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Molecular properties of apelin: tissue distribution and receptor binding
Y Kawamata1, Y Habata, S Fukusumi
1Discovery Research Laboratories 1, Pharmaceutical Discovery Research Division, Takeda Chemical Industries, Ltd., Wadai 10, Tsukuba, 300-4293, Ibaraki, Japan.
Abstract:
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 [
Insights
Apelin, a peptide hormone, exists in different molecular forms that interact distinctly with its receptor, APJ. These findings reveal tissue-specific variations in apelin processing and binding dynamics.
Area of Science:
- Biochemistry
- Molecular Biology
- Endocrinology
Background:
- Apelin is a peptide hormone with diverse physiological roles.
- Understanding apelin's molecular forms and receptor interactions is crucial for elucidating its functions.
Purpose of the Study:
- To investigate the tissue distribution of apelin mRNA and immunoreactive apelin (ir-apelin) in rats.
- To characterize the molecular forms of apelin in different tissues.
- To analyze the binding kinetics of apelin variants with the APJ receptor.
Main Methods:
- Quantitative reverse transcription-polymerase chain reaction (RT-PCR) for apelin mRNA.
- Enzyme immunoassay (EIA) for ir-apelin.
- Gel filtration chromatography combined with EIA for molecular form analysis.
- Scatchard and competitive binding assays to study apelin-APJ interactions.
Main Results:
- Apelin mRNA and ir-apelin were highly expressed in the lung and mammary gland.
- Tissue-specific molecular forms of apelin were identified, with longer forms (e.g., apelin-36) predominant in the lung, testis, and uterus, and both long and short forms in the mammary gland.
- Apelin-36 and apelin-19 demonstrated higher affinity and faster dissociation rates with the APJ receptor compared to shorter forms like [
Conclusions:
- The study reveals distinct tissue-specific expression patterns and molecular forms of apelin.
- Longer apelin forms exhibit differential binding kinetics with the APJ receptor compared to shorter forms.
- These findings highlight the complex interactions between apelin variants and their receptor, influencing physiological responses.