This Article Full Text Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Chen, J. Articles by Randeva, H. S. Search for Related Content PubMed PubMed Citation Articles by Chen, J. Articles by Randeva, H. S.

Genomic Organization of Mouse Orexin Receptors: Characterization of Two Novel Tissue-Specific Splice Variants

Molecular Medicine Group, Biological Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom

Address all correspondence and requests for reprints to: Dr. Harpal S. Randeva, Molecular Medicine Research Group, Biological Sciences, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, United Kingdom. E-mail: hrandeva{at}bio.warwick.ac.uk.

In humans and rat, orexins orchestrate divergent actions through their G protein-coupled receptors, orexin-1 (OX1R) and orexin-2 (OX2R). Orexins also play an important physiological role in mouse, but the receptors through which they function are not characterized. To characterize the physiological role(s) of orexins in the mouse, we cloned and characterized the mouse orexin receptor(s), mOX1R and mOX2R, using rapid amplification of cDNA (mouse brain) ends, RT-PCR, and gene structure analysis. The mOX1R cDNA encodes a 416-amino acid (aa) receptor. We have identified two alternative C terminus splice variants of the mOX2R; mOX2R (443 aa) and mOX2ßR (460 aa). Binding studies in human embryonic kidney 293 cells transfected with mOX1R, mOX2R, and the mOX2ßR revealed specific, saturable sites for both orexin-A and -B. Activation of these receptors by orexins induced inositol triphosphate (IP₃) turnover. However, human embryonic kidney 293 cells transfected with mOXRs demonstrated no cAMP response to either orexin-A or orexin-B challenge, although forskolin and GTPS revealed a dose-dependent increase in cAMP. Although, orexin-A and -B showed no difference in binding characteristics between the splice variants; interestingly, orexin-B led to an increase in IP₃ production at all concentrations in the mOX2ßR variant. Orexin-A, however, showed no difference in IP₃ production between the two variants. Additionally, in the mouse, we demonstrate that these splice variants are distributed in a tissue-specific manner, where OX2R mRNA was undetectable in skeletal muscle and kidney. Moreover, food deprivation led to a greater increase in hypothalamic mOX2ßR gene expression, compared with both mOX1R and mOX2R. This potentially implicates a fundamental physiological role for these splice variants.