Overexpression of apolipoprotein A-IV enhances lipid secretion in IPEC-1 cells by increasing chylomicron size

Song Lu, Ying Yao, Xiangying Cheng, Sonya Mitchell, Shuangying Leng, Songmei Meng, James W. Gallagher, Gregory S. Shelness, Gabriel S. Morris, James Mahan, Sharon Frase, Charles M. Mansbach, Richard B. Weinberg, Dennis Black

Research output: Contribution to journalArticle

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Abstract

Intestinal apolipoprotein A-IV expression is highly regulated by dietary lipid in newborn swine, suggesting a role in lipid absorption. Constitutive overexpression of apoA-IV in newborn swine enterocytes enhances basolateral secretion of triacylglycerol (TG) in TG-rich lipoproteins 4.9-fold (Lu, S., Yao, Y., Meng, S., Cheng, X., and Black, D. D. (2002) J. Biol. Chem. 277, 31929-31937). To investigate the mechanism of this enhancement, IPEC-1 cells were transfected with a tetracycline-regulatable expression system (Tet-On). In cells incubated with oleic acid, a dose response relationship was observed between medium doxycycline concentration and basolateral apoA-IV and TG secretion. Similarly regulated expression of apoA-I did not enhance lipid secretion. The mean diameter of TG-rich lipoproteins secreted from doxycycline-treated cells was larger than from untreated cells (87.0 nm versus 53.4 nm). Basolateral apoB secretion decreased. Using the same expression system, full-length human apoA-IV (376 amino acids); a "pig-like"human apoA-IV, lacking the C-terminal EQQQ repeats (361 amino acids); and a "chicken-like" apoA-IV, further truncated to 343 amino acids, were expressed in IPEC-1 cells. With increasing protein secretion, cells expressing the full-length human apoA-IV displayed a 2-fold increase in TG secretion; in sharp contrast, cells expressing the pig-like human apoA-IV displayed a 25-fold increase in TG secretion and a 27-fold increase in lipoprotein diameter. When human apoA-IV was further truncated to yield a chicken-like protein, TG secretion was inhibited. We conclude that overexpression of swine apoA-IV enhances basolateral TG secretion in a dose-dependent manner by increasing the size of secreted lipoproteins. These data suggest that the region in the human apoA-IV protein from residues 344 to 354 is critical to its ability to enhance lipid secretion, perhaps by enabling the packaging of additional core TG into chylomicron particles. The EQQQ-rich region may play an inhibitory or modulatory role in chylomicron packaging in humans.

Original languageEnglish (US)
Pages (from-to)3473-3483
Number of pages11
JournalJournal of Biological Chemistry
Volume281
Issue number6
DOIs
StatePublished - Feb 10 2006
Externally publishedYes

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Apolipoproteins A
Chylomicrons
Triglycerides
Lipids
Swine
Lipoproteins
Doxycycline
Cells
Product Packaging
Amino Acids
Chickens
Packaging
apolipoprotein A-IV
Proteins
Terminal Repeat Sequences
Enterocytes
Apolipoprotein A-I
Apolipoproteins B
Oleic Acid
Tetracycline

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Cite this

Overexpression of apolipoprotein A-IV enhances lipid secretion in IPEC-1 cells by increasing chylomicron size. / Lu, Song; Yao, Ying; Cheng, Xiangying; Mitchell, Sonya; Leng, Shuangying; Meng, Songmei; Gallagher, James W.; Shelness, Gregory S.; Morris, Gabriel S.; Mahan, James; Frase, Sharon; Mansbach, Charles M.; Weinberg, Richard B.; Black, Dennis.

In: Journal of Biological Chemistry, Vol. 281, No. 6, 10.02.2006, p. 3473-3483.

Research output: Contribution to journalArticle

Lu, S, Yao, Y, Cheng, X, Mitchell, S, Leng, S, Meng, S, Gallagher, JW, Shelness, GS, Morris, GS, Mahan, J, Frase, S, Mansbach, CM, Weinberg, RB & Black, D 2006, 'Overexpression of apolipoprotein A-IV enhances lipid secretion in IPEC-1 cells by increasing chylomicron size', Journal of Biological Chemistry, vol. 281, no. 6, pp. 3473-3483. https://doi.org/10.1074/jbc.M502501200
Lu, Song ; Yao, Ying ; Cheng, Xiangying ; Mitchell, Sonya ; Leng, Shuangying ; Meng, Songmei ; Gallagher, James W. ; Shelness, Gregory S. ; Morris, Gabriel S. ; Mahan, James ; Frase, Sharon ; Mansbach, Charles M. ; Weinberg, Richard B. ; Black, Dennis. / Overexpression of apolipoprotein A-IV enhances lipid secretion in IPEC-1 cells by increasing chylomicron size. In: Journal of Biological Chemistry. 2006 ; Vol. 281, No. 6. pp. 3473-3483.
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T1 - Overexpression of apolipoprotein A-IV enhances lipid secretion in IPEC-1 cells by increasing chylomicron size

AU - Lu, Song

AU - Yao, Ying

AU - Cheng, Xiangying

AU - Mitchell, Sonya

AU - Leng, Shuangying

AU - Meng, Songmei

AU - Gallagher, James W.

AU - Shelness, Gregory S.

AU - Morris, Gabriel S.

AU - Mahan, James

AU - Frase, Sharon

AU - Mansbach, Charles M.

AU - Weinberg, Richard B.

AU - Black, Dennis

PY - 2006/2/10

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N2 - Intestinal apolipoprotein A-IV expression is highly regulated by dietary lipid in newborn swine, suggesting a role in lipid absorption. Constitutive overexpression of apoA-IV in newborn swine enterocytes enhances basolateral secretion of triacylglycerol (TG) in TG-rich lipoproteins 4.9-fold (Lu, S., Yao, Y., Meng, S., Cheng, X., and Black, D. D. (2002) J. Biol. Chem. 277, 31929-31937). To investigate the mechanism of this enhancement, IPEC-1 cells were transfected with a tetracycline-regulatable expression system (Tet-On). In cells incubated with oleic acid, a dose response relationship was observed between medium doxycycline concentration and basolateral apoA-IV and TG secretion. Similarly regulated expression of apoA-I did not enhance lipid secretion. The mean diameter of TG-rich lipoproteins secreted from doxycycline-treated cells was larger than from untreated cells (87.0 nm versus 53.4 nm). Basolateral apoB secretion decreased. Using the same expression system, full-length human apoA-IV (376 amino acids); a "pig-like"human apoA-IV, lacking the C-terminal EQQQ repeats (361 amino acids); and a "chicken-like" apoA-IV, further truncated to 343 amino acids, were expressed in IPEC-1 cells. With increasing protein secretion, cells expressing the full-length human apoA-IV displayed a 2-fold increase in TG secretion; in sharp contrast, cells expressing the pig-like human apoA-IV displayed a 25-fold increase in TG secretion and a 27-fold increase in lipoprotein diameter. When human apoA-IV was further truncated to yield a chicken-like protein, TG secretion was inhibited. We conclude that overexpression of swine apoA-IV enhances basolateral TG secretion in a dose-dependent manner by increasing the size of secreted lipoproteins. These data suggest that the region in the human apoA-IV protein from residues 344 to 354 is critical to its ability to enhance lipid secretion, perhaps by enabling the packaging of additional core TG into chylomicron particles. The EQQQ-rich region may play an inhibitory or modulatory role in chylomicron packaging in humans.

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