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Alternative transcript of the nonselective-type endothelin receptor from rat brain
1National Laboratories of Foods and Drugs, Department of Health, Executive Yuan, Taipei, Taiwan, Republic of China.
Molecular Pharmacology
|September 1, 1993
Summary
Researchers discovered an alternative transcript for the rat endothelin B (ETB) receptor gene in the brain. This novel cDNA sequence may be tissue-specifically regulated, suggesting broader roles for the ETB receptor.
Area of Science:
- Molecular Biology
- Neuroscience
- Pharmacology
Background:
- The endothelin (ET) system plays crucial roles in cardiovascular and nervous system functions.
- Endothelin receptors (ETA and ETB) mediate the diverse actions of ET peptides.
- Understanding the full spectrum of ET receptor isoforms and their regulation is vital for therapeutic development.
Purpose of the Study:
- To isolate and characterize a novel cDNA encoding a nonselective endothelin receptor from rat brain.
- To determine the relationship between the novel brain cDNA and previously identified rat ETB receptor cDNA.
- To investigate the genomic origin and expression patterns of the novel rat brain ETB receptor transcript.
Main Methods:
- cDNA library screening (rat brain)
- Nucleotide sequencing and sequence analysis
- Heterologous expression in COS-1 cells
- Radioligand binding assays
- Southern and Northern blot analyses
- Genomic DNA cloning and sequencing
Main Results:
- A novel cDNA encoding a 442-amino acid protein with seven transmembrane domains was isolated from rat brain.
- The encoded receptor exhibited equal affinity for all three endothelin isopeptides, consistent with a nonselective ETB receptor.
- Sequence analysis revealed differences in coding and noncoding regions compared to rat lung ETB cDNA, but genomic analysis confirmed it encodes the authentic rat ETB receptor protein.
- The divergent 5' noncoding sequences were traced to an upstream exon, indicating an alternative transcript of the rat ETB gene.
- Preliminary Northern blot analysis suggested tissue-specific expression of this alternative transcript in brain and potentially other tissues.
Conclusions:
- The isolated rat brain cDNA represents an alternative transcript of the rat endothelin B (ETB) receptor gene.
- This alternative transcript may arise from alternative splicing or differential promoter usage.
- The tissue-specific expression suggests a regulated role for this ETB receptor variant in various physiological processes.