male

KW - microsomes, liver

KW - phosphatidylethanolamines

KW - rats

KW - rats, sprague-dawley

KW - trypsin

UR - http://www.jbc.org/

M3 - Article

VL - 268

SP - 25168

EP - 25175

JO - Journal of Biological Chemistry

T2 - Journal of Biological Chemistry

JF - Journal of Biological Chemistry

SN - 0021-9258

IS - 33

ER -