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ACC2 is expressed at high levels in human white adipose and has an isoform with a novel N-terminus [corrected].

Castle JC, Hara Y, Raymond CK, Garrett-Engele P, Ohwaki K, Kan Z, Kusunoki J, Johnson JM - PLoS ONE (2009)

Bottom Line: We find, however, that human adipose tissue, unlike rodent adipose, expresses more ACC2 mRNA relative to the oxidative tissues muscle and heart.Both ACC2 isoforms are capable of de novo lipogenesis, suggesting that ACC2, in addition to ACC1, may play a role in lipogenesis.The results demonstrate a significant difference in ACC expression between human and rodents, which may introduce difficulties for the use of rodent models for development of ACC inhibitors.

View Article: PubMed Central - PubMed

Affiliation: Rosetta Inpharmatics LLC, Seattle, Washington, United States of America. john_castle@merck.com

ABSTRACT
Acetyl-CoA carboxylases ACC1 and ACC2 catalyze the carboxylation of acetyl-CoA to malonyl-CoA, regulating fatty-acid synthesis and oxidation, and are potential targets for treatment of metabolic syndrome. Expression of ACC1 in rodent lipogenic tissues and ACC2 in rodent oxidative tissues, coupled with the predicted localization of ACC2 to the mitochondrial membrane, have suggested separate functional roles for ACC1 in lipogenesis and ACC2 in fatty acid oxidation. We find, however, that human adipose tissue, unlike rodent adipose, expresses more ACC2 mRNA relative to the oxidative tissues muscle and heart. Human adipose, along with human liver, expresses more ACC2 than ACC1. Using RT-PCR, real-time PCR, and immunoprecipitation we report a novel isoform of ACC2 (ACC2.v2) that is expressed at significant levels in human adipose. The protein generated by this isoform has enzymatic activity, is endogenously expressed in adipose, and lacks the N-terminal sequence. Both ACC2 isoforms are capable of de novo lipogenesis, suggesting that ACC2, in addition to ACC1, may play a role in lipogenesis. The results demonstrate a significant difference in ACC expression between human and rodents, which may introduce difficulties for the use of rodent models for development of ACC inhibitors.

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Novel ACC2 isoform.(A) Genomic alignment of the 5′ end of RefSeq transcript NM_001093, human EST CA392208 (exons are shown as boxes), ‘FirstExon’ predictions [33], including the CpG island, promoter region, and first exon location, and conservation score for human, mouse, rat, and chicken [34]. The green and red boxes in the top two rows are the alternative first exons. The vertical, dashed blue line in the zoomed image (lower left panel) shows the predicted start ATG codon. The gel image using RT-PCR primers in novel exon 1 and known exon 5 shows intensity in all tissues tested at the predicted size. (B) The RNA sequence of the novel exon 1 (red), the start of exon 2 (black), and the predicted protein. The first base is the beginning of the aligned mouse EST BB866065. The RT-PCR primer target sequence is underlined.
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pone-0004369-g002: Novel ACC2 isoform.(A) Genomic alignment of the 5′ end of RefSeq transcript NM_001093, human EST CA392208 (exons are shown as boxes), ‘FirstExon’ predictions [33], including the CpG island, promoter region, and first exon location, and conservation score for human, mouse, rat, and chicken [34]. The green and red boxes in the top two rows are the alternative first exons. The vertical, dashed blue line in the zoomed image (lower left panel) shows the predicted start ATG codon. The gel image using RT-PCR primers in novel exon 1 and known exon 5 shows intensity in all tissues tested at the predicted size. (B) The RNA sequence of the novel exon 1 (red), the start of exon 2 (black), and the predicted protein. The first base is the beginning of the aligned mouse EST BB866065. The RT-PCR primer target sequence is underlined.

Mentions: When mapped to the human genome, three human and mouse ESTs, human CA392208 and mouse BB854145 and BB866065, suggest the existence of an additional transcribed region between the first and second exons of the RefSeq ACC2 isoform (ACC2.v1) NM_001093 (Figure 2A). Other genomic data support this interpretation, including a candidate ATG start codon, high human, rodent and chicken sequence conservation, and the absence of termination codons (Figure 2A, Figure S2). Usage of this ATG codon as start site could generate an in-frame ACC2 protein in which the first 218 amino acids of the known RefSeq protein NP_001084, including the hydrophobic N-terminus, were replaced with a novel 16 amino-acid N-terminus (Figure 2B). This variant, referred to in what follows as ACC2.v2, is less likely to encode a membrane-associated protein because it lacks the putative mitochondrial localization sequence.


