Molecular properties of apelin: tissue distribution and receptor binding.
We analyzed the tissue distribution of apelin mRNA in rats by a quantitative reverse transcription-polymerase chain reaction and that of immunoreactive apelin (ir-apelin) by an enzyme immunoassay (EIA) using a monoclonal antibody. The expression levels of apelin mRNA and ir-apelin seemed to be consistent among tissues: they were highly expressed in the lung and mammary gland. By the combination of gel filtration and EIA, we found that the molecular forms of apelin differ among respective tissues: apelin molecules with sizes close to apelin-36 (long forms) were major components in the lung, testis, and uterus, but both long and short (whose sizes were close to [<Glu(65)]apelin-13) forms were detected in the mammary gland. In Scatchard analyses, the radioiodinated apelin-36 analogue bound to the receptor, APJ, with high affinity. In competitive binding assays, apelin-36 and apelin-19 far more efficiently inhibited the binding of the labeled apelin-36 analogue with APJ than [<Glu(65)]apelin-13. In analyses for the dissociation of apelin from APJ, unlabeled apelin-36 replaced more rapidly the labeled apelin-36 analogue bound with APJ than [<Glu(65)]apelin-13. Our results demonstrate that the long and short forms of apelin differently interact with APJ.
Kawamata
Y
Y
Discovery Research Laboratories 1, Pharmaceutical Discovery Research Division, Takeda Chemical Industries, Ltd., Wadai 10, Tsukuba, 300-4293, Ibaraki, Japan.
Habata
Y
Y
Fukusumi
S
S
Hosoya
M
M
Fujii
R
R
Hinuma
S
S
Nishizawa
N
N
Kitada
C
C
Onda
H
H
Nishimura
O
O
Fujino
M
M
D000595:Amino Acid Sequence; D000818:Animals; D000073861:Apelin; D000075244:Apelin Receptors; D002352:Carrier Proteins / Q000032:analysis* / Q000138:chemical synthesis / Q000378:metabolism; D002850:Chromatography, Gel; D005260:Female; D007124:Immunoenzyme Techniques; D036341:Intercellular Signaling Peptides and Proteins; D008168:Lung / Q000378:metabolism; D008297:Male; D008321:Mammary Glands, Animal / Q000378:metabolism; D008969:Molecular Sequence Data; D008970:Molecular Weight; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D017448:Receptors, Dopamine D2; D043562:Receptors, G-Protein-Coupled; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013737:Testis / Q000378:metabolism; D014599:Uterus / Q000378:metabolism
D000073861:Apelin; D000075244:Apelin Receptors; C498579:Apln protein, rat; C491284:Aplnr protein, rat; D002352:Carrier Proteins; D036341:Intercellular Signaling Peptides and Proteins; D012333:RNA, Messenger; D017448:Receptors, Dopamine D2; D043562:Receptors, G-Protein-Coupled