Characterization of the gene EPAC2: structure, chromosomal localization, tissue expression, and identification of the liver-specific isoform.
The liver-specific protein cAMP-GEFII (also known as Epac2) belongs to a family of cyclic adenosine monophosphate (cAMP) binding proteins having guanine nucleotide exchange factor (GEF) activity (the cAMP-GEF family). Here we clone the gene EPAC2, encoding cAMP-GEFII, from a human liver cDNA library. Human EPAC2 has at least 31 exons and is mapped to human chromosome 2q31. Analyses by primer extension, reverse transcriptase-polymerase chain reaction, and in situ hybridization revealed the presence of three transcription start sites of liver-specific Epac2: two major sites located in exon 10 and a minor site in intron 9. The same translation start site is used in all three transcripts. Liver-specific cAMP-GEFII protein, which lacks the first cAMP-binding domain and the Dishevelled/Egl-10/Pleckstrin domain, was detected at 79 kDa by immunoblot analysis, confirming the presence of the short form of cAMP-GEFII in the liver. Liver-specific cAMP-GEFII also has GEF activity toward Rap1. These results demonstrate the presence of liver-specific cAMP-GEFII. Together with the previous finding that cAMP-GEFII is responsible for cAMP-dependent exocytosis in secretory cells, our study suggests that cAMP-GEFII may have a distinct role in liver.
Ueno
H
H
Department of Cellular and Molecular Medicine, Graduate School of Medicine, Chiba University, 1-8-1, Inohana, Chuo-ku, Chiba, 260-8670, Japan.
Shibasaki
T
T
Iwanaga
T
T
Takahashi
K
K
Yokoyama
Y
Y
Liu
L M
LM
Yokoi
N
N
Ozaki
N
N
Matsukura
S
S
Yano
H
H
Seino
S
S
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002352:Carrier Proteins / Q000235:genetics*; D002874:Chromosome Mapping; D002889:Chromosomes, Human, Pair 2 / Q000235:genetics; D004247:DNA / Q000737:chemistry / Q000235:genetics; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D005091:Exons; D005260:Female; D015870:Gene Expression; D005796:Genes / Q000235:genetics*; D020662:Guanine Nucleotide Exchange Factors; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007438:Introns; D008099:Liver / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics; D020033:Protein Isoforms / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D021101:Radiation Hybrid Mapping; D017422:Sequence Analysis, DNA; D014018:Tissue Distribution; D024363:Transcription Initiation Site
D002352:Carrier Proteins; D018076:DNA, Complementary; D020662:Guanine Nucleotide Exchange Factors; D020033:Protein Isoforms; C442864:RAPGEF4 protein, human; D012333:RNA, Messenger; C486707:Rapgef4 protein, mouse; D004247:DNA