| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2006: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 2005: ¥2,200,000 (Direct Cost: ¥2,200,000)
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| Research Abstract |
Angiotensin II/vasopressin dual receptor (AT/VPR) gene was cloned from the rat, the protein product of which has unique receptor characteristics, i.e. both angiontensin II (AII) and vasopressin (VP) act as ligands. However, the structure of the gene has not characterized yet, and the functional characteristics of the receptor remains to be clarified. In this study, we cloned the mouse AT/VPR mRNA and gene (6.5 Kb). Although the mouse and the rat AT/AVPR genes showed extremely high similarity in their nucleotide sequences, unexpectedly, the initiation codon of the rat gene was changed from Met to Leu in the mouse, resulting in extended protein product at N-terminus (179 a.a.). The mouse AT/VPR gene consisted of at least 5 exons and 4 introns by comparing the nucleotide sequence of its cDNA. Interestingly, the gene partly shared that of NACHT/Nalp6,which belongs the pathogen-recognition receptor.
We then examined the tissue distribution of the AT/VPR mRNA, and found it to be expressed in the pituitary, thalamus, cerebral cortex, hippocampus, cerebellum, liver, gall bladder, adrenal gland, colon, testis, and white adipose tissue.
Expression in cardiomyocytes was weak, and no expression was observed in skeletal muscle, skin, and spleen.
Finally, we constructed an expression vector of the receptor and expressed it in A10 rat vascular smooth muscle cells in vitro. We fund that, at least in our experimental condition, AII did not activate any intracellular signaling pathways. On the other hand, vasopressin modestly enhanced the response of SRE-dependent transcription, whereas markedly attenuated that of NF-kB-dependent transcription, when the AT/VPR was overexpressed.
We thus conclude that AT/VPR may be working not as a classical "hormone receptor" but as a pattern recognition receptor, and is modifying the NF-kB-dependent gene transcription. The functional differences between the mouse and rat AT/VPR awaits further investigation.
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