ACC2 is expressed at high levels in human white adipose and has an isoform with a novel N-terminus [corrected].

Castle JC, Hara Y, Raymond CK, Garrett-Engele P, Ohwaki K, Kan Z, Kusunoki J, Johnson JM - PLoS ONE (2009)

Novel ACC2 isoform.(A) Genomic alignment of the 5′ end of RefSeq transcript NM_001093, human EST CA392208 (exons are shown as boxes), ‘FirstExon’ predictions [33], including the CpG island, promoter region, and first exon location, and conservation score for human, mouse, rat, and chicken [34]. The green and red boxes in the top two rows are the alternative first exons. The vertical, dashed blue line in the zoomed image (lower left panel) shows the predicted start ATG codon. The gel image using RT-PCR primers in novel exon 1 and known exon 5 shows intensity in all tissues tested at the predicted size. (B) The RNA sequence of the novel exon 1 (red), the start of exon 2 (black), and the predicted protein. The first base is the beginning of the aligned mouse EST BB866065. The RT-PCR primer target sequence is underlined.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2629817&req=5

pone-0004369-g002: Novel ACC2 isoform.(A) Genomic alignment of the 5′ end of RefSeq transcript NM_001093, human EST CA392208 (exons are shown as boxes), ‘FirstExon’ predictions [33], including the CpG island, promoter region, and first exon location, and conservation score for human, mouse, rat, and chicken [34]. The green and red boxes in the top two rows are the alternative first exons. The vertical, dashed blue line in the zoomed image (lower left panel) shows the predicted start ATG codon. The gel image using RT-PCR primers in novel exon 1 and known exon 5 shows intensity in all tissues tested at the predicted size. (B) The RNA sequence of the novel exon 1 (red), the start of exon 2 (black), and the predicted protein. The first base is the beginning of the aligned mouse EST BB866065. The RT-PCR primer target sequence is underlined.
Mentions: When mapped to the human genome, three human and mouse ESTs, human CA392208 and mouse BB854145 and BB866065, suggest the existence of an additional transcribed region between the first and second exons of the RefSeq ACC2 isoform (ACC2.v1) NM_001093 (Figure 2A). Other genomic data support this interpretation, including a candidate ATG start codon, high human, rodent and chicken sequence conservation, and the absence of termination codons (Figure 2A, Figure S2). Usage of this ATG codon as start site could generate an in-frame ACC2 protein in which the first 218 amino acids of the known RefSeq protein NP_001084, including the hydrophobic N-terminus, were replaced with a novel 16 amino-acid N-terminus (Figure 2B). This variant, referred to in what follows as ACC2.v2, is less likely to encode a membrane-associated protein because it lacks the putative mitochondrial localization sequence.

Bottom Line: We find, however, that human adipose tissue, unlike rodent adipose, expresses more ACC2 mRNA relative to the oxidative tissues muscle and heart.Both ACC2 isoforms are capable of de novo lipogenesis, suggesting that ACC2, in addition to ACC1, may play a role in lipogenesis.The results demonstrate a significant difference in ACC expression between human and rodents, which may introduce difficulties for the use of rodent models for development of ACC inhibitors.

View Article: PubMed Central - PubMed

Affiliation: Rosetta Inpharmatics LLC, Seattle, Washington, United States of America. john_castle@merck.com

ABSTRACT
Acetyl-CoA carboxylases ACC1 and ACC2 catalyze the carboxylation of acetyl-CoA to malonyl-CoA, regulating fatty-acid synthesis and oxidation, and are potential targets for treatment of metabolic syndrome. Expression of ACC1 in rodent lipogenic tissues and ACC2 in rodent oxidative tissues, coupled with the predicted localization of ACC2 to the mitochondrial membrane, have suggested separate functional roles for ACC1 in lipogenesis and ACC2 in fatty acid oxidation. We find, however, that human adipose tissue, unlike rodent adipose, expresses more ACC2 mRNA relative to the oxidative tissues muscle and heart. Human adipose, along with human liver, expresses more ACC2 than ACC1. Using RT-PCR, real-time PCR, and immunoprecipitation we report a novel isoform of ACC2 (ACC2.v2) that is expressed at significant levels in human adipose. The protein generated by this isoform has enzymatic activity, is endogenously expressed in adipose, and lacks the N-terminal sequence. Both ACC2 isoforms are capable of de novo lipogenesis, suggesting that ACC2, in addition to ACC1, may play a role in lipogenesis. The results demonstrate a significant difference in ACC expression between human and rodents, which may introduce difficulties for the use of rodent models for development of ACC inhibitors.

Show MeSH
Related in: MedlinePlus