Mole ghrelin: cDNA cloning, gene expression, and diverse molecular forms in Mogera imaizumii.
Here, we describe cDNA cloning and purification of the ghrelin gene sequences and ghrelin peptides from the Japanese true mole, Mogera imaizumii. The gene spans >2.9kbp, has four exons and three introns, and shares structural similarity with those of terrestrial animals. Mature mole ghrelin peptide was predicted to be 28 amino acids long (GSSFLSPEHQKVQQRKESKKPPSKPQPR) and processed from a prepropeptide of 116 amino acids. To further elucidate molecular characteristics, we purified ghrelin peptides from mole stomach. By mass spectrometry, we found that the mole ghrelin peptides had higher ratios of the odd-number fatty acids (C9 and C11 as much as C8) attached to the third serine residue than other vertebrate ghrelin. Truncated forms of ghrelins such as [1-27], [1-19], [1-16] and [1-15], and that lacked the 14th glutamine residue (des-Gln14 ghrelin) were produced in the stomach. Marked expression of ghrelin mRNA in lung was observed as in stomach and brain. Phylogenetic analysis indicated that the branch of M. imaizumii has slightly higher dN/dS ratios (the nucleotide substitution rates at non-synonymous and synonymous sites) than did other eulipotyphlans. Peptide length was positively correlated with human ghrelin receptor activation, whereas the length of fatty-acyl chains showed no obvious functional correlation. The basal higher luciferase activities of the 5'-proximal promoter region of mole ghrelin were detected in ghrelin-negative C2C12 cells and hypoxic culture conditions impaired transcriptional activity. These results indicated that moles have acquired diverse species of ghrelin probably through distinctive fatty acid metabolism because of their food preferences. The results provide a gateway to understanding ghrelin metabolism in fossorial animals.
Department of Biochemistry, Dokkyo Medical University School of Medicine, 880 Kitakobayashi, Mibu, Tochigi 321-0293, Japan.
Motoyasu
M
Satou
Department of Biochemistry, National Cardiovascular Center Research Institute, Suita, Osaka 565-8565, Japan.
Hiroyuki
H
Kaiya
Department of Physiology, Kurume University School of Medicine, Kurume, Fukuoka 830-0011, Japan.
Yoshihiro
Y
Nishi
Division of Bio-resources, Department of Biotechnology, Frontier Science Research Center, University of Miyazaki, Kihara 5200, Kiyotake, Miyazaki 889-1692, Japan.
Akio
A
Shinohara
Department of Zoology, National Museum of Nature and Science, 4-1-1 Amakubo, Tsukuba, Ibaraki 305-0005, Japan.
Shin-Ichiro
S
Kawada
Department of Biochemistry, National Cardiovascular Center Research Institute, Suita, Osaka 565-8565, Japan.
Mikiya
M
Miyazato
Department of Biochemistry, National Cardiovascular Center Research Institute, Suita, Osaka 565-8565, Japan.
Kenji
K
Kangawa
Department of Biochemistry, Dokkyo Medical University School of Medicine, 880 Kitakobayashi, Mibu, Tochigi 321-0293, Japan. Electronic address: h-sugi@dokkyomed.ac.jp.
Hiroyuki
H
Sugimoto
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018076:DNA, Complementary / Q000235:genetics*; D015870:Gene Expression; D054439:Ghrelin / Q000235:genetics*; D008971:Moles / Q000235:genetics*
D018076:DNA, Complementary; D054439:Ghrelin
Ghrelin; Lipidation; Mole; Purification; Stomach; cDN