Overexpression of a Modified Human Malonyl-CoA Decarboxylase Blocks the Glucose-induced Increase in Malonyl-CoA Level but Has No Impact on Insulin Secretion in INS-1-derived (832/13) β-Cells

Hindrik Mulder, Danhong Lu, John Finley IV, Jie An, Jonathan Cohen, Peter A. Antinozzi, J. Denis McGarry, Christopher B. Newgard

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Abstract

The long-chain acyl-CoA (LC-CoA) model of glucose-stimulated insulin secretion (GSIS) holds that secretion is linked to a glucose-induced increase in malonyl-CoA level and accumulation of LC-CoA in the cytosol. We have previously tested the validity of this proposal by overexpressing goose malonyl-CoA decarboxylase (MCD) in INS-1 cells, but these studies have been criticized due to: 1) the small insulin secretion response (2-4-fold) of the INS-1 cells used; 2) unknown contribution of the ATP-sensitive K+ (KATP) channel-independent pathway of GSIS in INS-1 cells, which has been implicated as the site at which lipids regulate insulin granule exocytosis; and 3) deletion of the N-terminal mitochondrial targeting sequence, but not the C-terminal peroxisomal targeting sequence in the goose MCD construct, raising the possibility that a significant fraction of the overexpressed enzyme was localized to peroxisomes. To address these outstanding concerns, INS-1-derived 832/13 cells, which exhibit robust KATP channel-dependent and -independent pathways of GSIS, were treated with a new adenovirus encoding human MCD lacking both its mitochondrial and peroxisomal targeting sequences (AdCMV-MCDΔ5), resulting in large increases in cytosolic MCD activity. Treatment of 832/13 cells with AdCMV-MCDΔ5 completely blocked the glucose-induced rise in malonyl-CoA and attenuated the inhibitory effect of glucose on fatty acid oxidation. However, MCD overexpression had no effect on KATP channel-dependent or -independent GSIS in 832/13 cells. Furthermore, combined treatment of 832/13 cells with AdCMV-MCDΔ5 and triacsin C, an inhibitor of long chain acyl-CoA synthetase that reduces LC-CoA levels, did not impair GSIS. These findings extend our previous observations and are not consistent with the LC-CoA hypothesis as originally set forth.

Original languageEnglish (US)
Pages (from-to)6479-6484
Number of pages6
JournalJournal of Biological Chemistry
Volume276
Issue number9
DOIs
StatePublished - Mar 2 2001

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malonyl-CoA decarboxylase
Malonyl Coenzyme A
Acyl Coenzyme A
Insulin
Glucose
KATP Channels
Geese
Cells
Coenzyme A Ligases
Human Adenoviruses
Peroxisomes
Exocytosis
Cytosol

ASJC Scopus subject areas

  • Biochemistry

Cite this

Overexpression of a Modified Human Malonyl-CoA Decarboxylase Blocks the Glucose-induced Increase in Malonyl-CoA Level but Has No Impact on Insulin Secretion in INS-1-derived (832/13) β-Cells. / Mulder, Hindrik; Lu, Danhong; Finley IV, John; An, Jie; Cohen, Jonathan; Antinozzi, Peter A.; McGarry, J. Denis; Newgard, Christopher B.

In: Journal of Biological Chemistry, Vol. 276, No. 9, 02.03.2001, p. 6479-6484.

Research output: Contribution to journalArticle

Mulder, Hindrik ; Lu, Danhong ; Finley IV, John ; An, Jie ; Cohen, Jonathan ; Antinozzi, Peter A. ; McGarry, J. Denis ; Newgard, Christopher B. / Overexpression of a Modified Human Malonyl-CoA Decarboxylase Blocks the Glucose-induced Increase in Malonyl-CoA Level but Has No Impact on Insulin Secretion in INS-1-derived (832/13) β-Cells. In: Journal of Biological Chemistry. 2001 ; Vol. 276, No. 9. pp. 6479-6484.
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abstract = "The long-chain acyl-CoA (LC-CoA) model of glucose-stimulated insulin secretion (GSIS) holds that secretion is linked to a glucose-induced increase in malonyl-CoA level and accumulation of LC-CoA in the cytosol. We have previously tested the validity of this proposal by overexpressing goose malonyl-CoA decarboxylase (MCD) in INS-1 cells, but these studies have been criticized due to: 1) the small insulin secretion response (2-4-fold) of the INS-1 cells used; 2) unknown contribution of the ATP-sensitive K+ (KATP) channel-independent pathway of GSIS in INS-1 cells, which has been implicated as the site at which lipids regulate insulin granule exocytosis; and 3) deletion of the N-terminal mitochondrial targeting sequence, but not the C-terminal peroxisomal targeting sequence in the goose MCD construct, raising the possibility that a significant fraction of the overexpressed enzyme was localized to peroxisomes. To address these outstanding concerns, INS-1-derived 832/13 cells, which exhibit robust KATP channel-dependent and -independent pathways of GSIS, were treated with a new adenovirus encoding human MCD lacking both its mitochondrial and peroxisomal targeting sequences (AdCMV-MCDΔ5), resulting in large increases in cytosolic MCD activity. Treatment of 832/13 cells with AdCMV-MCDΔ5 completely blocked the glucose-induced rise in malonyl-CoA and attenuated the inhibitory effect of glucose on fatty acid oxidation. However, MCD overexpression had no effect on KATP channel-dependent or -independent GSIS in 832/13 cells. Furthermore, combined treatment of 832/13 cells with AdCMV-MCDΔ5 and triacsin C, an inhibitor of long chain acyl-CoA synthetase that reduces LC-CoA levels, did not impair GSIS. These findings extend our previous observations and are not consistent with the LC-CoA hypothesis as originally set forth.",
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T1 - Overexpression of a Modified Human Malonyl-CoA Decarboxylase Blocks the Glucose-induced Increase in Malonyl-CoA Level but Has No Impact on Insulin Secretion in INS-1-derived (832/13) β-Cells

AU - Mulder, Hindrik

AU - Lu, Danhong

AU - Finley IV, John

AU - An, Jie

AU - Cohen, Jonathan

AU - Antinozzi, Peter A.

AU - McGarry, J. Denis

AU - Newgard, Christopher B.

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